package worker

import (
	"fmt"
	"math/big"
	"time"

	common2 "github.com/harmony-one/harmony/internal/common"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/harmony-one/harmony/block"
	blockfactory "github.com/harmony-one/harmony/block/factory"
	consensus_engine "github.com/harmony-one/harmony/consensus/engine"
	"github.com/harmony-one/harmony/core"
	"github.com/harmony-one/harmony/core/state"
	"github.com/harmony-one/harmony/core/types"
	"github.com/harmony-one/harmony/core/vm"
	"github.com/harmony-one/harmony/internal/ctxerror"
	"github.com/harmony-one/harmony/internal/params"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/shard"
	"github.com/harmony-one/harmony/shard/committee"
	staking "github.com/harmony-one/harmony/staking/types"
)

// environment is the worker's current environment and holds all of the current state information.
type environment struct {
	signer types.Signer

	state   *state.DB     // apply state changes here
	gasPool *core.GasPool // available gas used to pack transactions

	header     *block.Header
	txs        []*types.Transaction
	stakingTxs staking.StakingTransactions
	receipts   []*types.Receipt
	outcxs     []*types.CXReceipt       // cross shard transaction receipts (source shard)
	incxs      []*types.CXReceiptsProof // cross shard receipts and its proof (desitinatin shard)
}

// Worker is the main object which takes care of submitting new work to consensus engine
// and gathering the sealing result.
type Worker struct {
	config  *params.ChainConfig
	factory blockfactory.Factory
	chain   *core.BlockChain
	current *environment // An environment for current running cycle.

	engine consensus_engine.Engine

	gasFloor uint64
	gasCeil  uint64
}

// CommitTransactions commits transactions for new block.
func (w *Worker) CommitTransactions(pendingNormal map[common.Address]types.Transactions, pendingStaking staking.StakingTransactions, coinbase common.Address) error {

	if w.current.gasPool == nil {
		w.current.gasPool = new(core.GasPool).AddGas(w.current.header.GasLimit())
	}

	txs := types.NewTransactionsByPriceAndNonce(w.current.signer, pendingNormal)

	var coalescedLogs []*types.Log

	// NORMAL
	for {
		// If we don't have enough gas for any further transactions then we're done
		if w.current.gasPool.Gas() < params.TxGas {
			utils.Logger().Info().Uint64("have", w.current.gasPool.Gas()).Uint64("want", params.TxGas).Msg("Not enough gas for further transactions")
			break
		}
		// Retrieve the next transaction and abort if all done
		tx := txs.Peek()
		if tx == nil {
			break
		}
		// Error may be ignored here. The error has already been checked
		// during transaction acceptance is the transaction pool.
		//
		// We use the eip155 signer regardless of the current hf.
		from, _ := types.Sender(w.current.signer, tx)
		// Check whether the tx is replay protected. If we're not in the EIP155 hf
		// phase, start ignoring the sender until we do.
		if tx.Protected() && !w.config.IsEIP155(w.current.header.Number()) {
			utils.Logger().Info().Str("hash", tx.Hash().Hex()).Str("eip155Epoch", w.config.EIP155Epoch.String()).Msg("Ignoring reply protected transaction")

			txs.Pop()
			continue
		}
		// Start executing the transaction
		w.current.state.Prepare(tx.Hash(), common.Hash{}, len(w.current.txs))

		if tx.ShardID() != w.chain.ShardID() {
			txs.Shift()
			continue
		}

		logs, err := w.commitTransaction(tx, coinbase)
		sender, _ := common2.AddressToBech32(from)
		switch err {
		case core.ErrGasLimitReached:
			// Pop the current out-of-gas transaction without shifting in the next from the account
			utils.Logger().Info().Str("sender", sender).Msg("Gas limit exceeded for current block")
			txs.Pop()

		case core.ErrNonceTooLow:
			// New head notification data race between the transaction pool and miner, shift
			utils.Logger().Info().Str("sender", sender).Uint64("nonce", tx.Nonce()).Msg("Skipping transaction with low nonce")
			txs.Shift()

		case core.ErrNonceTooHigh:
			// Reorg notification data race between the transaction pool and miner, skip account =
			utils.Logger().Info().Str("sender", sender).Uint64("nonce", tx.Nonce()).Msg("Skipping account with high nonce")
			txs.Pop()

		case nil:
			// Everything ok, collect the logs and shift in the next transaction from the same account
			coalescedLogs = append(coalescedLogs, logs...)
			txs.Shift()

		default:
			// Strange error, discard the transaction and get the next in line (note, the
			// nonce-too-high clause will prevent us from executing in vain).
			utils.Logger().Info().Str("hash", tx.Hash().Hex()).AnErr("err", err).Msg("Transaction failed, account skipped")
			txs.Shift()
		}
	}

