package engine_v2

import (
	"fmt"
	"math/big"
	"sync"

	"github.com/XinFinOrg/XDPoSChain/common"
	"github.com/XinFinOrg/XDPoSChain/consensus"
	"github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/utils"
	"github.com/XinFinOrg/XDPoSChain/core/types"
	"github.com/XinFinOrg/XDPoSChain/log"
)

// Once Hot stuff voting rule has verified, this node can then send vote
func (x *XDPoS_v2) sendVote(chainReader consensus.ChainReader, blockInfo *utils.BlockInfo) error {
	// First step: Update the highest Voted round
	// Second step: Generate the signature by using node's private key(The signature is the blockInfo signature)
	// Third step: Construct the vote struct with the above signature & blockinfo struct
	// Forth step: Send the vote to broadcast channel

	signedHash, err := x.signSignature(utils.VoteSigHash(blockInfo))
	if err != nil {
		log.Error("signSignature when sending out Vote", "BlockInfoHash", blockInfo.Hash, "Error", err)
		return err
	}

	x.highestVotedRound = x.currentRound
	voteMsg := &utils.Vote{
		ProposedBlockInfo: blockInfo,
		Signature:         signedHash,
	}

	err = x.voteHandler(chainReader, voteMsg)
	if err != nil {
		log.Error("sendVote error", "BlockInfoHash", blockInfo.Hash, "Error", err)
		return err
	}
	x.broadcastToBftChannel(voteMsg)
	return nil
}

func (x *XDPoS_v2) voteHandler(chain consensus.ChainReader, voteMsg *utils.Vote) error {

	// 1. checkRoundNumber
	if (voteMsg.ProposedBlockInfo.Round != x.currentRound) && (voteMsg.ProposedBlockInfo.Round != x.currentRound+1) {
		return &utils.ErrIncomingMessageRoundTooFarFromCurrentRound{
			Type:          "vote",
			IncomingRound: voteMsg.ProposedBlockInfo.Round,
			CurrentRound:  x.currentRound,
		}
	}

	// Collect vote
	thresholdReached, numberOfVotesInPool, pooledVotes := x.votePool.Add(voteMsg)
	log.Info("[voteHandler] collect votes", "number", numberOfVotesInPool)
	if thresholdReached {
		log.Info(fmt.Sprintf("[voteHandler] Vote pool threashold reached: %v, number of items in the pool: %v", thresholdReached, numberOfVotesInPool))

		// Check if the block already exist, otherwise we try luck with the next vote
		proposedBlockHeader := chain.GetHeaderByHash(voteMsg.ProposedBlockInfo.Hash)
		if proposedBlockHeader == nil {
			log.Warn("[voteHandler] The proposed block from vote message does not exist yet, wait for the next vote to try again", "Hash", voteMsg.ProposedBlockInfo.Hash, "Round", voteMsg.ProposedBlockInfo.Round)
			return nil
		}

		err := x.VerifyBlockInfo(chain, voteMsg.ProposedBlockInfo)
		if err != nil {
			x.votePool.ClearPoolKeyByObj(voteMsg)
			return err
		}

		err = x.onVotePoolThresholdReached(chain, pooledVotes, voteMsg, proposedBlockHeader)
		if err != nil {
			return err
		}
	}

	return nil
}

/*
	Function that will be called by votePool when it reached threshold.
	In the engine v2, we will need to generate and process QC
*/
func (x *XDPoS_v2) onVotePoolThresholdReached(chain consensus.ChainReader, pooledVotes map[common.Hash]utils.PoolObj, currentVoteMsg utils.PoolObj, proposedBlockHeader *types.Header) error {

	masternodes := x.GetMasternodes(chain, proposedBlockHeader)

	// Filter out non-Master nodes signatures
	var wg sync.WaitGroup
	wg.Add(len(pooledVotes))
	signatureSlice := make([]utils.Signature, len(pooledVotes))
	counter := 0
	for h, vote := range pooledVotes {
		go func(hash common.Hash, v *utils.Vote, i int) {
			defer wg.Done()
			verified, _, err := x.verifyMsgSignature(utils.VoteSigHash(v.ProposedBlockInfo), v.Signature, masternodes)
			if !verified || err != nil {
				log.Warn("[onVotePoolThresholdReached] Skip not verified vote signatures when building QC", "Error", err.Error(), "verified", verified)
			} else {
				signatureSlice[i] = v.Signature
			}
		}(h, vote.(*utils.Vote), counter)
		counter++
	}
	wg.Wait()

