// Copyright (c) 2017-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <consensus/tx_verify.h>

#include <chain.h>

#include <coins.h>

#include <consensus/amount.h>

#include <consensus/consensus.h>

#include <consensus/validation.h>

#include <primitives/transaction.h>

#include <script/interpreter.h>

#include <util/check.h>

#include <util/moneystr.h>

bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)

{

    if (tx.nLockTime == 0)

        return true;

    if ((int64_t)tx.nLockTime < ((int64_t)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64_t)nBlockHeight : nBlockTime))

        return true;

    // Even if tx.nLockTime isn't satisfied by nBlockHeight/nBlockTime, a

    // transaction is still considered final if all inputs' nSequence ==

    // SEQUENCE_FINAL (0xffffffff), in which case nLockTime is ignored.

    //

    // Because of this behavior OP_CHECKLOCKTIMEVERIFY/CheckLockTime() will

    // also check that the spending input's nSequence != SEQUENCE_FINAL,

    // ensuring that an unsatisfied nLockTime value will actually cause

    // IsFinalTx() to return false here:

    for (const auto& txin : tx.vin) {

        if (!(txin.nSequence == CTxIn::SEQUENCE_FINAL))

            return false;

    }

    return true;

}

std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)

{

    assert(prevHeights.size() == tx.vin.size());

    // Will be set to the equivalent height- and time-based nLockTime

    // values that would be necessary to satisfy all relative lock-

    // time constraints given our view of block chain history.

    // The semantics of nLockTime are the last invalid height/time, so

    // use -1 to have the effect of any height or time being valid.

    int nMinHeight = -1;

    int64_t nMinTime = -1;

    bool fEnforceBIP68 = tx.version >= 2 && flags & LOCKTIME_VERIFY_SEQUENCE;

    // Do not enforce sequence numbers as a relative lock time

    // unless we have been instructed to

    if (!fEnforceBIP68) {

        return std::make_pair(nMinHeight, nMinTime);

    }

    for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {

        const CTxIn& txin = tx.vin[txinIndex];

        // Sequence numbers with the most significant bit set are not

        // treated as relative lock-times, nor are they given any

        // consensus-enforced meaning at this point.

        if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {

            // The height of this input is not relevant for sequence locks

            prevHeights[txinIndex] = 0;

            continue;

        }

        int nCoinHeight = prevHeights[txinIndex];

        if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {

            const int64_t nCoinTime{Assert(block.GetAncestor(std::max(nCoinHeight - 1, 0)))->GetMedianTimePast()};

            // NOTE: Subtract 1 to maintain nLockTime semantics

            // BIP 68 relative lock times have the semantics of calculating

            // the first block or time at which the transaction would be

            // valid. When calculating the effective block time or height

            // for the entire transaction, we switch to using the

            // semantics of nLockTime which is the last invalid block

            // time or height.  Thus we subtract 1 from the calculated

            // time or height.

            // Time-based relative lock-times are measured from the

            // smallest allowed timestamp of the block containing the

            // txout being spent, which is the median time past of the

            // block prior.

            nMinTime = std::max(nMinTime, nCoinTime + (int64_t)((txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) << CTxIn::SEQUENCE_LOCKTIME_GRANULARITY) - 1);

        } else {

            nMinHeight = std::max(nMinHeight, nCoinHeight + (int)(txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) - 1);

        }

    }

    return std::make_pair(nMinHeight, nMinTime);

}

bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair)

{

    assert(block.pprev);

    int64_t nBlockTime = block.pprev->GetMedianTimePast();

    if (lockPair.first >= block.nHeight || lockPair.second >= nBlockTime)

        return false;

    return true;

}

bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)

{

    return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));

}

unsigned int GetLegacySigOpCount(const CTransaction& tx)

{

    unsigned int nSigOps = 0;

    for (const auto& txin : tx.vin)

    {

        nSigOps += txin.scriptSig.GetSigOpCount(false);

