// IsFinalizedTransaction determines whether or not a transaction is finalized.
func IsFinalizedTransaction(tx *btcutil.Tx, blockHeight int32, blockTime time.Time) bool {
	msgTx := tx.MsgTx()

	// Lock time of zero means the transaction is finalized.
	lockTime := msgTx.LockTime
	if lockTime == 0 {
		return true
	}

	// The lock time field of a transaction is either a block height at
	// which the transaction is finalized or a timestamp depending on if the
	// value is before the txscript.LockTimeThreshold.  When it is under the
	// threshold it is a block height.
	blockTimeOrHeight := int64(0)
	if lockTime < txscript.LockTimeThreshold {
		blockTimeOrHeight = int64(blockHeight)
	} else {
		blockTimeOrHeight = blockTime.Unix()
	}
	if int64(lockTime) < blockTimeOrHeight {
		return true
	}

	// At this point, the transaction's lock time hasn't occured yet, but
	// the transaction might still be finalized if the sequence number
	// for all transaction inputs is maxed out.
	for _, txIn := range msgTx.TxIn {
		if txIn.Sequence != math.MaxUint32 {
			return false
		}
	}
	return true
}

// removeTransaction is the internal function which implements the public
// RemoveTransaction.  See the comment for RemoveTransaction for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) removeTransaction(tx *btcutil.Tx, removeRedeemers bool) {
	txHash := tx.Sha()
	if removeRedeemers {
		// Remove any transactions which rely on this one.
		for i := uint32(0); i < uint32(len(tx.MsgTx().TxOut)); i++ {
			outpoint := wire.NewOutPoint(txHash, i)
			if txRedeemer, exists := mp.outpoints[*outpoint]; exists {
				mp.removeTransaction(txRedeemer, true)
			}
		}
	}

	// Remove the transaction and mark the referenced outpoints as unspent
	// by the pool.
	if txDesc, exists := mp.pool[*txHash]; exists {
		if mp.cfg.EnableAddrIndex {
			mp.removeTransactionFromAddrIndex(tx)
		}

		for _, txIn := range txDesc.Tx.MsgTx().TxIn {
			delete(mp.outpoints, txIn.PreviousOutPoint)
		}
		delete(mp.pool, *txHash)
		mp.lastUpdated = time.Now()
	}

}

// ValidateTransactionScripts validates the scripts for the passed transaction
// using multiple goroutines.
func ValidateTransactionScripts(tx *btcutil.Tx, txStore TxStore, flags txscript.ScriptFlags, sigCache *txscript.SigCache) error {
	// Collect all of the transaction inputs and required information for
	// validation.
	txIns := tx.MsgTx().TxIn
	txValItems := make([]*txValidateItem, 0, len(txIns))
	for txInIdx, txIn := range txIns {
		// Skip coinbases.
		if txIn.PreviousOutPoint.Index == math.MaxUint32 {
			continue
		}

		txVI := &txValidateItem{
			txInIndex: txInIdx,
			txIn:      txIn,
			tx:        tx,
		}
		txValItems = append(txValItems, txVI)
	}

	// Validate all of the inputs.
	validator := newTxValidator(txStore, flags, sigCache)
	if err := validator.Validate(txValItems); err != nil {
		return err
	}

	return nil
}

// ExtractCoinbaseHeight attempts to extract the height of the block from the
// scriptSig of a coinbase transaction.  Coinbase heights are only present in
// blocks of version 2 or later.  This was added as part of BIP0034.
func ExtractCoinbaseHeight(coinbaseTx *btcutil.Tx) (int32, error) {
	sigScript := coinbaseTx.MsgTx().TxIn[0].SignatureScript
	if len(sigScript) < 1 {
		str := "the coinbase signature script for blocks of " +
			"version %d or greater must start with the " +
			"length of the serialized block height"
		str = fmt.Sprintf(str, serializedHeightVersion)
		return 0, ruleError(ErrMissingCoinbaseHeight, str)
	}

