// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// Package core implements the Ethereum consensus protocol.
package core

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"math/big"
	"runtime"
	"slices"
	"sort"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/lru"
	"github.com/ethereum/go-ethereum/common/mclock"
	"github.com/ethereum/go-ethereum/common/prque"
	"github.com/ethereum/go-ethereum/consensus"
	"github.com/ethereum/go-ethereum/consensus/misc/eip4844"
	"github.com/ethereum/go-ethereum/core/history"
	"github.com/ethereum/go-ethereum/core/rawdb"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/state/snapshot"
	"github.com/ethereum/go-ethereum/core/stateless"
	"github.com/ethereum/go-ethereum/core/tracing"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/eth/downloader/whitelist"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/internal/syncx"
	"github.com/ethereum/go-ethereum/internal/version"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/metrics"
	"github.com/ethereum/go-ethereum/params"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/ethereum/go-ethereum/triedb"
	"github.com/ethereum/go-ethereum/triedb/hashdb"
	"github.com/ethereum/go-ethereum/triedb/pathdb"
)

var (
	headBlockGauge          = metrics.NewRegisteredGauge("chain/head/block", nil)
	headHeaderGauge         = metrics.NewRegisteredGauge("chain/head/header", nil)
	headFastBlockGauge      = metrics.NewRegisteredGauge("chain/head/receipt", nil)
	headFinalizedBlockGauge = metrics.NewRegisteredGauge("chain/head/finalized", nil)
	headSafeBlockGauge      = metrics.NewRegisteredGauge("chain/head/safe", nil)

	chainInfoGauge = metrics.NewRegisteredGaugeInfo("chain/info", nil)

	accountReadTimer   = metrics.NewRegisteredResettingTimer("chain/account/reads", nil)
	accountHashTimer   = metrics.NewRegisteredResettingTimer("chain/account/hashes", nil)
	accountUpdateTimer = metrics.NewRegisteredResettingTimer("chain/account/updates", nil)
	accountCommitTimer = metrics.NewRegisteredResettingTimer("chain/account/commits", nil)

	storageReadTimer   = metrics.NewRegisteredResettingTimer("chain/storage/reads", nil)
	storageHashTimer   = metrics.NewRegisteredTimer("chain/storage/hashes", nil)
	storageUpdateTimer = metrics.NewRegisteredResettingTimer("chain/storage/updates", nil)
	storageCommitTimer = metrics.NewRegisteredResettingTimer("chain/storage/commits", nil)

	accountReadSingleTimer = metrics.NewRegisteredResettingTimer("chain/account/single/reads", nil) //nolint:revive,unused
	storageReadSingleTimer = metrics.NewRegisteredResettingTimer("chain/storage/single/reads", nil) //nolint:revive,unused

	snapshotCommitTimer      = metrics.NewRegisteredResettingTimer("chain/snapshot/commits", nil)
	triedbCommitTimer        = metrics.NewRegisteredResettingTimer("chain/triedb/commits", nil)
	snapshotAccountReadTimer = metrics.NewRegisteredResettingTimer("chain/snapshot/account/reads", nil)
	snapshotStorageReadTimer = metrics.NewRegisteredResettingTimer("chain/snapshot/storage/reads", nil)

	borConsensusTime = metrics.NewRegisteredTimer("chain/bor/consensus", nil)

	blockImportTimer = metrics.NewRegisteredMeter("chain/imports", nil)

	blockInsertTimer                   = metrics.NewRegisteredTimer("chain/inserts", nil)
	blockValidationTimer               = metrics.NewRegisteredTimer("chain/validation", nil)
	blockCrossValidationTimer          = metrics.NewRegisteredResettingTimer("chain/crossvalidation", nil) //nolint:revive,unused
	blockExecutionTimer                = metrics.NewRegisteredTimer("chain/execution", nil)
	blockWriteTimer                    = metrics.NewRegisteredTimer("chain/write", nil)
	blockExecutionParallelCounter      = metrics.NewRegisteredCounter("chain/execution/parallel", nil)
	blockExecutionSerialCounter        = metrics.NewRegisteredCounter("chain/execution/serial", nil)
	blockExecutionParallelErrorCounter = metrics.NewRegisteredCounter("chain/execution/parallel/error", nil)
	blockExecutionParallelTimer        = metrics.NewRegisteredTimer("chain/execution/parallel/timer", nil)
	blockExecutionSerialTimer          = metrics.NewRegisteredTimer("chain/execution/serial/timer", nil)

	blockReorgMeter     = metrics.NewRegisteredMeter("chain/reorg/executes", nil)
	blockReorgAddMeter  = metrics.NewRegisteredMeter("chain/reorg/add", nil)
	blockReorgDropMeter = metrics.NewRegisteredMeter("chain/reorg/drop", nil)

	blockPrefetchExecuteTimer   = metrics.NewRegisteredTimer("chain/prefetch/executes", nil)
	blockPrefetchInterruptMeter = metrics.NewRegisteredMeter("chain/prefetch/interrupts", nil)

	errInsertionInterrupted = errors.New("insertion is interrupted")
	errChainStopped         = errors.New("blockchain is stopped")
	errInvalidOldChain      = errors.New("invalid old chain")
	errInvalidNewChain      = errors.New("invalid new chain")
	// errWitnessTimeout           = errors.New("timeout waiting for witness computation")     // New error
	// errWitnessComputationFailed = errors.New("witness computation failed or was cancelled") // New error
)

const (
	bodyCacheLimit      = 256
	blockCacheLimit     = 256
	receiptsCacheLimit  = 1024
	txLookupCacheLimit  = 1024
	maxFutureBlocks     = 256
	maxTimeFutureBlocks = 30

	// BlockChainVersion ensures that an incompatible database forces a resync from scratch.
	//
	// Changelog:
	//
	// - Version 4
	//   The following incompatible database changes were added:
	//   * the `BlockNumber`, `TxHash`, `TxIndex`, `BlockHash` and `Index` fields of log are deleted
	//   * the `Bloom` field of receipt is deleted
	//   * the `BlockIndex` and `TxIndex` fields of txlookup are deleted
	//
	// - Version 5
	//  The following incompatible database changes were added:
	//    * the `TxHash`, `GasCost`, and `ContractAddress` fields are no longer stored for a receipt
	//    * the `TxHash`, `GasCost`, and `ContractAddress` fields are computed by looking up the
	//      receipts' corresponding block
	//
	// - Version 6
	//  The following incompatible database changes were added:
	//    * Transaction lookup information stores the corresponding block number instead of block hash
	//
	// - Version 7
	//  The following incompatible database changes were added:
	//    * Use freezer as the ancient database to maintain all ancient data
	//
	// - Version 8
	//  The following incompatible database changes were added:
	//    * New scheme for contract code in order to separate the codes and trie nodes
	//
	// - Version 9
	//  The following incompatible database changes were added:
	//  * (not applicable for bor) Total difficulty has been removed from both the key-value store and the ancient store.
	//  * The metadata structure of freezer is changed by adding 'flushOffset'
	BlockChainVersion uint64 = 9
)

// CacheConfig contains the configuration values for the trie database
// and state snapshot these are resident in a blockchain.
type CacheConfig struct {
	TrieCleanLimit      int           // Memory allowance (MB) to use for caching trie nodes in memory
	TrieCleanNoPrefetch bool          // Whether to disable heuristic state prefetching for followup blocks
	TrieDirtyLimit      int           // Memory limit (MB) at which to start flushing dirty trie nodes to disk
	TrieDirtyDisabled   bool          // Whether to disable trie write caching and GC altogether (archive node)
	TrieTimeLimit       time.Duration // Time limit after which to flush the current in-memory trie to disk
	SnapshotLimit       int           // Memory allowance (MB) to use for caching snapshot entries in memory
	Preimages           bool          // Whether to store preimage of trie key to the disk
	TriesInMemory       uint64        // Number of recent tries to keep in memory
	StateHistory        uint64        // Number of blocks from head whose state histories are reserved.
	StateScheme         string        // Scheme used to store ethereum states and merkle tree nodes on top

	SnapshotNoBuild bool // Whether the background generation is allowed
	SnapshotWait    bool // Wait for snapshot construction on startup. TODO(karalabe): This is a dirty hack for testing, nuke it

	ChainHistoryMode history.HistoryMode
	// This defines the cutoff block for history expiry.
	// Blocks before this number may be unavailable in the chain database.
	HistoryPruningCutoff uint64
	Stateless            bool // Whether the node is in stateless mode
}

// triedbConfig derives the configures for trie database.
func (c *CacheConfig) triedbConfig(isVerkle bool) *triedb.Config {
	config := &triedb.Config{
		Preimages: c.Preimages,
		IsVerkle:  isVerkle,
	}
	if c.StateScheme == rawdb.HashScheme {
		config.HashDB = &hashdb.Config{
			CleanCacheSize: c.TrieCleanLimit * 1024 * 1024,
		}
	}
	if c.StateScheme == rawdb.PathScheme {
		config.PathDB = &pathdb.Config{
			StateHistory:    c.StateHistory,
			CleanCacheSize:  c.TrieCleanLimit * 1024 * 1024,
			WriteBufferSize: c.TrieDirtyLimit * 1024 * 1024,
		}
	}
	return config
}

// defaultCacheConfig are the default caching values if none are specified by the
// user (also used during testing).
var defaultCacheConfig = &CacheConfig{
	TrieCleanLimit: 256,
	TrieDirtyLimit: 256,
	TrieTimeLimit:  5 * time.Minute,
	SnapshotLimit:  256,
	SnapshotWait:   true,
	TriesInMemory:  128,
	StateScheme:    rawdb.HashScheme,
}

// DefaultCacheConfigWithScheme returns a deep copied default cache config with
// a provided trie node scheme.
func DefaultCacheConfigWithScheme(scheme string) *CacheConfig {
	config := *defaultCacheConfig
	config.StateScheme = scheme
	return &config
}

var DefaultCacheConfig = defaultCacheConfig

// txLookup is wrapper over transaction lookup along with the corresponding
// transaction object.
type txLookup struct {
	lookup      *rawdb.LegacyTxLookupEntry
	transaction *types.Transaction
}

// BlockChain represents the canonical chain given a database with a genesis
// block. The Blockchain manages chain imports, reverts, chain reorganisations.
//
// Importing blocks in to the block chain happens according to the set of rules
// defined by the two stage Validator. Processing of blocks is done using the
// Processor which processes the included transaction. The validation of the state
// is done in the second part of the Validator. Failing results in aborting of
// the import.
//
// The BlockChain also helps in returning blocks from **any** chain included
// in the database as well as blocks that represents the canonical chain. It's
// important to note that GetBlock can return any block and does not need to be
// included in the canonical one where as GetBlockByNumber always represents the
// canonical chain.
type BlockChain struct {
	chainConfig *params.ChainConfig // Chain & network configuration
	cacheConfig *CacheConfig        // Cache configuration for pruning

	db            ethdb.Database                   // Low level persistent database to store final content in
	snaps         *snapshot.Tree                   // Snapshot tree for fast trie leaf access
	triegc        *prque.Prque[int64, common.Hash] // Priority queue mapping block numbers to tries to gc
	gcproc        time.Duration                    // Accumulates canonical block processing for trie dumping
	lastWrite     uint64                           // Last block when the state was flushed
	flushInterval atomic.Int64                     // Time interval (processing time) after which to flush a state
	triedb        *triedb.Database                 // The database handler for maintaining trie nodes.
	statedb       *state.CachingDB                 // State database to reuse between imports (contains state cache)
	txIndexer     *txIndexer                       // Transaction indexer, might be nil if not enabled

	hc               *HeaderChain
	rmLogsFeed       event.Feed
	chainFeed        event.Feed
	chainHeadFeed    event.Feed
	logsFeed         event.Feed
	blockProcFeed    event.Feed
	blockProcCounter int32
	scope            event.SubscriptionScope
	genesisBlock     *types.Block

	// This mutex synchronizes chain write operations.
	// Readers don't need to take it, they can just read the database.
	chainmu *syncx.ClosableMutex

	currentBlock      atomic.Pointer[types.Header] // Current head of the chain
	currentSnapBlock  atomic.Pointer[types.Header] // Current head of snap-sync
	currentFinalBlock atomic.Pointer[types.Header] // Latest (consensus) finalized block
	currentSafeBlock  atomic.Pointer[types.Header] // Latest (consensus) safe block
	historyPrunePoint atomic.Pointer[history.PrunePoint]

	bodyCache     *lru.Cache[common.Hash, *types.Body]
	bodyRLPCache  *lru.Cache[common.Hash, rlp.RawValue]
	receiptsCache *lru.Cache[common.Hash, []*types.Receipt]
	blockCache    *lru.Cache[common.Hash, *types.Block]

	txLookupLock  sync.RWMutex
	txLookupCache *lru.Cache[common.Hash, txLookup]

	// future blocks are blocks added for later processing
	futureBlocks *lru.Cache[common.Hash, *types.Block]

	wg            sync.WaitGroup
	quit          chan struct{} // shutdown signal, closed in Stop.
	stopping      atomic.Bool   // false if chain is running, true when stopped
	procInterrupt atomic.Bool   // interrupt signaler for block processing

	engine                       consensus.Engine
	validator                    Validator // Block and state validator interface
	prefetcher                   Prefetcher
	processor                    Processor // Block transaction processor interface
	parallelProcessor            Processor // Parallel block transaction processor interface
	parallelSpeculativeProcesses int       // Number of parallel speculative processes
	enforceParallelProcessor     bool
	forker                       *ForkChoice
	vmConfig                     vm.Config
	logger                       *tracing.Hooks

	// Bor related changes
	borReceiptsCache *lru.Cache[common.Hash, *types.Receipt] // Cache for the most recent bor receipt receipts per block
	stateSyncMu      sync.RWMutex                            // Mutex to protect the stateSyncData access
	stateSyncData    []*types.StateSyncData                  // State sync data
	stateSyncFeed    event.Feed                              // State sync feed
	chain2HeadFeed   event.Feed                              // Reorg/NewHead/Fork data feed
	chainSideFeed    event.Feed                              // Side chain data feed (removed from geth but needed in bor)
	checker          ethereum.ChainValidator
}

// NewBlockChain returns a fully initialised block chain using information
// available in the database. It initialises the default Ethereum Validator
// and Processor.
//
//nolint:gocognit
func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis, overrides *ChainOverrides, engine consensus.Engine, vmConfig vm.Config, shouldPreserve func(header *types.Header) bool, txLookupLimit *uint64, checker ethereum.ChainValidator) (*BlockChain, error) {
	if cacheConfig == nil {
		cacheConfig = defaultCacheConfig
	}

	// Open trie database with provided config
	enableVerkle, err := EnableVerkleAtGenesis(db, genesis)
	if err != nil {
		return nil, err
	}
	triedb := triedb.NewDatabase(db, cacheConfig.triedbConfig(enableVerkle))

	// Write the supplied genesis to the database if it has not been initialized
	// yet. The corresponding chain config will be returned, either from the
	// provided genesis or from the locally stored configuration if the genesis
	// has already been initialized.
	chainConfig, genesisHash, compatErr, err := SetupGenesisBlockWithOverride(db, triedb, genesis, overrides)
	if err != nil {
		return nil, err
	}

	log.Info("")
	log.Info(strings.Repeat("-", 153))

	for _, line := range strings.Split(chainConfig.Description(), "\n") {
		log.Info(line)
	}

	log.Info(strings.Repeat("-", 153))
	log.Info("")

	bc := &BlockChain{
		chainConfig:   chainConfig,
		cacheConfig:   cacheConfig,
		db:            db,
		triedb:        triedb,
		triegc:        prque.New[int64, common.Hash](nil),
		quit:          make(chan struct{}),
		chainmu:       syncx.NewClosableMutex(),
		bodyCache:     lru.NewCache[common.Hash, *types.Body](bodyCacheLimit),
		bodyRLPCache:  lru.NewCache[common.Hash, rlp.RawValue](bodyCacheLimit),
		receiptsCache: lru.NewCache[common.Hash, []*types.Receipt](receiptsCacheLimit),
		blockCache:    lru.NewCache[common.Hash, *types.Block](blockCacheLimit),
		txLookupCache: lru.NewCache[common.Hash, txLookup](txLookupCacheLimit),
		futureBlocks:  lru.NewCache[common.Hash, *types.Block](maxFutureBlocks),
		engine:        engine,
		vmConfig:      vmConfig,

		borReceiptsCache: lru.NewCache[common.Hash, *types.Receipt](receiptsCacheLimit),
		logger:           vmConfig.Tracer,
		checker:          checker,
	}

	bc.hc, err = NewHeaderChain(db, chainConfig, engine, bc.insertStopped)
	if err != nil {
		return nil, err
	}

	bc.flushInterval.Store(int64(cacheConfig.TrieTimeLimit))
	bc.forker = NewForkChoice(bc, shouldPreserve, checker)
	bc.statedb = state.NewDatabase(bc.triedb, nil)
	bc.validator = NewBlockValidator(chainConfig, bc)
	bc.prefetcher = newStatePrefetcher(chainConfig, bc.hc)
	bc.processor = NewStateProcessor(chainConfig, bc.hc)

	genesisHeader := bc.GetHeaderByNumber(0)
	bc.genesisBlock = types.NewBlockWithHeader(genesisHeader)
	if bc.genesisBlock == nil {
		return nil, ErrNoGenesis
	}

	bc.currentBlock.Store(nil)
	bc.currentSnapBlock.Store(nil)
	bc.currentFinalBlock.Store(nil)
	bc.currentSafeBlock.Store(nil)

	// Update chain info data metrics
	chainInfoGauge.Update(metrics.GaugeInfoValue{"chain_id": bc.chainConfig.ChainID.String()})

	// If Geth is initialized with an external ancient store, re-initialize the
	// missing chain indexes and chain flags. This procedure can survive crash
	// and can be resumed in next restart since chain flags are updated in last step.
	if bc.empty() {
		rawdb.InitDatabaseFromFreezer(bc.db)
	}
	// Load blockchain states from disk
	if err := bc.loadLastState(); err != nil {
		return nil, err
	}
	// Make sure the state associated with the block is available, or log out
	// if there is no available state, waiting for state sync.
	head := bc.CurrentBlock()
	// nolint:nestif

