// Copyright (c) 2009-2010 Satoshi Nakamoto

// Copyright (c) 2009-2022 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 <node/miner.h>

#include <chain.h>

#include <chainparams.h>

#include <coins.h>

#include <common/args.h>

#include <consensus/amount.h>

#include <consensus/consensus.h>

#include <consensus/merkle.h>

#include <consensus/tx_verify.h>

#include <consensus/validation.h>

#include <deploymentstatus.h>

#include <logging.h>

#include <policy/feerate.h>

#include <policy/policy.h>

#include <pow.h>

#include <primitives/transaction.h>

#include <util/moneystr.h>

#include <util/time.h>

#include <validation.h>

#include <algorithm>

#include <utility>

namespace node {

int64_t GetMinimumTime(const CBlockIndex* pindexPrev, const int64_t difficulty_adjustment_interval)

{

    int64_t min_time{pindexPrev->GetMedianTimePast() + 1};

    // Height of block to be mined.

    const int height{pindexPrev->nHeight + 1};

    // Account for BIP94 timewarp rule on all networks. This makes future

    // activation safer.

    if (height % difficulty_adjustment_interval == 0) {

        min_time = std::max<int64_t>(min_time, pindexPrev->GetBlockTime() - MAX_TIMEWARP);

    }

    return min_time;

}

int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)

{

    int64_t nOldTime = pblock->nTime;

    int64_t nNewTime{std::max<int64_t>(GetMinimumTime(pindexPrev, consensusParams.DifficultyAdjustmentInterval()),

                                       TicksSinceEpoch<std::chrono::seconds>(NodeClock::now()))};

    if (nOldTime < nNewTime) {

        pblock->nTime = nNewTime;

    }

    // Updating time can change work required on testnet:

    if (consensusParams.fPowAllowMinDifficultyBlocks) {

        pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);

    }

    return nNewTime - nOldTime;

}

void RegenerateCommitments(CBlock& block, ChainstateManager& chainman)

{

    CMutableTransaction tx{*block.vtx.at(0)};

    tx.vout.erase(tx.vout.begin() + GetWitnessCommitmentIndex(block));

    block.vtx.at(0) = MakeTransactionRef(tx);

    const CBlockIndex* prev_block = WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(block.hashPrevBlock));

    chainman.GenerateCoinbaseCommitment(block, prev_block);

    block.hashMerkleRoot = BlockMerkleRoot(block);

}

static BlockAssembler::Options ClampOptions(BlockAssembler::Options options)

{

    Assert(options.block_reserved_weight <= MAX_BLOCK_WEIGHT);

    Assert(options.block_reserved_weight >= MINIMUM_BLOCK_RESERVED_WEIGHT);

    Assert(options.coinbase_output_max_additional_sigops <= MAX_BLOCK_SIGOPS_COST);

    // Limit weight to between block_reserved_weight and MAX_BLOCK_WEIGHT for sanity:

    // block_reserved_weight can safely exceed -blockmaxweight, but the rest of the block template will be empty.

    options.nBlockMaxWeight = std::clamp<size_t>(options.nBlockMaxWeight, options.block_reserved_weight, MAX_BLOCK_WEIGHT);

    return options;

}

BlockAssembler::BlockAssembler(Chainstate& chainstate, const CTxMemPool* mempool, const Options& options)

    : chainparams{chainstate.m_chainman.GetParams()},

      m_mempool{options.use_mempool ? mempool : nullptr},

      m_chainstate{chainstate},

      m_options{ClampOptions(options)}

{

}

void ApplyArgsManOptions(const ArgsManager& args, BlockAssembler::Options& options)

{

    // Block resource limits

    options.nBlockMaxWeight = args.GetIntArg("-blockmaxweight", options.nBlockMaxWeight);

    if (const auto blockmintxfee{args.GetArg("-blockmintxfee")}) {

        if (const auto parsed{ParseMoney(*blockmintxfee)}) options.blockMinFeeRate = CFeeRate{*parsed};

