package chain

import (
	"math/big"
	"sort"

	"github.com/harmony-one/harmony/shard/committee"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/harmony-one/bls/ffi/go/bls"
	"github.com/harmony-one/harmony/block"
	"github.com/harmony-one/harmony/common/denominations"
	"github.com/harmony-one/harmony/consensus/engine"
	"github.com/harmony-one/harmony/consensus/reward"
	"github.com/harmony-one/harmony/consensus/votepower"
	"github.com/harmony-one/harmony/core/state"
	"github.com/harmony-one/harmony/core/types"
	bls2 "github.com/harmony-one/harmony/crypto/bls"
	common2 "github.com/harmony-one/harmony/internal/common"
	"github.com/harmony-one/harmony/internal/ctxerror"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/numeric"
	"github.com/harmony-one/harmony/shard"
	"github.com/harmony-one/harmony/staking/slash"
	"github.com/pkg/errors"
)

var (
	// BlockReward is the block reward, to be split evenly among block signers.
	BlockReward = new(big.Int).Mul(big.NewInt(24), big.NewInt(denominations.One))
	// BlockRewardStakedCase is the baseline block reward in staked case -
	BlockRewardStakedCase = numeric.NewDecFromBigInt(new(big.Int).Mul(
		big.NewInt(18), big.NewInt(denominations.One),
	))
	totalTokens                  = numeric.NewDec(12600000000)
	targetStakedPercentage       = numeric.MustNewDecFromStr("0.35")
	dynamicAdjust                = numeric.MustNewDecFromStr("0.4")
	errPayoutNotEqualBlockReward = errors.New("total payout not equal to blockreward")
)

func blockSigners(
	header *block.Header, parentCommittee *shard.Committee,
) (shard.SlotList, shard.SlotList, error) {
	committerKeys := []*bls.PublicKey{}

	for _, member := range parentCommittee.Slots {
		committerKey := new(bls.PublicKey)
		err := member.BlsPublicKey.ToLibBLSPublicKey(committerKey)
		if err != nil {
			return nil, nil, ctxerror.New(
				"cannot convert BLS public key",
				"blsPublicKey",
				member.BlsPublicKey,
			).WithCause(err)
		}
		committerKeys = append(committerKeys, committerKey)
	}
	mask, err := bls2.NewMask(committerKeys, nil)
	if err != nil {
		return nil, nil, ctxerror.New(
			"cannot create group sig mask",
		).WithCause(err)
	}
	if err := mask.SetMask(header.LastCommitBitmap()); err != nil {
		return nil, nil, ctxerror.New(
			"cannot set group sig mask bits",
		).WithCause(err)
	}

	payable, missing := shard.SlotList{}, shard.SlotList{}

	for idx, member := range parentCommittee.Slots {
		switch signed, err := mask.IndexEnabled(idx); true {
		case err != nil:
			return nil, nil, ctxerror.New("cannot check for committer bit",
				"committerIndex", idx,
			).WithCause(err)
		case signed:
			payable = append(payable, member)
		default:
			missing = append(missing, member)
		}
	}
	return payable, missing, nil
}

func ballotResult(
	bc engine.ChainReader, header *block.Header, shardID uint32,
) (shard.SlotList, shard.SlotList, shard.SlotList, error) {
	// TODO ek – retrieving by parent number (blockNum - 1) doesn't work,
	//  while it is okay with hash.  Sounds like DB inconsistency.
	//  Figure out why.
	parentHeader := bc.GetHeaderByHash(header.ParentHash())
	if parentHeader == nil {
		return nil, nil, nil, ctxerror.New(
			"cannot find parent block header in DB",
			"parentHash", header.ParentHash(),
		)
	}
	parentShardState, err := bc.ReadShardState(parentHeader.Epoch())
	if err != nil {
		return nil, nil, nil, ctxerror.New(
			"cannot read shard state", "epoch", parentHeader.Epoch(),
		).WithCause(err)
	}
	parentCommittee := parentShardState.FindCommitteeByID(shardID)

	if parentCommittee == nil {
		return nil, nil, nil, ctxerror.New(
			"cannot find shard in the shard state",
			"parentBlockNumber", parentHeader.Number(),
			"shardID", parentHeader.ShardID(),
		)
	}

