package eth1

import (
	"context"
	"errors"
	"math/big"

	"github.com/ledgerwatch/erigon-lib/chain"
	libcommon "github.com/ledgerwatch/erigon-lib/common"
	"github.com/ledgerwatch/erigon-lib/gointerfaces"
	"github.com/ledgerwatch/erigon-lib/gointerfaces/execution"
	"github.com/ledgerwatch/log/v3"
	"golang.org/x/sync/semaphore"
	"google.golang.org/protobuf/types/known/emptypb"

	"github.com/ledgerwatch/erigon-lib/kv"
	"github.com/ledgerwatch/erigon/common/math"
	"github.com/ledgerwatch/erigon/consensus"
	"github.com/ledgerwatch/erigon/core"
	"github.com/ledgerwatch/erigon/core/rawdb"
	"github.com/ledgerwatch/erigon/core/types"
	"github.com/ledgerwatch/erigon/eth/stagedsync"
	"github.com/ledgerwatch/erigon/turbo/builder"
	"github.com/ledgerwatch/erigon/turbo/engineapi/engine_helpers"
	"github.com/ledgerwatch/erigon/turbo/engineapi/engine_types"
	"github.com/ledgerwatch/erigon/turbo/services"
	"github.com/ledgerwatch/erigon/turbo/shards"
	"github.com/ledgerwatch/erigon/turbo/stages"
)

const maxBlocksLookBehind = 32

// EthereumExecutionModule describes ethereum execution logic and indexing.
type EthereumExecutionModule struct {
	// Snapshots + MDBX
	blockReader services.FullBlockReader

	// MDBX database
	db                kv.RwDB // main database
	semaphore         *semaphore.Weighted
	executionPipeline *stagedsync.Sync
	forkValidator     *engine_helpers.ForkValidator

	logger log.Logger
	// Block building
	nextPayloadId  uint64
	lastParameters *core.BlockBuilderParameters
	builderFunc    builder.BlockBuilderFunc
	builders       map[uint64]*builder.BlockBuilder

	// Changes accumulator
	hook                *stages.Hook
	accumulator         *shards.Accumulator
	stateChangeConsumer shards.StateChangeConsumer

	// configuration
	config    *chain.Config
	historyV3 bool
	// consensus
	engine consensus.Engine

	execution.UnimplementedExecutionServer
}

func NewEthereumExecutionModule(blockReader services.FullBlockReader, db kv.RwDB, executionPipeline *stagedsync.Sync, forkValidator *engine_helpers.ForkValidator,
	config *chain.Config, builderFunc builder.BlockBuilderFunc, hook *stages.Hook, accumulator *shards.Accumulator, stateChangeConsumer shards.StateChangeConsumer, logger log.Logger, engine consensus.Engine, historyV3 bool) *EthereumExecutionModule {
	return &EthereumExecutionModule{
		blockReader:         blockReader,
		db:                  db,
		executionPipeline:   executionPipeline,
		logger:              logger,
		forkValidator:       forkValidator,
		builders:            make(map[uint64]*builder.BlockBuilder),
		builderFunc:         builderFunc,
		config:              config,
		semaphore:           semaphore.NewWeighted(1),
		hook:                hook,
		accumulator:         accumulator,
		stateChangeConsumer: stateChangeConsumer,
		engine:              engine,
	}
}

func (e *EthereumExecutionModule) getHeader(ctx context.Context, tx kv.Tx, blockHash libcommon.Hash, blockNumber uint64) (*types.Header, error) {
	td, err := rawdb.ReadTd(tx, blockHash, blockNumber)
	if err != nil {
		return nil, err
	}
	if td == nil {
		return nil, nil
	}
	if e.blockReader == nil {
		return rawdb.ReadHeader(tx, blockHash, blockNumber), nil
	}
	return e.blockReader.Header(ctx, tx, blockHash, blockNumber)
}

func (e *EthereumExecutionModule) getTD(ctx context.Context, tx kv.Tx, blockHash libcommon.Hash, blockNumber uint64) (*big.Int, error) {
	return rawdb.ReadTd(tx, blockHash, blockNumber)

}

func (e *EthereumExecutionModule) getBody(ctx context.Context, tx kv.Tx, blockHash libcommon.Hash, blockNumber uint64) (*types.Body, error) {
	td, err := rawdb.ReadTd(tx, blockHash, blockNumber)
	if err != nil {
		return nil, err
	}
	if td == nil {
		return nil, nil
	}
	if e.blockReader == nil {
		body, _, _ := rawdb.ReadBody(tx, blockHash, blockNumber)
		return body, nil
	}
	return e.blockReader.BodyWithTransactions(ctx, tx, blockHash, blockNumber)
}

func (e *EthereumExecutionModule) canonicalHash(ctx context.Context, tx kv.Tx, blockNumber uint64) (libcommon.Hash, error) {
	var canonical libcommon.Hash
	var err error
	if e.blockReader == nil {
		canonical, err = rawdb.ReadCanonicalHash(tx, blockNumber)
	} else {
		canonical, err = e.blockReader.CanonicalHash(ctx, tx, blockNumber)
	}
	if err != nil {
		return libcommon.Hash{}, err
	}

	td, err := rawdb.ReadTd(tx, canonical, blockNumber)
	if err != nil {
		return libcommon.Hash{}, err
	}
	if td == nil {
		return libcommon.Hash{}, nil
	}
	return canonical, nil

