// Copyright (c) 2017-2018 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 <chainparams.h>
#include <index/txindex.h>
#include <init.h>
#include <tinyformat.h>
#include <ui_interface.h>
#include <util.h>
#include <validation.h>
#include <warnings.h>

constexpr int64_t SYNC_LOG_INTERVAL = 30; // seconds
constexpr int64_t SYNC_LOCATOR_WRITE_INTERVAL = 30; // seconds

template<typename... Args>
static void FatalError(const char* fmt, const Args&... args)
{
    std::string strMessage = tfm::format(fmt, args...);
    SetMiscWarning(strMessage);
    LogPrintf("*** %s\n", strMessage);
    uiInterface.ThreadSafeMessageBox(
        "Error: A fatal internal error occurred, see debug.log for details",
        "", CClientUIInterface::MSG_ERROR);
    StartShutdown();
}

TxIndex::TxIndex(std::unique_ptr<TxIndexDB> db) :
    m_db(std::move(db)), m_synced(false), m_best_block_index(nullptr)
{}

bool TxIndex::Init()
{
    LOCK(cs_main);

    // Attempt to migrate txindex from the old database to the new one. Even if
    // chain_tip is null, the node could be reindexing and we still want to
    // delete txindex records in the old database.
    if (!m_db->MigrateData(*pblocktree, chainActive.GetLocator())) {
        return false;
    }

    CBlockLocator locator;
    if (!m_db->ReadBestBlock(locator)) {
        locator.SetNull();
    }

    m_best_block_index = FindForkInGlobalIndex(chainActive, locator);
    m_synced = m_best_block_index.load() == chainActive.Tip();
    return true;
}

static const CBlockIndex* NextSyncBlock(const CBlockIndex* pindex_prev)
{
    AssertLockHeld(cs_main);

    if (!pindex_prev) {
        return chainActive.Genesis();
    }

    const CBlockIndex* pindex = chainActive.Next(pindex_prev);
    if (pindex) {
        return pindex;
    }

    return chainActive.Next(chainActive.FindFork(pindex_prev));
}

void TxIndex::ThreadSync()
{
    const CBlockIndex* pindex = m_best_block_index.load();
    if (!m_synced) {
        auto& consensus_params = Params().GetConsensus();

        int64_t last_log_time = 0;
        int64_t last_locator_write_time = 0;
        while (true) {
            {
                LOCK(cs_main);
                const CBlockIndex* pindex_next = NextSyncBlock(pindex);
                if (!pindex_next) {
                    WriteBestBlock(pindex);
                    m_best_block_index = pindex;
                    m_synced = true;
                    break;
                }
                pindex = pindex_next;
            }

            int64_t current_time = GetTime();
            if (last_log_time + SYNC_LOG_INTERVAL < current_time) {
                LogPrintf("Syncing txindex with block chain from height %d\n", pindex->nHeight);
                last_log_time = current_time;
            }

            if (last_locator_write_time + SYNC_LOCATOR_WRITE_INTERVAL < current_time) {
                WriteBestBlock(pindex);
                last_locator_write_time = current_time;
            }

            CBlock block;
            if (!ReadBlockFromDisk(block, pindex, consensus_params)) {
                FatalError("%s: Failed to read block %s from disk",
                           __func__, pindex->GetBlockHash().ToString());
                return;
            }
            if (!WriteBlock(block, pindex)) {
                FatalError("%s: Failed to write block %s to tx index database",
                           __func__, pindex->GetBlockHash().ToString());
                return;
            }
        }
    }

    if (pindex) {
        LogPrintf("txindex is enabled at height %d\n", pindex->nHeight);
    } else {
        LogPrintf("txindex is enabled\n");
    }
}

bool TxIndex::WriteBlock(const CBlock& block, const CBlockIndex* pindex)
{
    CDiskTxPos pos(pindex->GetBlockPos(), GetSizeOfCompactSize(block.vtx.size()));
    std::vector<std::pair<uint256, CDiskTxPos>> vPos;
    vPos.reserve(block.vtx.size());
    for (const auto& tx : block.vtx) {
        vPos.emplace_back(tx->GetHash(), pos);
        pos.nTxOffset += ::GetSerializeSize(*tx, SER_DISK, CLIENT_VERSION);
    }
    return m_db->WriteTxs(vPos);
}