	// If the node is in stateless mode, it should not load the state from disk
	if !bc.HasState(head.Root) && !bc.cacheConfig.Stateless {
		if head.Number.Uint64() == 0 {
			// The genesis state is missing, which is only possible in the path-based
			// scheme. This situation occurs when the initial state sync is not finished
			// yet, or the chain head is rewound below the pivot point. In both scenarios,
			// there is no possible recovery approach except for rerunning a snap sync.
			// Do nothing here until the state syncer picks it up.
			log.Info("Genesis state is missing, wait state sync")
		} else {
			// Head state is missing, before the state recovery, find out the
			// disk layer point of snapshot(if it's enabled). Make sure the
			// rewound point is lower than disk layer.
			var diskRoot common.Hash
			if bc.cacheConfig.SnapshotLimit > 0 {
				diskRoot = rawdb.ReadSnapshotRoot(bc.db)
			}
			if diskRoot != (common.Hash{}) {
				log.Warn("Head state missing, repairing", "number", head.Number, "hash", head.Hash(), "snaproot", diskRoot)

				snapDisk, err := bc.setHeadBeyondRoot(head.Number.Uint64(), 0, diskRoot, true)
				if err != nil {
					return nil, err
				}
				// Chain rewound, persist old snapshot number to indicate recovery procedure
				if snapDisk != 0 {
					rawdb.WriteSnapshotRecoveryNumber(bc.db, snapDisk)
				}
			} else {
				log.Warn("Head state missing, repairing", "number", head.Number, "hash", head.Hash())
				if _, err := bc.setHeadBeyondRoot(head.Number.Uint64(), 0, common.Hash{}, true); err != nil {
					return nil, err
				}
			}
		}
	}
	// Ensure that a previous crash in SetHead doesn't leave extra ancients
	//nolint:nestif
	if frozen, err := bc.db.ItemAmountInAncient(); err == nil && frozen > 0 {
		frozen, err = bc.db.Ancients()
		if err != nil {
			return nil, err
		}
		var (
			needRewind bool
			low        uint64
		)
		// The head full block may be rolled back to a very low height due to
		// blockchain repair. If the head full block is even lower than the ancient
		// chain, truncate the ancient store.
		fullBlock := bc.CurrentBlock()
		if fullBlock != nil && fullBlock.Hash() != bc.genesisBlock.Hash() && fullBlock.Number.Uint64() < frozen-1 {
			needRewind = true
			low = fullBlock.Number.Uint64()
		}
		// In snap sync, it may happen that ancient data has been written to the
		// ancient store, but the LastFastBlock has not been updated, truncate the
		// extra data here.
		snapBlock := bc.CurrentSnapBlock()
		if snapBlock != nil && snapBlock.Number.Uint64() < frozen-1 {
			needRewind = true

			if snapBlock.Number.Uint64() < low || low == 0 {
				low = snapBlock.Number.Uint64()
			}
		}

		if needRewind {
			log.Error("Truncating ancient chain", "from", bc.CurrentHeader().Number.Uint64(), "to", low)

			if err := bc.SetHead(low); err != nil {
				return nil, err
			}
		}
	}
	// The first thing the node will do is reconstruct the verification data for
	// the head block (ethash cache or clique voting snapshot). Might as well do
	// it in advance.
	// BOR - commented out intentionally
	// bc.engine.VerifyHeader(bc, bc.CurrentHeader())

	// Check the current state of the block hashes and make sure that we do not have any of the bad blocks in our chain
	for hash := range BadHashes {
		if header := bc.GetHeaderByHash(hash); header != nil {
			// get the canonical block corresponding to the offending header's number
			headerByNumber := bc.GetHeaderByNumber(header.Number.Uint64())
			// make sure the headerByNumber (if present) is in our current canonical chain
			if headerByNumber != nil && headerByNumber.Hash() == header.Hash() {
				log.Error("Found bad hash, rewinding chain", "number", header.Number, "hash", header.ParentHash)

				if err := bc.SetHead(header.Number.Uint64() - 1); err != nil {
					return nil, err
				}

				log.Error("Chain rewind was successful, resuming normal operation")
			}
		}
	}

	if bc.logger != nil && bc.logger.OnBlockchainInit != nil {
		bc.logger.OnBlockchainInit(chainConfig)
	}
	if bc.logger != nil && bc.logger.OnGenesisBlock != nil {
		if block := bc.CurrentBlock(); block.Number.Uint64() == 0 {
			alloc, err := getGenesisState(bc.db, block.Hash())
			if err != nil {
				return nil, fmt.Errorf("failed to get genesis state: %w", err)
			}
			if alloc == nil {
				return nil, errors.New("live blockchain tracer requires genesis alloc to be set")
			}
			bc.logger.OnGenesisBlock(bc.genesisBlock, alloc)
		}
	}

	// Load any existing snapshot, regenerating it if loading failed
	if bc.cacheConfig.SnapshotLimit > 0 {
		// If the chain was rewound past the snapshot persistent layer (causing
		// a recovery block number to be persisted to disk), check if we're still
		// in recovery mode and in that case, don't invalidate the snapshot on a
		// head mismatch.
		var recover bool

		head := bc.CurrentBlock()
		if layer := rawdb.ReadSnapshotRecoveryNumber(bc.db); layer != nil && *layer >= head.Number.Uint64() {
			log.Warn("Enabling snapshot recovery", "chainhead", head.Number, "diskbase", *layer)

			recover = true
		}

		snapconfig := snapshot.Config{
			CacheSize:  bc.cacheConfig.SnapshotLimit,
			Recovery:   recover,
			NoBuild:    bc.cacheConfig.SnapshotNoBuild,
			AsyncBuild: !bc.cacheConfig.SnapshotWait,
		}
		bc.snaps, _ = snapshot.New(snapconfig, bc.db, bc.triedb, head.Root)

		// Re-initialize the state database with snapshot
		bc.statedb = state.NewDatabase(bc.triedb, bc.snaps)
	}

	// Rewind the chain in case of an incompatible config upgrade.
	if compatErr != nil {
		log.Warn("Rewinding chain to upgrade configuration", "err", compatErr)
		if compatErr.RewindToTime > 0 {
			bc.SetHeadWithTimestamp(compatErr.RewindToTime)
		} else {
			bc.SetHead(compatErr.RewindToBlock)
		}

		rawdb.WriteChainConfig(db, genesisHash, chainConfig)
	}
	// Start tx indexer if it's enabled.
	if txLookupLimit != nil {
		bc.txIndexer = newTxIndexer(*txLookupLimit, bc)
	}

	// Start header verification loop
	bc.startHeaderVerificationLoop()

	return bc, nil
}

// NewParallelBlockChain , similar to NewBlockChain, creates a new blockchain object, but with a parallel state processor
func NewParallelBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis, overrides *ChainOverrides, engine consensus.Engine, vmConfig vm.Config, shouldPreserve func(header *types.Header) bool, txLookupLimit *uint64, checker ethereum.ChainValidator, numprocs int, enforce bool) (*BlockChain, error) {
	bc, err := NewBlockChain(db, cacheConfig, genesis, overrides, engine, vmConfig, shouldPreserve, txLookupLimit, checker)

	if err != nil {
		return nil, err
	}

	bc.parallelProcessor = NewParallelStateProcessor(bc.chainConfig, bc, engine)
	bc.parallelSpeculativeProcesses = numprocs
	bc.enforceParallelProcessor = enforce

	return bc, nil
}

func (bc *BlockChain) ProcessBlock(block *types.Block, parent *types.Header, witness *stateless.Witness) (_ types.Receipts, _ []*types.Log, _ uint64, _ *state.StateDB, vtime time.Duration, blockEndErr error) {
	// Process the block using processor and parallelProcessor at the same time, take the one which finishes first, cancel the other, and return the result
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	if bc.logger != nil && bc.logger.OnBlockStart != nil {
		td := bc.GetTd(block.ParentHash(), block.NumberU64()-1)
		bc.logger.OnBlockStart(tracing.BlockEvent{
			Block:     block,
			TD:        td,
			Finalized: bc.CurrentFinalBlock(),
			Safe:      bc.CurrentSafeBlock(),
		})
	}

	if bc.logger != nil && bc.logger.OnBlockEnd != nil {
		defer func() {
			bc.logger.OnBlockEnd(blockEndErr)
		}()
	}

	type Result struct {
		receipts types.Receipts
		logs     []*types.Log
		usedGas  uint64
		err      error
		statedb  *state.StateDB
		counter  *metrics.Counter
		parallel bool
	}

	// temporary disabled block STM because witness not work on parallel.
	// TODO: how to enable witness on parallel state processing
	bc.parallelProcessor = nil
	bc.enforceParallelProcessor = false

	var resultChanLen int = 2
	if bc.enforceParallelProcessor {
		log.Debug("Processing block using Block STM only", "number", block.NumberU64())
		resultChanLen = 1
	}
	resultChan := make(chan Result, resultChanLen)

	processorCount := 0

	if bc.parallelProcessor != nil {
		parallelStatedb, err := state.New(parent.Root, bc.statedb)
		if err != nil {
			return nil, nil, 0, nil, 0, err
		}

		processorCount++

		go func() {
			parallelStatedb.StartPrefetcher("chain", witness)
			pstart := time.Now()
			res, err := bc.parallelProcessor.Process(block, parallelStatedb, bc.vmConfig, nil, ctx)
			blockExecutionParallelTimer.UpdateSince(pstart)
			if err == nil {
				vstart := time.Now()
				err = bc.validator.ValidateState(block, parallelStatedb, res, false)
				vtime = time.Since(vstart)
			}
			if res == nil {
				res = &ProcessResult{}
			}
			resultChan <- Result{res.Receipts, res.Logs, res.GasUsed, err, parallelStatedb, blockExecutionParallelCounter, true}
		}()
	}

	if bc.processor != nil && !bc.enforceParallelProcessor {
		statedb, err := state.New(parent.Root, bc.statedb)
		if err != nil {
			return nil, nil, 0, nil, 0, err
		}

		processorCount++

		go func() {
			statedb.StartPrefetcher("chain", witness)
			pstart := time.Now()
			res, err := bc.processor.Process(block, statedb, bc.vmConfig, nil, ctx)
			blockExecutionSerialTimer.UpdateSince(pstart)
			if err == nil {
				vstart := time.Now()
				err = bc.validator.ValidateState(block, statedb, res, false)
				vtime = time.Since(vstart)
			}
			if res == nil {
				res = &ProcessResult{}
			}
			resultChan <- Result{res.Receipts, res.Logs, res.GasUsed, err, statedb, blockExecutionSerialCounter, false}
		}()
	}

	result := <-resultChan

	if result.parallel && result.err != nil {
		log.Warn("Parallel state processor failed", "err", result.err)
		blockExecutionParallelErrorCounter.Inc(1)
		// If the parallel processor failed, we will fallback to the serial processor if enabled
		if processorCount == 2 {
			result = <-resultChan
			result.statedb.StopPrefetcher()
			processorCount--
		}
	}

	result.counter.Inc(1)

	// Make sure we are not leaking any prefetchers
	if processorCount == 2 {
		go func() {
			second_result := <-resultChan
			second_result.statedb.StopPrefetcher()
		}()
	}

	return result.receipts, result.logs, result.usedGas, result.statedb, vtime, result.err
}

// empty returns an indicator whether the blockchain is empty.
// Note, it's a special case that we connect a non-empty ancient
// database with an empty node, so that we can plugin the ancient
// into node seamlessly.
func (bc *BlockChain) empty() bool {
	genesis := bc.genesisBlock.Hash()
	for _, hash := range []common.Hash{rawdb.ReadHeadBlockHash(bc.db), rawdb.ReadHeadHeaderHash(bc.db), rawdb.ReadHeadFastBlockHash(bc.db)} {
		if hash != genesis {
			return false
		}
	}

	return true
}

// loadLastState loads the last known chain state from the database. This method
// assumes that the chain manager mutex is held.
func (bc *BlockChain) loadLastState() error {
	// Restore the last known head block
	head := rawdb.ReadHeadBlockHash(bc.db)
	if head == (common.Hash{}) {
		// Corrupt or empty database, init from scratch
		log.Warn("Empty database, resetting chain")
		return bc.Reset()
	}
	headHeader := bc.GetHeaderByHash(head)
	if headHeader == nil {
		// Corrupt or empty database, init from scratch
		log.Warn("Head header missing, resetting chain", "hash", head)
		return bc.Reset()
	}

	var headBlock *types.Block
	if cmp := headHeader.Number.Cmp(new(big.Int)); cmp == 1 {
		// Make sure the entire head block is available.
		headBlock = bc.GetBlockByHash(head)
	} else if cmp == 0 {
		// On a pruned node the block body might not be available. But a pruned
		// block should never be the head block. The only exception is when, as
		// a last resort, chain is reset to genesis.
		headBlock = bc.genesisBlock
	}
	if headBlock == nil {
		// Corrupt or empty database, init from scratch
		log.Warn("Head block missing, resetting chain", "hash", head)
		return bc.Reset()
	}
	// Everything seems to be fine, set as the head block
	bc.currentBlock.Store(headHeader)
	headBlockGauge.Update(int64(headBlock.NumberU64()))

	// Restore the last known head header
	if head := rawdb.ReadHeadHeaderHash(bc.db); head != (common.Hash{}) {
		if header := bc.GetHeaderByHash(head); header != nil {
			headHeader = header
		}
	}

	bc.hc.SetCurrentHeader(headHeader)

	// Initialize history pruning.
	latest := max(headBlock.NumberU64(), headHeader.Number.Uint64())
	if err := bc.initializeHistoryPruning(latest); err != nil {
		return err
	}

	// Restore the last known head snap block
	bc.currentSnapBlock.Store(headBlock.Header())
	headFastBlockGauge.Update(int64(headBlock.NumberU64()))

	if head := rawdb.ReadHeadFastBlockHash(bc.db); head != (common.Hash{}) {
		if block := bc.GetBlockByHash(head); block != nil {
			bc.currentSnapBlock.Store(block.Header())
			headFastBlockGauge.Update(int64(block.NumberU64()))
		}
	}

	// Restore the last known finalized block and safe block
	// Note: the safe block is not stored on disk and it is set to the last
	// known finalized block on startup
	if head := rawdb.ReadFinalizedBlockHash(bc.db); head != (common.Hash{}) {
		if block := bc.GetBlockByHash(head); block != nil {
			bc.currentFinalBlock.Store(block.Header())
			headFinalizedBlockGauge.Update(int64(block.NumberU64()))
			bc.currentSafeBlock.Store(block.Header())
			headSafeBlockGauge.Update(int64(block.NumberU64()))
		}
	}

	// Issue a status log for the user
	var (
		currentSnapBlock  = bc.CurrentSnapBlock()
		currentFinalBlock = bc.CurrentFinalBlock()

		headerTd = bc.GetTd(headHeader.Hash(), headHeader.Number.Uint64())
		blockTd  = bc.GetTd(headBlock.Hash(), headBlock.NumberU64())
	)

	if headHeader.Hash() != headBlock.Hash() {
		log.Info("Loaded most recent local header", "number", headHeader.Number, "hash", headHeader.Hash(), "td", headerTd, "age", common.PrettyAge(time.Unix(int64(headHeader.Time), 0)))
	}
	log.Info("Loaded most recent local block", "number", headBlock.Number(), "hash", headBlock.Hash(), "td", blockTd, "age", common.PrettyAge(time.Unix(int64(headBlock.Time()), 0)))
	if headBlock.Hash() != currentSnapBlock.Hash() {
		snapTd := bc.GetTd(currentSnapBlock.Hash(), currentSnapBlock.Number.Uint64())
		log.Info("Loaded most recent local snap block", "number", currentSnapBlock.Number, "hash", currentSnapBlock.Hash(), "td", snapTd, "age", common.PrettyAge(time.Unix(int64(currentSnapBlock.Time), 0)))
	}

	if currentFinalBlock != nil {
		finalTd := bc.GetTd(currentFinalBlock.Hash(), currentFinalBlock.Number.Uint64())
		log.Info("Loaded most recent local finalized block", "number", currentFinalBlock.Number, "hash", currentFinalBlock.Hash(), "td", finalTd, "age", common.PrettyAge(time.Unix(int64(currentFinalBlock.Time), 0)))
	}

	if pivot := rawdb.ReadLastPivotNumber(bc.db); pivot != nil {
		log.Info("Loaded last snap-sync pivot marker", "number", *pivot)
	}
	if pruning := bc.historyPrunePoint.Load(); pruning != nil {
		log.Info("Chain history is pruned", "earliest", pruning.BlockNumber, "hash", pruning.BlockHash)
	}
	return nil
}

// initializeHistoryPruning sets bc.historyPrunePoint.
func (bc *BlockChain) initializeHistoryPruning(latest uint64) error {
	freezerTail, _ := bc.db.Tail()

	switch bc.cacheConfig.ChainHistoryMode {
	case history.KeepAll:
		if freezerTail == 0 {
			return nil
		}
		// The database was pruned somehow, so we need to figure out if it's a known
		// configuration or an error.
		predefinedPoint := history.PrunePoints[bc.genesisBlock.Hash()]
		if predefinedPoint == nil || freezerTail != predefinedPoint.BlockNumber {
			log.Error("Chain history database is pruned with unknown configuration", "tail", freezerTail)
			return fmt.Errorf("unexpected database tail")
		}
		bc.historyPrunePoint.Store(predefinedPoint)
		return nil

	// nolint:staticcheck
	case history.KeepPostMerge:
		if freezerTail == 0 && latest != 0 {
			// This is the case where a user is trying to run with --history.chain
			// postmerge directly on an existing DB. We could just trigger the pruning
			// here, but it'd be a bit dangerous since they may not have intended this
			// action to happen. So just tell them how to do it.
			log.Error(fmt.Sprintf("Chain history mode is configured as %q, but database is not pruned.", bc.cacheConfig.ChainHistoryMode.String()))
			log.Error(fmt.Sprintf("Run 'geth prune-history' to prune pre-merge history."))
			return fmt.Errorf("history pruning requested via configuration")
		}
		predefinedPoint := history.PrunePoints[bc.genesisBlock.Hash()]
		if predefinedPoint == nil {
			log.Error("Chain history pruning is not supported for this network", "genesis", bc.genesisBlock.Hash())
			return fmt.Errorf("history pruning requested for unknown network")
		} else if freezerTail > 0 && freezerTail != predefinedPoint.BlockNumber {
			log.Error("Chain history database is pruned to unknown block", "tail", freezerTail)
			return fmt.Errorf("unexpected database tail")
		}
		bc.historyPrunePoint.Store(predefinedPoint)
		return nil

	default:
		return fmt.Errorf("invalid history mode: %d", bc.cacheConfig.ChainHistoryMode)
	}
}