    }

    for (const auto& txout : tx.vout)

    {

        nSigOps += txout.scriptPubKey.GetSigOpCount(false);

    }

    return nSigOps;

}

unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& inputs)

{

    if (tx.IsCoinBase())

        return 0;

    unsigned int nSigOps = 0;

    for (unsigned int i = 0; i < tx.vin.size(); i++)

    {

        const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);

        assert(!coin.IsSpent());

        const CTxOut &prevout = coin.out;

        if (prevout.scriptPubKey.IsPayToScriptHash())

            nSigOps += prevout.scriptPubKey.GetSigOpCount(tx.vin[i].scriptSig);

    }

    return nSigOps;

}

int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, script_verify_flags flags)

{

    int64_t nSigOps = GetLegacySigOpCount(tx) * WITNESS_SCALE_FACTOR;

    if (tx.IsCoinBase())

        return nSigOps;

    if (flags & SCRIPT_VERIFY_P2SH) {

        nSigOps += GetP2SHSigOpCount(tx, inputs) * WITNESS_SCALE_FACTOR;

    }

    for (unsigned int i = 0; i < tx.vin.size(); i++)

    {

        const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);

        assert(!coin.IsSpent());

        const CTxOut &prevout = coin.out;

        nSigOps += CountWitnessSigOps(tx.vin[i].scriptSig, prevout.scriptPubKey, tx.vin[i].scriptWitness, flags);

    }

    return nSigOps;

}

bool Consensus::CheckTxInputs(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight, CAmount& txfee)

{

    // are the actual inputs available?

    if (!inputs.HaveInputs(tx)) {

        return state.Invalid(TxValidationResult::TX_MISSING_INPUTS, "bad-txns-inputs-missingorspent",

                         strprintf("%s: inputs missing/spent", __func__));

    }

    CAmount nValueIn = 0;

    for (unsigned int i = 0; i < tx.vin.size(); ++i) {

        const COutPoint &prevout = tx.vin[i].prevout;

        const Coin& coin = inputs.AccessCoin(prevout);

        assert(!coin.IsSpent());

        // If prev is coinbase, check that it's matured

        if (coin.IsCoinBase() && nSpendHeight - coin.nHeight < COINBASE_MATURITY) {

            return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND, "bad-txns-premature-spend-of-coinbase",

                strprintf("tried to spend coinbase at depth %d", nSpendHeight - coin.nHeight));

        }

        // Check for negative or overflow input values

        nValueIn += coin.out.nValue;

        if (!MoneyRange(coin.out.nValue) || !MoneyRange(nValueIn)) {

            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-inputvalues-outofrange");

        }

    }

    // `tx.GetValueOut()` won't throw in validation paths because output-range checks run first

    // (`bad-txns-vout-negative`, `bad-txns-vout-toolarge`, `bad-txns-txouttotal-toolarge`):

    // * `MemPoolAccept::PreChecks`: `CheckTransaction()` is called before this method;

    // * `Chainstate::ConnectBlock`: `CheckTransaction()` is called via `CheckBlock()` before this method.

    const CAmount value_out = tx.GetValueOut();

    if (nValueIn < value_out) {

        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-in-belowout",

            strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(value_out)));

    }

    // Tally transaction fees

    const CAmount txfee_aux = nValueIn - value_out;

    if (!MoneyRange(txfee_aux)) {

        // Unreachable, given the following preconditions:

        // * `value_out` comes from `tx.GetValueOut()`, which throws unless `MoneyRange(value_out)` and asserts `MoneyRange(nValueOut)` on return.

        // * `MoneyRange(nValueIn)` was enforced in the input loop.

        // * `nValueIn < value_out` was handled above, so `nValueIn >= value_out` here (and `txfee_aux >= 0`).

        // Therefore `0 <= txfee_aux = nValueIn - value_out <= nValueIn <= MAX_MONEY`.

        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-fee-outofrange");

    }

    txfee = txfee_aux;

    return true;

}