	serializedLen := int(sigScript[0])
	if len(sigScript[1:]) < serializedLen {
		str := "the coinbase signature script for blocks of " +
			"version %d or greater must start with the " +
			"serialized block height"
		str = fmt.Sprintf(str, serializedHeightVersion)
		return 0, ruleError(ErrMissingCoinbaseHeight, str)
	}

	serializedHeightBytes := make([]byte, 8, 8)
	copy(serializedHeightBytes, sigScript[1:serializedLen+1])
	serializedHeight := binary.LittleEndian.Uint64(serializedHeightBytes)

	return int32(serializedHeight), nil
}

// logSkippedDeps logs any dependencies which are also skipped as a result of
// skipping a transaction while generating a block template at the trace level.
func logSkippedDeps(tx *btcutil.Tx, deps *list.List) {
	if deps == nil {
		return
	}

	for e := deps.Front(); e != nil; e = e.Next() {
		item := e.Value.(*txPrioItem)
		minrLog.Tracef("Skipping tx %s since it depends on %s\n",
			item.tx.Sha(), tx.Sha())
	}
}

// checkPoolDoubleSpend checks whether or not the passed transaction is
// attempting to spend coins already spent by other transactions in the pool.
// Note it does not check for double spends against transactions already in the
// main chain.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) checkPoolDoubleSpend(tx *btcutil.Tx) error {
	for _, txIn := range tx.MsgTx().TxIn {
		if txR, exists := mp.outpoints[txIn.PreviousOutPoint]; exists {
			str := fmt.Sprintf("output %v already spent by "+
				"transaction %v in the memory pool",
				txIn.PreviousOutPoint, txR.Sha())
			return txRuleError(wire.RejectDuplicate, str)
		}
	}

	return nil
}

// isNonstandardTransaction determines whether a transaction contains any
// scripts which are not one of the standard types.
func isNonstandardTransaction(tx *btcutil.Tx) bool {
	// TODO(davec): Should there be checks for the input signature scripts?

	// Check all of the output public key scripts for non-standard scripts.
	for _, txOut := range tx.MsgTx().TxOut {
		scriptClass := txscript.GetScriptClass(txOut.PkScript)
		if scriptClass == txscript.NonStandardTy {
			return true
		}
	}
	return false
}

// RemoveDoubleSpends removes all transactions which spend outputs spent by the
// passed transaction from the memory pool.  Removing those transactions then
// leads to removing all transactions which rely on them, recursively.  This is
// necessary when a block is connected to the main chain because the block may
// contain transactions which were previously unknown to the memory pool
//
// This function is safe for concurrent access.
func (mp *txMemPool) RemoveDoubleSpends(tx *btcutil.Tx) {
	// Protect concurrent access.
	mp.Lock()
	defer mp.Unlock()

	for _, txIn := range tx.MsgTx().TxIn {
		if txRedeemer, ok := mp.outpoints[txIn.PreviousOutPoint]; ok {
			if !txRedeemer.Sha().IsEqual(tx.Sha()) {
				mp.removeTransaction(txRedeemer, true)
			}
		}
	}
}

// removeScriptFromAddrIndex dissociates the address encoded by the
// passed pkScript from the passed tx in our address based tx index.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) removeScriptFromAddrIndex(pkScript []byte, tx *btcutil.Tx) error {
	_, addresses, _, err := txscript.ExtractPkScriptAddrs(pkScript,
		activeNetParams.Params)
	if err != nil {
		txmpLog.Errorf("Unable to extract encoded addresses from script "+
			"for addrindex (addrindex): %v", err)
		return err
	}
	for _, addr := range addresses {
		delete(mp.addrindex[addr.EncodeAddress()], *tx.Sha())
	}

	return nil
}

// FetchTransactionStore fetches the input transactions referenced by the
// passed transaction from the point of view of the end of the main chain.  It
// also attempts to fetch the transaction itself so the returned TxStore can be
// examined for duplicate transactions.
func (b *BlockChain) FetchTransactionStore(tx *btcutil.Tx, includeSpent bool) (TxStore, error) {
	// Create a set of needed transactions from the transactions referenced
	// by the inputs of the passed transaction.  Also, add the passed
	// transaction itself as a way for the caller to detect duplicates.
	txNeededSet := make(map[wire.ShaHash]struct{})
	txNeededSet[*tx.Sha()] = struct{}{}
	for _, txIn := range tx.MsgTx().TxIn {
		txNeededSet[txIn.PreviousOutPoint.Hash] = struct{}{}
	}