// SetHead rewinds the local chain to a new head. Depending on whether the node
// was snap synced or full synced and in which state, the method will try to
// delete minimal data from disk whilst retaining chain consistency.
func (bc *BlockChain) SetHead(head uint64) error {
	if _, err := bc.setHeadBeyondRoot(head, 0, common.Hash{}, false); err != nil {
		return err
	}
	// Send chain head event to update the transaction pool
	header := bc.CurrentBlock()
	if block := bc.GetBlock(header.Hash(), header.Number.Uint64()); block == nil {
		// In a pruned node the genesis block will not exist in the freezer.
		// It should not happen that we set head to any other pruned block.
		if header.Number.Uint64() > 0 {
			// This should never happen. In practice, previously currentBlock
			// contained the entire block whereas now only a "marker", so there
			// is an ever so slight chance for a race we should handle.
			log.Error("Current block not found in database", "block", header.Number, "hash", header.Hash())
			return fmt.Errorf("current block missing: #%d [%x..]", header.Number, header.Hash().Bytes()[:4])
		}
	}
	bc.chainHeadFeed.Send(ChainHeadEvent{Header: header})
	return nil
}

// SetHeadWithTimestamp rewinds the local chain to a new head that has at max
// the given timestamp. Depending on whether the node was snap synced or full
// synced and in which state, the method will try to delete minimal data from
// disk whilst retaining chain consistency.
func (bc *BlockChain) SetHeadWithTimestamp(timestamp uint64) error {
	if _, err := bc.setHeadBeyondRoot(0, timestamp, common.Hash{}, false); err != nil {
		return err
	}
	// Send chain head event to update the transaction pool
	header := bc.CurrentBlock()
	if block := bc.GetBlock(header.Hash(), header.Number.Uint64()); block == nil {
		// In a pruned node the genesis block will not exist in the freezer.
		// It should not happen that we set head to any other pruned block.
		if header.Number.Uint64() > 0 {
			// This should never happen. In practice, previously currentBlock
			// contained the entire block whereas now only a "marker", so there
			// is an ever so slight chance for a race we should handle.
			log.Error("Current block not found in database", "block", header.Number, "hash", header.Hash())
			return fmt.Errorf("current block missing: #%d [%x..]", header.Number, header.Hash().Bytes()[:4])
		}
	}
	bc.chainHeadFeed.Send(ChainHeadEvent{Header: header})
	return nil
}

// SetFinalized sets the finalized block.
func (bc *BlockChain) SetFinalized(header *types.Header) {
	bc.currentFinalBlock.Store(header)

	if header != nil {
		rawdb.WriteFinalizedBlockHash(bc.db, header.Hash())
		headFinalizedBlockGauge.Update(int64(header.Number.Uint64()))
	} else {
		rawdb.WriteFinalizedBlockHash(bc.db, common.Hash{})
		headFinalizedBlockGauge.Update(0)
	}
}

// SetSafe sets the safe block.
func (bc *BlockChain) SetSafe(header *types.Header) {
	bc.currentSafeBlock.Store(header)

	if header != nil {
		headSafeBlockGauge.Update(int64(header.Number.Uint64()))
	} else {
		headSafeBlockGauge.Update(0)
	}
}

// rewindHashHead implements the logic of rewindHead in the context of hash scheme.
func (bc *BlockChain) rewindHashHead(head *types.Header, root common.Hash) (*types.Header, uint64) {
	var (
		limit      uint64                             // The oldest block that will be searched for this rewinding
		beyondRoot = root == common.Hash{}            // Flag whether we're beyond the requested root (no root, always true)
		pivot      = rawdb.ReadLastPivotNumber(bc.db) // Associated block number of pivot point state
		rootNumber uint64                             // Associated block number of requested root

		start  = time.Now() // Timestamp the rewinding is restarted
		logged = time.Now() // Timestamp last progress log was printed
	)
	// The oldest block to be searched is determined by the pivot block or a constant
	// searching threshold. The rationale behind this is as follows:
	//
	// - Snap sync is selected if the pivot block is available. The earliest available
	//   state is the pivot block itself, so there is no sense in going further back.
	//
	// - Full sync is selected if the pivot block does not exist. The hash database
	//   periodically flushes the state to disk, and the used searching threshold is
	//   considered sufficient to find a persistent state, even for the testnet. It
	//   might be not enough for a chain that is nearly empty. In the worst case,
	//   the entire chain is reset to genesis, and snap sync is re-enabled on top,
	//   which is still acceptable.
	if pivot != nil {
		limit = *pivot
	} else if head.Number.Uint64() > params.FullImmutabilityThreshold {
		limit = head.Number.Uint64() - params.FullImmutabilityThreshold
	}
	for {
		logger := log.Trace
		if time.Since(logged) > time.Second*8 {
			logged = time.Now()
			logger = log.Info
		}
		logger("Block state missing, rewinding further", "number", head.Number, "hash", head.Hash(), "elapsed", common.PrettyDuration(time.Since(start)))

		// If a root threshold was requested but not yet crossed, check
		if !beyondRoot && head.Root == root {
			beyondRoot, rootNumber = true, head.Number.Uint64()
		}
		// If search limit is reached, return the genesis block as the
		// new chain head.
		if head.Number.Uint64() < limit {
			log.Info("Rewinding limit reached, resetting to genesis", "number", head.Number, "hash", head.Hash(), "limit", limit)
			return bc.genesisBlock.Header(), rootNumber
		}
		// If the associated state is not reachable, continue searching
		// backwards until an available state is found.
		if !bc.HasState(head.Root) {
			// If the chain is gapped in the middle, return the genesis
			// block as the new chain head.
			parent := bc.GetHeader(head.ParentHash, head.Number.Uint64()-1)
			if parent == nil {
				log.Error("Missing block in the middle, resetting to genesis", "number", head.Number.Uint64()-1, "hash", head.ParentHash)
				return bc.genesisBlock.Header(), rootNumber
			}
			head = parent

			// If the genesis block is reached, stop searching.
			if head.Number.Uint64() == 0 {
				log.Info("Genesis block reached", "number", head.Number, "hash", head.Hash())
				return head, rootNumber
			}
			continue // keep rewinding
		}
		// Once the available state is found, ensure that the requested root
		// has already been crossed. If not, continue rewinding.
		if beyondRoot || head.Number.Uint64() == 0 {
			log.Info("Rewound to block with state", "number", head.Number, "hash", head.Hash())
			return head, rootNumber
		}
		log.Debug("Skipping block with threshold state", "number", head.Number, "hash", head.Hash(), "root", head.Root)
		head = bc.GetHeader(head.ParentHash, head.Number.Uint64()-1) // Keep rewinding
	}
}

// rewindPathHead implements the logic of rewindHead in the context of path scheme.
func (bc *BlockChain) rewindPathHead(head *types.Header, root common.Hash) (*types.Header, uint64) {
	var (
		pivot      = rawdb.ReadLastPivotNumber(bc.db) // Associated block number of pivot block
		rootNumber uint64                             // Associated block number of requested root

		// BeyondRoot represents whether the requested root is already
		// crossed. The flag value is set to true if the root is empty.
		beyondRoot = root == common.Hash{}

		// noState represents if the target state requested for search
		// is unavailable and impossible to be recovered.
		noState = !bc.HasState(root) && !bc.stateRecoverable(root)

		start  = time.Now() // Timestamp the rewinding is restarted
		logged = time.Now() // Timestamp last progress log was printed
	)
	// Rewind the head block tag until an available state is found.
	for {
		logger := log.Trace
		if time.Since(logged) > time.Second*8 {
			logged = time.Now()
			logger = log.Info
		}
		logger("Block state missing, rewinding further", "number", head.Number, "hash", head.Hash(), "elapsed", common.PrettyDuration(time.Since(start)))

		// If a root threshold was requested but not yet crossed, check
		if !beyondRoot && head.Root == root {
			beyondRoot, rootNumber = true, head.Number.Uint64()
		}
		// If the root threshold hasn't been crossed but the available
		// state is reached, quickly determine if the target state is
		// possible to be reached or not.
		if !beyondRoot && noState && bc.HasState(head.Root) {
			beyondRoot = true
			log.Info("Disable the search for unattainable state", "root", root)
		}
		// Check if the associated state is available or recoverable if
		// the requested root has already been crossed.
		if beyondRoot && (bc.HasState(head.Root) || bc.stateRecoverable(head.Root)) {
			break
		}
		// If pivot block is reached, return the genesis block as the
		// new chain head. Theoretically there must be a persistent
		// state before or at the pivot block, prevent endless rewinding
		// towards the genesis just in case.
		if pivot != nil && *pivot >= head.Number.Uint64() {
			log.Info("Pivot block reached, resetting to genesis", "number", head.Number, "hash", head.Hash())
			return bc.genesisBlock.Header(), rootNumber
		}
		// If the chain is gapped in the middle, return the genesis
		// block as the new chain head
		parent := bc.GetHeader(head.ParentHash, head.Number.Uint64()-1) // Keep rewinding
		if parent == nil {
			log.Error("Missing block in the middle, resetting to genesis", "number", head.Number.Uint64()-1, "hash", head.ParentHash)
			return bc.genesisBlock.Header(), rootNumber
		}
		head = parent

		// If the genesis block is reached, stop searching.
		if head.Number.Uint64() == 0 {
			log.Info("Genesis block reached", "number", head.Number, "hash", head.Hash())
			return head, rootNumber
		}
	}
	// Recover if the target state if it's not available yet.
	if !bc.HasState(head.Root) {
		if err := bc.triedb.Recover(head.Root); err != nil {
			log.Crit("Failed to rollback state", "err", err)
		}
	}
	log.Info("Rewound to block with state", "number", head.Number, "hash", head.Hash())
	return head, rootNumber
}

// rewindHead searches the available states in the database and returns the associated
// block as the new head block.
//
// If the given root is not empty, then the rewind should attempt to pass the specified
// state root and return the associated block number as well. If the root, typically
// representing the state corresponding to snapshot disk layer, is deemed impassable,
// then block number zero is returned, indicating that snapshot recovery is disabled
// and the whole snapshot should be auto-generated in case of head mismatch.
func (bc *BlockChain) rewindHead(head *types.Header, root common.Hash) (*types.Header, uint64) {
	if bc.triedb.Scheme() == rawdb.PathScheme {
		return bc.rewindPathHead(head, root)
	}
	return bc.rewindHashHead(head, root)
}

// setHeadBeyondRoot rewinds the local chain to a new head with the extra condition
// that the rewind must pass the specified state root. This method is meant to be
// used when rewinding with snapshots enabled to ensure that we go back further than
// persistent disk layer. Depending on whether the node was snap synced or full, and
// in which state, the method will try to delete minimal data from disk whilst
// retaining chain consistency.
//
// The method also works in timestamp mode if `head == 0` but `time != 0`. In that
// case blocks are rolled back until the new head becomes older or equal to the
// requested time. If both `head` and `time` is 0, the chain is rewound to genesis.
//
// The method returns the block number where the requested root cap was found.
// nolint:gocognit
func (bc *BlockChain) setHeadBeyondRoot(head uint64, time uint64, root common.Hash, repair bool) (uint64, error) {
	if !bc.chainmu.TryLock() {
		return 0, errChainStopped
	}
	defer bc.chainmu.Unlock()

	var (
		// Track the block number of the requested root hash
		rootNumber uint64 // (no root == always 0)

		// Retrieve the last pivot block to short circuit rollbacks beyond it
		// and the current freezer limit to start nuking it's underflown.
		pivot = rawdb.ReadLastPivotNumber(bc.db)
	)
	updateFn := func(db ethdb.KeyValueWriter, header *types.Header) (*types.Header, bool) {
		// Rewind the blockchain, ensuring we don't end up with a stateless head
		// block. Note, depth equality is permitted to allow using SetHead as a
		// chain reparation mechanism without deleting any data!
		// nolint:nestif
		if currentBlock := bc.CurrentBlock(); currentBlock != nil && header.Number.Uint64() <= currentBlock.Number.Uint64() {
			var newHeadBlock *types.Header
			if !bc.cacheConfig.Stateless {
				newHeadBlock, rootNumber = bc.rewindHead(header, root)
			} else {
				newHeadBlock = header
				rootNumber = header.Number.Uint64()
			}
			rawdb.WriteHeadBlockHash(db, newHeadBlock.Hash())

			// Degrade the chain markers if they are explicitly reverted.
			// In theory we should update all in-memory markers in the
			// last step, however the direction of SetHead is from high
			// to low, so it's safe to update in-memory markers directly.
			bc.currentBlock.Store(newHeadBlock)
			headBlockGauge.Update(int64(newHeadBlock.Number.Uint64()))

			// The head state is missing, which is only possible in the path-based
			// scheme. This situation occurs when the chain head is rewound below
			// the pivot point. In this scenario, there is no possible recovery
			// approach except for rerunning a snap sync. Do nothing here until the
			// state syncer picks it up.
			// Skip state checking for stateless nodes
			if !bc.cacheConfig.Stateless && !bc.HasState(newHeadBlock.Root) {
				if newHeadBlock.Number.Uint64() != 0 {
					log.Crit("Chain is stateless at a non-genesis block")
				}
				log.Info("Chain is stateless, wait state sync", "number", newHeadBlock.Number, "hash", newHeadBlock.Hash())
			}
		}
		// Rewind the snap block in a simpleton way to the target head
		if currentSnapBlock := bc.CurrentSnapBlock(); currentSnapBlock != nil && header.Number.Uint64() < currentSnapBlock.Number.Uint64() {
			newHeadSnapBlock := bc.GetBlock(header.Hash(), header.Number.Uint64())
			// If either blocks reached nil, reset to the genesis state
			if newHeadSnapBlock == nil {
				newHeadSnapBlock = bc.genesisBlock
			}

			rawdb.WriteHeadFastBlockHash(db, newHeadSnapBlock.Hash())

			// Degrade the chain markers if they are explicitly reverted.
			// In theory, we should update all in-memory markers in the
			// last step, however the direction of SetHead is from high
			// to low, so it's safe the update in-memory markers directly.
			bc.currentSnapBlock.Store(newHeadSnapBlock.Header())
			headFastBlockGauge.Update(int64(newHeadSnapBlock.NumberU64()))
		}

		var (
			headHeader = bc.CurrentBlock()
			headNumber = headHeader.Number.Uint64()
		)
		// If setHead underflown the freezer threshold and the block processing
		// intent afterwards is full block importing, delete the chain segment
		// between the stateful-block and the sethead target.
		var wipe bool
		frozen, _ := bc.db.Ancients()
		if headNumber+1 < frozen {
			wipe = pivot == nil || headNumber >= *pivot
		}

		return headHeader, wipe // Only force wipe if full synced
	}
	// Rewind the header chain, deleting all block bodies until then
	delFn := func(db ethdb.KeyValueWriter, hash common.Hash, num uint64) {
		// Ignore the error here since light client won't hit this path
		frozen, _ := bc.db.Ancients()
		if num+1 <= frozen {
			// Truncate all relative data(header, total difficulty, body, receipt
			// and canonical hash) from ancient store.
			if _, err := bc.db.TruncateHead(num); err != nil {
				log.Crit("Failed to truncate ancient data", "number", num, "err", err)
			}
			// Remove the hash <-> number mapping from the active store.
			rawdb.DeleteHeaderNumber(db, hash)
		} else {
			// Remove relative body and receipts from the active store.
			// The header, total difficulty and canonical hash will be
			// removed in the hc.SetHead function.
			rawdb.DeleteBody(db, hash, num)
			rawdb.DeleteReceipts(db, hash, num)
			rawdb.DeleteBorReceipt(db, hash, num)
			rawdb.DeleteBorTxLookupEntry(db, hash, num)
		}
		// Todo(rjl493456442) txlookup, log index, etc
	}
	// If SetHead was only called as a chain reparation method, try to skip
	// touching the header chain altogether, unless the freezer is broken
	if repair {
		if target, force := updateFn(bc.db, bc.CurrentBlock()); force {
			bc.hc.SetHead(target.Number.Uint64(), nil, delFn)
		}
	} else {
		// Rewind the chain to the requested head and keep going backwards until a
		// block with a state is found or snap sync pivot is passed
		if time > 0 {
			log.Warn("Rewinding blockchain to timestamp", "target", time)
			bc.hc.SetHeadWithTimestamp(time, updateFn, delFn)
		} else {
			log.Warn("Rewinding blockchain to block", "target", head)
			bc.hc.SetHead(head, updateFn, delFn)
		}
	}
	// Clear out any stale content from the caches
	bc.bodyCache.Purge()
	bc.bodyRLPCache.Purge()
	bc.receiptsCache.Purge()
	bc.blockCache.Purge()
	bc.txLookupCache.Purge()
	bc.borReceiptsCache.Purge()

	// Clear safe block, finalized block if needed
	if safe := bc.CurrentSafeBlock(); safe != nil && head < safe.Number.Uint64() {
		log.Warn("SetHead invalidated safe block")
		bc.SetSafe(nil)
	}

	if finalized := bc.CurrentFinalBlock(); finalized != nil && head < finalized.Number.Uint64() {
		log.Error("SetHead invalidated finalized block")
		bc.SetFinalized(nil)
	}

	return rootNumber, bc.loadLastState()
}

// SnapSyncCommitHead sets the current head block to the one defined by the hash
// irrelevant what the chain contents were prior.
func (bc *BlockChain) SnapSyncCommitHead(hash common.Hash) error {
	// Make sure that both the block as well at its state trie exists
	block := bc.GetBlockByHash(hash)
	if block == nil {
		return fmt.Errorf("non existent block [%x..]", hash[:4])
	}
	// Reset the trie database with the fresh snap synced state.
	root := block.Root()
	if bc.triedb.Scheme() == rawdb.PathScheme {
		if err := bc.triedb.Enable(root); err != nil {
			return err
		}
	}
	if !bc.HasState(root) {
		return fmt.Errorf("non existent state [%x..]", root[:4])
	}
	// If all checks out, manually set the head block.
	if !bc.chainmu.TryLock() {
		return errChainStopped
	}

	bc.currentBlock.Store(block.Header())
	headBlockGauge.Update(int64(block.NumberU64()))
	bc.chainmu.Unlock()

