package eth

import (
	"context"
	"errors"
	"fmt"
	"hash"
	"math/big"
	"time"

	"github.com/DeBankDeFi/eth/txtrace"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/eth/tracers"
	"github.com/ethereum/go-ethereum/internal/ethapi"
	"github.com/ethereum/go-ethereum/rpc"
	"golang.org/x/crypto/sha3"
)

type helpHash struct {
	hashed hash.Hash
}

func newHash() *helpHash {

	return &helpHash{hashed: sha3.NewLegacyKeccak256()}
}

func (h *helpHash) Reset() {
	h.hashed.Reset()
}

func (h *helpHash) Update(key, val []byte) {
	h.hashed.Write(key)
	h.hashed.Write(val)
}

func (h *helpHash) Hash() common.Hash {
	return common.BytesToHash(h.hashed.Sum(nil))
}

type PreExecTx struct {
	ChainId                                     *big.Int
	From, To, Data, Value, Gas, GasPrice, Nonce string
}

type preData struct {
	block   *types.Block
	tx      *types.Transaction
	msg     types.Message
	stateDb *state.StateDB
	header  *types.Header
}

// PreExecAPI provides pre exec info for rpc
type PreExecAPI struct {
	e *Ethereum
}

func NewPreExecAPI(e *Ethereum) *PreExecAPI {
	return &PreExecAPI{e: e}
}

func (api *PreExecAPI) getBlockAndMsg(origin *PreExecTx, number *big.Int) (*types.Block, types.Message) {
	fromAddr := common.HexToAddress(origin.From)
	toAddr := common.HexToAddress(origin.To)

	tx := types.NewTx(&types.LegacyTx{
		Nonce:    hexutil.MustDecodeUint64(origin.Nonce),
		To:       &toAddr,
		Value:    hexutil.MustDecodeBig(origin.Value),
		Gas:      hexutil.MustDecodeUint64(origin.Gas),
		GasPrice: hexutil.MustDecodeBig(origin.GasPrice),
		Data:     hexutil.MustDecode(origin.Data),
	})

	number.Add(number, big.NewInt(1))
	block := types.NewBlock(
		&types.Header{Number: number},
		[]*types.Transaction{tx}, nil, nil, newHash())

	msg := types.NewMessage(
		fromAddr,
		&toAddr,
		hexutil.MustDecodeUint64(origin.Nonce),
		hexutil.MustDecodeBig(origin.Value),
		hexutil.MustDecodeUint64(origin.Gas),
		hexutil.MustDecodeBig(origin.GasPrice),
		tx.GasFeeCap(),
		tx.GasTipCap(),
		hexutil.MustDecode(origin.Data),
		nil, false,
	)

	return block, msg
}

func (api *PreExecAPI) prepareData(ctx context.Context, origin *PreExecTx) (*preData, error) {
	var (
		d   preData
		err error
	)
	bc := api.e.blockchain
	d.header, err = api.e.APIBackend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
	if err != nil {
		return nil, err
	}
	latestNumber := d.header.Number
	parent := api.e.blockchain.GetBlockByNumber(latestNumber.Uint64())
	d.stateDb, err = state.New(parent.Header().Root, bc.StateCache(), bc.Snapshots())
	if err != nil {
		return nil, err
	}
	d.block, d.msg = api.getBlockAndMsg(origin, latestNumber)
	d.tx = d.block.Transactions()[0]
	return &d, nil
}

func (api *PreExecAPI) GetLogs(ctx context.Context, origin *PreExecTx) (*types.Receipt, error) {
	var (
		bc = api.e.blockchain
	)
	d, err := api.prepareData(ctx, origin)
	if err != nil {
		return nil, err
	}
	gas := d.tx.Gas()
	gp := new(core.GasPool).AddGas(gas)

	d.stateDb.Prepare(d.tx.Hash(), 0)
	receipt, err := core.ApplyTransactionForPreExec(
		bc.Config(), bc, nil, gp, d.stateDb, d.header, d.tx, d.msg, &gas, *bc.GetVMConfig())
	if err != nil {
		return nil, err
	}
	return receipt, receipt.Err
}