	// Request the input transactions from the point of view of the end of
	// the main chain with or without without including fully spent transactions
	// in the results.
	txStore := fetchTxStoreMain(b.db, txNeededSet, includeSpent)
	return txStore, nil
}

// fetchReferencedOutputScripts looks up and returns all the scriptPubKeys
// referenced by inputs of the passed transaction.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *txMemPool) fetchReferencedOutputScripts(tx *btcutil.Tx) ([][]byte, error) {
	txStore, err := mp.fetchInputTransactions(tx, false)
	if err != nil || len(txStore) == 0 {
		return nil, err
	}

	previousOutScripts := make([][]byte, 0, len(tx.MsgTx().TxIn))
	for _, txIn := range tx.MsgTx().TxIn {
		outPoint := txIn.PreviousOutPoint
		if txStore[outPoint.Hash].Err == nil {
			referencedOutPoint := txStore[outPoint.Hash].Tx.MsgTx().TxOut[outPoint.Index]
			previousOutScripts = append(previousOutScripts, referencedOutPoint.PkScript)
		}
	}
	return previousOutScripts, nil
}

// removeTransactionFromAddrIndex removes the passed transaction from our
// address based index.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) removeTransactionFromAddrIndex(tx *btcutil.Tx) error {
	previousOutputScripts, err := mp.fetchReferencedOutputScripts(tx)
	if err != nil {
		txmpLog.Errorf("Unable to obtain referenced output scripts for "+
			"the passed tx (addrindex): %v", err)
		return err
	}

	for _, pkScript := range previousOutputScripts {
		mp.removeScriptFromAddrIndex(pkScript, tx)
	}

	for _, txOut := range tx.MsgTx().TxOut {
		mp.removeScriptFromAddrIndex(txOut.PkScript, tx)
	}

	return nil
}

// indexScriptByAddress alters our address index by indexing the payment address
// encoded by the passed scriptPubKey to the passed transaction.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) indexScriptAddressToTx(pkScript []byte, tx *btcutil.Tx) error {
	_, addresses, _, err := txscript.ExtractPkScriptAddrs(pkScript,
		activeNetParams.Params)
	if err != nil {
		txmpLog.Errorf("Unable to extract encoded addresses from script "+
			"for addrindex: %v", err)
		return err
	}

	for _, addr := range addresses {
		if mp.addrindex[addr.EncodeAddress()] == nil {
			mp.addrindex[addr.EncodeAddress()] = make(map[wire.ShaHash]struct{})
		}
		mp.addrindex[addr.EncodeAddress()][*tx.Sha()] = struct{}{}
	}

	return nil
}

// checkInputsStandard performs a series of checks on a transaction's inputs
// to ensure they are "standard".  A standard transaction input is one that
// that consumes the expected number of elements from the stack and that number
// is the same as the output script pushes.  This help prevent resource
// exhaustion attacks by "creative" use of scripts that are super expensive to
// process like OP_DUP OP_CHECKSIG OP_DROP repeated a large number of times
// followed by a final OP_TRUE.
func checkInputsStandard(tx *btcutil.Tx, txStore blockchain.TxStore) error {
	// NOTE: The reference implementation also does a coinbase check here,
	// but coinbases have already been rejected prior to calling this
	// function so no need to recheck.

	for i, txIn := range tx.MsgTx().TxIn {
		// It is safe to elide existence and index checks here since
		// they have already been checked prior to calling this
		// function.
		prevOut := txIn.PreviousOutPoint
		originTx := txStore[prevOut.Hash].Tx.MsgTx()
		originPkScript := originTx.TxOut[prevOut.Index].PkScript