	// Destroy any existing state snapshot and regenerate it in the background,
	// also resuming the normal maintenance of any previously paused snapshot.
	if bc.snaps != nil {
		bc.snaps.Rebuild(root)
	}

	log.Info("Committed new head block", "number", block.Number(), "hash", hash)

	return nil
}

// Reset purges the entire blockchain, restoring it to its genesis state.
func (bc *BlockChain) Reset() error {
	return bc.ResetWithGenesisBlock(bc.genesisBlock)
}

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) error {
	// Dump the entire block chain and purge the caches
	if err := bc.SetHead(0); err != nil {
		return err
	}

	if !bc.chainmu.TryLock() {
		return errChainStopped
	}
	defer bc.chainmu.Unlock()

	// Prepare the genesis block and reinitialise the chain
	batch := bc.db.NewBatch()
	rawdb.WriteTd(batch, genesis.Hash(), genesis.NumberU64(), genesis.Difficulty())
	rawdb.WriteBlock(batch, genesis)

	if err := batch.Write(); err != nil {
		log.Crit("Failed to write genesis block", "err", err)
	}

	bc.writeHeadBlock(genesis)

	// Last update all in-memory chain markers
	bc.genesisBlock = genesis
	bc.currentBlock.Store(bc.genesisBlock.Header())
	headBlockGauge.Update(int64(bc.genesisBlock.NumberU64()))
	bc.hc.SetGenesis(bc.genesisBlock.Header())
	bc.hc.SetCurrentHeader(bc.genesisBlock.Header())
	bc.currentSnapBlock.Store(bc.genesisBlock.Header())
	headFastBlockGauge.Update(int64(bc.genesisBlock.NumberU64()))

	// Reset history pruning status.
	return bc.initializeHistoryPruning(0)
}

// Export writes the active chain to the given writer.
func (bc *BlockChain) Export(w io.Writer) error {
	return bc.ExportN(w, uint64(0), bc.CurrentBlock().Number.Uint64())
}

// ExportN writes a subset of the active chain to the given writer.
func (bc *BlockChain) ExportN(w io.Writer, first uint64, last uint64) error {
	if first > last {
		return fmt.Errorf("export failed: first (%d) is greater than last (%d)", first, last)
	}

	log.Info("Exporting batch of blocks", "count", last-first+1)

	var (
		parentHash common.Hash
		start      = time.Now()
		reported   = time.Now()
	)

	for nr := first; nr <= last; nr++ {
		block := bc.GetBlockByNumber(nr)
		if block == nil {
			return fmt.Errorf("export failed on #%d: not found", nr)
		}

		if nr > first && block.ParentHash() != parentHash {
			return errors.New("export failed: chain reorg during export")
		}

		parentHash = block.Hash()

		if err := block.EncodeRLP(w); err != nil {
			return err
		}

		if time.Since(reported) >= statsReportLimit {
			log.Info("Exporting blocks", "exported", block.NumberU64()-first, "elapsed", common.PrettyDuration(time.Since(start)))
			reported = time.Now()
		}
	}

	return nil
}

// writeHeadBlock injects a new head block into the current block chain. This method
// assumes that the block is indeed a true head. It will also reset the head
// header and the head snap sync block to this very same block if they are older
// or if they are on a different side chain.
//
// Note, this function assumes that the `mu` mutex is held!
func (bc *BlockChain) writeHeadBlock(block *types.Block) {
	// Add the block to the canonical chain number scheme and mark as the head
	batch := bc.db.NewBatch()
	rawdb.WriteHeadHeaderHash(batch, block.Hash())
	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
	rawdb.WriteCanonicalHash(batch, block.Hash(), block.NumberU64())
	rawdb.WriteTxLookupEntriesByBlock(batch, block)
	rawdb.WriteHeadBlockHash(batch, block.Hash())

	// Flush the whole batch into the disk, exit the node if failed
	if err := batch.Write(); err != nil {
		log.Crit("Failed to update chain indexes and markers", "err", err)
	}
	// Update all in-memory chain markers in the last step
	bc.hc.SetCurrentHeader(block.Header())

	bc.currentSnapBlock.Store(block.Header())
	headFastBlockGauge.Update(int64(block.NumberU64()))

	bc.currentBlock.Store(block.Header())
	headBlockGauge.Update(int64(block.NumberU64()))
}

// stopWithoutSaving stops the blockchain service. If any imports are currently in progress
// it will abort them using the procInterrupt. This method stops all running
// goroutines, but does not do all the post-stop work of persisting data.
// OBS! It is generally recommended to use the Stop method!
// This method has been exposed to allow tests to stop the blockchain while simulating
// a crash.
func (bc *BlockChain) stopWithoutSaving() {
	if !bc.stopping.CompareAndSwap(false, true) {
		return
	}
	// Signal shutdown tx indexer.
	if bc.txIndexer != nil {
		bc.txIndexer.close()
	}
	// Unsubscribe all subscriptions registered from blockchain.
	bc.scope.Close()

	// Signal shutdown to all goroutines.
	close(bc.quit)
	bc.StopInsert()

	// Now wait for all chain modifications to end and persistent goroutines to exit.
	//
	// Note: Close waits for the mutex to become available, i.e. any running chain
	// modification will have exited when Close returns. Since we also called StopInsert,
	// the mutex should become available quickly. It cannot be taken again after Close has
	// returned.
	bc.chainmu.Close()
	bc.wg.Wait()
}

// Stop stops the blockchain service. If any imports are currently in progress
// it will abort them using the procInterrupt.
func (bc *BlockChain) Stop() {
	bc.stopWithoutSaving()

	// Ensure that the entirety of the state snapshot is journaled to disk.
	var snapBase common.Hash

	if bc.snaps != nil {
		var err error
		if snapBase, err = bc.snaps.Journal(bc.CurrentBlock().Root); err != nil {
			log.Error("Failed to journal state snapshot", "err", err)
		}
		bc.snaps.Release()
	}
	if bc.triedb.Scheme() == rawdb.PathScheme {
		// Ensure that the in-memory trie nodes are journaled to disk properly.
		if !bc.cacheConfig.Stateless {
			if err := bc.triedb.Journal(bc.CurrentBlock().Root); err != nil {
				log.Info("Failed to journal in-memory trie nodes", "err", err)
			}
		}
	} else {
		// Ensure the state of a recent block is also stored to disk before exiting.
		// We're writing three different states to catch different restart scenarios:
		//  - HEAD:     So we don't need to reprocess any blocks in the general case
		//  - HEAD-1:   So we don't do large reorgs if our HEAD becomes an uncle
		//  - HEAD-127: So we have a hard limit on the number of blocks reexecuted
		if !bc.cacheConfig.TrieDirtyDisabled {
			triedb := bc.triedb

			for _, offset := range []uint64{0, 1, state.TriesInMemory - 1} {
				if number := bc.CurrentBlock().Number.Uint64(); number > offset {
					recent := bc.GetBlockByNumber(number - offset)

					log.Info("Writing cached state to disk", "block", recent.Number(), "hash", recent.Hash(), "root", recent.Root())
					if err := triedb.Commit(recent.Root(), true); err != nil {
						log.Error("Failed to commit recent state trie", "err", err)
					}
				}
			}
			if snapBase != (common.Hash{}) {
				log.Info("Writing snapshot state to disk", "root", snapBase)
				if err := triedb.Commit(snapBase, true); err != nil {
					log.Error("Failed to commit recent state trie", "err", err)
				}
			}
			for !bc.triegc.Empty() {
				triedb.Dereference(bc.triegc.PopItem())
			}
			if _, nodes, _ := triedb.Size(); nodes != 0 { // all memory is contained within the nodes return for hashdb
				log.Error("Dangling trie nodes after full cleanup")
			}
		}
	}
	// Allow tracers to clean-up and release resources.
	if bc.logger != nil && bc.logger.OnClose != nil {
		bc.logger.OnClose()
	}
	// Close the trie database, release all the held resources as the last step.
	if err := bc.triedb.Close(); err != nil {
		log.Error("Failed to close trie database", "err", err)
	}

	log.Info("Blockchain stopped")
}

// StopInsert interrupts all insertion methods, causing them to return
// errInsertionInterrupted as soon as possible. Insertion is permanently disabled after
// calling this method.
func (bc *BlockChain) StopInsert() {
	bc.procInterrupt.Store(true)
}

// insertStopped returns true after StopInsert has been called.
func (bc *BlockChain) insertStopped() bool {
	return bc.procInterrupt.Load()
}

// WriteStatus status of write
type WriteStatus byte

const (
	NonStatTy WriteStatus = iota
	CanonStatTy
	SideStatTy
)

// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts, ancientLimit uint64) (int, error) {
	// We don't require the chainMu here since we want to maximize the
	// concurrency of header insertion and receipt insertion.
	bc.wg.Add(1)
	defer bc.wg.Done()

	var (
		ancientBlocks, liveBlocks     types.Blocks
		ancientReceipts, liveReceipts []types.Receipts
	)
	// Do a sanity check that the provided chain is actually ordered and linked
	for i, block := range blockChain {
		if i != 0 {
			prev := blockChain[i-1]
			if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
				log.Error("Non contiguous receipt insert",
					"number", block.Number(), "hash", block.Hash(), "parent", block.ParentHash(),
					"prevnumber", prev.Number(), "prevhash", prev.Hash())
				return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x..], item %d is #%d [%x..] (parent [%x..])",
					i-1, prev.NumberU64(), prev.Hash().Bytes()[:4],
					i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
			}
		}
		if block.NumberU64() <= ancientLimit {
			ancientBlocks, ancientReceipts = append(ancientBlocks, block), append(ancientReceipts, receiptChain[i])
		} else {
			liveBlocks, liveReceipts = append(liveBlocks, block), append(liveReceipts, receiptChain[i])
		}

		// Here we also validate that blob transactions in the block do not contain a sidecar.
		// While the sidecar does not affect the block hash / tx hash, sending blobs within a block is not allowed.
		for txIndex, tx := range block.Transactions() {
			if tx.Type() == types.BlobTxType && tx.BlobTxSidecar() != nil {
				return 0, fmt.Errorf("block #%d contains unexpected blob sidecar in tx at index %d", block.NumberU64(), txIndex)
			}
		}
	}

	var (
		stats = struct{ processed, ignored int32 }{}
		start = time.Now()
		size  = int64(0)
	)

	// updateHead updates the head snap sync block if the inserted blocks are better
	// and returns an indicator whether the inserted blocks are canonical.
	updateHead := func(head *types.Block, headers []*types.Header) bool {
		if !bc.chainmu.TryLock() {
			return false
		}
		defer bc.chainmu.Unlock()

		// Rewind may have occurred, skip in that case.
		if bc.CurrentHeader().Number.Cmp(head.Number()) >= 0 {
			reorg, err := bc.forker.ReorgNeeded(bc.CurrentSnapBlock(), head.Header())
			if err != nil {
				log.Warn("Reorg failed", "err", err)
				return false
			} else if !reorg {
				return false
			}

			isValid, err := bc.forker.ValidateReorg(bc.CurrentSnapBlock(), headers)
			if err != nil {
				log.Warn("Reorg failed", "err", err)
				return false
			} else if !isValid {
				return false
			}

			rawdb.WriteHeadFastBlockHash(bc.db, head.Hash())
			bc.currentSnapBlock.Store(head.Header())
			headFastBlockGauge.Update(int64(head.NumberU64()))

			return true
		}

		return false
	}
	// writeAncient writes blockchain and corresponding receipt chain into ancient store.
	//
	// this function only accepts canonical chain data. All side chain will be reverted
	// eventually.
	writeAncient := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
		first := blockChain[0]
		last := blockChain[len(blockChain)-1]

		// Ensure genesis is in ancients.
		if first.NumberU64() == 1 {
			if frozen, _ := bc.db.Ancients(); frozen == 0 {
				td := bc.genesisBlock.Difficulty()
				writeSize, err := rawdb.WriteAncientBlocks(bc.db, []*types.Block{bc.genesisBlock}, []types.Receipts{nil}, []types.Receipts{nil}, td)
				if err != nil {
					log.Error("Error writing genesis to ancients", "err", err)
					return 0, err
				}

				size += writeSize

				log.Info("Wrote genesis to ancients")
			}
		}
		// BOR: Retrieve all the bor receipts and also maintain the array of headers
		// for bor specific reorg check.
		borReceipts := []types.Receipts{}

		var headers []*types.Header

		for _, block := range blockChain {
			borReceipts = append(borReceipts, []*types.Receipt{bc.GetBorReceiptByHash(block.Hash())})
			headers = append(headers, block.Header())
		}

		// Write all chain data to ancients.
		td := bc.GetTd(first.Hash(), first.NumberU64())
		writeSize, err := rawdb.WriteAncientBlocks(bc.db, blockChain, receiptChain, borReceipts, td)
		if err != nil {
			log.Error("Error importing chain data to ancients", "err", err)
			return 0, err
		}
		size += writeSize

		// Write tx indices if any condition is satisfied:
		// * If user requires to reserve all tx indices(txlookuplimit=0)
		// * If all ancient tx indices are required to be reserved(txlookuplimit is even higher than ancientlimit)
		// * If block number is large enough to be regarded as a recent block
		// It means blocks below the ancientLimit-txlookupLimit won't be indexed.
		//
		// But if the `TxIndexTail` is not nil, e.g. Geth is initialized with
		// an external ancient database, during the setup, blockchain will start
		// a background routine to re-indexed all indices in [ancients - txlookupLimit, ancients)
		// range. In this case, all tx indices of newly imported blocks should be
		// generated.
		batch := bc.db.NewBatch()
		for i, block := range blockChain {
			if bc.txIndexer == nil || bc.txIndexer.limit == 0 || ancientLimit <= bc.txIndexer.limit || block.NumberU64() >= ancientLimit-bc.txIndexer.limit {
				rawdb.WriteTxLookupEntriesByBlock(batch, block)
			} else if rawdb.ReadTxIndexTail(bc.db) != nil {
				rawdb.WriteTxLookupEntriesByBlock(batch, block)
			}

			stats.processed++

			if batch.ValueSize() > ethdb.IdealBatchSize || i == len(blockChain)-1 {
				size += int64(batch.ValueSize())

				if err = batch.Write(); err != nil {
					snapBlock := bc.CurrentSnapBlock().Number.Uint64()
					if _, err := bc.db.TruncateHead(snapBlock + 1); err != nil {
						log.Error("Can't truncate ancient store after failed insert", "err", err)
					}

					return 0, err
				}

				batch.Reset()
			}
		}

		// Sync the ancient store explicitly to ensure all data has been flushed to disk.
		if err := bc.db.Sync(); err != nil {
			return 0, err
		}
		// Update the current snap block because all block data is now present in DB.
		previousSnapBlock := bc.CurrentSnapBlock().Number.Uint64()
		if !updateHead(blockChain[len(blockChain)-1], headers) {
			// We end up here if the header chain has reorg'ed, and the blocks/receipts
			// don't match the canonical chain.
			if _, err := bc.db.TruncateHead(previousSnapBlock + 1); err != nil {
				log.Error("Can't truncate ancient store after failed insert", "err", err)
			}

			return 0, errSideChainReceipts
		}

		// Delete block data from the main database.
		var (
			canonHashes = make(map[common.Hash]struct{}, len(blockChain))
		)
		batch = bc.db.NewBatch()
		for _, block := range blockChain {
			canonHashes[block.Hash()] = struct{}{}

			if block.NumberU64() == 0 {
				continue
			}

			rawdb.DeleteCanonicalHash(batch, block.NumberU64())
			rawdb.DeleteBlockWithoutNumber(batch, block.Hash(), block.NumberU64())
		}
		// Delete side chain hash-to-number mappings.
		for _, nh := range rawdb.ReadAllHashesInRange(bc.db, first.NumberU64(), last.NumberU64()) {
			if _, canon := canonHashes[nh.Hash]; !canon {
				rawdb.DeleteHeader(batch, nh.Hash, nh.Number)
			}
		}

		if err := batch.Write(); err != nil {
			return 0, err
		}
		stats.processed += int32(len(blockChain))
		return 0, nil
	}

	// writeLive writes blockchain and corresponding receipt chain into active store.
	writeLive := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
		headers := make([]*types.Header, 0, len(blockChain))
		var (
			skipPresenceCheck = false
			batch             = bc.db.NewBatch()
		)
		for i, block := range blockChain {
			// Update the headers for bor specific reorg check
			headers = append(headers, block.Header())

			// Short circuit insertion if shutting down or processing failed
			if bc.insertStopped() {
				return 0, errInsertionInterrupted
			}
			// Short circuit if the owner header is unknown
			if !bc.HasHeader(block.Hash(), block.NumberU64()) {
				return i, fmt.Errorf("containing header #%d [%x..] unknown", block.Number(), block.Hash().Bytes()[:4])
			}

			if !skipPresenceCheck {
				// Ignore if the entire data is already known
				if bc.HasBlock(block.Hash(), block.NumberU64()) {
					stats.ignored++
					continue
				} else {
					// If block N is not present, neither are the later blocks.
					// This should be true, but if we are mistaken, the shortcut
					// here will only cause overwriting of some existing data
					skipPresenceCheck = true
				}
			}
			// Write all the data out into the database
			rawdb.WriteBody(batch, block.Hash(), block.NumberU64(), block.Body())
			rawdb.WriteReceipts(batch, block.Hash(), block.NumberU64(), receiptChain[i])

			// Write everything belongs to the blocks into the database. So that
			// we can ensure all components of body is completed(body, receipts)
			// except transaction indexes(will be created once sync is finished).
			if batch.ValueSize() >= ethdb.IdealBatchSize {
				if err := batch.Write(); err != nil {
					return 0, err
				}

				size += int64(batch.ValueSize())
				batch.Reset()
			}

			stats.processed++
		}
		// Write everything belongs to the blocks into the database. So that
		// we can ensure all components of body is completed(body, receipts,
		// tx indexes)
		if batch.ValueSize() > 0 {
			size += int64(batch.ValueSize())

			if err := batch.Write(); err != nil {
				return 0, err
			}
		}

		updateHead(blockChain[len(blockChain)-1], headers)

		return 0, nil
	}

	// Write downloaded chain data and corresponding receipt chain data
	if len(ancientBlocks) > 0 {
		if n, err := writeAncient(ancientBlocks, ancientReceipts); err != nil {
			if err == errInsertionInterrupted {
				return 0, nil
			}

			return n, err
		}
	}
	if len(liveBlocks) > 0 {
		if n, err := writeLive(liveBlocks, liveReceipts); err != nil {
			if err == errInsertionInterrupted {
				return 0, nil
			}

			return n, err
		}
	}
	var (
		head = blockChain[len(blockChain)-1]

		context = []interface{}{
			"count", stats.processed, "elapsed", common.PrettyDuration(time.Since(start)),
			"number", head.Number(), "hash", head.Hash(), "age", common.PrettyAge(time.Unix(int64(head.Time()), 0)),
			"size", common.StorageSize(size),
		}
	)
	if stats.ignored > 0 {
		context = append(context, []interface{}{"ignored", stats.ignored}...)
	}

	log.Debug("Imported new block receipts", context...)

