package blockchain

import (
	"bytes"
	"encoding/gob"
	"encoding/hex"
	"errors"
	"fmt"
	"sync"

	"github.com/dedis/kyber/sign/schnorr"
	"github.com/harmony-one/harmony/crypto"
	"github.com/harmony-one/harmony/log"
)

// Vout2AmountMap is a TODO type.
type Vout2AmountMap = map[uint32]int

// TXHash2Vout2AmountMap is a TODO type.
type TXHash2Vout2AmountMap = map[string]Vout2AmountMap

// UtxoMap is a TODO type.
type UtxoMap = map[[20]byte]TXHash2Vout2AmountMap

// UTXOPool stores transactions and balance associated with each address.
type UTXOPool struct {
	// Mapping from address to a map of transaction id to a map of the index of output
	// array in that transaction to that balance.
	/*
	   The 3-d map's structure:
	     address - [
	                txID1 - [
	                        outputIndex1 - value1
	                        outputIndex2 - value2
	                       ]
	                txID2 - [
	                        outputIndex1 - value1
	                        outputIndex2 - value2
	                       ]
	               ]
	*/
	UtxoMap       UtxoMap
	LockedUtxoMap UtxoMap
	ShardID       uint32
	mutex         sync.Mutex
}

// MergeUtxoMap merges the utxoMap into that of the UtxoPool
func (utxoPool *UTXOPool) MergeUtxoMap(utxoMap UtxoMap) {
	for address, txHash2Vout2AmountMap := range utxoMap {
		clientTxHashMap, ok := utxoPool.UtxoMap[address]
		if ok {
			for txHash, vout2AmountMap := range txHash2Vout2AmountMap {
				clientVout2AmountMap, ok := clientTxHashMap[txHash]
				if ok {
					for vout, amount := range vout2AmountMap {
						clientVout2AmountMap[vout] = amount
					}
				} else {
					clientTxHashMap[txHash] = vout2AmountMap
				}

			}
		} else {
			utxoPool.UtxoMap[address] = txHash2Vout2AmountMap
		}
	}
}

// GetUtxoMapByAddresses gets the Utxo map for specific addresses
func (utxoPool *UTXOPool) GetUtxoMapByAddresses(addresses [][20]byte) UtxoMap {
	result := make(UtxoMap)
	for _, address := range addresses {
		utxos, ok := utxoPool.UtxoMap[address]
		if ok {
			result[address] = utxos
		}
	}
	return result
}

// VerifyTransactions verifies if a list of transactions valid for this shard.
func (utxoPool *UTXOPool) VerifyTransactions(transactions []*Transaction) bool {
	spentTXOs := make(map[[20]byte]map[string]map[uint32]bool)
	if utxoPool != nil {
		for _, tx := range transactions {
			if crossShard, err := utxoPool.VerifyOneTransaction(tx, &spentTXOs); !crossShard && err != nil {
				return false
			}
		}
	}
	return true
}

// VerifyStateBlock verifies if the given state block matches the current utxo pool.
func (utxoPool *UTXOPool) VerifyStateBlock(stateBlock *Block) bool {
	accountBalanceInUtxoPool := make(map[[20]byte]int)

	for address, txHash2Vout2AmountMap := range utxoPool.UtxoMap {
		for _, vout2AmountMap := range txHash2Vout2AmountMap {
			for _, amount := range vout2AmountMap {
				accountBalanceInUtxoPool[address] = accountBalanceInUtxoPool[address] + amount
			}
		}
	}
	for _, transaction := range stateBlock.Transactions {
		for _, txOutput := range transaction.TxOutput {
			if txOutput.ShardID != utxoPool.ShardID {
				return false
			}
			accountBalanceInUtxoPool[txOutput.Address] = accountBalanceInUtxoPool[txOutput.Address] - txOutput.Amount
		}
	}

	for _, amount := range accountBalanceInUtxoPool {
		if amount != 0 {
			return false
		}
	}
	return true
}

