// Copyright (c) 2009-2010 Satoshi Nakamoto

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

#include <chain.h>

#include <chainparams.h>

#include <common/args.h>

#include <consensus/amount.h>

#include <consensus/consensus.h>

#include <consensus/merkle.h>

#include <consensus/params.h>

#include <consensus/tx_verify.h>

#include <consensus/validation.h>

#include <interfaces/types.h>

#include <node/blockstorage.h>

#include <node/kernel_notifications.h>

#include <node/mining_args.h>

#include <node/mining_types.h>

#include <policy/feerate.h>

#include <policy/policy.h>

#include <pow.h>

#include <primitives/block.h>

#include <primitives/transaction.h>

#include <script/script.h>

#include <sync.h>

#include <tinyformat.h>

#include <txgraph.h>

#include <txmempool.h>

#include <uint256.h>

#include <util/check.h>

#include <util/feefrac.h>

#include <util/log.h>

#include <util/result.h>

#include <util/signalinterrupt.h>

#include <util/time.h>

#include <util/translation.h>

#include <validation.h>

#include <validationinterface.h>

#include <versionbits.h>

#include <algorithm>

#include <compare>

#include <condition_variable>

#include <cstddef>

#include <functional>

#include <numeric>

#include <span>

#include <stdexcept>

#include <string>

#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);

}

BlockAssembler::BlockAssembler(Chainstate& chainstate,

                               const CTxMemPool* mempool,

                               BlockCreateOptions options)

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

      m_mempool{options.use_mempool ? mempool : nullptr},

      m_chainstate{chainstate},

      m_options{[&] {

          if (auto result{CheckMiningOptions(options, /*use_argnames=*/false)}; !result) {

              throw std::runtime_error(util::ErrorString(result).original);

          }

          return FlattenMiningOptions(std::move(options));

      }()}

{

}

void BlockAssembler::resetBlock()

{

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

    nBlockWeight = *Assert(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();

    if (m_mempool) {

        LOCK(m_mempool->cs);

        m_mempool->StartBlockBuilding();

        addChunks();

        m_mempool->StopBlockBuilding();

    }

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

    m_last_block_num_txs = nBlockTx;

    m_last_block_weight = nBlockWeight;

    // Create coinbase transaction.

    CMutableTransaction coinbaseTx;

    // Construct coinbase transaction struct in parallel

    CoinbaseTx& coinbase_tx{pblocktemplate->m_coinbase_tx};

    coinbase_tx.version = coinbaseTx.version;

    coinbaseTx.vin.resize(1);

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

    coinbaseTx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL; // Make sure timelock is enforced.

    coinbase_tx.sequence = coinbaseTx.vin[0].nSequence;

    // Add an output that spends the full coinbase reward.

    coinbaseTx.vout.resize(1);

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

    // Block subsidy + fees

    const CAmount block_reward{nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus())};

    coinbaseTx.vout[0].nValue = block_reward;

    coinbase_tx.block_reward_remaining = block_reward;

    // Start the coinbase scriptSig with the block height as required by BIP34.

    // Mining clients are expected to append extra data to this prefix, so

    // increasing its length would reduce the space they can use and may break

    // existing clients.

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

    // Set script_sig_prefix here, so IPC mining clients are not affected by

    // the optional scriptSig padding below. They provide their own extraNonce,

    // and in a typical setup a pool name or realistic extraNonce already makes

    // the scriptSig long enough.

    coinbase_tx.script_sig_prefix = coinbaseTx.vin[0].scriptSig;

    if (nHeight <= 16) {

        // For blocks at heights <= 16, the BIP34-encoded height alone is only

        // one byte. Consensus requires coinbase scriptSigs to be at least two

        // bytes long (bad-cb-length), so an OP_0 is always appended at those

        // heights.

        coinbaseTx.vin[0].scriptSig << OP_0;

    }

    Assert(nHeight > 0);

    coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);

    coinbase_tx.lock_time = coinbaseTx.nLockTime;

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

    m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);

    const CTransactionRef& final_coinbase{pblock->vtx[0]};

    if (final_coinbase->HasWitness()) {

        const auto& witness_stack{final_coinbase->vin[0].scriptWitness.stack};

        // Consensus requires the coinbase witness stack to have exactly one

        // element of 32 bytes.