	return 0, nil
}

// writeBlockWithoutState writes only the block and its metadata to the database,
// but does not write any state. This is used to construct competing side forks
// up to the point where they exceed the canonical total difficulty.
func (bc *BlockChain) writeBlockWithoutState(block *types.Block, td *big.Int) (err error) {
	if bc.insertStopped() {
		return errInsertionInterrupted
	}
	batch := bc.db.NewBatch()
	rawdb.WriteTd(batch, block.Hash(), block.NumberU64(), td)
	rawdb.WriteBlock(batch, block)

	if err := batch.Write(); err != nil {
		log.Crit("Failed to write block into disk", "err", err)
	}

	return nil
}

// writeKnownBlock updates the head block flag with a known block
// and introduces chain reorg if necessary.
func (bc *BlockChain) writeKnownBlock(block *types.Block) error {
	current := bc.CurrentBlock()
	if block.ParentHash() != current.Hash() {
		if err := bc.reorg(current, block.Header()); err != nil {
			return err
		}
	}

	bc.writeHeadBlock(block)

	return nil
}

// writeBlockWithState writes block, metadata and corresponding state data to the
// database.
func (bc *BlockChain) writeBlockWithState(block *types.Block, receipts []*types.Receipt, logs []*types.Log, statedb *state.StateDB) ([]*types.Log, error) {
	// Calculate the total difficulty of the block
	ptd := bc.GetTd(block.ParentHash(), block.NumberU64()-1)
	var externTd *big.Int
	if ptd == nil {
		return []*types.Log{}, consensus.ErrUnknownAncestor
	}

	// Make sure no inconsistent state is leaked during insertion
	externTd = new(big.Int).Add(block.Difficulty(), ptd)

	// Irrelevant of the canonical status, write the block itself to the database.
	//
	// Note all the components of block(td, hash->number map, header, body, receipts)
	// should be written atomically. BlockBatch is used for containing all components.
	blockBatch := bc.db.NewBatch()
	rawdb.WriteTd(blockBatch, block.Hash(), block.NumberU64(), externTd)
	rawdb.WriteBlock(blockBatch, block)
	rawdb.WriteReceipts(blockBatch, block.Hash(), block.NumberU64(), receipts)

	// System call appends state-sync logs into state. So, `state.Logs()` contains
	// all logs including system-call logs (state sync logs) while `logs` contains
	// only logs generated by transactions (receipts).
	//
	// That means that state.Logs() can have more logs than receipt logs.
	// In that case, we can safely assume that extra logs are from state sync logs.
	//
	// block logs = receipt logs + state sync logs = `state.Logs()`
	blockLogs := statedb.Logs()

	var stateSyncLogs []*types.Log

	if len(blockLogs) > 0 {
		sort.SliceStable(blockLogs, func(i, j int) bool {
			return blockLogs[i].Index < blockLogs[j].Index
		})

		if len(blockLogs) > len(logs) {
			stateSyncLogs = blockLogs[len(logs):] // get state-sync logs from `state.Logs()`

			// State sync logs don't have tx index, tx hash and other necessary fields
			// DeriveFieldsForBorLogs will fill those fields for websocket subscriptions
			types.DeriveFieldsForBorLogs(stateSyncLogs, block.Hash(), block.NumberU64(), uint(len(receipts)), uint(len(logs)))

			// Write bor receipt
			rawdb.WriteBorReceipt(blockBatch, block.Hash(), block.NumberU64(), &types.ReceiptForStorage{
				Status: types.ReceiptStatusSuccessful, // make receipt status successful
				Logs:   stateSyncLogs,
			})

			// Write bor tx reverse lookup
			rawdb.WriteBorTxLookupEntry(blockBatch, block.Hash(), block.NumberU64())
		}
	}

	rawdb.WritePreimages(blockBatch, statedb.Preimages())

	if statedb.Witness() != nil {
		var witBuf bytes.Buffer
		if err := statedb.Witness().EncodeRLP(&witBuf); err != nil {
			log.Error("error in witness encoding", "caughterr", err)
		}

		log.Debug("Writing witness", "block", block.NumberU64(), "hash", block.Hash(), "header", statedb.Witness().Header())

		rawdb.WriteWitness(blockBatch, block.Hash(), witBuf.Bytes())
	} else {
		log.Debug("No witness to write", "block", block.NumberU64())
	}

	if err := blockBatch.Write(); err != nil {
		log.Crit("Failed to write block into disk", "err", err)
	}
	// Commit all cached state changes into underlying memory database.

	var root common.Hash
	var err error
	if statedb.Database() != nil {
		root, err = statedb.Commit(block.NumberU64(), bc.chainConfig.IsEIP158(block.Number()), bc.chainConfig.IsCancun(block.Number()))
		if err != nil {
			return []*types.Log{}, err
		}
	}

	rawdb.WriteBytecodeSyncLastBlock(bc.db, block.NumberU64())

	// If node is running in path mode, skip explicit gc operation
	// which is unnecessary in this mode.
	if bc.triedb.Scheme() == rawdb.PathScheme {
		return []*types.Log{}, nil
	}
	// If we're running an archive node, always flush
	if bc.cacheConfig.TrieDirtyDisabled {
		return []*types.Log{}, bc.triedb.Commit(root, false)
	}
	// Full but not archive node, do proper garbage collection
	bc.triedb.Reference(root, common.Hash{}) // metadata reference to keep trie alive
	bc.triegc.Push(root, -int64(block.NumberU64()))

	// Flush limits are not considered for the first TriesInMemory blocks.
	current := block.NumberU64()
	if current <= state.TriesInMemory {
		return []*types.Log{}, nil
	}
	// If we exceeded our memory allowance, flush matured singleton nodes to disk
	var (
		_, nodes, imgs = bc.triedb.Size() // all memory is contained within the nodes return for hashdb
		limit          = common.StorageSize(bc.cacheConfig.TrieDirtyLimit) * 1024 * 1024
	)

	if nodes > limit || imgs > 4*1024*1024 {
		_ = bc.triedb.Cap(limit - ethdb.IdealBatchSize)
	}
	// Find the next state trie we need to commit
	chosen := current - state.TriesInMemory
	flushInterval := time.Duration(bc.flushInterval.Load())
	// If we exceeded time allowance, flush an entire trie to disk
	if bc.gcproc > flushInterval {
		// If the header is missing (canonical chain behind), we're reorging a low
		// diff sidechain. Suspend committing until this operation is completed.
		header := bc.GetHeaderByNumber(chosen)
		if header == nil {
			log.Warn("Reorg in progress, trie commit postponed", "number", chosen)
		} else {
			// If we're exceeding limits but haven't reached a large enough memory gap,
			// warn the user that the system is becoming unstable.
			if chosen < bc.lastWrite+state.TriesInMemory && bc.gcproc >= 2*flushInterval {
				log.Info("State in memory for too long, committing", "time", bc.gcproc, "allowance", flushInterval, "optimum", float64(chosen-bc.lastWrite)/state.TriesInMemory)
			}
			// Flush an entire trie and restart the counters
			_ = bc.triedb.Commit(header.Root, true)
			bc.lastWrite = chosen
			bc.gcproc = 0
		}
	}
	// Garbage collect anything below our required write retention
	for !bc.triegc.Empty() {
		root, number := bc.triegc.Pop()
		if uint64(-number) > chosen {
			bc.triegc.Push(root, number)
			break
		}

		bc.triedb.Dereference(root)
	}

	return stateSyncLogs, nil
}

// WriteBlockAndSetHead writes the given block and all associated state to the database,
// and applies the block as the new chain head.
func (bc *BlockChain) WriteBlockAndSetHead(block *types.Block, receipts []*types.Receipt, logs []*types.Log, state *state.StateDB, emitHeadEvent bool) (status WriteStatus, err error) {
	if !bc.chainmu.TryLock() {
		return NonStatTy, errChainStopped
	}
	defer bc.chainmu.Unlock()

	return bc.writeBlockAndSetHead(block, receipts, logs, state, emitHeadEvent, false)
}

// writeBlockAndSetHead is the internal implementation of WriteBlockAndSetHead.
// This function expects the chain mutex to be held.
func (bc *BlockChain) writeBlockAndSetHead(block *types.Block, receipts []*types.Receipt, logs []*types.Log, state *state.StateDB, emitHeadEvent bool, stateless bool) (status WriteStatus, err error) {
	stateSyncLogs, err := bc.writeBlockWithState(block, receipts, logs, state)
	if err != nil {
		return NonStatTy, err
	}

	currentBlock := bc.CurrentBlock()
	reorg, err := bc.forker.ReorgNeeded(currentBlock, block.Header())
	if err != nil {
		return NonStatTy, err
	}

	if reorg {
		// Reorganise the chain if the parent is not the head block
		if block.ParentHash() != currentBlock.Hash() {
			if err = bc.reorg(currentBlock, block.Header()); err != nil {
				if !(stateless && err == errInvalidNewChain) { // fast forward may raise an invalid new chain error, skipping for stateless
					return NonStatTy, err
				}
			}
		}

		status = CanonStatTy
	} else {
		status = SideStatTy
	}

	// Set new head.
	if status == CanonStatTy {
		bc.writeHeadBlock(block)

		bc.chainFeed.Send(ChainEvent{Header: block.Header()})

		if len(logs) > 0 {
			bc.logsFeed.Send(logs)
		}
		// send state sync logs into logs feed
		if len(stateSyncLogs) > 0 {
			bc.logsFeed.Send(stateSyncLogs)
		}
		// In theory, we should fire a ChainHeadEvent when we inject
		// a canonical block, but sometimes we can insert a batch of
		// canonical blocks. Avoid firing too many ChainHeadEvents,
		// we will fire an accumulated ChainHeadEvent and disable fire
		// event here.
		if emitHeadEvent {
			bc.chainHeadFeed.Send(ChainHeadEvent{Header: block.Header()})
			// BOR state sync feed related changes
			bc.stateSyncMu.RLock()
			for _, data := range bc.stateSyncData {
				bc.stateSyncFeed.Send(StateSyncEvent{Data: data})
			}
			bc.stateSyncMu.RUnlock()
			// BOR
		}
	} else {
		bc.chainSideFeed.Send(ChainSideEvent{Header: block.Header()})

		bc.chain2HeadFeed.Send(Chain2HeadEvent{
			Type:     Chain2HeadForkEvent,
			NewChain: []*types.Header{block.Header()},
		})
	}

	return status, nil
}

// addFutureBlock checks if the block is within the max allowed window to get
// accepted for future processing, and returns an error if the block is too far
// ahead and was not added.
//
// TODO after the transition, the future block shouldn't be kept. Because
// it's not checked in the Geth side anymore.
func (bc *BlockChain) addFutureBlock(block *types.Block) error {
	max := uint64(time.Now().Unix() + maxTimeFutureBlocks)
	if block.Time() > max {
		return fmt.Errorf("future block timestamp %v > allowed %v", block.Time(), max)
	}

	if block.Difficulty().Cmp(common.Big0) == 0 {
		// Never add PoS blocks into the future queue
		return nil
	}

	bc.futureBlocks.Add(block.Hash(), block)

	return nil
}

// InsertChain attempts to insert the given batch of blocks in to the canonical
// chain or, otherwise, create a fork. If an error is returned it will return
// the index number of the failing block as well an error describing what went
// wrong. After insertion is done, all accumulated events will be fired.
func (bc *BlockChain) InsertChain(chain types.Blocks, makeWitnesses bool) (int, error) {
	return bc.InsertChainWithWitnesses(chain, makeWitnesses, nil)
}

func (bc *BlockChain) InsertChainWithWitnesses(chain types.Blocks, makeWitness bool, witnesses []*stateless.Witness) (int, error) {
	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return 0, nil
	}

	// Do a sanity check that the provided chain is actually ordered and linked.
	for i := 1; i < len(chain); i++ {
		block, prev := chain[i], chain[i-1]
		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
			log.Error("Non contiguous block insert",
				"number", block.Number(),
				"hash", block.Hash(),
				"parent", block.ParentHash(),
				"prevnumber", prev.Number(),
				"prevhash", prev.Hash(),
			)

			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x..], item %d is #%d [%x..] (parent [%x..])", i-1, prev.NumberU64(),
				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
		}
	}
	// Pre-checks passed, start the full block imports
	if !bc.chainmu.TryLock() {
		return 0, errChainStopped
	}
	defer bc.chainmu.Unlock()

	_, n, err := bc.insertChainWithWitnesses(chain, true, makeWitness, witnesses)
	return n, err
}

func (bc *BlockChain) InsertChainStateless(chain types.Blocks, witnesses []*stateless.Witness) (int, error) {
	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return 0, nil
	}

	bc.blockProcFeed.Send(true)
	defer bc.blockProcFeed.Send(false)

	stats := insertStats{startTime: mclock.Now()}

	// Do a sanity check that the provided chain is actually ordered and linked.
	for i := 1; i < len(chain); i++ {
		block, prev := chain[i], chain[i-1]
		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
			log.Error("Non contiguous block insert",
				"number", block.Number(),
				"hash", block.Hash(),
				"parent", block.ParentHash(),
				"prevnumber", prev.Number(),
				"prevhash", prev.Hash(),
			)

			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x..], item %d is #%d [%x..] (parent [%x..])", i-1, prev.NumberU64(),
				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
		}
	}

	// Pre-checks passed, start the full block imports
	if !bc.chainmu.TryLock() {
		return 0, errChainStopped
	}
	defer bc.chainmu.Unlock()

	// Start the parallel header verifier
	headers := make([]*types.Header, len(chain))
	for i, block := range chain {
		headers[i] = block.Header()
	}
	abort, results := bc.engine.VerifyHeaders(bc, headers)
	defer close(abort)

	// Check the validity of incoming chain
	isValid, err := bc.forker.ValidateReorg(bc.CurrentBlock(), headers)
	if err != nil {
		return 0, err
	}

	if !isValid {
		// The chain to be imported is invalid as the blocks doesn't match with
		// the whitelisted block number.
		return 0, whitelist.ErrMismatch
	}

	// In stateless mode, we process blocks one by one without committing the state
	var processed int
	for i, block := range chain {
		// Check if block is already known before attempting to process

		if bc.HasBlock(block.Hash(), block.NumberU64()) {
			log.Trace("Skipping known block in InsertChainStateless", "number", block.NumberU64(), "hash", block.Hash())
			processed++ // Count as processed since we're skipping it
			// We need to ensure the header verification result for this block is consumed
			// even though we are skipping the processing.
			if err := <-results; err != nil {
				// If header verification failed for this known block (shouldn't happen often),
				// it might indicate a deeper issue, but we can't proceed with the chain.
				log.Warn("Header verification failed for known block", "number", block.NumberU64(), "hash", block.Hash(), "err", err)
				return processed - 1, fmt.Errorf("header verification failed for known block %d (%s): %w", block.NumberU64(), block.Hash(), err)
			}
			continue // Skip to the next block
		}
		// If the chain is terminating, don't even bother starting up.
		if bc.insertStopped() {
			return processed, errInsertionInterrupted
		}

		// Wait for the block's verification to complete
		if err := <-results; err != nil {
			if err == consensus.ErrUnknownAncestor {
				// For stateless nodes, check if this is a reorg situation
				parentNum := block.NumberU64() - 1
				existingBlock := bc.GetBlockByNumber(parentNum)

				if existingBlock != nil && existingBlock.Hash() != block.ParentHash() {
					// We have a different block at the parent's height - this could be a reorg
					log.Info("Conflicting block detected in stateless sync",
						"blockNum", block.NumberU64(),
						"parentNum", parentNum,
						"existingParent", existingBlock.Hash(),
						"expectedParent", block.ParentHash())

					// Verify the existing parent block to see if it's valid
					// This helps avoid unnecessary rewinds if the existing block is correct
					existingHeader := existingBlock.Header()
					verifyErr := bc.engine.VerifyHeader(bc, existingHeader)

					// Check if the existing parent is valid
					if verifyErr == nil {
						// Existing parent is valid, so the new block is on a wrong fork
						log.Info("Existing parent block is valid, rejecting new fork",
							"existingParent", existingBlock.Hash(),
							"rejectedParent", block.ParentHash())
						return processed, fmt.Errorf("rejecting block %d: existing parent %s is valid",
							block.NumberU64(), existingBlock.Hash())
					}

					// Existing parent is invalid, we need to rewind and accept the new chain
					log.Info("Existing parent block is invalid, accepting reorg",
						"existingParent", existingBlock.Hash(),
						"newParent", block.ParentHash(),
						"verifyErr", verifyErr)

					// For stateless nodes, we need to rewind and let the sync continue
					// This will cause the correct parent block to be fetched and imported
					if err := bc.SetHead(parentNum - 1); err != nil {
						return processed, fmt.Errorf("failed to rewind for reorg: %w", err)
					}

					// Return to let the downloader retry with the correct chain
					return processed, fmt.Errorf("reorg detected, rewound to block %d", parentNum-1)
				} else if i != 0 {
					// Not the first block and no reorg detected
					return processed, err
				}
				// First block in batch or successful reorg handling - continue
			} else {
				return processed, err
			}
		}

		// Get the witness for this block if available
		var witness *stateless.Witness
		if i < len(witnesses) {
			witness = witnesses[i]
		}

		// Process the block using stateless execution
		statedb, res, err := bc.ProcessBlockWithWitnesses(block, witness)
		if err != nil {
			return processed, err
		}

		statedb.SetWitness(witness)