	// STAKING - only beaconchain process staking transaction
	if w.chain.ShardID() == shard.BeaconChainShardID {
		for _, tx := range pendingStaking {
			logs, err := w.commitStakingTransaction(tx, coinbase)
			if err != nil {
				utils.Logger().Error().Err(err).Str("stakingTxId", tx.Hash().Hex()).Msg("Commit staking transaction error")
			} else {
				coalescedLogs = append(coalescedLogs, logs...)
				utils.Logger().Info().Str("stakingTxId", tx.Hash().Hex()).Uint64("txGasLimit", tx.Gas()).Msg("StakingTransaction gas limit info")
			}
		}
	}

	utils.Logger().Info().Int("newTxns", len(w.current.txs)).Uint64("blockGasLimit", w.current.header.GasLimit()).Uint64("blockGasUsed", w.current.header.GasUsed()).Msg("Block gas limit and usage info")

	return nil
}

func (w *Worker) commitStakingTransaction(tx *staking.StakingTransaction, coinbase common.Address) ([]*types.Log, error) {
	snap := w.current.state.Snapshot()
	gasUsed := w.current.header.GasUsed()
	receipt, _, err :=
		core.ApplyStakingTransaction(w.config, w.chain, &coinbase, w.current.gasPool, w.current.state, w.current.header, tx, &gasUsed, vm.Config{})
	w.current.header.SetGasUsed(gasUsed)
	if err != nil {
		w.current.state.RevertToSnapshot(snap)
		return nil, err
	}
	if receipt == nil {
		return nil, fmt.Errorf("nil staking receipt")
	}

	w.current.stakingTxs = append(w.current.stakingTxs, tx)
	w.current.receipts = append(w.current.receipts, receipt)
	return receipt.Logs, nil
}

func (w *Worker) commitTransaction(tx *types.Transaction, coinbase common.Address) ([]*types.Log, error) {
	snap := w.current.state.Snapshot()

	gasUsed := w.current.header.GasUsed()
	receipt, cx, _, err := core.ApplyTransaction(w.config, w.chain, &coinbase, w.current.gasPool, w.current.state, w.current.header, tx, &gasUsed, vm.Config{})
	w.current.header.SetGasUsed(gasUsed)
	if err != nil {
		w.current.state.RevertToSnapshot(snap)
		utils.Logger().Error().Err(err).Str("stakingTxId", tx.Hash().Hex()).Msg("Offchain ValidatorMap Read/Write Error")
		return nil, err
	}
	if receipt == nil {
		utils.Logger().Warn().Interface("tx", tx).Interface("cx", cx).Msg("Receipt is Nil!")
		return nil, fmt.Errorf("Receipt is Nil")
	}
	w.current.txs = append(w.current.txs, tx)
	w.current.receipts = append(w.current.receipts, receipt)
	if cx != nil {
		w.current.outcxs = append(w.current.outcxs, cx)
	}

	return receipt.Logs, nil
}

// CommitReceipts commits a list of already verified incoming cross shard receipts
func (w *Worker) CommitReceipts(receiptsList []*types.CXReceiptsProof) error {
	if w.current.gasPool == nil {
		w.current.gasPool = new(core.GasPool).AddGas(w.current.header.GasLimit())
	}

	if len(receiptsList) == 0 {
		w.current.header.SetIncomingReceiptHash(types.EmptyRootHash)
	} else {
		w.current.header.SetIncomingReceiptHash(types.DeriveSha(types.CXReceiptsProofs(receiptsList)))
	}

	for _, cx := range receiptsList {
		err := core.ApplyIncomingReceipt(w.config, w.current.state, w.current.header, cx)
		if err != nil {
			return ctxerror.New("cannot apply receiptsList").WithCause(err)
		}
	}

	for _, cx := range receiptsList {
		w.current.incxs = append(w.current.incxs, cx)
	}
	return nil
}