// VerifyOneTransaction verifies if a list of transactions valid.
// Add another sanity check function (e.g. spending the same utxo) called before this one.
func (utxoPool *UTXOPool) VerifyOneTransaction(tx *Transaction, spentTXOs *map[[20]byte]map[string]map[uint32]bool) (crossShard bool, err error) {
	var nilPubKey [32]byte
	// TODO(ricl): remove. just for btc replay.
	if tx.PublicKey == nilPubKey {
		return false, nil
	}
	if len(tx.Proofs) > 1 {
		return utxoPool.VerifyUnlockTransaction(tx)
	}

	if spentTXOs == nil {
		spentTXOs = &map[[20]byte]map[string]map[uint32]bool{}
	}
	inTotal := 0
	// Calculate the sum of TxInput
	for _, in := range tx.TxInput {
		// Only check the input for my own shard.
		if in.ShardID != utxoPool.ShardID {
			crossShard = true
			continue
		}

		inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])
		index := in.PreviousOutPoint.Index
		// Check if the transaction with the address is spent or not.
		if val, ok := (*spentTXOs)[in.Address][inTxID][index]; ok {
			if val {
				return crossShard, errors.New("TxInput is already spent")
			}
		}
		// Mark the transactions with the address and index spent.
		if _, ok := (*spentTXOs)[in.Address]; !ok {
			(*spentTXOs)[in.Address] = make(map[string]map[uint32]bool)
		}
		if _, ok := (*spentTXOs)[in.Address][inTxID]; !ok {
			(*spentTXOs)[in.Address][inTxID] = make(map[uint32]bool)
		}
		(*spentTXOs)[in.Address][inTxID][index] = true

		// Sum the balance up to the inTotal.
		utxoPool.mutex.Lock()
		if val, ok := utxoPool.UtxoMap[in.Address][inTxID][index]; ok {
			inTotal += val
		} else {
			utxoPool.mutex.Unlock()
			return crossShard, errors.New("Specified TxInput does not exist in utxo pool")
		}
		utxoPool.mutex.Unlock()
	}

	outTotal := 0
	// Calculate the sum of TxOutput
	for _, out := range tx.TxOutput {
		outTotal += out.Amount

		if out.ShardID != utxoPool.ShardID {
			crossShard = true
		}
	}

	// TODO: improve this checking logic
	if (crossShard && inTotal > outTotal) || (!crossShard && inTotal != outTotal) {
		return crossShard, errors.New("Input and output amount doesn't match")
	}

	if inTotal == 0 {
		return false, errors.New("Input amount is 0") // Here crossShard is false, because if there is no business for this shard, it's effectively not crossShard no matter what.
	}

	// Verify the signature
	pubKey := crypto.Ed25519Curve.Point()
	tempErr := pubKey.UnmarshalBinary(tx.PublicKey[:])
	if tempErr != nil {
		log.Error("Failed to deserialize public key", "error", tempErr)
	}
	tempErr = schnorr.Verify(crypto.Ed25519Curve, pubKey, tx.GetContentToVerify(), tx.Signature[:])
	if tempErr != nil {
		log.Error("Failed to verify signature", "error", tempErr, "public key", pubKey, "pubKey in bytes", tx.PublicKey[:])
		return crossShard, errors.New("Invalid signature")
	}
	return crossShard, nil
}

// VerifyUnlockTransaction verifies a cross shard transaction that contains proofs for unlock-to-commit/abort.
func (utxoPool *UTXOPool) VerifyUnlockTransaction(tx *Transaction) (crossShard bool, err error) {
	err = nil
	crossShard = false // unlock transaction is treated as crossShard=false because it will be finalized now (doesn't need more steps)
	txInputs := make(map[TXInput]bool)
	for _, curProof := range tx.Proofs {
		for _, txInput := range curProof.TxInput {
			txInputs[txInput] = true
		}
	}
	for _, txInput := range tx.TxInput {
		val, ok := txInputs[txInput]
		if !ok || !val {
			err = errors.New("Invalid unlock transaction: not all proofs are provided for tx inputs")
		}
	}
	return
}

// Update updates Utxo balances with a list of new transactions.
func (utxoPool *UTXOPool) Update(transactions []*Transaction) {
	if utxoPool != nil {
		for _, tx := range transactions {
			utxoPool.UpdateOneTransaction(tx)
		}
	}
}