		// Write the block to the chain without committing state
		if _, err := bc.writeBlockAndSetHead(block, nil, nil, statedb, false, true); err != nil {
			return processed, err
		}

		processed++

		stats.processed = processed
		stats.usedGas += res.GasUsed

		stats.report(chain, i, 0, 0, 0, 0, true, true)
	}

	return processed, nil
}

// insertChain is the internal implementation of InsertChain, which assumes that
// 1) chains are contiguous, and 2) The chain mutex is held.
//
// This method is split out so that import batches that require re-injecting
// historical blocks can do so without releasing the lock, which could lead to
// racey behaviour. If a sidechain import is in progress, and the historic state
// is imported, but then new canon-head is added before the actual sidechain
// completes, then the historic state could be pruned again
func (bc *BlockChain) insertChain(chain types.Blocks, setHead bool, makeWitness bool) (*stateless.Witness, int, error) {
	return bc.insertChainWithWitnesses(chain, setHead, makeWitness, nil)
}

func (bc *BlockChain) insertChainWithWitnesses(chain types.Blocks, setHead bool, makeWitness bool, witnesses []*stateless.Witness) (*stateless.Witness, int, error) {
	// If the chain is terminating, don't even bother starting up.
	if bc.insertStopped() {
		return nil, 0, nil
	}

	if atomic.AddInt32(&bc.blockProcCounter, 1) == 1 {
		bc.blockProcFeed.Send(true)
	}
	defer func() {
		if atomic.AddInt32(&bc.blockProcCounter, -1) == 0 {
			bc.blockProcFeed.Send(false)
		}
	}()

	// Start a parallel signature recovery (signer will fluke on fork transition, minimal perf loss)
	SenderCacher().RecoverFromBlocks(types.MakeSigner(bc.chainConfig, chain[0].Number(), chain[0].Time()), chain)

	var (
		stats     = insertStats{startTime: mclock.Now()}
		lastCanon *types.Block
	)
	// Fire a single chain head event if we've progressed the chain
	defer func() {
		if lastCanon != nil && bc.CurrentBlock().Hash() == lastCanon.Hash() {
			bc.chainHeadFeed.Send(ChainHeadEvent{Header: lastCanon.Header()})
		}
	}()
	// Start the parallel header verifier
	headers := make([]*types.Header, len(chain))
	for i, block := range chain {
		headers[i] = block.Header()
	}
	abort, results := bc.engine.VerifyHeaders(bc, headers)
	defer close(abort)

	// Peek the error for the first block to decide the directing import logic
	it := newInsertIterator(chain, results, bc.validator)
	block, err := it.next()

	// Update the block import meter; it will just record chains we've received
	// from other peers. (Note that the actual chain which gets imported would be
	// quite low).
	blockImportTimer.Mark(int64(len(headers)))

	// Check the validity of incoming chain
	isValid, err1 := bc.forker.ValidateReorg(bc.CurrentBlock(), headers)
	if err1 != nil {
		return nil, it.index, err1
	}

	if !isValid {
		// The chain to be imported is invalid as the blocks doesn't match with
		// the whitelisted block number.
		return nil, it.index, whitelist.ErrMismatch
	}

	// Left-trim all the known blocks that don't need to build snapshot
	if bc.skipBlock(err, it) {
		// First block (and state) is known
		//   1. We did a roll-back, and should now do a re-import
		//   2. The block is stored as a sidechain, and is lying about it's stateroot, and passes a stateroot
		//      from the canonical chain, which has not been verified.
		// Skip all known blocks that are behind us.
		var (
			reorg   bool
			current = bc.CurrentBlock()
		)

		for block != nil && bc.skipBlock(err, it) {
			reorg, err = bc.forker.ReorgNeeded(current, block.Header())
			if err != nil {
				return nil, it.index, err
			}

			if reorg {
				// Switch to import mode if the forker says the reorg is necessary
				// and also the block is not on the canonical chain.
				// In eth2 the forker always returns true for reorg decision (blindly trusting
				// the external consensus engine), but in order to prevent the unnecessary
				// reorgs when importing known blocks, the special case is handled here.
				if block.NumberU64() > current.Number.Uint64() || bc.GetCanonicalHash(block.NumberU64()) != block.Hash() {
					break
				}
			}

			log.Debug("Ignoring already known block", "number", block.Number(), "hash", block.Hash())

			stats.ignored++

			block, err = it.next()
		}
		// The remaining blocks are still known blocks, the only scenario here is:
		// During the snap sync, the pivot point is already submitted but rollback
		// happens. Then node resets the head full block to a lower height via `rollback`
		// and leaves a few known blocks in the database.
		//
		// When node runs a snap sync again, it can re-import a batch of known blocks via
		// `insertChain` while a part of them have higher total difficulty than current
		// head full block(new pivot point).
		for block != nil && bc.skipBlock(err, it) {
			log.Debug("Writing previously known block", "number", block.Number(), "hash", block.Hash())

			if err := bc.writeKnownBlock(block); err != nil {
				return nil, it.index, err
			}

			lastCanon = block

			block, err = it.next()
		}
		// Falls through to the block import
	}

	switch {
	// First block is pruned
	case errors.Is(err, consensus.ErrPrunedAncestor):
		if setHead {
			// First block is pruned, insert as sidechain and reorg only if TD grows enough
			log.Debug("Pruned ancestor, inserting as sidechain", "number", block.Number(), "hash", block.Hash())
			return bc.insertSideChain(block, it, makeWitness)
		} else {
			// We're post-merge and the parent is pruned, try to recover the parent state
			log.Debug("Pruned ancestor", "number", block.Number(), "hash", block.Hash())
			_, err := bc.recoverAncestors(block, makeWitness)
			return nil, it.index, err
		}
	// First block is future, shove it (and all children) to the future queue (unknown ancestor)
	case errors.Is(err, consensus.ErrFutureBlock) || (errors.Is(err, consensus.ErrUnknownAncestor) && bc.futureBlocks.Contains(it.first().ParentHash())):
		for block != nil && (it.index == 0 || errors.Is(err, consensus.ErrUnknownAncestor)) {
			log.Debug("Future block, postponing import", "number", block.Number(), "hash", block.Hash())

			if err := bc.addFutureBlock(block); err != nil {
				return nil, it.index, err
			}

			block, err = it.next()
		}

		stats.queued += it.processed()
		stats.ignored += it.remaining()

		// If there are any still remaining, mark as ignored
		return nil, it.index, err

	// Some other error(except ErrKnownBlock) occurred, abort.
	// ErrKnownBlock is allowed here since some known blocks
	// still need re-execution to generate snapshots that are missing
	case err != nil && !errors.Is(err, ErrKnownBlock):
		stats.ignored += len(it.chain)

		bc.reportBlock(block, nil, err)
		return nil, it.index, err
	}
	// No validation errors for the first block (or chain prefix skipped)
	var activeState *state.StateDB
	defer func() {
		// The chain importer is starting and stopping trie prefetchers. If a bad
		// block or other error is hit however, an early return may not properly
		// terminate the background threads. This defer ensures that we clean up
		// and dangling prefetcher, without deferring each and holding on live refs.
		if activeState != nil {
			activeState.StopPrefetcher()
		}
	}()

	// Track the singleton witness from this chain insertion (if any)
	var witness *stateless.Witness

	// accumulator for canonical blocks
	var canonAccum []*types.Block

	emitAccum := func() {
		size := len(canonAccum)
		if size == 0 || size > 5 {
			// avoid reporting events for large sync events
			return
		}

		headers := make([]*types.Header, size)
		for i, block := range canonAccum {
			headers[i] = block.Header()
		}
		bc.chain2HeadFeed.Send(Chain2HeadEvent{
			Type:     Chain2HeadCanonicalEvent,
			NewChain: headers,
		})

		canonAccum = canonAccum[:0]
	}

	for ; block != nil && err == nil || errors.Is(err, ErrKnownBlock); block, err = it.next() {
		// If the chain is terminating, stop processing blocks
		if bc.insertStopped() {
			log.Debug("Abort during block processing")
			break
		}

		// If the header is a banned one, straight out abort
		if BadHashes[block.Hash()] {
			bc.reportBlock(block, nil, ErrBannedHash)
			return nil, it.index, ErrBannedHash
		}

		// If the block is known (in the middle of the chain), it's a special case for
		// Clique blocks where they can share state among each other, so importing an
		// older block might complete the state of the subsequent one. In this case,
		// just skip the block (we already validated it once fully (and crashed), since
		// its header and body was already in the database). But if the corresponding
		// snapshot layer is missing, forcibly rerun the execution to build it.
		if bc.skipBlock(err, it) {
			logger := log.Debug
			if bc.chainConfig.Clique == nil {
				logger = log.Warn
			}

			logger("Inserted known block", "number", block.Number(), "hash", block.Hash(),
				"uncles", len(block.Uncles()), "txs", len(block.Transactions()), "gas", block.GasUsed(),
				"root", block.Root())

			// Special case. Commit the empty receipt slice if we meet the known
			// block in the middle. It can only happen in the clique chain. Whenever
			// we insert blocks via `insertSideChain`, we only commit `td`, `header`
			// and `body` if it's non-existent. Since we don't have receipts without
			// reexecution, so nothing to commit. But if the sidechain will be adopted
			// as the canonical chain eventually, it needs to be reexecuted for missing
			// state, but if it's this special case here(skip reexecution) we will lose
			// the empty receipt entry.
			if len(block.Transactions()) == 0 {
				rawdb.WriteReceipts(bc.db, block.Hash(), block.NumberU64(), nil)
			} else {
				log.Error("Please file an issue, skip known block execution without receipt",
					"hash", block.Hash(), "number", block.NumberU64())
			}

			if err := bc.writeKnownBlock(block); err != nil {
				return nil, it.index, err
			}

			stats.processed++
			if bc.logger != nil && bc.logger.OnSkippedBlock != nil {
				bc.logger.OnSkippedBlock(tracing.BlockEvent{
					Block:     block,
					TD:        bc.GetTd(block.ParentHash(), block.NumberU64()-1),
					Finalized: bc.CurrentFinalBlock(),
					Safe:      bc.CurrentSafeBlock(),
				})
			}
			// We can assume that logs are empty here, since the only way for consecutive
			// Clique blocks to have the same state is if there are no transactions.
			lastCanon = block

			continue
		}
		// Retrieve the parent block and it's state to execute on top
		start := time.Now()

		parent := it.previous()
		if parent == nil {
			parent = bc.GetHeader(block.ParentHash(), block.NumberU64()-1)
		}
		statedb, err := state.New(parent.Root, bc.statedb)
		if err != nil {
			return nil, it.index, err
		}

		// If we are past Byzantium, enable prefetching to pull in trie node paths
		// while processing transactions. Before Byzantium the prefetcher is mostly
		// useless due to the intermediate root hashing after each transaction.
		if bc.chainConfig.IsByzantium(block.Number()) {
			// Generate witnesses either if we're self-testing, or if it's the
			// only block being inserted. A bit crude, but witnesses are huge,
			// so we refuse to make an entire chain of them.
			if bc.vmConfig.StatelessSelfValidation || (makeWitness && len(chain) == 1) {
				witness, err = stateless.NewWitness(block.Header(), bc)
				if err != nil {
					return nil, it.index, err
				}
			}
			// Bor: We start the prefetcher in process block function called below
			// and not here as we copy state for block-stm in that function. Also,
			// we don't want to start duplicate prefetchers per block.
			// statedb.StartPrefetcher("chain", witness)
		}
		activeState = statedb

		// If we have a followup block, run that against the current state to pre-cache
		// transactions and probabilistically some of the account/storage trie nodes.
		var followupInterrupt atomic.Bool

		if !bc.cacheConfig.TrieCleanNoPrefetch {
			if followup, err := it.peek(); followup != nil && err == nil {
				throwaway, _ := state.New(parent.Root, bc.statedb)

				go func(start time.Time, followup *types.Block, throwaway *state.StateDB) {
					// Disable tracing for prefetcher executions.
					vmCfg := bc.vmConfig
					vmCfg.Tracer = nil
					bc.prefetcher.Prefetch(followup, throwaway, vmCfg, &followupInterrupt)

					blockPrefetchExecuteTimer.Update(time.Since(start))

					if followupInterrupt.Load() {
						blockPrefetchInterruptMeter.Mark(1)
					}
				}(time.Now(), followup, throwaway)
			}
		}

		// Process block using the parent state as reference point
		pstart := time.Now()

		computeWitness := makeWitness

		if witnesses != nil && len(witnesses) > it.processed()-1 && witnesses[it.processed()-1] != nil {
			// 1. Validate the witness.
			if err := stateless.ValidateWitnessPreState(witnesses[it.processed()-1], bc); err != nil {
				log.Error("Witness validation failed during chain insertion", "blockNumber", block.Number(), "blockHash", block.Hash(), "err", err)
				bc.reportBlock(block, &ProcessResult{}, err)
				followupInterrupt.Store(true)
				return nil, it.index, fmt.Errorf("witness validation failed: %w", err)
			}

			// 2. Set the witness to the statedb.
			memdb := witnesses[it.processed()-1].MakeHashDB(bc.statedb.TrieDB().Disk())
			bc.statedb.TrieDB().SetReadBackend(hashdb.New(memdb, triedb.HashDefaults.HashDB))
			computeWitness = false
			bc.statedb.DisableSnapInReader()
		}

		if computeWitness {
			witness, err = stateless.NewWitness(block.Header(), bc)
			if err != nil {
				log.Error("Error in witness generation", "err", err)
			}
		}

		receipts, logs, usedGas, statedb, vtime, err := bc.ProcessBlock(block, parent, witness)
		bc.statedb.TrieDB().SetReadBackend(nil)
		bc.statedb.EnableSnapInReader()
		activeState = statedb

		if err != nil {
			bc.reportBlock(block, &ProcessResult{Receipts: receipts}, err)
			followupInterrupt.Store(true)
			return nil, it.index, err
		}

		// BOR state sync feed related changes
		bc.stateSyncMu.RLock()
		for _, data := range bc.stateSyncData {
			bc.stateSyncFeed.Send(StateSyncEvent{Data: data})
		}
		bc.stateSyncMu.RUnlock()
		// BOR
		ptime := time.Since(pstart) - vtime - statedb.BorConsensusTime

		proctime := time.Since(start) // processing + validation

		// Update the metrics touched during block processing and validation
		accountReadTimer.Update(statedb.AccountReads)                   // Account reads are complete(in processing)
		storageReadTimer.Update(statedb.StorageReads)                   // Storage reads are complete(in processing)
		snapshotAccountReadTimer.Update(statedb.SnapshotAccountReads)   // Account reads are complete(in processing)
		snapshotStorageReadTimer.Update(statedb.SnapshotStorageReads)   // Storage reads are complete(in processing)
		accountUpdateTimer.Update(statedb.AccountUpdates)               // Account updates are complete(in validation)
		storageUpdateTimer.Update(statedb.StorageUpdates)               // Storage updates are complete(in validation)
		accountHashTimer.Update(statedb.AccountHashes)                  // Account hashes are complete(in validation)
		storageHashTimer.Update(statedb.StorageHashes)                  // Storage hashes are complete(in validation)
		triehash := statedb.AccountHashes + statedb.StorageHashes       // The time spent on tries hashing
		trieUpdate := statedb.AccountUpdates + statedb.StorageUpdates   // The time spent on tries update
		trieRead := statedb.SnapshotAccountReads + statedb.AccountReads // The time spent on account read
		trieRead += statedb.SnapshotStorageReads + statedb.StorageReads // The time spent on storage read
		blockExecutionTimer.Update(ptime - trieRead)                    // The time spent on EVM processing
		blockValidationTimer.Update(vtime - (triehash + trieUpdate))    // The time spent on block validation
		borConsensusTime.Update(statedb.BorConsensusTime)               // The time spent on bor consensus (span + state sync)
		// Write the block to the chain and get the status.
		var (
			wstart = time.Now()
			status WriteStatus
		)

		// Before the actual db insertion happens, verify the block against the whitelisted
		// milestone and checkpoint. This is to prevent a race condition where a milestone
		// or checkpoint was whitelisted while the block execution happened (and wasn't
		// available sometime before) and the block turns out to be invalid (i.e. not
		// honouring the milestone or checkpoint). Use the block itself as current block
		// so that it's considered as a `past` chain and the validation doesn't get bypassed.
		isValid, err = bc.forker.ValidateReorg(block.Header(), []*types.Header{block.Header()})
		if err != nil {
			return nil, it.index, err
		}

		if !isValid {
			return nil, it.index, whitelist.ErrMismatch
		}

		if !setHead {
			// Don't set the head, only insert the block
			_, err = bc.writeBlockWithState(block, receipts, logs, statedb)
		} else {
			status, err = bc.writeBlockAndSetHead(block, receipts, logs, statedb, false, false)
		}

		followupInterrupt.Store(true)

		if err != nil {
			return nil, it.index, err
		}

		// Update the metrics touched during block commit
		accountCommitTimer.Update(statedb.AccountCommits)   // Account commits are complete, we can mark them
		storageCommitTimer.Update(statedb.StorageCommits)   // Storage commits are complete, we can mark them
		snapshotCommitTimer.Update(statedb.SnapshotCommits) // Snapshot commits are complete, we can mark them
		triedbCommitTimer.Update(statedb.TrieDBCommits)     // Trie database commits are complete, we can mark them

		blockWriteTimer.Update(time.Since(wstart) - statedb.AccountCommits - statedb.StorageCommits - statedb.SnapshotCommits - statedb.TrieDBCommits)
		blockInsertTimer.UpdateSince(start)

		// Report the import stats before returning the various results
		stats.processed++
		stats.usedGas += usedGas

		var snapDiffItems, snapBufItems common.StorageSize
		if bc.snaps != nil {
			snapDiffItems, snapBufItems = bc.snaps.Size()
		}
		trieDiffNodes, trieBufNodes, _ := bc.triedb.Size()
		stats.report(chain, it.index, snapDiffItems, snapBufItems, trieDiffNodes, trieBufNodes, setHead, false)

		/*
			// Print confirmation that a future fork is scheduled, but not yet active.
			bc.logForkReadiness(block)
		*/

		if !setHead {
			// After merge we expect few side chains. Simply count
			// all blocks the CL gives us for GC processing time
			bc.gcproc += proctime
			return witness, it.index, nil // Direct block insertion of a single block
		}

