// Copyright (c) 2009-2021 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/amount.h>

#include <primitives/transaction.h>

#include <script/interpreter.h>

#include <serialize.h>

#include <streams.h>

#include <test/fuzz/fuzz.h>

#include <test/util/script.h>

#include <cassert>

#include <ios>

#include <utility>

#include <vector>

FUZZ_TARGET(script_flags)

{

    if (buffer.size() > 100'000) return;

    DataStream ds{buffer};

    try {

        const CTransaction tx(deserialize, TX_WITH_WITNESS, ds);

        unsigned int verify_flags;

        ds >> verify_flags;

        if (!IsValidFlagCombination(verify_flags)) return;

        unsigned int fuzzed_flags;

        ds >> fuzzed_flags;

        std::vector<CTxOut> spent_outputs;

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

            CTxOut prevout;

            ds >> prevout;

            if (!MoneyRange(prevout.nValue)) {

                // prevouts should be consensus-valid

                prevout.nValue = 1;

            }

            spent_outputs.push_back(prevout);

        }

        PrecomputedTransactionData txdata;

        txdata.Init(tx, std::move(spent_outputs));

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

            const CTxOut& prevout = txdata.m_spent_outputs.at(i);

            const TransactionSignatureChecker checker{&tx, i, prevout.nValue, txdata, MissingDataBehavior::ASSERT_FAIL};

            ScriptError serror;

            const bool ret = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror);

            assert(ret == (serror == SCRIPT_ERR_OK));

            // Verify that removing flags from a passing test or adding flags to a failing test does not change the result

            if (ret) {

                verify_flags &= ~fuzzed_flags;

            } else {

                verify_flags |= fuzzed_flags;

            }

            if (!IsValidFlagCombination(verify_flags)) return;

            ScriptError serror_fuzzed;

            const bool ret_fuzzed = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror_fuzzed);

            assert(ret_fuzzed == (serror_fuzzed == SCRIPT_ERR_OK));

            assert(ret_fuzzed == ret);

        }

    } catch (const std::ios_base::failure&) {

        return;

    }

}