    }

    options.print_modified_fee = args.GetBoolArg("-printpriority", options.print_modified_fee);

    options.block_reserved_weight = args.GetIntArg("-blockreservedweight", options.block_reserved_weight);

}

void BlockAssembler::resetBlock()

{

    inBlock.clear();

    // Reserve space for fixed-size block header, txs count, and coinbase tx.

    nBlockWeight = m_options.block_reserved_weight;

    nBlockSigOpsCost = m_options.coinbase_output_max_additional_sigops;

    // These counters do not include coinbase tx

    nBlockTx = 0;

    nFees = 0;

}

std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()

{

    const auto time_start{SteadyClock::now()};

    resetBlock();

    pblocktemplate.reset(new CBlockTemplate());

    CBlock* const pblock = &pblocktemplate->block; // pointer for convenience

    // Add dummy coinbase tx as first transaction. It is skipped by the

    // getblocktemplate RPC and mining interface consumers must not use it.

    pblock->vtx.emplace_back();

    LOCK(::cs_main);

    CBlockIndex* pindexPrev = m_chainstate.m_chain.Tip();

    assert(pindexPrev != nullptr);

    nHeight = pindexPrev->nHeight + 1;

    pblock->nVersion = m_chainstate.m_chainman.m_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());

    // -regtest only: allow overriding block.nVersion with

    // -blockversion=N to test forking scenarios

    if (chainparams.MineBlocksOnDemand()) {

        pblock->nVersion = gArgs.GetIntArg("-blockversion", pblock->nVersion);

    }

    pblock->nTime = TicksSinceEpoch<std::chrono::seconds>(NodeClock::now());

    m_lock_time_cutoff = pindexPrev->GetMedianTimePast();

    int nPackagesSelected = 0;

    int nDescendantsUpdated = 0;

    if (m_mempool) {

        addPackageTxs(nPackagesSelected, nDescendantsUpdated);

    }

    const auto time_1{SteadyClock::now()};

    m_last_block_num_txs = nBlockTx;

    m_last_block_weight = nBlockWeight;

    // Create coinbase transaction.

    CMutableTransaction coinbaseTx;

    coinbaseTx.vin.resize(1);

    coinbaseTx.vin[0].prevout.SetNull();

    coinbaseTx.vout.resize(1);

    coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;

    coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());

    coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;

    pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));

    pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);

    LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);

    // Fill in header

    pblock->hashPrevBlock  = pindexPrev->GetBlockHash();

    UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);

    pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());

    pblock->nNonce         = 0;

    BlockValidationState state;

    if (m_options.test_block_validity && !TestBlockValidity(state, chainparams, m_chainstate, *pblock, pindexPrev,

                                                            /*fCheckPOW=*/false, /*fCheckMerkleRoot=*/false)) {

        throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));

    }

    const auto time_2{SteadyClock::now()};

    LogDebug(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n",

             Ticks<MillisecondsDouble>(time_1 - time_start), nPackagesSelected, nDescendantsUpdated,

             Ticks<MillisecondsDouble>(time_2 - time_1),

             Ticks<MillisecondsDouble>(time_2 - time_start));

    return std::move(pblocktemplate);

}

void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)

{

    for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {

        // Only test txs not already in the block

        if (inBlock.count((*iit)->GetSharedTx()->GetHash())) {

            testSet.erase(iit++);

        } else {

            iit++;

        }

    }

}

bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const

{

    // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.

    if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= m_options.nBlockMaxWeight) {

        return false;

    }

    if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST) {

        return false;

    }

    return true;

}

// Perform transaction-level checks before adding to block:

// - transaction finality (locktime)

bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package) const

{

    for (CTxMemPool::txiter it : package) {

        if (!IsFinalTx(it->GetTx(), nHeight, m_lock_time_cutoff)) {

            return false;

        }

    }

    return true;

}

void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)

{

    pblocktemplate->block.vtx.emplace_back(iter->GetSharedTx());

    pblocktemplate->vTxFees.push_back(iter->GetFee());

    pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());

    nBlockWeight += iter->GetTxWeight();