		// BOR
		if status == CanonStatTy {
			canonAccum = append(canonAccum, block)
		} else {
			emitAccum()
		}
		// BOR

		switch status {
		case CanonStatTy:
			log.Debug("Inserted new block", "number", block.Number(), "hash", block.Hash(),
				"uncles", len(block.Uncles()), "txs", len(block.Transactions()), "gas", block.GasUsed(),
				"elapsed", common.PrettyDuration(time.Since(start)),
				"root", block.Root())

			lastCanon = block

			// Only count canonical blocks for GC processing time
			bc.gcproc += proctime

		case SideStatTy:
			log.Debug("Inserted forked block", "number", block.Number(), "hash", block.Hash(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())

		default:
			// This in theory is impossible, but lets be nice to our future selves and leave
			// a log, instead of trying to track down blocks imports that don't emit logs.
			log.Warn("Inserted block with unknown status", "number", block.Number(), "hash", block.Hash(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())
		}
	}

	// BOR
	emitAccum()
	// BOR

	// Any blocks remaining here? The only ones we care about are the future ones
	if block != nil && errors.Is(err, consensus.ErrFutureBlock) {
		if err := bc.addFutureBlock(block); err != nil {
			return nil, it.index, err
		}

		block, err = it.next()

		for ; block != nil && errors.Is(err, consensus.ErrUnknownAncestor); block, err = it.next() {
			if err := bc.addFutureBlock(block); err != nil {
				return nil, it.index, err
			}

			stats.queued++
		}
	}

	stats.ignored += it.remaining()
	return witness, it.index, err
}

// blockProcessingResult is a summary of block processing
// used for updating the stats.
// nolint : unused
type blockProcessingResult struct {
	usedGas  uint64
	procTime time.Duration
	status   WriteStatus
}

// processBlock executes and validates the given block. If there was no error
// it writes the block and associated state to database.
// nolint : unused
func (bc *BlockChain) processBlock(block *types.Block, statedb *state.StateDB, start time.Time, setHead bool, diskdb ethdb.Database) (_ *blockProcessingResult, blockEndErr error) {
	if bc.logger != nil && bc.logger.OnBlockStart != nil {
		td := bc.GetTd(block.ParentHash(), block.NumberU64()-1)
		bc.logger.OnBlockStart(tracing.BlockEvent{
			Block:     block,
			TD:        td,
			Finalized: bc.CurrentFinalBlock(),
			Safe:      bc.CurrentSafeBlock(),
		})
	}
	if bc.logger != nil && bc.logger.OnBlockEnd != nil {
		defer func() {
			bc.logger.OnBlockEnd(blockEndErr)
		}()
	}

	// Process block using the parent state as reference point
	pstart := time.Now()
	res, err := bc.processor.Process(block, statedb, bc.vmConfig, nil, context.Background())
	if err != nil {
		bc.reportBlock(block, res, err)
		return nil, err
	}
	ptime := time.Since(pstart)

	vstart := time.Now()
	if err := bc.validator.ValidateState(block, statedb, res, false); err != nil {
		bc.reportBlock(block, res, err)
		return nil, err
	}
	vtime := time.Since(vstart)

	// If witnesses was generated and stateless self-validation requested, do
	// that now. Self validation should *never* run in production, it's more of
	// a tight integration to enable running *all* consensus tests through the
	// witness builder/runner, which would otherwise be impossible due to the
	// various invalid chain states/behaviors being contained in those tests.
	xvstart := time.Now()
	if witness := statedb.Witness(); witness != nil && bc.vmConfig.StatelessSelfValidation {
		log.Warn("Running stateless self-validation", "block", block.Number(), "hash", block.Hash())

		// Remove critical computed fields from the block to force true recalculation
		context := block.Header()
		context.Root = common.Hash{}
		context.ReceiptHash = common.Hash{}

		task := types.NewBlockWithHeader(context).WithBody(*block.Body())
		author := NewEVMBlockContext(block.Header(), bc.hc, nil).Coinbase

		// Run the stateless self-cross-validation
		crossStateRoot, crossReceiptRoot, _, _, err := ExecuteStateless(bc.chainConfig, bc.vmConfig, task, witness, &author, bc.engine, diskdb)
		if err != nil {
			return nil, fmt.Errorf("stateless self-validation failed: %v", err)
		}
		if crossStateRoot != block.Root() {
			return nil, fmt.Errorf("stateless self-validation root mismatch (cross: %x local: %x)", crossStateRoot, block.Root())
		}
		if crossReceiptRoot != block.ReceiptHash() {
			return nil, fmt.Errorf("stateless self-validation receipt root mismatch (cross: %x local: %x)", crossReceiptRoot, block.ReceiptHash())
		}
	}
	xvtime := time.Since(xvstart)
	proctime := time.Since(start) // processing + validation + cross validation

	// Update the metrics touched during block processing and validation
	accountReadTimer.Update(statedb.AccountReads) // Account reads are complete(in processing)
	storageReadTimer.Update(statedb.StorageReads) // Storage reads are complete(in processing)
	if statedb.AccountLoaded != 0 {
		accountReadSingleTimer.Update(statedb.AccountReads / time.Duration(statedb.AccountLoaded))
	}
	if statedb.StorageLoaded != 0 {
		storageReadSingleTimer.Update(statedb.StorageReads / time.Duration(statedb.StorageLoaded))
	}
	accountUpdateTimer.Update(statedb.AccountUpdates)                                 // Account updates are complete(in validation)
	storageUpdateTimer.Update(statedb.StorageUpdates)                                 // Storage updates are complete(in validation)
	accountHashTimer.Update(statedb.AccountHashes)                                    // Account hashes are complete(in validation)
	triehash := statedb.AccountHashes                                                 // The time spent on tries hashing
	trieUpdate := statedb.AccountUpdates + statedb.StorageUpdates                     // The time spent on tries update
	blockExecutionTimer.Update(ptime - (statedb.AccountReads + statedb.StorageReads)) // The time spent on EVM processing
	blockValidationTimer.Update(vtime - (triehash + trieUpdate))                      // The time spent on block validation
	blockCrossValidationTimer.Update(xvtime)                                          // The time spent on stateless cross validation

	// Write the block to the chain and get the status.
	var (
		wstart = time.Now()
		status WriteStatus
	)
	if !setHead {
		// Don't set the head, only insert the block
		_, err = bc.writeBlockWithState(block, res.Receipts, res.Logs, statedb)
	} else {
		status, err = bc.writeBlockAndSetHead(block, res.Receipts, res.Logs, statedb, false, false)
	}
	if err != nil {
		return nil, err
	}
	// Update the metrics touched during block commit
	accountCommitTimer.Update(statedb.AccountCommits)   // Account commits are complete, we can mark them
	storageCommitTimer.Update(statedb.StorageCommits)   // Storage commits are complete, we can mark them
	snapshotCommitTimer.Update(statedb.SnapshotCommits) // Snapshot commits are complete, we can mark them
	triedbCommitTimer.Update(statedb.TrieDBCommits)     // Trie database commits are complete, we can mark them

	blockWriteTimer.Update(time.Since(wstart) - max(statedb.AccountCommits, statedb.StorageCommits) /* concurrent */ - statedb.SnapshotCommits - statedb.TrieDBCommits)
	blockInsertTimer.UpdateSince(start)

	return &blockProcessingResult{usedGas: res.GasUsed, procTime: proctime, status: status}, nil
}

// insertSideChain is called when an import batch hits upon a pruned ancestor
// error, which happens when a sidechain with a sufficiently old fork-block is
// found.
//
// The method writes all (header-and-body-valid) blocks to disk, then tries to
// switch over to the new chain if the TD exceeded the current chain.
// insertSideChain is only used pre-merge.
func (bc *BlockChain) insertSideChain(block *types.Block, it *insertIterator, makeWitness bool) (*stateless.Witness, int, error) {
	var (
		lastBlock = block
		current   = bc.CurrentBlock()
		headers   []*types.Header
		externTd  *big.Int
	)

	// The first sidechain block error is already verified to be ErrPrunedAncestor.
	// Since we don't import them here, we expect ErrUnknownAncestor for the remaining
	// ones. Any other errors means that the block is invalid, and should not be written
	// to disk.
	err := consensus.ErrPrunedAncestor
	for ; block != nil && errors.Is(err, consensus.ErrPrunedAncestor); block, err = it.next() {
		headers = append(headers, block.Header())
		// Check the canonical state root for that number
		if number := block.NumberU64(); current.Number.Uint64() >= number {
			canonical := bc.GetBlockByNumber(number)
			if canonical != nil && canonical.Hash() == block.Hash() {
				// Not a sidechain block, this is a re-import of a canon block which has it's state pruned

				// Collect the TD of the block. Since we know it's a canon one,
				// we can get it directly, and not (like further below) use
				// the parent and then add the block on top
				externTd = bc.GetTd(block.Hash(), block.NumberU64())
				continue
			}

			if canonical != nil && canonical.Root() == block.Root() {
				// This is most likely a shadow-state attack. When a fork is imported into the
				// database, and it eventually reaches a block height which is not pruned, we
				// just found that the state already exist! This means that the sidechain block
				// refers to a state which already exists in our canon chain.
				//
				// If left unchecked, we would now proceed importing the blocks, without actually
				// having verified the state of the previous blocks.
				log.Warn("Sidechain ghost-state attack detected", "number", block.NumberU64(), "sideroot", block.Root(), "canonroot", canonical.Root())

				// If someone legitimately side-mines blocks, they would still be imported as usual. However,
				// we cannot risk writing unverified blocks to disk when they obviously target the pruning
				// mechanism.
				return nil, it.index, errors.New("sidechain ghost-state attack")
			}
		}
		if externTd == nil {
			externTd = bc.GetTd(block.ParentHash(), block.NumberU64()-1)
		}
		externTd = new(big.Int).Add(externTd, block.Difficulty())

		if !bc.HasBlock(block.Hash(), block.NumberU64()) {
			start := time.Now()
			if err := bc.writeBlockWithoutState(block, externTd); err != nil {
				return nil, it.index, err
			}

			log.Debug("Injected sidechain block", "number", block.Number(), "hash", block.Hash(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())
		}

		lastBlock = block
	}
	// At this point, we've written all sidechain blocks to database. Loop ended
	// either on some other error or all were processed. If there was some other
	// error, we can ignore the rest of those blocks.
	//
	// If the externTd was larger than our local TD, we now need to reimport the previous
	// blocks to regenerate the required state
	reorg, err := bc.forker.ReorgNeeded(current, lastBlock.Header())
	if err != nil {
		return nil, it.index, err
	}

	isValid, err := bc.forker.ValidateReorg(current, headers)
	if err != nil {
		return nil, it.index, err
	}

	if !reorg || !isValid {
		localTd := bc.GetTd(current.Hash(), current.Number.Uint64())
		log.Info("Sidechain written to disk", "start", it.first().NumberU64(), "end", it.previous().Number, "sidetd", externTd, "localtd", localTd)

		return nil, it.index, err
	}
	// Gather all the sidechain hashes (full blocks may be memory heavy)
	var (
		hashes  []common.Hash
		numbers []uint64
	)

	parent := it.previous()
	for parent != nil && !bc.HasState(parent.Root) {
		if bc.stateRecoverable(parent.Root) {
			if err := bc.triedb.Recover(parent.Root); err != nil {
				return nil, 0, err
			}
			break
		}
		hashes = append(hashes, parent.Hash())
		numbers = append(numbers, parent.Number.Uint64())

		parent = bc.GetHeader(parent.ParentHash, parent.Number.Uint64()-1)
	}

	if parent == nil {
		return nil, it.index, errors.New("missing parent")
	}
	// Import all the pruned blocks to make the state available
	var (
		blocks []*types.Block
		memory uint64
	)

	for i := len(hashes) - 1; i >= 0; i-- {
		// Append the next block to our batch
		block := bc.GetBlock(hashes[i], numbers[i])

		blocks = append(blocks, block)
		memory += block.Size()

		// If memory use grew too large, import and continue. Sadly we need to discard
		// all raised events and logs from notifications since we're too heavy on the
		// memory here.
		if len(blocks) >= 2048 || memory > 64*1024*1024 {
			log.Info("Importing heavy sidechain segment", "blocks", len(blocks), "start", blocks[0].NumberU64(), "end", block.NumberU64())
			if _, _, err := bc.insertChain(blocks, true, false); err != nil {
				return nil, 0, err
			}

			blocks, memory = blocks[:0], 0

			// If the chain is terminating, stop processing blocks
			if bc.insertStopped() {
				log.Debug("Abort during blocks processing")
				return nil, 0, nil
			}
		}
	}

	if len(blocks) > 0 {
		log.Info("Importing sidechain segment", "start", blocks[0].NumberU64(), "end", blocks[len(blocks)-1].NumberU64())
		return bc.insertChain(blocks, true, makeWitness)
	}
	return nil, 0, nil
}

// recoverAncestors finds the closest ancestor with available state and re-execute
// all the ancestor blocks since that.
// recoverAncestors is only used post-merge.
// We return the hash of the latest block that we could correctly validate.
func (bc *BlockChain) recoverAncestors(block *types.Block, makeWitness bool) (common.Hash, error) {
	// Gather all the sidechain hashes (full blocks may be memory heavy)
	var (
		hashes  []common.Hash
		numbers []uint64
		parent  = block
	)

	for parent != nil && !bc.HasState(parent.Root()) {
		if bc.stateRecoverable(parent.Root()) {
			if err := bc.triedb.Recover(parent.Root()); err != nil {
				return common.Hash{}, err
			}
			break
		}
		hashes = append(hashes, parent.Hash())
		numbers = append(numbers, parent.NumberU64())
		parent = bc.GetBlock(parent.ParentHash(), parent.NumberU64()-1)

		// If the chain is terminating, stop iteration
		if bc.insertStopped() {
			log.Debug("Abort during blocks iteration")
			return common.Hash{}, errInsertionInterrupted
		}
	}

	if parent == nil {
		return common.Hash{}, errors.New("missing parent")
	}
	// Import all the pruned blocks to make the state available
	for i := len(hashes) - 1; i >= 0; i-- {
		// If the chain is terminating, stop processing blocks
		if bc.insertStopped() {
			log.Debug("Abort during blocks processing")
			return common.Hash{}, errInsertionInterrupted
		}

		var b *types.Block
		if i == 0 {
			b = block
		} else {
			b = bc.GetBlock(hashes[i], numbers[i])
		}
		if _, _, err := bc.insertChain(types.Blocks{b}, false, makeWitness && i == 0); err != nil {
			return b.ParentHash(), err
		}
	}

	return block.Hash(), nil
}

// collectLogs collects the logs that were generated or removed during the
// processing of a block. These logs are later announced as deleted or reborn.
func (bc *BlockChain) collectLogs(b *types.Block, removed bool) []*types.Log {
	var blobGasPrice *big.Int
	if b.ExcessBlobGas() != nil {
		blobGasPrice = eip4844.CalcBlobFee(bc.chainConfig, b.Header())
	}
	receipts := rawdb.ReadRawReceipts(bc.db, b.Hash(), b.NumberU64())

	// Append bor receipt
	borReceipt := rawdb.ReadBorReceipt(bc.db, b.Hash(), b.NumberU64(), bc.chainConfig)
	if borReceipt != nil {
		receipts = append(receipts, borReceipt)
	}

	if err := receipts.DeriveFields(bc.chainConfig, b.Hash(), b.NumberU64(), b.Time(), b.BaseFee(), blobGasPrice, b.Transactions()); err != nil {
		log.Error("Failed to derive block receipts fields", "hash", b.Hash(), "number", b.NumberU64(), "err", err)
	}
	var logs []*types.Log

	for _, receipt := range receipts {
		for _, log := range receipt.Logs {
			if removed {
				log.Removed = true
			}
			logs = append(logs, log)
		}
	}

	return logs
}

// reorg takes two blocks, an old chain and a new chain and will reconstruct the
// blocks and inserts them to be part of the new canonical chain and accumulates
// potential missing transactions and post an event about them.
//
// Note the new head block won't be processed here, callers need to handle it
// externally.
func (bc *BlockChain) reorg(oldHead *types.Header, newHead *types.Header) error {
	var (
		newChain    []*types.Header
		oldChain    []*types.Header
		commonBlock *types.Header
	)
	// Reduce the longer chain to the same number as the shorter one
	if oldHead.Number.Uint64() > newHead.Number.Uint64() {
		// Old chain is longer, gather all transactions and logs as deleted ones
		for ; oldHead != nil && oldHead.Number.Uint64() != newHead.Number.Uint64(); oldHead = bc.GetHeader(oldHead.ParentHash, oldHead.Number.Uint64()-1) {
			oldChain = append(oldChain, oldHead)
		}
	} else {
		// New chain is longer, stash all blocks away for subsequent insertion
		for ; newHead != nil && newHead.Number.Uint64() != oldHead.Number.Uint64(); newHead = bc.GetHeader(newHead.ParentHash, newHead.Number.Uint64()-1) {
			newChain = append(newChain, newHead)
		}
	}
	if oldHead == nil {
		return errInvalidOldChain
	}
	if newHead == nil {
		return errInvalidNewChain
	}
	// Both sides of the reorg are at the same number, reduce both until the common
	// ancestor is found
	for {
		// If the common ancestor was found, bail out
		if oldHead.Hash() == newHead.Hash() {
			commonBlock = oldHead
			break
		}
		// Remove an old block as well as stash away a new block
		oldChain = append(oldChain, oldHead)
		newChain = append(newChain, newHead)

		// Step back with both chains
		oldHead = bc.GetHeader(oldHead.ParentHash, oldHead.Number.Uint64()-1)
		if oldHead == nil {
			return errInvalidOldChain
		}
		newHead = bc.GetHeader(newHead.ParentHash, newHead.Number.Uint64()-1)
		if newHead == nil {
			return errInvalidNewChain
		}
	}

	// Ensure the user sees large reorgs
	if len(oldChain) == 0 && len(newChain) == 0 {
		// No actual reorg, same block
		log.Info("No reorg needed; old and new head are identical", "number", oldHead.Number, "hash", oldHead.Hash())
		return nil
	}

	if len(oldChain) > 0 && len(newChain) > 0 {
		bc.chain2HeadFeed.Send(Chain2HeadEvent{
			Type:     Chain2HeadReorgEvent,
			NewChain: newChain,
			OldChain: oldChain,
		})

		logFn := log.Info

		msg := "Chain reorg detected"
		if len(oldChain) > 63 {
			msg = "Large chain reorg detected"
			logFn = log.Warn
		}
		logFn(msg, "number", commonBlock.Number, "hash", commonBlock.Hash(),
			"drop", len(oldChain), "dropfrom", oldChain[0].Hash(), "add", len(newChain), "addfrom", newChain[0].Hash())
		blockReorgAddMeter.Mark(int64(len(newChain)))
		blockReorgDropMeter.Mark(int64(len(oldChain)))
		blockReorgMeter.Mark(1)
	} else if len(newChain) > 0 {
		// Special case happens in the post merge stage that current head is
		// the ancestor of new head while these two blocks are not consecutive
		log.Info("Extend chain", "add", len(newChain), "number", newChain[0].Number, "hash", newChain[0].Hash())
		blockReorgAddMeter.Mark(int64(len(newChain)))
	} else {
		// len(newChain) == 0 && len(oldChain) > 0
		// rewind the canonical chain to a lower point.
		log.Error("Impossible reorg, please file an issue", "oldnum", oldHead.Number, "oldhash", oldHead.Hash(), "oldblocks", len(oldChain), "newnum", newHead.Number, "newhash", newHead.Hash(), "newblocks", len(newChain))
	}
	// Acquire the tx-lookup lock before mutation. This step is essential
	// as the txlookups should be changed atomically, and all subsequent
	// reads should be blocked until the mutation is complete.
	bc.txLookupLock.Lock()