// TraceTransaction tracing pre-exec transaction object.
func (api *PreExecAPI) TraceTransaction(ctx context.Context, origin *PreExecTx, config *tracers.TraceConfig) (interface{}, error) {
	var (
		bc     = api.e.blockchain
		tracer vm.Tracer
		err    error
	)
	d, err := api.prepareData(ctx, origin)
	if err != nil {
		return nil, err
	}
	txContext := core.NewEVMTxContext(d.msg)
	txIndex := 0

	switch {
	case config != nil && config.Tracer != nil:
		// Define a meaningful timeout of a single transaction trace
		timeout := 5 * time.Second
		if config.Timeout != nil {
			if timeout, err = time.ParseDuration(*config.Timeout); err != nil {
				return nil, err
			}
		}
		// Constuct the JavaScript tracer to execute with
		if tracer, err = tracers.New(*config.Tracer, &tracers.Context{
			BlockHash: d.block.Hash(),
			TxIndex:   txIndex,
			TxHash:    d.tx.Hash(),
		}); err != nil {
			return nil, err
		}
		// Handle timeouts and RPC cancellations
		deadlineCtx, cancel := context.WithTimeout(ctx, timeout)
		defer cancel()
		go func() {
			<-deadlineCtx.Done()
			if deadlineCtx.Err() == context.DeadlineExceeded {
				tracer.(*tracers.Tracer).Stop(errors.New("execution timeout"))
			}
		}()
	case config == nil:
		fallthrough
	default:
		// Constuct the txtrace.StructLogger tracer to execute with
		tracer = txtrace.NewTraceStructLogger(nil)
	}
	// Run the transaction with tracing enabled.
	vmenv := vm.NewEVM(core.NewEVMBlockContext(d.header, bc, nil), txContext, d.stateDb, bc.Config(), vm.Config{Debug: true, Tracer: tracer})

	// Call Prepare to clear out the statedb access list
	d.stateDb.Prepare(d.tx.Hash(), txIndex)

	// check if type of tracer is txtrace.StructLogger, in that case, fill info.
	var traceLogger *txtrace.StructLogger
	switch tracer.(type) {
	case *txtrace.StructLogger:
		traceLogger = tracer.(*txtrace.StructLogger)
		traceLogger.SetFrom(d.msg.From())
		traceLogger.SetTo(d.msg.To())
		traceLogger.SetValue(*d.msg.Value())
		traceLogger.SetGasUsed(d.tx.Gas())
		traceLogger.SetBlockHash(d.block.Hash())
		traceLogger.SetBlockNumber(d.block.Number())
		traceLogger.SetTx(d.tx.Hash())
		traceLogger.SetTxIndex(uint(txIndex))
	}

	result, err := core.ApplyMessage(vmenv, d.msg, new(core.GasPool).AddGas(d.msg.Gas()))
	if err != nil {
		return nil, fmt.Errorf("tracing failed: %v", err)
	}
	// Depending on the tracer type, format and return the output.
	switch tracer := tracer.(type) {
	case *vm.StructLogger:
		// If the result contains a revert reason, return it.
		returnVal := fmt.Sprintf("%x", result.Return())
		if len(result.Revert()) > 0 {
			returnVal = fmt.Sprintf("%x", result.Revert())
		}
		return &ethapi.ExecutionResult{
			Gas:         result.UsedGas,
			Failed:      result.Failed(),
			ReturnValue: returnVal,
			StructLogs:  ethapi.FormatLogs(tracer.StructLogs()),
		}, nil
	case *tracers.Tracer:
		return tracer.GetResult()
	case *txtrace.StructLogger:
		tracer.Finalize()
		return tracer.GetResult(), nil
	default:
		panic(fmt.Sprintf("bad tracer type %T", tracer))
	}
}