    ++nBlockTx;

    nBlockSigOpsCost += iter->GetSigOpCost();

    nFees += iter->GetFee();

    inBlock.insert(iter->GetSharedTx()->GetHash());

    if (m_options.print_modified_fee) {

        LogPrintf("fee rate %s txid %s\n",

                  CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),

                  iter->GetTx().GetHash().ToString());

    }

}

/** Add descendants of given transactions to mapModifiedTx with ancestor

 * state updated assuming given transactions are inBlock. Returns number

 * of updated descendants. */

static int UpdatePackagesForAdded(const CTxMemPool& mempool,

                                  const CTxMemPool::setEntries& alreadyAdded,

                                  indexed_modified_transaction_set& mapModifiedTx) EXCLUSIVE_LOCKS_REQUIRED(mempool.cs)

{

    AssertLockHeld(mempool.cs);

    int nDescendantsUpdated = 0;

    for (CTxMemPool::txiter it : alreadyAdded) {

        CTxMemPool::setEntries descendants;

        mempool.CalculateDescendants(it, descendants);

        // Insert all descendants (not yet in block) into the modified set

        for (CTxMemPool::txiter desc : descendants) {

            if (alreadyAdded.count(desc)) {

                continue;

            }

            ++nDescendantsUpdated;

            modtxiter mit = mapModifiedTx.find(desc);

            if (mit == mapModifiedTx.end()) {

                CTxMemPoolModifiedEntry modEntry(desc);

                mit = mapModifiedTx.insert(modEntry).first;

            }

            mapModifiedTx.modify(mit, update_for_parent_inclusion(it));

        }

    }

    return nDescendantsUpdated;

}

void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, std::vector<CTxMemPool::txiter>& sortedEntries)

{

    // Sort package by ancestor count

    // If a transaction A depends on transaction B, then A's ancestor count

    // must be greater than B's.  So this is sufficient to validly order the

    // transactions for block inclusion.

    sortedEntries.clear();

    sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());

    std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());

}

// This transaction selection algorithm orders the mempool based

// on feerate of a transaction including all unconfirmed ancestors.

// Since we don't remove transactions from the mempool as we select them

// for block inclusion, we need an alternate method of updating the feerate

// of a transaction with its not-yet-selected ancestors as we go.

// This is accomplished by walking the in-mempool descendants of selected

// transactions and storing a temporary modified state in mapModifiedTxs.

// Each time through the loop, we compare the best transaction in

// mapModifiedTxs with the next transaction in the mempool to decide what

// transaction package to work on next.

void BlockAssembler::addPackageTxs(int& nPackagesSelected, int& nDescendantsUpdated)

{

    const auto& mempool{*Assert(m_mempool)};

    LOCK(mempool.cs);

    // mapModifiedTx will store sorted packages after they are modified

    // because some of their txs are already in the block

    indexed_modified_transaction_set mapModifiedTx;

    // Keep track of entries that failed inclusion, to avoid duplicate work

    std::set<Txid> failedTx;

    CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();

    CTxMemPool::txiter iter;

    // Limit the number of attempts to add transactions to the block when it is

    // close to full; this is just a simple heuristic to finish quickly if the

    // mempool has a lot of entries.

    const int64_t MAX_CONSECUTIVE_FAILURES = 1000;

    int64_t nConsecutiveFailed = 0;

    while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty()) {

        // First try to find a new transaction in mapTx to evaluate.

        //

        // Skip entries in mapTx that are already in a block or are present

        // in mapModifiedTx (which implies that the mapTx ancestor state is

        // stale due to ancestor inclusion in the block)

        // Also skip transactions that we've already failed to add. This can happen if

        // we consider a transaction in mapModifiedTx and it fails: we can then

        // potentially consider it again while walking mapTx.  It's currently

        // guaranteed to fail again, but as a belt-and-suspenders check we put it in

        // failedTx and avoid re-evaluation, since the re-evaluation would be using

        // cached size/sigops/fee values that are not actually correct.