	// Reorg can be executed, start reducing the chain's old blocks and appending
	// the new blocks
	var (
		deletedTxs []common.Hash
		rebirthTxs []common.Hash

		deletedLogs []*types.Log
		rebirthLogs []*types.Log
	)
	// Deleted log emission on the API uses forward order, which is borked, but
	// we'll leave it in for legacy reasons.
	//
	// TODO(karalabe): This should be nuked out, no idea how, deprecate some APIs?
	{
		for i := len(oldChain) - 1; i >= 0; i-- {
			// Also send event for blocks removed from the canon chain. Note: Geth has removed
			// the concept of side chains but we need them in bor.
			bc.chainSideFeed.Send(ChainSideEvent{Header: oldChain[i]})

			block := bc.GetBlock(oldChain[i].Hash(), oldChain[i].Number.Uint64())
			if block == nil {
				return errInvalidOldChain // Corrupt database, mostly here to avoid weird panics
			}
			if logs := bc.collectLogs(block, true); len(logs) > 0 {
				deletedLogs = append(deletedLogs, logs...)
			}
			if len(deletedLogs) > 512 {
				bc.rmLogsFeed.Send(RemovedLogsEvent{deletedLogs})
				deletedLogs = nil
			}
		}
		if len(deletedLogs) > 0 {
			bc.rmLogsFeed.Send(RemovedLogsEvent{deletedLogs})
		}
	}
	// Undo old blocks in reverse order
	for i := 0; i < len(oldChain); i++ {
		// Collect all the deleted transactions
		block := bc.GetBlock(oldChain[i].Hash(), oldChain[i].Number.Uint64())
		if block == nil {
			return errInvalidOldChain // Corrupt database, mostly here to avoid weird panics
		}
		for _, tx := range block.Transactions() {
			deletedTxs = append(deletedTxs, tx.Hash())
		}
		// Collect deleted logs and emit them for new integrations
		if logs := bc.collectLogs(block, true); len(logs) > 0 {
			// Emit revertals latest first, older then
			slices.Reverse(logs)

			// TODO(karalabe): Hook into the reverse emission part
		}
	}
	// Apply new blocks in forward order
	for i := len(newChain) - 1; i >= 1; i-- {
		// Collect all the included transactions
		block := bc.GetBlock(newChain[i].Hash(), newChain[i].Number.Uint64())
		if block == nil {
			return errInvalidNewChain // Corrupt database, mostly here to avoid weird panics
		}
		for _, tx := range block.Transactions() {
			rebirthTxs = append(rebirthTxs, tx.Hash())
		}
		// Collect inserted logs and emit them
		if logs := bc.collectLogs(block, false); len(logs) > 0 {
			rebirthLogs = append(rebirthLogs, logs...)
		}
		if len(rebirthLogs) > 512 {
			bc.logsFeed.Send(rebirthLogs)
			rebirthLogs = nil
		}
		// Update the head block
		bc.writeHeadBlock(block)
	}
	if len(rebirthLogs) > 0 {
		bc.logsFeed.Send(rebirthLogs)
	}
	// Delete useless indexes right now which includes the non-canonical
	// transaction indexes, canonical chain indexes which above the head.
	batch := bc.db.NewBatch()
	for _, tx := range types.HashDifference(deletedTxs, rebirthTxs) {
		rawdb.DeleteTxLookupEntry(batch, tx)
	}
	// Delete all hash markers that are not part of the new canonical chain.
	// Because the reorg function does not handle new chain head, all hash
	// markers greater than or equal to new chain head should be deleted.
	number := commonBlock.Number
	if len(newChain) > 1 {
		number = newChain[1].Number
	}
	for i := number.Uint64() + 1; ; i++ {
		hash := rawdb.ReadCanonicalHash(bc.db, i)
		if hash == (common.Hash{}) {
			break
		}
		rawdb.DeleteCanonicalHash(batch, i)
	}
	if err := batch.Write(); err != nil {
		log.Crit("Failed to delete useless indexes", "err", err)
	}
	// Reset the tx lookup cache to clear stale txlookup cache.
	bc.txLookupCache.Purge()

	// Release the tx-lookup lock after mutation.
	bc.txLookupLock.Unlock()

	return nil
}

// InsertBlockWithoutSetHead executes the block, runs the necessary verification
// upon it and then persist the block and the associate state into the database.
// The key difference between the InsertChain is it won't do the canonical chain
// updating. It relies on the additional SetCanonical call to finalize the entire
// procedure.
func (bc *BlockChain) InsertBlockWithoutSetHead(block *types.Block, makeWitness bool) (*stateless.Witness, error) {
	if !bc.chainmu.TryLock() {
		return nil, errChainStopped
	}
	defer bc.chainmu.Unlock()

	witness, _, err := bc.insertChain(types.Blocks{block}, false, makeWitness)
	return witness, err
}

// SetCanonical rewinds the chain to set the new head block as the specified
// block. It's possible that the state of the new head is missing, and it will
// be recovered in this function as well.
func (bc *BlockChain) SetCanonical(head *types.Block) (common.Hash, error) {
	if !bc.chainmu.TryLock() {
		return common.Hash{}, errChainStopped
	}
	defer bc.chainmu.Unlock()

	// Re-execute the reorged chain in case the head state is missing.
	if !bc.HasState(head.Root()) {
		if latestValidHash, err := bc.recoverAncestors(head, false); err != nil {
			return latestValidHash, err
		}

		log.Info("Recovered head state", "number", head.Number(), "hash", head.Hash())
	}
	// Run the reorg if necessary and set the given block as new head.
	start := time.Now()

	if head.ParentHash() != bc.CurrentBlock().Hash() {
		if err := bc.reorg(bc.CurrentBlock(), head.Header()); err != nil {
			return common.Hash{}, err
		}
	}

	bc.writeHeadBlock(head)

	// Emit events
	logs := bc.collectLogs(head, false)
	bc.chainFeed.Send(ChainEvent{Header: head.Header()})
	if len(logs) > 0 {
		bc.logsFeed.Send(logs)
	}
	bc.chainHeadFeed.Send(ChainHeadEvent{Header: head.Header()})

	context := []interface{}{
		"number", head.Number(),
		"hash", head.Hash(),
		"root", head.Root(),
		"elapsed", time.Since(start),
	}
	if timestamp := time.Unix(int64(head.Time()), 0); time.Since(timestamp) > time.Minute {
		context = append(context, []interface{}{"age", common.PrettyAge(timestamp)}...)
	}

	log.Info("Chain head was updated", context...)

	return head.Hash(), nil
}

// skipBlock returns 'true', if the block being imported can be skipped over, meaning
// that the block does not need to be processed but can be considered already fully 'done'.
func (bc *BlockChain) skipBlock(err error, it *insertIterator) bool {
	// We can only ever bypass processing if the only error returned by the validator
	// is ErrKnownBlock, which means all checks passed, but we already have the block
	// and state.
	if !errors.Is(err, ErrKnownBlock) {
		return false
	}
	// If we're not using snapshots, we can skip this, since we have both block
	// and (trie-) state
	if bc.snaps == nil {
		return true
	}

	var (
		header     = it.current() // header can't be nil
		parentRoot common.Hash
	)
	// If we also have the snapshot-state, we can skip the processing.
	if bc.snaps.Snapshot(header.Root) != nil {
		return true
	}
	// In this case, we have the trie-state but not snapshot-state. If the parent
	// snapshot-state exists, we need to process this in order to not get a gap
	// in the snapshot layers.
	// Resolve parent block
	if parent := it.previous(); parent != nil {
		parentRoot = parent.Root
	} else if parent = bc.GetHeaderByHash(header.ParentHash); parent != nil {
		parentRoot = parent.Root
	}

	if parentRoot == (common.Hash{}) {
		return false // Theoretically impossible case
	}
	// Parent is also missing snapshot: we can skip this. Otherwise process.
	if bc.snaps.Snapshot(parentRoot) == nil {
		return true
	}

	return false
}

// reportBlock logs a bad block error.
func (bc *BlockChain) reportBlock(block *types.Block, res *ProcessResult, err error) {
	var receipts types.Receipts
	if res != nil {
		receipts = res.Receipts
	}
	rawdb.WriteBadBlock(bc.db, block)
	log.Error(summarizeBadBlock(block, receipts, bc.Config(), err))
}

/*
// logForkReadiness will write a log when a future fork is scheduled, but not
// active. This is useful so operators know their client is ready for the fork.
func (bc *BlockChain) logForkReadiness(block *types.Block) {
	c := bc.Config()
	current, last := c.LatestFork(block.Time()), c.LatestFork(math.MaxUint64)
	t := c.Timestamp(last)
	if t == nil {
		return
	}
	at := time.Unix(int64(*t), 0)
	if current < last && time.Now().After(bc.lastForkReadyAlert.Add(forkReadyInterval)) {
		log.Info("Ready for fork activation", "fork", last, "date", at.Format(time.RFC822),
			"remaining", time.Until(at).Round(time.Second), "timestamp", at.Unix())
		bc.lastForkReadyAlert = time.Now()
	}
}
*/

// summarizeBadBlock returns a string summarizing the bad block and other
// relevant information.
func summarizeBadBlock(block *types.Block, receipts []*types.Receipt, config *params.ChainConfig, err error) string {
	var receiptString string
	for i, receipt := range receipts {
		receiptString += fmt.Sprintf("\n  %d: cumulative: %v gas: %v contract: %v status: %v tx: %v logs: %v bloom: %x state: %x",
			i, receipt.CumulativeGasUsed, receipt.GasUsed, receipt.ContractAddress.Hex(),
			receipt.Status, receipt.TxHash.Hex(), receipt.Logs, receipt.Bloom, receipt.PostState)
	}

	version, vcs := version.Info()
	platform := fmt.Sprintf("%s %s %s %s", version, runtime.Version(), runtime.GOARCH, runtime.GOOS)

	if vcs != "" {
		vcs = fmt.Sprintf("\nVCS: %s", vcs)
	}

	return fmt.Sprintf(`
########## BAD BLOCK #########
Block: %v (%#x)
Error: %v
Platform: %v%v
Chain config: %#v
Receipts: %v
##############################
`, block.Number(), block.Hash(), err, platform, vcs, config, receiptString)
}

// InsertHeaderChain attempts to insert the given header chain in to the local
// chain, possibly creating a reorg. If an error is returned, it will return the
// index number of the failing header as well an error describing what went wrong.
func (bc *BlockChain) InsertHeaderChain(chain []*types.Header) (int, error) {
	if len(chain) == 0 {
		return 0, nil
	}

	start := time.Now()
	if i, err := bc.hc.ValidateHeaderChain(chain); err != nil {
		return i, err
	}

	if !bc.chainmu.TryLock() {
		return 0, errChainStopped
	}
	defer bc.chainmu.Unlock()
	_, err := bc.hc.InsertHeaderChain(chain, start, bc.forker)
	return 0, err
}

func (bc *BlockChain) InsertHeaderChainWithoutValidation(chain []*types.Header) (int, error) {
	if len(chain) == 0 {
		return 0, nil
	}

	if !bc.chainmu.TryLock() {
		return 0, errChainStopped
	}
	defer bc.chainmu.Unlock()

	count, err := bc.hc.WriteHeaders(chain)
	return count, err
}

func (bc *BlockChain) GetChainConfig() *params.ChainConfig {
	return bc.chainConfig
}

// SetBlockValidatorAndProcessorForTesting sets the current validator and processor.
// This method can be used to force an invalid blockchain to be verified for tests.
// This method is unsafe and should only be used before block import starts.
func (bc *BlockChain) SetBlockValidatorAndProcessorForTesting(v Validator, p Processor) {
	bc.validator = v
	bc.processor = p
}

// SetTrieFlushInterval configures how often in-memory tries are persisted to disk.
// The interval is in terms of block processing time, not wall clock.
// It is thread-safe and can be called repeatedly without side effects.
func (bc *BlockChain) SetTrieFlushInterval(interval time.Duration) {
	bc.flushInterval.Store(int64(interval))
}

// GetTrieFlushInterval gets the in-memory tries flushAlloc interval
func (bc *BlockChain) GetTrieFlushInterval() time.Duration {
	return time.Duration(bc.flushInterval.Load())
}

func (bc *BlockChain) SubscribeChain2HeadEvent(ch chan<- Chain2HeadEvent) event.Subscription {
	return bc.scope.Track(bc.chain2HeadFeed.Subscribe(ch))
}

// ProcessBlockWithWitnesses processes a block in stateless mode using the provided witnesses.
func (bc *BlockChain) ProcessBlockWithWitnesses(block *types.Block, witness *stateless.Witness) (*state.StateDB, *ProcessResult, error) {
	if witness == nil {
		return nil, nil, errors.New("nil witness")
	}

	// Validate witness.
	if err := stateless.ValidateWitnessPreState(witness, bc); err != nil {
		log.Error("Witness validation failed during stateless processing", "blockNumber", block.Number(), "blockHash", block.Hash(), "err", err)
		return nil, nil, fmt.Errorf("witness validation failed: %w", err)
	}

	// Remove critical computed fields from the block to force true recalculation
	context := block.Header()
	context.Root = common.Hash{}
	context.ReceiptHash = common.Hash{}

	task := types.NewBlockWithHeader(context).WithBody(*block.Body())

	// Bor: Calculate EvmBlockContext with Root and ReceiptHash to properly get the author
	author := NewEVMBlockContext(block.Header(), bc.hc, nil).Coinbase

	crossStateRoot, crossReceiptRoot, statedb, res, err := ExecuteStateless(bc.chainConfig, bc.vmConfig, task, witness, &author, bc.engine, bc.statedb.TrieDB().Disk())

	// Currently, we don't return the error, because we don't have a way to handle Span update statelessly
	// TODO: Return the error once we have a way to handle Span update
	if err != nil {
		log.Error("Stateless self-validation failed", "block", block.Number(), "hash", block.Hash(), "error", err)
		return nil, nil, err
	}
	if crossStateRoot != block.Root() {
		log.Error("Stateless self-validation root mismatch", "block", block.Number(), "hash", block.Hash(), "cross", crossStateRoot, "local", block.Root())
		err = fmt.Errorf("stateless self-validation state root mismatch: remote %x != local %x", block.Root(), crossStateRoot)
		return nil, nil, err
	}
	if crossReceiptRoot != block.ReceiptHash() {
		log.Error("Stateless self-validation receipt root mismatch", "block", block.Number(), "hash", block.Hash(), "cross", crossReceiptRoot, "local", block.ReceiptHash())
		err = fmt.Errorf("stateless self-validation receipt root mismatch: remote %x != local %x", block.ReceiptHash(), crossReceiptRoot)
		return nil, nil, err
	}
	return statedb, res, nil
}

// startHeaderVerificationLoop starts a background goroutine that periodically
// verifies headers after the latest finalized block and rewinds the chain if
// invalid headers are detected.
func (bc *BlockChain) startHeaderVerificationLoop() {
	if bc.checker == nil {
		return // No checker available
	}

	bc.wg.Add(1)
	go func() {
		defer bc.wg.Done()
		ticker := time.NewTicker(2 * time.Second)
		defer ticker.Stop()

		log.Info("Started header verification loop")

		for {
			select {
			case <-bc.quit:
				log.Info("Stopping header verification loop")
				return
			case <-ticker.C:
				bc.verifyPendingHeaders()
			}
		}
	}()
}

// verifyPendingHeaders checks headers after the latest finalized block
// and rewinds the chain if invalid headers are found.
func (bc *BlockChain) verifyPendingHeaders() {
	// Get the latest finalized block
	hasMilestone, milestoneNumber, _ := bc.checker.GetWhitelistedMilestone()
	if !hasMilestone {
		return // No finalized block yet
	}

	currentHead := bc.CurrentBlock()
	if currentHead.Number.Uint64() <= milestoneNumber {
		return // Nothing to verify
	}

	chainConfig := bc.Config()

	// We don't need to verify headers before Rio
	if chainConfig.Bor == nil || !chainConfig.Bor.IsRio(currentHead.Number) {
		return // Rio is not enabled yet
	}

	// Collect headers from finalized block + 1 to current head
	var headers []*types.Header
	for i := milestoneNumber + 1; i <= currentHead.Number.Uint64(); i++ {
		header := bc.GetHeaderByNumber(i)
		if header == nil {
			log.Debug("Missing header during verification", "number", i)
			return // Missing header, skip verification
		}
		headers = append(headers, header)
	}

	if len(headers) == 0 {
		return
	}

	log.Debug("Verifying pending headers", "from", headers[0].Number.Uint64(),
		"to", headers[len(headers)-1].Number.Uint64(), "count", len(headers))

	// Verify headers
	abort, results := bc.engine.VerifyHeaders(bc, headers)
	defer close(abort)

	// Check results and find the last valid header
	lastValidNumber := milestoneNumber
	for _, header := range headers {
		select {
		case <-bc.quit:
			return
		case err := <-results:
			if err != nil {
				log.Warn("Invalid header detected during background verification",
					"number", header.Number.Uint64(), "hash", header.Hash(), "err", err)
				// Rewind to the last valid block
				if lastValidNumber < currentHead.Number.Uint64() {
					log.Warn("Rewinding chain due to invalid header",
						"from", currentHead.Number.Uint64(), "to", lastValidNumber)
					if err := bc.SetHead(lastValidNumber); err != nil {
						log.Error("Failed to rewind chain", "err", err)
					}
				}
				return
			}
			lastValidNumber = header.Number.Uint64()
		}
	}
}