// UpdateCurrent updates the current environment with the current state and header.
func (w *Worker) UpdateCurrent() error {
	parent := w.chain.CurrentBlock()
	num := parent.Number()
	timestamp := time.Now().Unix()

	epoch := w.GetNewEpoch()
	header := w.factory.NewHeader(epoch).With().
		ParentHash(parent.Hash()).
		Number(num.Add(num, common.Big1)).
		GasLimit(core.CalcGasLimit(parent, w.gasFloor, w.gasCeil)).
		Time(big.NewInt(timestamp)).
		ShardID(w.chain.ShardID()).
		Header()
	return w.makeCurrent(parent, header)
}

// GetCurrentHeader returns the current header to propose
func (w *Worker) GetCurrentHeader() *block.Header {
	return w.current.header
}

// makeCurrent creates a new environment for the current cycle.
func (w *Worker) makeCurrent(parent *types.Block, header *block.Header) error {
	state, err := w.chain.StateAt(parent.Root())
	if err != nil {
		return err
	}
	env := &environment{
		signer: types.NewEIP155Signer(w.config.ChainID),
		state:  state,
		header: header,
	}

	w.current = env
	return nil
}

// GetCurrentState gets the current state.
func (w *Worker) GetCurrentState() *state.DB {
	return w.current.state
}

// GetNewEpoch gets the current epoch.
func (w *Worker) GetNewEpoch() *big.Int {
	parent := w.chain.CurrentBlock()
	epoch := new(big.Int).Set(parent.Header().Epoch())

	shardState, err := parent.Header().GetShardState()
	if err == nil && shardState.Epoch != nil {
		// For shard state of staking epochs, the shard state will have an epoch and it will decide the next epoch for following blocks
		epoch = new(big.Int).Set(shardState.Epoch)
	} else {
		if len(parent.Header().ShardState()) > 0 && parent.NumberU64() != 0 {
			// if parent has proposed a new shard state it increases by 1, except for genesis block.
			epoch = epoch.Add(epoch, common.Big1)
		}
	}
	return epoch
}

// GetCurrentReceipts get the receipts generated starting from the last state.
func (w *Worker) GetCurrentReceipts() []*types.Receipt {
	return w.current.receipts
}

// OutgoingReceipts get the receipts generated starting from the last state.
func (w *Worker) OutgoingReceipts() []*types.CXReceipt {
	return w.current.outcxs
}

// IncomingReceipts get incoming receipts in destination shard that is received from source shard
func (w *Worker) IncomingReceipts() []*types.CXReceiptsProof {
	return w.current.incxs
}

// SuperCommitteeForNextEpoch assumes only called by consensus leader
func (w *Worker) SuperCommitteeForNextEpoch(
	shardID uint32,
	beacon *core.BlockChain,
) (*shard.State, error) {
	var (
		nextCommittee = new(shard.State)
		err           error
	)
	switch shardID {
	case shard.BeaconChainShardID:
		if shard.Schedule.IsLastBlock(w.current.header.Number().Uint64()) {
			nextCommittee, err = committee.WithStakingEnabled.Compute(
				new(big.Int).Add(w.current.header.Epoch(), common.Big1),
				beacon,
			)
		}
	default:
		// TODO: needs to make sure beacon chain sync works.
		beaconEpoch := beacon.CurrentHeader().Epoch()
		nextEpoch := new(big.Int).Add(w.current.header.Epoch(), common.Big1)
		if w.config.IsStaking(nextEpoch) {
			// If next epoch is staking epoch, I should wait and listen for beacon chain for epoch changes
			switch beaconEpoch.Cmp(w.current.header.Epoch()) {
			case 1:
				// If beacon chain is bigger than shard chain in epoch, it means I should catch up with beacon chain now
				nextCommittee, err = committee.WithStakingEnabled.ReadFromDB(
					beaconEpoch, beacon,
				)

				utils.Logger().Debug().
					Uint64("blockNum", w.current.header.Number().Uint64()).
					Uint64("myCurEpoch", w.current.header.Epoch().Uint64()).
					Uint64("beaconEpoch", beaconEpoch.Uint64()).
					Msg("Propose new epoch as beacon chain's epoch")
			case 0:
				// If it's same epoch, no need to propose new shard state (new epoch change)
			case -1:
				// If beacon chain is behind, shard chain should wait for the beacon chain by not changing epochs.
			}
		} else {
			if w.config.IsStaking(beaconEpoch) {
				// If I am not even in the last epoch before staking epoch and beacon chain is already in staking epoch,
				// I should just catch up with beacon chain's epoch
				nextCommittee, err = committee.WithStakingEnabled.ReadFromDB(
					beaconEpoch, beacon,
				)

