// 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 <txdb.h>

#include <coins.h>

#include <dbwrapper.h>

#include <logging.h>

#include <primitives/transaction.h>

#include <random.h>

#include <serialize.h>

#include <uint256.h>

#include <util/vector.h>

#include <cassert>

#include <cstdlib>

#include <iterator>

#include <utility>

static constexpr uint8_t DB_COIN{'C'};

static constexpr uint8_t DB_BEST_BLOCK{'B'};

static constexpr uint8_t DB_HEAD_BLOCKS{'H'};

// Keys used in previous version that might still be found in the DB:

static constexpr uint8_t DB_COINS{'c'};

bool CCoinsViewDB::NeedsUpgrade()

{

    std::unique_ptr<CDBIterator> cursor{m_db->NewIterator()};

    // DB_COINS was deprecated in v0.15.0, commit

    // 1088b02f0ccd7358d2b7076bb9e122d59d502d02

    cursor->Seek(std::make_pair(DB_COINS, uint256{}));

    return cursor->Valid();

}

namespace {

struct CoinEntry {

    COutPoint* outpoint;

    uint8_t key;

    explicit CoinEntry(const COutPoint* ptr) : outpoint(const_cast<COutPoint*>(ptr)), key(DB_COIN)  {}

    SERIALIZE_METHODS(CoinEntry, obj) { READWRITE(obj.key, obj.outpoint->hash, VARINT(obj.outpoint->n)); }

Unexecuted instantiation: txdb.cpp:_ZN12_GLOBAL__N_19CoinEntry16SerializationOpsI10DataStreamKS0_15ActionSerializeEEvRT0_RT_T1_

Unexecuted instantiation: txdb.cpp:_ZN12_GLOBAL__N_19CoinEntry16SerializationOpsI10DataStreamS0_17ActionUnserializeEEvRT0_RT_T1_

};

} // namespace

CCoinsViewDB::CCoinsViewDB(DBParams db_params, CoinsViewOptions options) :

    m_db_params{std::move(db_params)},

    m_options{std::move(options)},

    m_db{std::make_unique<CDBWrapper>(m_db_params)} { }

void CCoinsViewDB::ResizeCache(size_t new_cache_size)

{

    // We can't do this operation with an in-memory DB since we'll lose all the coins upon

    // reset.

    if (!m_db_params.memory_only) {

        // Have to do a reset first to get the original `m_db` state to release its

        // filesystem lock.

        m_db.reset();

        m_db_params.cache_bytes = new_cache_size;

        m_db_params.wipe_data = false;

        m_db = std::make_unique<CDBWrapper>(m_db_params);

    }

}

std::optional<Coin> CCoinsViewDB::GetCoin(const COutPoint& outpoint) const

{

    if (Coin coin; m_db->Read(CoinEntry(&outpoint), coin)) return coin;

    return std::nullopt;

}

bool CCoinsViewDB::HaveCoin(const COutPoint &outpoint) const {

    return m_db->Exists(CoinEntry(&outpoint));

}

uint256 CCoinsViewDB::GetBestBlock() const {

    uint256 hashBestChain;

    if (!m_db->Read(DB_BEST_BLOCK, hashBestChain))

        return uint256();

    return hashBestChain;

}

std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {

    std::vector<uint256> vhashHeadBlocks;

    if (!m_db->Read(DB_HEAD_BLOCKS, vhashHeadBlocks)) {

        return std::vector<uint256>();

    }

    return vhashHeadBlocks;

}

bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashBlock) {

    CDBBatch batch(*m_db);

    size_t count = 0;

    size_t changed = 0;

    assert(!hashBlock.IsNull());

    uint256 old_tip = GetBestBlock();

    if (old_tip.IsNull()) {

        // We may be in the middle of replaying.

        std::vector<uint256> old_heads = GetHeadBlocks();

        if (old_heads.size() == 2) {

            if (old_heads[0] != hashBlock) {

                LogPrintLevel(BCLog::COINDB, BCLog::Level::Error, "The coins database detected an inconsistent state, likely due to a previous crash or shutdown. You will need to restart bitcoind with the -reindex-chainstate or -reindex configuration option.\n");

            }

            assert(old_heads[0] == hashBlock);

            old_tip = old_heads[1];

        }

    }

    // In the first batch, mark the database as being in the middle of a

    // transition from old_tip to hashBlock.