        Assert(witness_stack.size() == 1 && witness_stack[0].size() == 32);

        coinbase_tx.witness = uint256(witness_stack[0]);

    }

    if (const int witness_index = GetWitnessCommitmentIndex(*pblock); witness_index != NO_WITNESS_COMMITMENT) {

        Assert(witness_index >= 0 && static_cast<size_t>(witness_index) < final_coinbase->vout.size());

        coinbase_tx.required_outputs.push_back(final_coinbase->vout[witness_index]);

    }

    LogInfo("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;

    if (m_options.test_block_validity) {

        if (BlockValidationState state{TestBlockValidity(m_chainstate, *pblock, /*check_pow=*/false, /*check_merkle_root=*/false)}; !state.IsValid()) {

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

        }

    }

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

    LogDebug(BCLog::BENCH, "CreateNewBlock() chunks: %.2fms, validity: %.2fms (total %.2fms)\n",

             Ticks<MillisecondsDouble>(time_1 - time_start),

             Ticks<MillisecondsDouble>(time_2 - time_1),

             Ticks<MillisecondsDouble>(time_2 - time_start));

    return std::move(pblocktemplate);

}

bool BlockAssembler::TestChunkBlockLimits(FeePerWeight chunk_feerate, int64_t chunk_sigops_cost) const

{

    // block_max_weight has been flattened before block assembly limit checks.

    Assert(m_options.block_max_weight);

    if (nBlockWeight + chunk_feerate.size >= *m_options.block_max_weight) {

        return false;

    }

    if (nBlockSigOpsCost + chunk_sigops_cost >= MAX_BLOCK_SIGOPS_COST) {

        return false;

    }

    return true;

}

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

// - transaction finality (locktime)

bool BlockAssembler::TestChunkTransactions(const std::vector<CTxMemPoolEntryRef>& txs) const

{

    for (const auto tx : txs) {

        if (!IsFinalTx(tx.get().GetTx(), nHeight, m_lock_time_cutoff)) {

            return false;

        }

    }

    return true;

}

void BlockAssembler::AddToBlock(const CTxMemPoolEntry& entry)

{

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

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

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

    nBlockWeight += entry.GetTxWeight();

    ++nBlockTx;

    nBlockSigOpsCost += entry.GetSigOpCost();

    nFees += entry.GetFee();

    if (*m_options.print_modified_fee) {

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

                  CFeeRate(entry.GetModifiedFee(), entry.GetTxSize()).ToString(),

                  entry.GetTx().GetHash().ToString());

    }

}

void BlockAssembler::addChunks()

{

    // 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;

    constexpr int32_t BLOCK_FULL_ENOUGH_WEIGHT_DELTA = 4000;

    int64_t nConsecutiveFailed = 0;

    std::vector<CTxMemPoolEntry::CTxMemPoolEntryRef> selected_transactions;

    selected_transactions.reserve(MAX_CLUSTER_COUNT_LIMIT);

    FeePerWeight chunk_feerate;

    // This fills selected_transactions

    chunk_feerate = m_mempool->GetBlockBuilderChunk(selected_transactions);

    FeePerVSize chunk_feerate_vsize = ToFeePerVSize(chunk_feerate);

    while (selected_transactions.size() > 0) {

        // Check to see if min fee rate is still respected.

        if (ByRatio{chunk_feerate_vsize} < ByRatio{m_options.block_min_fee_rate->GetFeePerVSize()}) {

            // Everything else we might consider has a lower feerate

            return;

        }

        int64_t chunk_sig_ops = 0;

        for (const auto& tx : selected_transactions) {

            chunk_sig_ops += tx.get().GetSigOpCost();

        }

        // Check to see if this chunk will fit.

        if (!TestChunkBlockLimits(chunk_feerate, chunk_sig_ops) || !TestChunkTransactions(selected_transactions)) {

            // This chunk won't fit, so we skip it and will try the next best one.

            m_mempool->SkipBuilderChunk();

            ++nConsecutiveFailed;

            // block_max_weight has been flattened before block assembly limit checks.

            Assert(m_options.block_max_weight);

            if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight +

                    BLOCK_FULL_ENOUGH_WEIGHT_DELTA > *m_options.block_max_weight) {

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

                return;

            }

        } else {

            m_mempool->IncludeBuilderChunk();

            // This chunk will fit, so add it to the block.

            nConsecutiveFailed = 0;

            for (const auto& tx : selected_transactions) {

                AddToBlock(tx);

            }

            pblocktemplate->m_package_feerates.emplace_back(chunk_feerate_vsize);

        }

        selected_transactions.clear();

        chunk_feerate = m_mempool->GetBlockBuilderChunk(selected_transactions);

        chunk_feerate_vsize = ToFeePerVSize(chunk_feerate);

    }

}

void AddMerkleRootAndCoinbase(CBlock& block, CTransactionRef coinbase, uint32_t version, uint32_t timestamp, uint32_t nonce)

{

    if (block.vtx.size() == 0) {

        block.vtx.emplace_back(coinbase);

    } else {

        block.vtx[0] = coinbase;

    }

    block.nVersion = version;

    block.nTime = timestamp;

    block.nNonce = nonce;

    block.hashMerkleRoot = BlockMerkleRoot(block);

    // Reset cached checks

    block.m_checked_witness_commitment = false;

    block.m_checked_merkle_root = false;

    block.fChecked = false;