// UpdateOneTransaction updates utxoPool in respect to the new Transaction.
func (utxoPool *UTXOPool) UpdateOneTransaction(tx *Transaction) {
	isUnlockTx := len(tx.Proofs) > 1
	unlockToCommit := true
	if isUnlockTx {
		for _, proof := range tx.Proofs {
			if !proof.Accept {
				unlockToCommit = false // if any proof is a rejection, they it's a unlock-to-abort tx. Otherwise, it's unlock-to-commit
			}
		}
	}

	isCrossShard := false
	// check whether it's a cross shard tx.
	for _, in := range tx.TxInput {
		if in.ShardID != utxoPool.ShardID {
			isCrossShard = true
			break
		}
	}
	for _, out := range tx.TxOutput {
		if out.ShardID != utxoPool.ShardID {
			isCrossShard = true
			break
		}
	}

	isValidCrossShard := true
	if isCrossShard {
		// Check whether for this cross shard transaction is valid or not.
		for _, in := range tx.TxInput {
			// Only check the input for my own shard.
			if in.ShardID != utxoPool.ShardID {
				continue
			}
			inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])
			if _, ok := utxoPool.UtxoMap[in.Address][inTxID][in.PreviousOutPoint.Index]; !ok {
				isValidCrossShard = false
			}
		}
	}

	utxoPool.mutex.Lock()
	defer utxoPool.mutex.Unlock()
	if utxoPool != nil {
		txID := hex.EncodeToString(tx.ID[:])

		// Remove
		if !isUnlockTx {
			if isValidCrossShard {
				for _, in := range tx.TxInput {
					// Only check the input for my own shard.
					if in.ShardID != utxoPool.ShardID {
						continue
					}

					// NOTE: for the locking phase of cross tx, the utxo is simply removed from the pool.
					inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])
					value := utxoPool.UtxoMap[in.Address][inTxID][in.PreviousOutPoint.Index]
					utxoPool.DeleteOneUtxo(in.Address, inTxID, in.PreviousOutPoint.Index)
					if isCrossShard {
						// put the delete (locked) utxo into a separate locked utxo pool
						inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])
						if _, ok := utxoPool.LockedUtxoMap[in.Address]; !ok {
							utxoPool.LockedUtxoMap[in.Address] = make(TXHash2Vout2AmountMap)
						}
						if _, ok := utxoPool.LockedUtxoMap[in.Address][inTxID]; !ok {
							utxoPool.LockedUtxoMap[in.Address][inTxID] = make(Vout2AmountMap)
						}
						utxoPool.LockedUtxoMap[in.Address][inTxID][in.PreviousOutPoint.Index] = value
					}
				}
			}
		}

		// Update
		if !isCrossShard || isUnlockTx {
			if !unlockToCommit {
				// unlock-to-abort, bring back (unlock) the utxo input
				for _, in := range tx.TxInput {
					// Only unlock the input for my own shard.
					if in.ShardID != utxoPool.ShardID {
						continue
					}

					inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])

					if utxoPool.LockedUtxoExists(in.Address, inTxID, in.PreviousOutPoint.Index) {
						// bring back the locked (removed) utxo
						if _, ok := utxoPool.UtxoMap[in.Address]; !ok {
							utxoPool.UtxoMap[in.Address] = make(TXHash2Vout2AmountMap)
							utxoPool.UtxoMap[in.Address][inTxID] = make(Vout2AmountMap)
						}
						if _, ok := utxoPool.UtxoMap[in.Address][inTxID]; !ok {
							utxoPool.UtxoMap[in.Address][inTxID] = make(Vout2AmountMap)
						}
						value := utxoPool.LockedUtxoMap[in.Address][inTxID][in.PreviousOutPoint.Index]
						utxoPool.UtxoMap[in.Address][inTxID][in.PreviousOutPoint.Index] = value

						utxoPool.DeleteOneLockedUtxo(in.Address, inTxID, in.PreviousOutPoint.Index)
					}
				}
			} else {
				// normal utxo output update
				for index, out := range tx.TxOutput {
					// Only check the input for my own shard.
					if out.ShardID != utxoPool.ShardID {
						continue
					}
					if _, ok := utxoPool.UtxoMap[out.Address]; !ok {
						utxoPool.UtxoMap[out.Address] = make(TXHash2Vout2AmountMap)
						utxoPool.UtxoMap[out.Address][txID] = make(Vout2AmountMap)
					}
					if _, ok := utxoPool.UtxoMap[out.Address][txID]; !ok {
						utxoPool.UtxoMap[out.Address][txID] = make(Vout2AmountMap)
					}
					utxoPool.UtxoMap[out.Address][txID][uint32(index)] = out.Amount
				}
				if isUnlockTx { // for unlock-to-commit transaction, also need to delete the locked utxo
					for _, in := range tx.TxInput {
						// Only unlock the input for my own shard.
						if in.ShardID != utxoPool.ShardID {
							continue
						}