	payable, missing, err := blockSigners(header, parentCommittee)
	return parentCommittee.Slots, payable, missing, err
}

func ballotResultBeaconchain(
	bc engine.ChainReader, header *block.Header,
) (shard.SlotList, shard.SlotList, shard.SlotList, error) {
	return ballotResult(bc, header, shard.BeaconChainShardID)
}

func whatPercentStakedNow(
	beaconchain engine.ChainReader,
) (*numeric.Dec, error) {
	stakedNow := numeric.ZeroDec()
	active, err := beaconchain.ReadActiveValidatorList()

	if err != nil {
		return nil, err
	}
	for i := range active {
		wrapper, err := beaconchain.ReadValidatorInformation(active[i])
		if err != nil {
			return nil, err
		}
		stakedNow = stakedNow.Add(
			numeric.NewDecFromBigInt(wrapper.TotalDelegation()),
		)
	}
	percentage := stakedNow.Quo(totalTokens)
	return &percentage, nil
}

// AccumulateRewards credits the coinbase of the given block with the mining
// reward. The total reward consists of the static block reward and rewards for
// included uncles. The coinbase of each uncle block is also rewarded.
func AccumulateRewards(
	bc engine.ChainReader, state *state.DB, header *block.Header,
	rewarder reward.Distributor, slasher slash.Slasher,
	beaconChain engine.ChainReader,
) error {

	blockNum := header.Number().Uint64()
	if blockNum == 0 {
		// genesis block has no parent to reward.
		return nil
	}

	if bc.Config().IsStaking(header.Epoch()) &&
		bc.CurrentHeader().ShardID() != shard.BeaconChainShardID {
		return nil
	}

	//// After staking
	if bc.Config().IsStaking(header.Epoch()) &&
		bc.CurrentHeader().ShardID() == shard.BeaconChainShardID {

		defaultReward := BlockRewardStakedCase

		if len(header.ShardState()) > 0 {
			// TODO Use cached result in off-chain db instead of full computation
			percentageStaked, err := whatPercentStakedNow(beaconChain)
			if err != nil {
				return err
			}
			howMuchOff := targetStakedPercentage.Sub(*percentageStaked)
			adjustBy := howMuchOff.MulTruncate(numeric.NewDec(100)).Mul(dynamicAdjust)
			defaultReward = defaultReward.Add(adjustBy)
			utils.Logger().Info().
				Str("percentage-token-staked", percentageStaked.String()).
				Str("how-much-off", howMuchOff.String()).
				Str("adjusting-by", adjustBy.String()).
				Str("block-reward", defaultReward.String()).
				Msg("dynamic adjustment of block-reward ")
			// If too much is staked, then possible to have negative reward,
			// not an error, just a possible economic situation, hence we return
			if defaultReward.IsNegative() {
				return nil
			}
		}

		// Take care of my own beacon chain committee, _ is missing, for slashing
		members, payable, _, err := ballotResultBeaconchain(beaconChain, header)
		if err != nil {
			return err
		}

		votingPower := votepower.Compute(members)

		for beaconMember := range payable {
			// TODO Give out whatever leftover to the last voter/handle
			// what to do about share of those that didn't sign
			voter := votingPower.Voters[payable[beaconMember].BlsPublicKey]
			if !voter.IsHarmonyNode {
				due := defaultReward.Mul(
					voter.EffectivePercent.Quo(votepower.StakersShare),
				)
				snapshot, err := bc.ReadValidatorSnapshot(voter.EarningAccount)
				if err != nil {
					return err
				}
				state.AddReward(snapshot, due.RoundInt())
			}
		}