}

namespace {

class SubmitBlockStateCatcher final : public CValidationInterface

{

public:

    uint256 m_hash;

    bool m_found{false};

    BlockValidationState m_state;

    explicit SubmitBlockStateCatcher(const uint256& hash) : m_hash{hash} {}

protected:

    void BlockChecked(const std::shared_ptr<const CBlock>& block, const BlockValidationState& state) override

    {

        if (block->GetHash() != m_hash) return;

        // ProcessNewBlock emits BlockChecked synchronously while holding cs_main,

        // so SubmitBlock can read these fields after ProcessNewBlock returns

        // without extra synchronization.

        m_found = true;

        m_state = state;

    }

};

} // namespace

bool SubmitBlock(ChainstateManager& chainman, const std::shared_ptr<const CBlock>& block, std::string& reason, std::string& debug)

{

    reason.clear();

    debug.clear();

    // This follows the submitblock RPC's validation-state capture pattern, but

    // is intentionally kept separate from the RPC implementation. The RPC entry

    // point decodes hex, formats BIP22/JSONRPC results, and calls

    // UpdateUncommittedBlockStructures() for legacy witness handling. IPC

    // callers submit already-formed blocks and need bool + reason/debug

    // results.

    auto sc = std::make_shared<SubmitBlockStateCatcher>(block->GetHash());

    CHECK_NONFATAL(chainman.m_options.signals)->RegisterSharedValidationInterface(sc);

    bool new_block;

    bool accepted = chainman.ProcessNewBlock(block, /*force_processing=*/true, /*min_pow_checked=*/true, /*new_block=*/&new_block);

    // No queue drain is needed. The BlockChecked notification used above is

    // emitted synchronously by ProcessNewBlock, unlike most validation signals.

    CHECK_NONFATAL(chainman.m_options.signals)->UnregisterSharedValidationInterface(sc);

    if (!new_block && accepted) {

        reason = "duplicate";

    } else if (!accepted && (!sc->m_found || sc->m_state.IsValid())) {

        // ProcessNewBlock can fail without a validation result, for example

        // from an activation or system error. It can also fail after a valid

        // BlockChecked result. In these cases the validation result is

        // inconclusive.

        reason = "inconclusive";

    } else if (!sc->m_found) {

        // The block was accepted but not connected, for example if it does not

        // have more work than the current tip.

        reason = "inconclusive";

    } else if (!sc->m_state.IsValid()) {

        reason = sc->m_state.GetRejectReason();

        debug = sc->m_state.GetDebugMessage();

    }

    const bool result{accepted && new_block && reason.empty()};

    CHECK_NONFATAL(result == reason.empty());

    return result;

}

void InterruptWait(KernelNotifications& kernel_notifications, bool& interrupt_wait)

{

    LOCK(kernel_notifications.m_tip_block_mutex);

    interrupt_wait = true;

    kernel_notifications.m_tip_block_cv.notify_all();

}

std::unique_ptr<CBlockTemplate> WaitAndCreateNewBlock(ChainstateManager& chainman,

                                                      KernelNotifications& kernel_notifications,

                                                      CTxMemPool* mempool,

                                                      const std::unique_ptr<CBlockTemplate>& block_template,

                                                      const BlockWaitOptions& wait_options,

                                                      const BlockCreateOptions& create_options,

                                                      bool& interrupt_wait)

{

    // Delay calculating the current template fees, just in case a new block

    // comes in before the next tick.

    CAmount current_fees = -1;

    // Alternate waiting for a new tip and checking if fees have risen.

    // The latter check is expensive so we only run it once per second.

    auto now{NodeClock::now()};

    const auto deadline = now + wait_options.timeout;

    const MillisecondsDouble tick{1000};

    const bool allow_min_difficulty{chainman.GetParams().GetConsensus().fPowAllowMinDifficultyBlocks};

    do {

        bool tip_changed{false};

        {

            WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);

            // Note that wait_until() checks the predicate before waiting

            kernel_notifications.m_tip_block_cv.wait_until(lock, std::min(now + tick, deadline), [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {

                AssertLockHeld(kernel_notifications.m_tip_block_mutex);

                const auto tip_block{kernel_notifications.TipBlock()};

                // We assume tip_block is set, because this is an instance

                // method on BlockTemplate and no template could have been

                // generated before a tip exists.

                tip_changed = Assume(tip_block) && tip_block != block_template->block.hashPrevBlock;

                return tip_changed || chainman.m_interrupt || interrupt_wait;

            });

            if (interrupt_wait) {

                interrupt_wait = false;

                return nullptr;

            }

        }

        if (chainman.m_interrupt) return nullptr;

        // At this point the tip changed, a full tick went by or we reached

        // the deadline.

        // Must release m_tip_block_mutex before locking cs_main, to avoid deadlocks.