}

func (e *EthereumExecutionModule) ValidateChain(ctx context.Context, req *execution.ValidationRequest) (*execution.ValidationReceipt, error) {
	if !e.semaphore.TryAcquire(1) {
		return &execution.ValidationReceipt{
			LatestValidHash:  gointerfaces.ConvertHashToH256(libcommon.Hash{}),
			ValidationStatus: execution.ExecutionStatus_Busy,
		}, nil
	}
	defer e.semaphore.Release(1)
	tx, err := e.db.BeginRw(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()
	e.forkValidator.ClearWithUnwind(e.accumulator, e.stateChangeConsumer)
	blockHash := gointerfaces.ConvertH256ToHash(req.Hash)
	header, err := e.blockReader.Header(ctx, tx, blockHash, req.Number)
	if err != nil {
		return nil, err
	}

	body, err := e.blockReader.BodyWithTransactions(ctx, tx, blockHash, req.Number)
	if err != nil {
		return nil, err
	}

	if header == nil || body == nil {
		return &execution.ValidationReceipt{
			LatestValidHash:  gointerfaces.ConvertHashToH256(libcommon.Hash{}),
			ValidationStatus: execution.ExecutionStatus_MissingSegment,
		}, nil
	}
	currentBlockNumber := rawdb.ReadCurrentBlockNumber(tx)

	if math.AbsoluteDifference(*currentBlockNumber, req.Number) >= maxBlocksLookBehind {
		return &execution.ValidationReceipt{
			ValidationStatus: execution.ExecutionStatus_TooFarAway,
			LatestValidHash:  gointerfaces.ConvertHashToH256(libcommon.Hash{}),
		}, tx.Commit()
	}

	currentHeadHash := rawdb.ReadHeadHeaderHash(tx)

	extendingHash := e.forkValidator.ExtendingForkHeadHash()
	extendCanonical := extendingHash == libcommon.Hash{} && header.ParentHash == currentHeadHash

	status, lvh, validationError, criticalError := e.forkValidator.ValidatePayload(tx, header, body.RawBody(), extendCanonical)
	if criticalError != nil {
		return nil, criticalError
	}

	// if the block is deemed invalid then we delete it. perhaps we want to keep bad blocks and just keep an index of bad ones.
	validationStatus := execution.ExecutionStatus_Success
	if status == engine_types.AcceptedStatus {
		validationStatus = execution.ExecutionStatus_MissingSegment
	}
	isInvalidChain := status == engine_types.InvalidStatus || status == engine_types.InvalidBlockHashStatus || validationError != nil
	if isInvalidChain && (lvh != libcommon.Hash{}) && lvh != blockHash {
		if err := e.purgeBadChain(ctx, tx, lvh, blockHash); err != nil {
			return nil, err
		}
	}
	if isInvalidChain {
		e.logger.Warn("ethereumExecutionModule.ValidateChain: chain is invalid", "hash", libcommon.Hash(blockHash))
		validationStatus = execution.ExecutionStatus_BadBlock
	}
	return &execution.ValidationReceipt{
		ValidationStatus: validationStatus,
		LatestValidHash:  gointerfaces.ConvertHashToH256(lvh),
	}, tx.Commit()
}

func (e *EthereumExecutionModule) purgeBadChain(ctx context.Context, tx kv.RwTx, latestValidHash, headHash libcommon.Hash) error {
	tip := rawdb.ReadHeaderNumber(tx, headHash)

	currentHash := headHash
	currentNumber := *tip
	for currentHash != latestValidHash {
		currentHeader, err := e.getHeader(ctx, tx, currentHash, currentNumber)
		if err != nil {
			return err
		}
		rawdb.DeleteHeader(tx, currentHash, currentNumber)
		currentHash = currentHeader.ParentHash
		currentNumber--
	}
	return nil
}

func (e *EthereumExecutionModule) Start(ctx context.Context) {
	e.semaphore.Acquire(ctx, 1)
	defer e.semaphore.Release(1)
	// Run the forkchoice
	if err := e.executionPipeline.Run(e.db, nil, true); err != nil {
		if !errors.Is(err, context.Canceled) {
			e.logger.Error("Could not start execution service", "err", err)
		}
		return
	}
	if err := e.executionPipeline.RunPrune(e.db, nil, true); err != nil {
		if !errors.Is(err, context.Canceled) {
			e.logger.Error("Could not start execution service", "err", err)
		}
		return
	}
}

func (e *EthereumExecutionModule) Ready(context.Context, *emptypb.Empty) (*execution.ReadyResponse, error) {
	if !e.semaphore.TryAcquire(1) {
		return &execution.ReadyResponse{Ready: false}, nil
	}
	defer e.semaphore.Release(1)
	return &execution.ReadyResponse{Ready: true}, nil
}