						inTxID := hex.EncodeToString(in.PreviousOutPoint.TxID[:])
						utxoPool.DeleteOneLockedUtxo(in.Address, inTxID, in.PreviousOutPoint.Index)
					}
				}
			}
		} // If it's a cross shard locking Tx, then don't update so the input UTXOs are locked (removed), and the money is not spendable until unlock-to-commit or unlock-to-abort
	}
}

// VerifyOneTransactionAndUpdate verifies and update a valid transaction.
// Return false if the transaction is not valid.
func (utxoPool *UTXOPool) VerifyOneTransactionAndUpdate(tx *Transaction) bool {
	if _, err := utxoPool.VerifyOneTransaction(tx, nil); err == nil {
		utxoPool.UpdateOneTransaction(tx)
		return true
	}
	return false
}

// VerifyAndUpdate verifies a list of transactions and update utxoPool.
func (utxoPool *UTXOPool) VerifyAndUpdate(transactions []*Transaction) bool {
	if utxoPool.VerifyTransactions(transactions) {
		utxoPool.Update(transactions)
		return true
	}
	return false
}

// CreateUTXOPoolFromGenesisBlock a Utxo pool from a genesis block.
func CreateUTXOPoolFromGenesisBlock(block *Block) *UTXOPool {
	shardID := block.ShardID
	var utxoPool UTXOPool
	utxoPool.UtxoMap = make(UtxoMap)
	utxoPool.LockedUtxoMap = make(UtxoMap)
	for _, tx := range block.Transactions {
		txID := hex.EncodeToString(tx.ID[:])
		for index, out := range tx.TxOutput {
			_, ok := utxoPool.UtxoMap[out.Address]
			if !ok {
				utxoPool.UtxoMap[out.Address] = make(TXHash2Vout2AmountMap)
			}

			_, ok = utxoPool.UtxoMap[out.Address][txID]
			if !ok {
				utxoPool.UtxoMap[out.Address][txID] = make(Vout2AmountMap)
			}
			utxoPool.UtxoMap[out.Address][txID][uint32(index)] = out.Amount
		}
	}
	utxoPool.ShardID = shardID
	return &utxoPool
}

// SelectTransactionsForNewBlock returns a list of index of valid transactions for the new block.
func (utxoPool *UTXOPool) SelectTransactionsForNewBlock(transactions []*Transaction, maxNumTxs int) ([]*Transaction, []*Transaction, []*Transaction, []*CrossShardTxAndProof) {
	selected, unselected, invalid, crossShardTxs := []*Transaction{}, []*Transaction{}, []*Transaction{}, []*CrossShardTxAndProof{}
	spentTXOs := make(map[[20]byte]map[string]map[uint32]bool)
	for _, tx := range transactions {
		crossShard, err := utxoPool.VerifyOneTransaction(tx, &spentTXOs)

		if len(selected) < maxNumTxs {
			//if err != nil && rand.Intn(10) < 1 {
			//	log.Warn("Invalid Transaction", "Reason", err)
			//}
			if err == nil || crossShard {
				if crossShard {
					proof := CrossShardTxProof{Accept: err == nil, TxID: tx.ID, TxInput: getShardTxInput(tx, utxoPool.ShardID)}
					txAndProof := CrossShardTxAndProof{tx, &proof}
					crossShardTxs = append(crossShardTxs, &txAndProof)
					tx.Proofs = append(tx.Proofs, proof)
				}
				selected = append(selected, tx)
			} else {
				invalid = append(invalid, tx)
			}
		} else {
			unselected = append(unselected, tx)
		}
	}
	return selected, unselected, invalid, crossShardTxs
}

func getShardTxInput(transaction *Transaction, shardID uint32) []TXInput {
	result := []TXInput{}
	for _, txInput := range transaction.TxInput {
		if txInput.ShardID == shardID {
			result = append(result, txInput)
		}
	}
	return result
}