        LOCK(::cs_main);

        // On test networks return a minimum difficulty block after 20 minutes

        if (!tip_changed && allow_min_difficulty) {

            const NodeClock::time_point tip_time{std::chrono::seconds{chainman.ActiveChain().Tip()->GetBlockTime()}};

            if (now > tip_time + 20min) {

                tip_changed = true;

            }

        }

        /**

         * We determine if fees increased compared to the previous template by generating

         * a fresh template. There may be more efficient ways to determine how much

         * (approximate) fees for the next block increased, perhaps more so after

         * Cluster Mempool.

         *

         * We'll also create a new template if the tip changed during this iteration.

         */

        if (wait_options.fee_threshold < MAX_MONEY || tip_changed) {

            auto new_tmpl{BlockAssembler{

                chainman.ActiveChainstate(),

                mempool,

                create_options

                }.CreateNewBlock()};

            // If the tip changed, return the new template regardless of its fees.

            if (tip_changed) return new_tmpl;

            // Calculate the original template total fees if we haven't already

            if (current_fees == -1) {

                current_fees = std::accumulate(block_template->vTxFees.begin(), block_template->vTxFees.end(), CAmount{0});

            }

            // Check if fees increased enough to return the new template

            const CAmount new_fees = std::accumulate(new_tmpl->vTxFees.begin(), new_tmpl->vTxFees.end(), CAmount{0});

            Assume(wait_options.fee_threshold != MAX_MONEY);

            if (new_fees >= current_fees + wait_options.fee_threshold) return new_tmpl;

        }

        now = NodeClock::now();

    } while (now < deadline);

    return nullptr;

}

std::optional<BlockRef> GetTip(ChainstateManager& chainman)

{

    LOCK(::cs_main);

    CBlockIndex* tip{chainman.ActiveChain().Tip()};

    if (!tip) return {};

    return BlockRef{tip->GetBlockHash(), tip->nHeight};

}

bool CooldownIfHeadersAhead(ChainstateManager& chainman, KernelNotifications& kernel_notifications, const BlockRef& last_tip, bool& interrupt_mining)

{

    uint256 last_tip_hash{last_tip.hash};

    while (const std::optional<int> remaining = chainman.BlocksAheadOfTip()) {

        const int cooldown_seconds = std::clamp(*remaining, 3, 20);

        const auto cooldown_deadline{MockableSteadyClock::now() + std::chrono::seconds{cooldown_seconds}};

        {

            WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);

            kernel_notifications.m_tip_block_cv.wait_until(lock, cooldown_deadline, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {

                const auto tip_block = kernel_notifications.TipBlock();

                return chainman.m_interrupt || interrupt_mining || (tip_block && *tip_block != last_tip_hash);

            });

            if (chainman.m_interrupt || interrupt_mining) {

                interrupt_mining = false;

                return false;

            }

            // If the tip changed during the wait, extend the deadline

            const auto tip_block = kernel_notifications.TipBlock();

            if (tip_block && *tip_block != last_tip_hash) {

                last_tip_hash = *tip_block;

                continue;

            }

        }

        // No tip change and the cooldown window has expired.

        if (MockableSteadyClock::now() >= cooldown_deadline) break;

    }

    return true;

}

std::optional<BlockRef> WaitTipChanged(ChainstateManager& chainman, KernelNotifications& kernel_notifications, const uint256& current_tip, MillisecondsDouble& timeout, bool& interrupt)

{

    Assume(timeout >= 0ms); // No internal callers should use a negative timeout

    if (timeout < 0ms) timeout = 0ms;

    if (timeout > std::chrono::years{100}) timeout = std::chrono::years{100}; // Upper bound to avoid UB in std::chrono

    auto deadline{std::chrono::steady_clock::now() + timeout};

    {

        WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);

        // For callers convenience, wait longer than the provided timeout

        // during startup for the tip to be non-null. That way this function

        // always returns valid tip information when possible and only

        // returns null when shutting down, not when timing out.

        kernel_notifications.m_tip_block_cv.wait(lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {

            return kernel_notifications.TipBlock() || chainman.m_interrupt || interrupt;

        });

        if (chainman.m_interrupt || interrupt) {

            interrupt = false;

            return {};

        }

        // At this point TipBlock is set, so continue to wait until it is

        // different then `current_tip` provided by caller.

        kernel_notifications.m_tip_block_cv.wait_until(lock, deadline, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {

            return Assume(kernel_notifications.TipBlock()) != current_tip || chainman.m_interrupt || interrupt;

        });

        if (chainman.m_interrupt || interrupt) {

            interrupt = false;

            return {};

        }

    }

    // Must release m_tip_block_mutex before getTip() locks cs_main, to

    // avoid deadlocks.

    return GetTip(chainman);

}

} // namespace node