bool TxIndex::WriteBestBlock(const CBlockIndex* block_index)
{
    LOCK(cs_main);
    if (!m_db->WriteBestBlock(chainActive.GetLocator(block_index))) {
        return error("%s: Failed to write locator to disk", __func__);
    }
    return true;
}

void TxIndex::BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex,
                    const std::vector<CTransactionRef>& txn_conflicted)
{
    if (!m_synced) {
        return;
    }

    const CBlockIndex* best_block_index = m_best_block_index.load();
    if (!best_block_index) {
        if (pindex->nHeight != 0) {
            FatalError("%s: First block connected is not the genesis block (height=%d)",
                       __func__, pindex->nHeight);
            return;
        }
    } else {
        // Ensure block connects to an ancestor of the current best block. This should be the case
        // most of the time, but may not be immediately after the the sync thread catches up and sets
        // m_synced. Consider the case where there is a reorg and the blocks on the stale branch are
        // in the ValidationInterface queue backlog even after the sync thread has caught up to the
        // new chain tip. In this unlikely event, log a warning and let the queue clear.
        if (best_block_index->GetAncestor(pindex->nHeight - 1) != pindex->pprev) {
            LogPrintf("%s: WARNING: Block %s does not connect to an ancestor of " /* Continued */
                      "known best chain (tip=%s); not updating txindex\n",
                      __func__, pindex->GetBlockHash().ToString(),
                      best_block_index->GetBlockHash().ToString());
            return;
        }
    }

    if (WriteBlock(*block, pindex)) {
        m_best_block_index = pindex;
    } else {
        FatalError("%s: Failed to write block %s to txindex",
                   __func__, pindex->GetBlockHash().ToString());
        return;
    }
}

void TxIndex::SetBestChain(const CBlockLocator& locator)
{
    if (!m_synced) {
        return;
    }

    const uint256& locator_tip_hash = locator.vHave.front();
    const CBlockIndex* locator_tip_index;
    {
        LOCK(cs_main);
        locator_tip_index = LookupBlockIndex(locator_tip_hash);
    }

    if (!locator_tip_index) {
        FatalError("%s: First block (hash=%s) in locator was not found",
                   __func__, locator_tip_hash.ToString());
        return;
    }

    // This checks that SetBestChain callbacks are received after BlockConnected. The check may fail
    // immediately after the the sync thread catches up and sets m_synced. Consider the case where
    // there is a reorg and the blocks on the stale branch are in the ValidationInterface queue
    // backlog even after the sync thread has caught up to the new chain tip. In this unlikely
    // event, log a warning and let the queue clear.
    const CBlockIndex* best_block_index = m_best_block_index.load();
    if (best_block_index->GetAncestor(locator_tip_index->nHeight) != locator_tip_index) {
        LogPrintf("%s: WARNING: Locator contains block (hash=%s) not on known best " /* Continued */
                  "chain (tip=%s); not writing txindex locator\n",
                  __func__, locator_tip_hash.ToString(),
                  best_block_index->GetBlockHash().ToString());
        return;
    }

    if (!m_db->WriteBestBlock(locator)) {
        error("%s: Failed to write locator to disk", __func__);
    }
}

bool TxIndex::FindTx(const uint256& txid, CDiskTxPos& pos) const
{
    return m_db->ReadTxPos(txid, pos);
}

void TxIndex::Start()
{
    // Need to register this ValidationInterface before running Init(), so that
    // callbacks are not missed if Init sets m_synced to true.
    RegisterValidationInterface(this);
    if (!Init()) {
        FatalError("%s: txindex failed to initialize", __func__);
        return;
    }

    m_thread_sync = std::thread(&TraceThread<std::function<void()>>, "txindex",
                                std::bind(&TxIndex::ThreadSync, this));
}

void TxIndex::Stop()
{
    UnregisterValidationInterface(this);

    if (m_thread_sync.joinable()) {
        m_thread_sync.join();
    }
}