				utils.Logger().Debug().
					Uint64("blockNum", w.current.header.Number().Uint64()).
					Uint64("myCurEpoch", w.current.header.Epoch().Uint64()).
					Uint64("beaconEpoch", beaconEpoch.Uint64()).
					Msg("Propose entering staking along with beacon chain's epoch")
			} else {
				// If I are not in staking nor has beacon chain proposed a staking-based shard state,
				// do pre-staking committee calculation
				if shard.Schedule.IsLastBlock(w.current.header.Number().Uint64()) {
					nextCommittee, err = committee.WithStakingEnabled.Compute(
						nextEpoch,
						w.chain,
					)
				}
			}
		}

	}
	return nextCommittee, err
}

// FinalizeNewBlock generate a new block for the next consensus round.
func (w *Worker) FinalizeNewBlock(sig []byte, signers []byte, viewID uint64, coinbase common.Address, crossLinks types.CrossLinks, shardState *shard.State) (*types.Block, error) {
	if len(sig) > 0 && len(signers) > 0 {
		sig2 := w.current.header.LastCommitSignature()
		copy(sig2[:], sig[:])
		w.current.header.SetLastCommitSignature(sig2)
		w.current.header.SetLastCommitBitmap(signers)
	}
	w.current.header.SetCoinbase(coinbase)
	w.current.header.SetViewID(new(big.Int).SetUint64(viewID))

	// Cross Links
	if crossLinks != nil && len(crossLinks) != 0 {
		crossLinks.Sort()
		crossLinkData, err := rlp.EncodeToBytes(crossLinks)
		if err == nil {
			utils.Logger().Debug().
				Uint64("blockNum", w.current.header.Number().Uint64()).
				Int("numCrossLinks", len(crossLinks)).
				Msg("Successfully proposed cross links into new block")
			w.current.header.SetCrossLinks(crossLinkData)
		} else {
			utils.Logger().Debug().Err(err).Msg("Failed to encode proposed cross links")
			return nil, err
		}
	} else {
		utils.Logger().Debug().Msg("Zero crosslinks to finalize")
	}

	// Shard State
	if shardState != nil && len(shardState.Shards) != 0 {
		w.current.header.SetShardStateHash(shardState.Hash())
		isStaking := false
		if shardState.Epoch != nil && w.config.IsStaking(shardState.Epoch) {
			isStaking = true
		}
		// NOTE: Besides genesis, this is the only place where the shard state is encoded.
		shardStateData, err := shard.EncodeWrapper(*shardState, isStaking)
		if err == nil {
			w.current.header.SetShardState(shardStateData)
		} else {
			utils.Logger().Debug().Err(err).Msg("Failed to encode proposed shard state")
			return nil, err
		}
	}

	state := w.current.state.Copy()

	copyHeader := types.CopyHeader(w.current.header)
	// TODO: feed coinbase into here so the proposer gets extra rewards.
	block, err := w.engine.Finalize(w.chain, copyHeader, state, w.current.txs, w.current.receipts, w.current.outcxs, w.current.incxs, w.current.stakingTxs)
	if err != nil {
		return nil, ctxerror.New("cannot finalize block").WithCause(err)
	}

	return block, nil
}

// New create a new worker object.
func New(config *params.ChainConfig, chain *core.BlockChain, engine consensus_engine.Engine) *Worker {
	worker := &Worker{
		config:  config,
		factory: blockfactory.NewFactory(config),
		chain:   chain,
		engine:  engine,
	}
	worker.gasFloor = 80000000
	worker.gasCeil = 120000000

	parent := worker.chain.CurrentBlock()
	num := parent.Number()
	timestamp := time.Now().Unix()

	epoch := worker.GetNewEpoch()
	header := worker.factory.NewHeader(epoch).With().
		ParentHash(parent.Hash()).
		Number(num.Add(num, common.Big1)).
		GasLimit(core.CalcGasLimit(parent, worker.gasFloor, worker.gasCeil)).
		Time(big.NewInt(timestamp)).
		ShardID(worker.chain.ShardID()).
		Header()
	worker.makeCurrent(parent, header)

	return worker
}