// Copyright 2024 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 state

import (
	"maps"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/trie/trienode"
	"github.com/ethereum/go-ethereum/triedb"
)

// contractCode represents a contract code with associated metadata.
type contractCode struct {
	hash common.Hash // hash is the cryptographic hash of the contract code.
	blob []byte      // blob is the binary representation of the contract code.
}

// accountDelete represents an operation for deleting an Ethereum account.
type accountDelete struct {
	address common.Address // address is the unique account identifier
	origin  []byte         // origin is the original value of account data in slim-RLP encoding.

	// storages stores mutated slots, the value should be nil.
	storages map[common.Hash][]byte

	// storagesOrigin stores the original values of mutated slots in
	// prefix-zero-trimmed RLP format. The map key refers to the **HASH**
	// of the raw storage slot key.
	storagesOrigin map[common.Hash][]byte
}

// accountUpdate represents an operation for updating an Ethereum account.
type accountUpdate struct {
	address  common.Address         // address is the unique account identifier
	data     []byte                 // data is the slim-RLP encoded account data.
	origin   []byte                 // origin is the original value of account data in slim-RLP encoding.
	code     *contractCode          // code represents mutated contract code; nil means it's not modified.
	storages map[common.Hash][]byte // storages stores mutated slots in prefix-zero-trimmed RLP format.

	// storagesOriginByKey and storagesOriginByHash both store the original values
	// of mutated slots in prefix-zero-trimmed RLP format. The difference is that
	// storagesOriginByKey uses the **raw** storage slot key as the map ID, while
	// storagesOriginByHash uses the **hash** of the storage slot key instead.
	storagesOriginByKey  map[common.Hash][]byte
	storagesOriginByHash map[common.Hash][]byte
}

// stateUpdate represents the difference between two states resulting from state
// execution. It contains information about mutated contract codes, accounts,
// and storage slots, along with their original values.
type stateUpdate struct {
	originRoot     common.Hash               // hash of the state before applying mutation
	root           common.Hash               // hash of the state after applying mutation
	accounts       map[common.Hash][]byte    // accounts stores mutated accounts in 'slim RLP' encoding
	accountsOrigin map[common.Address][]byte // accountsOrigin stores the original values of mutated accounts in 'slim RLP' encoding

	// storages stores mutated slots in 'prefix-zero-trimmed' RLP format.
	// The value is keyed by account hash and **storage slot key hash**.
	storages map[common.Hash]map[common.Hash][]byte

	// storagesOrigin stores the original values of mutated slots in
	// 'prefix-zero-trimmed' RLP format.
	// (a) the value is keyed by account hash and **storage slot key** if rawStorageKey is true;
	// (b) the value is keyed by account hash and **storage slot key hash** if rawStorageKey is false;
	storagesOrigin map[common.Address]map[common.Hash][]byte
	rawStorageKey  bool

	codes map[common.Address]contractCode // codes contains the set of dirty codes
	nodes *trienode.MergedNodeSet         // Aggregated dirty nodes caused by state changes
}

// empty returns a flag indicating the state transition is empty or not.
func (sc *stateUpdate) empty() bool {
	return sc.originRoot == sc.root
}

// newStateUpdate constructs a state update object by identifying the differences
// between two states through state execution. It combines the specified account
// deletions and account updates to create a complete state update.
//
// rawStorageKey is a flag indicating whether to use the raw storage slot key or
// the hash of the slot key for constructing state update object.
func newStateUpdate(rawStorageKey bool, originRoot common.Hash, root common.Hash, deletes map[common.Hash]*accountDelete, updates map[common.Hash]*accountUpdate, nodes *trienode.MergedNodeSet) *stateUpdate {
	var (
		accounts       = make(map[common.Hash][]byte)
		accountsOrigin = make(map[common.Address][]byte)
		storages       = make(map[common.Hash]map[common.Hash][]byte)
		storagesOrigin = make(map[common.Address]map[common.Hash][]byte)
		codes          = make(map[common.Address]contractCode)
		destructsAddrs = make(map[common.Address]struct{})
	)
	// Since some accounts might be destroyed and recreated within the same
	// block, deletions must be aggregated first.
	for addrHash, op := range deletes {
		addr := op.address
		accounts[addrHash] = nil
		destructsAddrs[addr] = struct{}{}
		accountsOrigin[addr] = op.origin

		// If storage wiping exists, the hash of the storage slot key must be used
		if len(op.storages) > 0 {
			storages[addrHash] = op.storages
		}
		if len(op.storagesOrigin) > 0 {
			storagesOrigin[addr] = op.storagesOrigin
		}
	}
	// Aggregate account updates then.
	for addrHash, op := range updates {
		// Aggregate dirty contract codes if they are available.
		addr := op.address
		if op.code != nil {
			codes[addr] = *op.code
		}
		accounts[addrHash] = op.data

		// Aggregate the account original value. If the account is already
		// present in the aggregated accountsOrigin set, skip it.
		if _, found := accountsOrigin[addr]; !found {
			accountsOrigin[addr] = op.origin
		}
		// Aggregate the storage mutation list. If a slot in op.storages is
		// already present in aggregated storages set, the value will be
		// overwritten.
		if len(op.storages) > 0 {
			if _, exist := storages[addrHash]; !exist {
				storages[addrHash] = op.storages
			} else {
				maps.Copy(storages[addrHash], op.storages)
			}
		}
		// Aggregate the storage original values. If the slot is already present
		// in aggregated storagesOrigin set, skip it.
		storageOriginSet := op.storagesOriginByHash
		if rawStorageKey {
			storageOriginSet = op.storagesOriginByKey
		}
		if len(storageOriginSet) > 0 {
			origin, exist := storagesOrigin[addr]
			if !exist {
				storagesOrigin[addr] = storageOriginSet
			} else {
				for key, slot := range storageOriginSet {
					if _, found := origin[key]; !found {
						origin[key] = slot
					}
				}
			}
		}
	}
	sc := &stateUpdate{
		originRoot:     originRoot,
		root:           root,
		accounts:       accounts,
		accountsOrigin: accountsOrigin,
		storages:       storages,
		storagesOrigin: storagesOrigin,
		rawStorageKey:  rawStorageKey,
		codes:          codes,
		nodes:          nodes,
	}

	return sc
}

// stateSet converts the current stateUpdate object into a triedb.StateSet
// object. This function extracts the necessary data from the stateUpdate
// struct and formats it into the StateSet structure consumed by the triedb
// package.
func (sc *stateUpdate) stateSet() *triedb.StateSet {
	return &triedb.StateSet{
		Accounts:       sc.accounts,
		AccountsOrigin: sc.accountsOrigin,
		Storages:       sc.storages,
		StoragesOrigin: sc.storagesOrigin,
		RawStorageKey:  sc.rawStorageKey,
	}
}