		// Calculate stats for the script pair.
		scriptInfo, err := txscript.CalcScriptInfo(txIn.SignatureScript,
			originPkScript, true)
		if err != nil {
			str := fmt.Sprintf("transaction input #%d script parse "+
				"failure: %v", i, err)
			return txRuleError(wire.RejectNonstandard, str)
		}

		// A negative value for expected inputs indicates the script is
		// non-standard in some way.
		if scriptInfo.ExpectedInputs < 0 {
			str := fmt.Sprintf("transaction input #%d expects %d "+
				"inputs", i, scriptInfo.ExpectedInputs)
			return txRuleError(wire.RejectNonstandard, str)
		}

		// The script pair is non-standard if the number of available
		// inputs does not match the number of expected inputs.
		if scriptInfo.NumInputs != scriptInfo.ExpectedInputs {
			str := fmt.Sprintf("transaction input #%d expects %d "+
				"inputs, but referenced output script provides "+
				"%d", i, scriptInfo.ExpectedInputs,
				scriptInfo.NumInputs)
			return txRuleError(wire.RejectNonstandard, str)
		}
	}

	return nil
}

// addTransactionToAddrIndex adds all addresses related to the transaction to
// our in-memory address index. Note that this address is only populated when
// we're running with the optional address index activated.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) addTransactionToAddrIndex(tx *btcutil.Tx) error {
	previousOutScripts, err := mp.fetchReferencedOutputScripts(tx)
	if err != nil {
		txmpLog.Errorf("Unable to obtain referenced output scripts for "+
			"the passed tx (addrindex): %v", err)
		return err
	}
	// Index addresses of all referenced previous output tx's.
	for _, pkScript := range previousOutScripts {
		mp.indexScriptAddressToTx(pkScript, tx)
	}

	// Index addresses of all created outputs.
	for _, txOut := range tx.MsgTx().TxOut {
		mp.indexScriptAddressToTx(txOut.PkScript, tx)
	}

	return nil
}

// CountSigOps returns the number of signature operations for all transaction
// input and output scripts in the provided transaction.  This uses the
// quicker, but imprecise, signature operation counting mechanism from
// txscript.
func CountSigOps(tx *btcutil.Tx) int {
	msgTx := tx.MsgTx()

	// Accumulate the number of signature operations in all transaction
	// inputs.
	totalSigOps := 0
	for _, txIn := range msgTx.TxIn {
		numSigOps := txscript.GetSigOpCount(txIn.SignatureScript)
		totalSigOps += numSigOps
	}

	// Accumulate the number of signature operations in all transaction
	// outputs.
	for _, txOut := range msgTx.TxOut {
		numSigOps := txscript.GetSigOpCount(txOut.PkScript)
		totalSigOps += numSigOps
	}

	return totalSigOps
}

// CountP2SHSigOps returns the number of signature operations for all input
// transactions which are of the pay-to-script-hash type.  This uses the
// precise, signature operation counting mechanism from the script engine which
// requires access to the input transaction scripts.
func CountP2SHSigOps(tx *btcutil.Tx, isCoinBaseTx bool, txStore TxStore) (int, error) {
	// Coinbase transactions have no interesting inputs.
	if isCoinBaseTx {
		return 0, nil
	}

	// Accumulate the number of signature operations in all transaction
	// inputs.
	msgTx := tx.MsgTx()
	totalSigOps := 0
	for _, txIn := range msgTx.TxIn {
		// Ensure the referenced input transaction is available.
		txInHash := &txIn.PreviousOutPoint.Hash
		originTx, exists := txStore[*txInHash]
		if !exists || originTx.Err != nil || originTx.Tx == nil {
			str := fmt.Sprintf("unable to find input transaction "+
				"%v referenced from transaction %v", txInHash,
				tx.Sha())
			return 0, ruleError(ErrMissingTx, str)
		}
		originMsgTx := originTx.Tx.MsgTx()

