package engine_v1

import (
	"errors"

	"github.com/XinFinOrg/XDPoSChain/common"
	"github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/utils"
	"github.com/XinFinOrg/XDPoSChain/core/types"
	"github.com/XinFinOrg/XDPoSChain/crypto"
	"github.com/XinFinOrg/XDPoSChain/params"
	"github.com/XinFinOrg/XDPoSChain/rlp"
	"golang.org/x/crypto/sha3"
)

// Get masternodes address from checkpoint Header.
func decodeMasternodesFromHeaderExtra(checkpointHeader *types.Header) []common.Address {
	masternodes := make([]common.Address, (len(checkpointHeader.Extra)-utils.ExtraVanity-utils.ExtraSeal)/common.AddressLength)
	for i := 0; i < len(masternodes); i++ {
		copy(masternodes[i][:], checkpointHeader.Extra[utils.ExtraVanity+i*common.AddressLength:])
	}
	return masternodes
}

// Get m2 list from checkpoint block.
func getM1M2FromCheckpointHeader(checkpointHeader *types.Header, currentHeader *types.Header, config *params.ChainConfig) (map[common.Address]common.Address, error) {
	if checkpointHeader.Number.Uint64()%common.EpocBlockRandomize != 0 {
		return nil, errors.New("this block is not checkpoint block")
	}
	// Get signers from this block.
	masternodes := decodeMasternodesFromHeaderExtra(checkpointHeader)
	validators := utils.ExtractValidatorsFromBytes(checkpointHeader.Validators)
	m1m2, _, err := getM1M2(masternodes, validators, currentHeader, config)
	if err != nil {
		return map[common.Address]common.Address{}, err
	}
	return m1m2, nil
}

func getM1M2(masternodes []common.Address, validators []int64, currentHeader *types.Header, config *params.ChainConfig) (map[common.Address]common.Address, uint64, error) {
	m1m2 := map[common.Address]common.Address{}
	maxMNs := len(masternodes)
	moveM2 := uint64(0)
	if len(validators) < maxMNs {
		return nil, moveM2, errors.New("len(m2) is less than len(m1)")
	}
	if maxMNs > 0 {
		isForked := config.IsTIPRandomize(currentHeader.Number)
		if isForked {
			moveM2 = ((currentHeader.Number.Uint64() % config.XDPoS.Epoch) / uint64(maxMNs)) % uint64(maxMNs)
		}
		for i, m1 := range masternodes {
			m2Index := uint64(validators[i] % int64(maxMNs))
			m2Index = (m2Index + moveM2) % uint64(maxMNs)
			m1m2[m1] = masternodes[m2Index]
		}
	}
	return m1m2, moveM2, nil
}

func sigHash(header *types.Header) (hash common.Hash) {
	hasher := sha3.NewLegacyKeccak256()

	enc := []interface{}{
		header.ParentHash,
		header.UncleHash,
		header.Coinbase,
		header.Root,
		header.TxHash,
		header.ReceiptHash,
		header.Bloom,
		header.Difficulty,
		header.Number,
		header.GasLimit,
		header.GasUsed,
		header.Time,
		header.Extra[:len(header.Extra)-crypto.SignatureLength], // Yes, this will panic if extra is too short
		header.MixDigest,
		header.Nonce,
	}
	if header.BaseFee != nil {
		enc = append(enc, header.BaseFee)
	}
	rlp.Encode(hasher, enc)
	hasher.Sum(hash[:0])
	return hash
}

// ecrecover extracts the Ethereum account address from a signed header.
func ecrecover(header *types.Header, sigcache *utils.SigLRU) (common.Address, error) {
	// If the signature's already cached, return that
	hash := header.Hash()
	if address, known := sigcache.Get(hash); known {
		return address, nil
	}
	// Retrieve the signature from the header extra-data
	if len(header.Extra) < utils.ExtraSeal {
		return common.Address{}, utils.ErrMissingSignature
	}
	signature := header.Extra[len(header.Extra)-utils.ExtraSeal:]

	// Recover the public key and the Ethereum address
	pubkey, err := crypto.Ecrecover(sigHash(header).Bytes(), signature)
	if err != nil {
		return common.Address{}, err
	}
	var signer common.Address
	copy(signer[:], crypto.Keccak256(pubkey[1:])[12:])

	sigcache.Add(hash, signer)
	return signer, nil
}