// Copyright 2017 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 consensus implements different Ethereum consensus engines.
package consensus

import (
	"context"
	"math/big"

	"github.com/autonity/autonity/common/fixsizecache"
	"github.com/autonity/autonity/p2p/enode"

	"github.com/autonity/autonity/common"
	"github.com/autonity/autonity/core/state"
	"github.com/autonity/autonity/core/types"
	"github.com/autonity/autonity/p2p"
	"github.com/autonity/autonity/params"
	"github.com/autonity/autonity/rpc"
)

// ChainHeaderReader defines a small collection of methods needed to access the local
// blockchain during header verification.
type ChainHeaderReader interface {
	// Config retrieves the blockchain's chain configuration.
	Config() *params.ChainConfig

	// CurrentHeader retrieves the current header from the local chain.
	CurrentHeader() *types.Header

	// GetHeader retrieves a block header from the database by hash and number.
	GetHeader(hash common.Hash, number uint64) *types.Header

	// GetHeaderByNumber retrieves a block header from the database by number.
	GetHeaderByNumber(number uint64) *types.Header

	// GetHeaderByHash retrieves a block header from the database by its hash.
	GetHeaderByHash(hash common.Hash) *types.Header

	// GetTd retrieves the total difficulty from the database by hash and number.
	GetTd(hash common.Hash, number uint64) *big.Int

	EpochByHeight(height uint64) (*types.EpochInfo, error)
}

type HeaderWithStateFn func() (*types.Header, *state.StateDB, error)

// ChainReader defines a small collection of methods needed to access the local
// blockchain during header and/or uncle verification.
type ChainReader interface {
	ChainHeaderReader

	// GetBlock retrieves a block from the database by hash and number.
	GetBlock(hash common.Hash, number uint64) *types.Block

	// Engine retrieves the chain's consensus engine.
	Engine() Engine

	Eip1559ParamsByHeight(height uint64) (*types.Eip1559Params, error)
}

// Engine is an algorithm agnostic consensus engine.
type Engine interface {
	// Author retrieves the Ethereum address of the account that minted the given
	// block, which may be different from the header's coinbase if a consensus
	// engine is based on signatures.
	Author(header *types.Header) (common.Address, error)

	// VerifyHeader checks whether a header conforms to the consensus rules of a
	// given engine. Verifying the seal may be done optionally here, or explicitly
	// via the VerifySeal method.
	VerifyHeader(chain ChainHeaderReader, header *types.Header, seal bool) error

	// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
	// concurrently. The method returns a quit channel to abort the operations and
	// a results channel to retrieve the async verifications (the order is that of
	// the input slice).
	VerifyHeaders(chain ChainHeaderReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error)

	// VerifyUncles verifies that the given block's uncles conform to the consensus
	// rules of a given engine.
	VerifyUncles(chain ChainReader, block *types.Block) error

	// Prepare initializes the consensus fields of a block header according to the
	// rules of a particular engine. The changes are executed inline.
	Prepare(chain ChainHeaderReader, parentHeader, header *types.Header, parentState *state.StateDB) error

	// Finalize runs any post-transaction state modifications (e.g. block rewards)
	// but does not assemble the block.
	//
	// Note: The block header and state database might be updated to reflect any
	// consensus rules that happen at finalization (e.g. block rewards).
	Finalize(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
		uncles []*types.Header, receipts []*types.Receipt) (*types.Receipt, *types.Epoch, *types.ContractsConfig, error)

	// FinalizeAndAssemble runs any post-transaction state modifications (e.g. block
	// rewards) and assembles the final block.
	//
	// Note: The block header and state database might be updated to reflect any
	// consensus rules that happen at finalization (e.g. block rewards).
	FinalizeAndAssemble(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
		uncles []*types.Header, receipts *[]*types.Receipt) (*types.Block, *types.ContractsConfig, error)

	// Seal generates a new sealing request for the given input block and pushes
	// the result into the given channel.
	//
	// Note, the method returns immediately and will send the result async. More
	// than one result may also be returned depending on the consensus algorithm.
	Seal(parent *types.Header, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error

	// SealHash returns the hash of a block prior to it being sealed.
	SealHash(header *types.Header) common.Hash

	// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
	// that a new block should have.
	CalcDifficulty(chain ChainHeaderReader, time uint64, parent *types.Header) *big.Int

	// APIs returns the RPC APIs this consensus engine provides.
	APIs(chain ChainReader) []rpc.API

	// Close terminates any background threads maintained by the consensus engine.
	Close() error

	// SetResultChan sets the result channel to handle sealing result
	SetResultChan(results chan<- *types.Block)

	// SetProposalVerifiedEventCh sets the proposal verified event channel to trigger new block preparation
	SetProposalVerifiedEventChan(proposalVerifiedEventCh chan<- *types.Block)
}

// Handler should be implemented is the consensus needs to handle and send peer's message
type Handler interface {
	// NewChainHead handles a new head block comes
	NewChainHead() error

	// HandleMsg handles a message from peer
	HandleMsg(address common.Address, data p2p.Msg, errCh chan<- error) (bool, error)

	// SetBroadcaster sets the broadcaster to send message to peers
	SetBroadcaster(Broadcaster)

	// SetEnqueuer sets the enqueuer to inject blocks in import queue
	SetEnqueuer(Enqueuer)
}

// PoW is a consensus engine based on proof-of-work.
type PoW interface {
	Engine

	// Hashrate returns the current mining hashrate of a PoW consensus engine.
	Hashrate() float64
}

// BFT is a consensus engine to avoid byzantine failure
type BFT interface {
	Engine

	// Start starts the engine
	Start(ctx context.Context) error
}

type Syncer interface {
	SyncPeer(address common.Address)
}

// Enqueuer defines the interface to enqueue blocks to fetcher
type Enqueuer interface {
	Enqueue(id string, block *types.Block)
}

// Broadcaster defines the interface to find peer
type Broadcaster interface {
	// FindPeers retrieves connected peers by addresses
	FindPeers([]common.Address) map[common.Address]Peer

	FindPeer(common.Address) (Peer, bool)

	CommitteeEnodes() []*enode.Node
}

// Peer defines the interface to communicate with peer
type Peer interface {
	// Send sends the message to this peer
	Send(msgcode uint64, data interface{}) error

	SendRaw(msgcode uint64, data []byte) error

	Cache() *fixsizecache.Cache[common.Hash, bool]
}