		// Ensure the output index in the referenced transaction is
		// available.
		originTxIndex := txIn.PreviousOutPoint.Index
		if originTxIndex >= uint32(len(originMsgTx.TxOut)) {
			str := fmt.Sprintf("out of bounds input index %d in "+
				"transaction %v referenced from transaction %v",
				originTxIndex, txInHash, tx.Sha())
			return 0, ruleError(ErrBadTxInput, str)
		}

		// We're only interested in pay-to-script-hash types, so skip
		// this input if it's not one.
		pkScript := originMsgTx.TxOut[originTxIndex].PkScript
		if !txscript.IsPayToScriptHash(pkScript) {
			continue
		}

		// Count the precise number of signature operations in the
		// referenced public key script.
		sigScript := txIn.SignatureScript
		numSigOps := txscript.GetPreciseSigOpCount(sigScript, pkScript,
			true)

		// We could potentially overflow the accumulator so check for
		// overflow.
		lastSigOps := totalSigOps
		totalSigOps += numSigOps
		if totalSigOps < lastSigOps {
			str := fmt.Sprintf("the public key script from "+
				"output index %d in transaction %v contains "+
				"too many signature operations - overflow",
				originTxIndex, txInHash)
			return 0, ruleError(ErrTooManySigOps, str)
		}
	}

	return totalSigOps, nil
}

// maybeAddOrphan potentially adds an orphan to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) maybeAddOrphan(tx *btcutil.Tx) error {
	// Ignore orphan transactions that are too large.  This helps avoid
	// a memory exhaustion attack based on sending a lot of really large
	// orphans.  In the case there is a valid transaction larger than this,
	// it will ultimtely be rebroadcast after the parent transactions
	// have been mined or otherwise received.
	//
	// Note that the number of orphan transactions in the orphan pool is
	// also limited, so this equates to a maximum memory used of
	// maxOrphanTxSize * mp.cfg.MaxOrphanTxs (which is ~5MB using the default
	// values at the time this comment was written).
	serializedLen := tx.MsgTx().SerializeSize()
	if serializedLen > maxOrphanTxSize {
		str := fmt.Sprintf("orphan transaction size of %d bytes is "+
			"larger than max allowed size of %d bytes",
			serializedLen, maxOrphanTxSize)
		return txRuleError(wire.RejectNonstandard, str)
	}

	// Add the orphan if the none of the above disqualified it.
	mp.addOrphan(tx)

	return nil
}

// addOrphan adds an orphan transaction to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) addOrphan(tx *btcutil.Tx) {
	// Limit the number orphan transactions to prevent memory exhaustion.  A
	// random orphan is evicted to make room if needed.
	mp.limitNumOrphans()

	mp.orphans[*tx.Sha()] = tx
	for _, txIn := range tx.MsgTx().TxIn {
		originTxHash := txIn.PreviousOutPoint.Hash
		if _, exists := mp.orphansByPrev[originTxHash]; !exists {
			mp.orphansByPrev[originTxHash] =
				make(map[wire.ShaHash]*btcutil.Tx)
		}
		mp.orphansByPrev[originTxHash][*tx.Sha()] = tx
	}

	txmpLog.Debugf("Stored orphan transaction %v (total: %d)", tx.Sha(),
		len(mp.orphans))
}

// spendTransaction updates the passed transaction store by marking the inputs
// to the passed transaction as spent.  It also adds the passed transaction to
// the store at the provided height.
func spendTransaction(txStore blockchain.TxStore, tx *btcutil.Tx, height int32) error {
	for _, txIn := range tx.MsgTx().TxIn {
		originHash := &txIn.PreviousOutPoint.Hash
		originIndex := txIn.PreviousOutPoint.Index
		if originTx, exists := txStore[*originHash]; exists {
			originTx.Spent[originIndex] = true
		}
	}

	txStore[*tx.Sha()] = &blockchain.TxData{
		Tx:          tx,
		Hash:        tx.Sha(),
		BlockHeight: height,
		Spent:       make([]bool, len(tx.MsgTx().TxOut)),
		Err:         nil,
	}

	return nil
}