package validation

import (
	"time"

	log "github.com/sirupsen/logrus"

	"github.com/vapor/chain"
	"github.com/vapor/consensus"
	engine "github.com/vapor/consensus/consensus"
	"github.com/vapor/errors"
	"github.com/vapor/protocol/bc"
	"github.com/vapor/protocol/bc/types"
	"github.com/vapor/protocol/state"
)

const logModule = "leveldb"

var (
	errBadTimestamp          = errors.New("block timestamp is not in the valid range")
	errBadBits               = errors.New("block bits is invalid")
	errMismatchedBlock       = errors.New("mismatched block")
	errMismatchedMerkleRoot  = errors.New("mismatched merkle root")
	errMisorderedBlockHeight = errors.New("misordered block height")
	errOverBlockLimit        = errors.New("block's gas is over the limit")
	errWorkProof             = errors.New("invalid difficulty proof of work")
	errVersionRegression     = errors.New("version regression")
)

func checkBlockTime(b *bc.Block, parent *state.BlockNode) error {
	if b.Timestamp > uint64(time.Now().Unix())+consensus.MaxTimeOffsetSeconds {
		return errBadTimestamp
	}

	if b.Timestamp <= parent.CalcPastMedianTime() {
		return errBadTimestamp
	}
	return nil
}

func checkCoinbaseAmount(b *bc.Block, amount uint64) error {
	if len(b.Transactions) == 0 {
		return errors.Wrap(ErrWrongCoinbaseTransaction, "block is empty")
	}

	tx := b.Transactions[0]
	output, err := tx.Output(*tx.TxHeader.ResultIds[0])
	if err != nil {
		return err
	}

	if output.Source.Value.Amount != amount {
		return errors.Wrap(ErrWrongCoinbaseTransaction, "dismatch output amount")
	}
	return nil
}

// ValidateBlockHeader check the block's header
func ValidateBlockHeader(b *bc.Block, block *types.Block, parent *state.BlockNode, c chain.Chain, engine engine.Engine) error {
	if b.Version < parent.Version {
		return errors.WithDetailf(errVersionRegression, "previous block verson %d, current block version %d", parent.Version, b.Version)
	}
	if b.Height != parent.Height+1 {
		return errors.WithDetailf(errMisorderedBlockHeight, "previous block height %d, current block height %d", parent.Height, b.Height)
	}
	if parent.Hash != *b.PreviousBlockId {
		return errors.WithDetailf(errMismatchedBlock, "previous block ID %x, current block wants %x", parent.Hash.Bytes(), b.PreviousBlockId.Bytes())
	}
	if err := checkBlockTime(b, parent); err != nil {
		return err
	}
	if err := engine.VerifyHeader(c, &block.BlockHeader, false); err != nil {
		return err
	}

	return nil
}

// ValidateBlock validates a block and the transactions within.
func ValidateBlock(b *bc.Block, parent *state.BlockNode, block *types.Block, c chain.Chain, engine engine.Engine, authoritys map[string]string, position uint64) error {
	startTime := time.Now()
	if err := ValidateBlockHeader(b, block, parent, c, engine); err != nil {
		return err
	}
	/*
		time.Sleep(3 * time.Second)
		// 验证出块人
		controlProgram := hex.EncodeToString(block.Proof.ControlProgram)
		xpub := &chainkd.XPub{}
		xpub.UnmarshalText([]byte(authoritys[controlProgram]))

		msg := block.BlockCommitment.TransactionsMerkleRoot.Bytes()
		if !xpub.Verify(msg, block.Proof.Sign) {
			return errors.New("Verification signature failed")
		}
	*/
	blockGasSum := uint64(0)
	coinbaseAmount := consensus.BlockSubsidy(b.BlockHeader.Height)
	b.TransactionStatus = bc.NewTransactionStatus()
	for i, tx := range b.Transactions {
		gasStatus, err := ValidateTx(tx, b)
		if !gasStatus.GasValid {
			return errors.Wrapf(err, "validate of transaction %d of %d", i, len(b.Transactions))
		}

		if err := b.TransactionStatus.SetStatus(i, err != nil); err != nil {
			return err
		}
		coinbaseAmount += gasStatus.BTMValue
		if blockGasSum += uint64(gasStatus.GasUsed); blockGasSum > consensus.MaxBlockGas {
			return errOverBlockLimit
		}
	}

	if err := checkCoinbaseAmount(b, coinbaseAmount); err != nil {
		return err
	}

	txMerkleRoot, err := types.TxMerkleRoot(b.Transactions)
	if err != nil {
		return errors.Wrap(err, "computing transaction id merkle root")
	}
	if txMerkleRoot != *b.TransactionsRoot {
		return errors.WithDetailf(errMismatchedMerkleRoot, "transaction id merkle root")
	}

	txStatusHash, err := types.TxStatusMerkleRoot(b.TransactionStatus.VerifyStatus)
	if err != nil {
		return errors.Wrap(err, "computing transaction status merkle root")
	}
	if txStatusHash != *b.TransactionStatusHash {
		return errors.WithDetailf(errMismatchedMerkleRoot, "transaction status merkle root")
	}

	log.WithFields(log.Fields{
		"module":   logModule,
		"height":   b.Height,
		"hash":     b.ID.String(),
		"duration": time.Since(startTime),
	}).Debug("finish validate block")
	return nil
}