// DeleteOneUtxo deletes TODO.
func (utxoPool *UTXOPool) DeleteOneUtxo(address [20]byte, txID string, index uint32) {
	delete(utxoPool.UtxoMap[address][txID], index)
	if len(utxoPool.UtxoMap[address][txID]) == 0 {
		delete(utxoPool.UtxoMap[address], txID)
		if len(utxoPool.UtxoMap[address]) == 0 {
			delete(utxoPool.UtxoMap, address)
		}
	}
}

// LockedUtxoExists checks if the looked utxo exists.
func (utxoPool *UTXOPool) LockedUtxoExists(address [20]byte, txID string, index uint32) bool {
	_, ok := utxoPool.LockedUtxoMap[address]
	if !ok {
		return false
	}
	_, ok = utxoPool.LockedUtxoMap[address][txID]
	if !ok {
		return false
	}
	_, ok = utxoPool.LockedUtxoMap[address][txID][index]
	return ok
}

// DeleteOneLockedUtxo deletes one balance item of UTXOPool and clean up if possible.
func (utxoPool *UTXOPool) DeleteOneLockedUtxo(address [20]byte, txID string, index uint32) {
	delete(utxoPool.LockedUtxoMap[address][txID], index)
	if len(utxoPool.LockedUtxoMap[address][txID]) == 0 {
		delete(utxoPool.LockedUtxoMap[address], txID)
		if len(utxoPool.LockedUtxoMap[address]) == 0 {
			delete(utxoPool.LockedUtxoMap, address)
		}
	}
}

// CleanUp cleans up UTXOPool.
func (utxoPool *UTXOPool) CleanUp() {
	for address, txMap := range utxoPool.UtxoMap {
		for txid, outIndexes := range txMap {
			for index, value := range outIndexes {
				if value == 0 {
					delete(utxoPool.UtxoMap[address][txid], index)
				}
			}
			if len(utxoPool.UtxoMap[address][txid]) == 0 {
				delete(utxoPool.UtxoMap[address], txid)
			}
		}
		if len(utxoPool.UtxoMap[address]) == 0 {
			delete(utxoPool.UtxoMap, address)
		}
	}
}

// Used for debugging.
func (utxoPool *UTXOPool) String() string {
	return printUtxos(&utxoPool.UtxoMap)
}

// StringOfLockedUtxos is used for debugging.
func (utxoPool *UTXOPool) StringOfLockedUtxos() string {
	return printUtxos(&utxoPool.LockedUtxoMap)
}

func printUtxos(utxos *UtxoMap) string {
	res := ""
	for address, v1 := range *utxos {
		for txid, v2 := range v1 {
			for index, value := range v2 {
				res += fmt.Sprintf("address: %v, tx id: %v, index: %v, value: %v\n", address, txid, index, value)

			}
		}
	}
	return res
}

// GetSizeInByteOfUtxoMap gets a snapshot copy of the current pool
func (utxoPool *UTXOPool) GetSizeInByteOfUtxoMap() int {
	utxoPool.mutex.Lock()
	defer utxoPool.mutex.Unlock()
	byteBuffer := bytes.NewBuffer([]byte{})
	encoder := gob.NewEncoder(byteBuffer)
	encoder.Encode(utxoPool.UtxoMap)
	return len(byteBuffer.Bytes())
}

// CountNumOfUtxos counts the total number of utxos in a pool.
func (utxoPool *UTXOPool) CountNumOfUtxos() int {
	return countNumOfUtxos(&utxoPool.UtxoMap)
}

// CountNumOfLockedUtxos counts the total number of locked utxos in a pool.
func (utxoPool *UTXOPool) CountNumOfLockedUtxos() int {
	return countNumOfUtxos(&utxoPool.LockedUtxoMap)
}

func countNumOfUtxos(utxos *UtxoMap) int {
	countAll := 0
	for _, utxoMap := range *utxos {
		for txIDStr, val := range utxoMap {
			_, err := hex.DecodeString(txIDStr)
			if err != nil {
				continue
			}

			countAll += len(val)
		}
	}
	return countAll
}