		// Handle rewards for shardchain
		if cxLinks := header.CrossLinks(); len(cxLinks) != 0 {
			crossLinks := types.CrossLinks{}
			err := rlp.DecodeBytes(cxLinks, &crossLinks)
			if err != nil {
				return err
			}

			type slotPayable struct {
				effective numeric.Dec
				payee     common.Address
				bucket    int
				index     int
			}

			allPayables := []slotPayable{}

			for i := range crossLinks {

				cxLink := crossLinks[i]

				shardState, err := bc.ReadShardState(cxLink.ChainHeader.Epoch())
				if !bc.Config().IsStaking(cxLink.Header().Epoch()) {
					shardState, err = committee.WithStakingEnabled.Compute(cxLink.ChainHeader.Epoch(), bc)
				}

				if err != nil {
					// TEMP HACK: IGNORE THE ERROR as THERE IS NO WAY TO VERIFY THE SIG OF FIRST BLOCK OF SHARD FIRST TIME ENTERING STAKING, NO WAY TO FIND THE LAST COMMITEE AS THERE IS GAP
					// TODO: FIX THIS WITH NEW CROSSLINK FORMAT
					continue
				}

				subComm := shardState.FindCommitteeByID(cxLink.ShardID())
				// _ are the missing signers, later for slashing
				payableSigners, _, err := blockSigners(cxLink.Header(), subComm)

				if err != nil {
					// TEMP HACK: IGNORE THE ERROR as THERE IS NO WAY TO VERIFY THE SIG OF FIRST BLOCK OF SHARD FIRST TIME ENTERING STAKING, NO WAY TO FIND THE LAST COMMITEE AS THERE IS GAP
					// TODO: FIX THIS WITH NEW CROSSLINK FORMAT
					continue
				}

				votingPower := votepower.Compute(payableSigners)
				for j := range payableSigners {
					voter := votingPower.Voters[payableSigners[j].BlsPublicKey]
					if !voter.IsHarmonyNode && !voter.EffectivePercent.IsZero() {
						due := defaultReward.Mul(
							voter.EffectivePercent.Quo(votepower.StakersShare),
						)
						to := voter.EarningAccount
						allPayables = append(allPayables, slotPayable{
							effective: due,
							payee:     to,
							bucket:    i,
							index:     j,
						})
					}
				}

			}

			resultsHandle := make([][]slotPayable, len(crossLinks))
			for i := range resultsHandle {
				resultsHandle[i] = []slotPayable{}
			}

			for _, payThem := range allPayables {
				bucket := payThem.bucket
				resultsHandle[bucket] = append(resultsHandle[bucket], payThem)
			}

			// Check if any errors and sort each bucket to enforce order
			for bucket := range resultsHandle {
				sort.SliceStable(resultsHandle[bucket],
					func(i, j int) bool {
						return resultsHandle[bucket][i].index < resultsHandle[bucket][j].index
					},
				)
			}

			// Finally do the pay
			for bucket := range resultsHandle {
				for payThem := range resultsHandle[bucket] {
					snapshot, err := bc.ReadValidatorSnapshot(resultsHandle[bucket][payThem].payee)
					if err != nil {
						return err
					}
					state.AddReward(
						snapshot,
						resultsHandle[bucket][payThem].effective.TruncateInt(),
					)
				}
			}
		}
		return nil
	}

	//// Before staking
	payable := []struct {
		string
		common.Address
		*big.Int
	}{}

	parentHeader := bc.GetHeaderByHash(header.ParentHash())
	if parentHeader.Number().Cmp(common.Big0) == 0 {
		// Parent is an epoch block,
		// which is not signed in the usual manner therefore rewards nothing.
		return nil
	}

	_, signers, _, err := ballotResult(bc, header, header.ShardID())

	if err != nil {
		return err
	}

	totalAmount := rewarder.Award(
		BlockReward, signers, func(receipient common.Address, amount *big.Int) {
			payable = append(payable, struct {
				string
				common.Address
				*big.Int
			}{common2.MustAddressToBech32(receipient), receipient, amount},
			)
		},
	)

	if totalAmount.Cmp(BlockReward) != 0 {
		utils.Logger().Error().
			Int64("block-reward", BlockReward.Int64()).
			Int64("total-amount-paid-out", totalAmount.Int64()).
			Msg("Total paid out was not equal to block-reward")
		return errors.Wrapf(
			errPayoutNotEqualBlockReward, "payout "+totalAmount.String(),
		)
	}

	for i := range payable {
		state.AddBalance(payable[i].Address, payable[i].Int)
	}

	header.Logger(utils.Logger()).Debug().
		Int("NumAccounts", len(payable)).
		Str("TotalAmount", totalAmount.String()).
		Msg("[Block Reward] Successfully paid out block reward")

	return nil
}