	// The signature list may contain empty entey. we only care the ones with values
	var validSignatureSlice []utils.Signature
	for _, v := range signatureSlice {
		if len(v) != 0 {
			validSignatureSlice = append(validSignatureSlice, v)
		}
	}

	// Skip and wait for the next vote to process again if valid votes is less than what we required
	if len(validSignatureSlice) < x.config.V2.CertThreshold {
		log.Warn("[onVotePoolThresholdReached] Not enough valid signatures to generate QC", "VotesSignaturesAfterFilter", validSignatureSlice, "NumberOfValidVotes", len(validSignatureSlice), "NumberOfVotes", len(pooledVotes))
		return nil
	}
	// Genrate QC
	quorumCert := &utils.QuorumCert{
		ProposedBlockInfo: currentVoteMsg.(*utils.Vote).ProposedBlockInfo,
		Signatures:        validSignatureSlice,
	}
	err := x.processQC(chain, quorumCert)
	if err != nil {
		log.Error("Error while processing QC in the Vote handler after reaching pool threshold, ", err)
		return err
	}
	log.Info("Successfully processed the vote and produced QC!", "QcRound", quorumCert.ProposedBlockInfo.Round, "QcNumOfSig", len(quorumCert.Signatures), "QcHash", quorumCert.ProposedBlockInfo.Hash, "QcNumber", quorumCert.ProposedBlockInfo.Number.Uint64())
	// clean up vote at the same poolKey. and pookKey is proposed block hash
	x.votePool.ClearPoolKeyByObj(currentVoteMsg)
	return nil
}

// Hot stuff rule to decide whether this node is eligible to vote for the received block
func (x *XDPoS_v2) verifyVotingRule(blockChainReader consensus.ChainReader, blockInfo *utils.BlockInfo, quorumCert *utils.QuorumCert) (bool, error) {
	// Make sure this node has not voted for this round.
	if x.currentRound <= x.highestVotedRound {
		return false, nil
	}
	/*
		HotStuff Voting rule:
		header's round == local current round, AND (one of the following two:)
		header's block extends lockQuorumCert's ProposedBlockInfo (we need a isExtending(block_a, block_b) function), OR
		header's QC's ProposedBlockInfo.Round > lockQuorumCert's ProposedBlockInfo.Round
	*/
	if blockInfo.Round != x.currentRound {
		return false, nil
	}
	// XDPoS v1.0 switch to v2.0, the proposed block can always pass voting rule
	if x.lockQuorumCert == nil {
		return true, nil
	}

	if quorumCert.ProposedBlockInfo.Round > x.lockQuorumCert.ProposedBlockInfo.Round {
		return true, nil
	}

	isExtended, err := x.isExtendingFromAncestor(blockChainReader, blockInfo, x.lockQuorumCert.ProposedBlockInfo)
	if err != nil {
		return false, err
	}
	if isExtended {
		return true, nil
	}

	return false, nil
}

func (x *XDPoS_v2) isExtendingFromAncestor(blockChainReader consensus.ChainReader, currentBlock *utils.BlockInfo, ancestorBlock *utils.BlockInfo) (bool, error) {
	blockNumDiff := int(big.NewInt(0).Sub(currentBlock.Number, ancestorBlock.Number).Int64())

	nextBlockHash := currentBlock.Hash
	for i := 0; i < blockNumDiff; i++ {
		parentBlock := blockChainReader.GetHeaderByHash(nextBlockHash)
		if parentBlock == nil {
			return false, fmt.Errorf("Could not find its parent block when checking whether currentBlock %v with hash %v is extending from the ancestorBlock %v", currentBlock.Number, currentBlock.Hash, ancestorBlock.Number)
		} else {
			nextBlockHash = parentBlock.ParentHash
		}
		log.Debug("[isExtendingFromAncestor] Found parent block", "CurrentBlockHash", currentBlock.Hash, "ParentHash", nextBlockHash)
	}

	if nextBlockHash == ancestorBlock.Hash {
		return true, nil
	}
	return false, nil
}