    // A vector is used for future extensibility, as we may want to support

    // interrupting after partial writes from multiple independent reorgs.

    batch.Erase(DB_BEST_BLOCK);

    batch.Write(DB_HEAD_BLOCKS, Vector(hashBlock, old_tip));

    for (auto it{cursor.Begin()}; it != cursor.End();) {

        if (it->second.IsDirty()) {

            CoinEntry entry(&it->first);

            if (it->second.coin.IsSpent())

                batch.Erase(entry);

            else

                batch.Write(entry, it->second.coin);

            changed++;

        }

        count++;

        it = cursor.NextAndMaybeErase(*it);

        if (batch.SizeEstimate() > m_options.batch_write_bytes) {

            LogDebug(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));

            m_db->WriteBatch(batch);

            batch.Clear();

            if (m_options.simulate_crash_ratio) {

                static FastRandomContext rng;

                if (rng.randrange(m_options.simulate_crash_ratio) == 0) {

                    LogPrintf("Simulating a crash. Goodbye.\n");

                    _Exit(0);

                }

            }

        }

    }

    // In the last batch, mark the database as consistent with hashBlock again.

    batch.Erase(DB_HEAD_BLOCKS);

    batch.Write(DB_BEST_BLOCK, hashBlock);

    LogDebug(BCLog::COINDB, "Writing final batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));

    bool ret = m_db->WriteBatch(batch);

    LogDebug(BCLog::COINDB, "Committed %u changed transaction outputs (out of %u) to coin database...\n", (unsigned int)changed, (unsigned int)count);

    return ret;

}

size_t CCoinsViewDB::EstimateSize() const

{

    return m_db->EstimateSize(DB_COIN, uint8_t(DB_COIN + 1));

}

/** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */

class CCoinsViewDBCursor: public CCoinsViewCursor

{

public:

    // Prefer using CCoinsViewDB::Cursor() since we want to perform some

    // cache warmup on instantiation.

    CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256&hashBlockIn):

        CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}

    ~CCoinsViewDBCursor() = default;

    bool GetKey(COutPoint &key) const override;

    bool GetValue(Coin &coin) const override;

    bool Valid() const override;

    void Next() override;

private:

    std::unique_ptr<CDBIterator> pcursor;

    std::pair<char, COutPoint> keyTmp;

    friend class CCoinsViewDB;

};

std::unique_ptr<CCoinsViewCursor> CCoinsViewDB::Cursor() const

{

    auto i = std::make_unique<CCoinsViewDBCursor>(

        const_cast<CDBWrapper&>(*m_db).NewIterator(), GetBestBlock());

    /* It seems that there are no "const iterators" for LevelDB.  Since we

       only need read operations on it, use a const-cast to get around

       that restriction.  */

    i->pcursor->Seek(DB_COIN);

    // Cache key of first record

    if (i->pcursor->Valid()) {

        CoinEntry entry(&i->keyTmp.second);

        i->pcursor->GetKey(entry);

        i->keyTmp.first = entry.key;

    } else {

        i->keyTmp.first = 0; // Make sure Valid() and GetKey() return false

    }

    return i;

}

bool CCoinsViewDBCursor::GetKey(COutPoint &key) const

{

    // Return cached key

    if (keyTmp.first == DB_COIN) {

        key = keyTmp.second;

        return true;

    }

    return false;

}

bool CCoinsViewDBCursor::GetValue(Coin &coin) const

{

    return pcursor->GetValue(coin);

}

bool CCoinsViewDBCursor::Valid() const

{

    return keyTmp.first == DB_COIN;

}

void CCoinsViewDBCursor::Next()

{

    pcursor->Next();

    CoinEntry entry(&keyTmp.second);

    if (!pcursor->Valid() || !pcursor->GetKey(entry)) {

        keyTmp.first = 0; // Invalidate cached key after last record so that Valid() and GetKey() return false

    } else {

        keyTmp.first = entry.key;

    }

}