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

#include <policy/fees/block_policy_estimator.h>

#include <script/solver.h>

#include <validation.h>

#include <wallet/coincontrol.h>

#include <wallet/spend.h>

#include <wallet/test/util.h>

#include <wallet/test/wallet_test_fixture.h>

#include <boost/test/unit_test.hpp>

namespace wallet {

BOOST_FIXTURE_TEST_SUITE(spend_tests, WalletTestingSetup)

BOOST_FIXTURE_TEST_CASE(SubtractFee, TestChain100Setup)

{

    CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));

    auto wallet = CreateSyncedWallet(*m_node.chain, WITH_LOCK(Assert(m_node.chainman)->GetMutex(), return m_node.chainman->ActiveChain()), coinbaseKey);

    // Check that a subtract-from-recipient transaction slightly less than the

    // coinbase input amount does not create a change output (because it would

    // be uneconomical to add and spend the output), and make sure it pays the

    // leftover input amount which would have been change to the recipient

    // instead of the miner.

    auto check_tx = [&wallet](CAmount leftover_input_amount) {

        CRecipient recipient{PubKeyDestination({}), 50 * COIN - leftover_input_amount, /*subtract_fee=*/true};

        CCoinControl coin_control;

        coin_control.m_feerate.emplace(10000);

        coin_control.fOverrideFeeRate = true;

        // We need to use a change type with high cost of change so that the leftover amount will be dropped to fee instead of added as a change output

        coin_control.m_change_type = OutputType::LEGACY;

        auto res = CreateTransaction(*wallet, {recipient}, /*change_pos=*/std::nullopt, coin_control);

        BOOST_CHECK(res);

        const auto& txr = *res;

        BOOST_CHECK_EQUAL(txr.tx->vout.size(), 1);

        BOOST_CHECK_EQUAL(txr.tx->vout[0].nValue, recipient.nAmount + leftover_input_amount - txr.fee);

        BOOST_CHECK_GT(txr.fee, 0);

        return txr.fee;

    };

    // Send full input amount to recipient, check that only nonzero fee is

    // subtracted (to_reduce == fee).

    const CAmount fee{check_tx(0)};

    // Send slightly less than full input amount to recipient, check leftover

    // input amount is paid to recipient not the miner (to_reduce == fee - 123)

    BOOST_CHECK_EQUAL(fee, check_tx(123));

    // Send full input minus fee amount to recipient, check leftover input

    // amount is paid to recipient not the miner (to_reduce == 0)

    BOOST_CHECK_EQUAL(fee, check_tx(fee));

    // Send full input minus more than the fee amount to recipient, check

    // leftover input amount is paid to recipient not the miner (to_reduce ==

    // -123). This overpays the recipient instead of overpaying the miner more

    // than double the necessary fee.

    BOOST_CHECK_EQUAL(fee, check_tx(fee + 123));

}

BOOST_FIXTURE_TEST_CASE(wallet_duplicated_preset_inputs_test, TestChain100Setup)

{

    // Verify that the wallet's Coin Selection process does not include pre-selected inputs twice in a transaction.

    // Add 4 spendable UTXO, 50 BTC each, to the wallet (total balance 200 BTC)

    for (int i = 0; i < 4; i++) CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));

    auto wallet = CreateSyncedWallet(*m_node.chain, WITH_LOCK(Assert(m_node.chainman)->GetMutex(), return m_node.chainman->ActiveChain()), coinbaseKey);

    LOCK(wallet->cs_wallet);

    auto available_coins = AvailableCoins(*wallet);

    std::vector<COutput> coins = available_coins.All();

    // Preselect the first 3 UTXO (150 BTC total)

    std::set<COutPoint> preset_inputs = {coins[0].outpoint, coins[1].outpoint, coins[2].outpoint};

    // Try to create a tx that spends more than what preset inputs + wallet selected inputs are covering for.

    // The wallet can cover up to 200 BTC, and the tx target is 299 BTC.

    std::vector<CRecipient> recipients{{*Assert(wallet->GetNewDestination(OutputType::BECH32, "dummy")),

                                           /*nAmount=*/299 * COIN, /*fSubtractFeeFromAmount=*/true}};

    CCoinControl coin_control;

    coin_control.m_allow_other_inputs = true;

    for (const auto& outpoint : preset_inputs) {

        coin_control.Select(outpoint);

    }

    // Attempt to send 299 BTC from a wallet that only has 200 BTC. The wallet should exclude

    // the preset inputs from the pool of available coins, realize that there is not enough

    // money to fund the 299 BTC payment, and fail with "Insufficient funds".

    //

    // Even with SFFO, the wallet can only afford to send 200 BTC.

    // If the wallet does not properly exclude preset inputs from the pool of available coins

    // prior to coin selection, it may create a transaction that does not fund the full payment

    // amount or, through SFFO, incorrectly reduce the recipient's amount by the difference

    // between the original target and the wrongly counted inputs (in this case 99 BTC)

    // so that the recipient's amount is no longer equal to the user's selected target of 299 BTC.

    // First case, use 'subtract_fee_from_outputs=true'

    BOOST_CHECK(!CreateTransaction(*wallet, recipients, /*change_pos=*/std::nullopt, coin_control));

    // Second case, don't use 'subtract_fee_from_outputs'.

    recipients[0].fSubtractFeeFromAmount = false;

    BOOST_CHECK(!CreateTransaction(*wallet, recipients, /*change_pos=*/std::nullopt, coin_control));

}

BOOST_AUTO_TEST_SUITE_END()

} // namespace wallet