        /** Return true if given transaction from mapTx has already been evaluated,

         * or if the transaction's cached data in mapTx is incorrect. */

        if (mi != mempool.mapTx.get<ancestor_score>().end()) {

            auto it = mempool.mapTx.project<0>(mi);

            assert(it != mempool.mapTx.end());

            if (mapModifiedTx.count(it) || inBlock.count(it->GetSharedTx()->GetHash()) || failedTx.count(it->GetSharedTx()->GetHash())) {

                ++mi;

                continue;

            }

        }

        // Now that mi is not stale, determine which transaction to evaluate:

        // the next entry from mapTx, or the best from mapModifiedTx?

        bool fUsingModified = false;

        modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();

        if (mi == mempool.mapTx.get<ancestor_score>().end()) {

            // We're out of entries in mapTx; use the entry from mapModifiedTx

            iter = modit->iter;

            fUsingModified = true;

        } else {

            // Try to compare the mapTx entry to the mapModifiedTx entry

            iter = mempool.mapTx.project<0>(mi);

            if (modit != mapModifiedTx.get<ancestor_score>().end() &&

                    CompareTxMemPoolEntryByAncestorFee()(*modit, CTxMemPoolModifiedEntry(iter))) {

                // The best entry in mapModifiedTx has higher score

                // than the one from mapTx.

                // Switch which transaction (package) to consider

                iter = modit->iter;

                fUsingModified = true;

            } else {

                // Either no entry in mapModifiedTx, or it's worse than mapTx.

                // Increment mi for the next loop iteration.

                ++mi;

            }

        }

        // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't

        // contain anything that is inBlock.

        assert(!inBlock.count(iter->GetSharedTx()->GetHash()));

        uint64_t packageSize = iter->GetSizeWithAncestors();

        CAmount packageFees = iter->GetModFeesWithAncestors();

        int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();

        if (fUsingModified) {

            packageSize = modit->nSizeWithAncestors;

            packageFees = modit->nModFeesWithAncestors;

            packageSigOpsCost = modit->nSigOpCostWithAncestors;

        }

        if (packageFees < m_options.blockMinFeeRate.GetFee(packageSize)) {

            // Everything else we might consider has a lower fee rate

            return;

        }

        if (!TestPackage(packageSize, packageSigOpsCost)) {

            if (fUsingModified) {

                // Since we always look at the best entry in mapModifiedTx,

                // we must erase failed entries so that we can consider the

                // next best entry on the next loop iteration

                mapModifiedTx.get<ancestor_score>().erase(modit);

                failedTx.insert(iter->GetSharedTx()->GetHash());

            }

            ++nConsecutiveFailed;

            if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >

                    m_options.nBlockMaxWeight - m_options.block_reserved_weight) {

                // Give up if we're close to full and haven't succeeded in a while

                break;

            }

            continue;

        }

        auto ancestors{mempool.AssumeCalculateMemPoolAncestors(__func__, *iter, CTxMemPool::Limits::NoLimits(), /*fSearchForParents=*/false)};

        onlyUnconfirmed(ancestors);

        ancestors.insert(iter);

        // Test if all tx's are Final

        if (!TestPackageTransactions(ancestors)) {

            if (fUsingModified) {

                mapModifiedTx.get<ancestor_score>().erase(modit);

                failedTx.insert(iter->GetSharedTx()->GetHash());

            }

            continue;

        }

        // This transaction will make it in; reset the failed counter.

        nConsecutiveFailed = 0;

        // Package can be added. Sort the entries in a valid order.

        std::vector<CTxMemPool::txiter> sortedEntries;

        SortForBlock(ancestors, sortedEntries);

        for (size_t i = 0; i < sortedEntries.size(); ++i) {

            AddToBlock(sortedEntries[i]);

            // Erase from the modified set, if present

            mapModifiedTx.erase(sortedEntries[i]);

        }

        ++nPackagesSelected;

        pblocktemplate->m_package_feerates.emplace_back(packageFees, static_cast<int32_t>(packageSize));

        // Update transactions that depend on each of these

        nDescendantsUpdated += UpdatePackagesForAdded(mempool, ancestors, mapModifiedTx);

    }

}

} // namespace node