// Copyright (c) 2017-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.

#ifndef BITCOIN_INDEX_TXINDEX_H

#define BITCOIN_INDEX_TXINDEX_H

#include <index/base.h>

#include <primitives/transaction.h>

#include <uint256.h>

#include <cstddef>

#include <memory>

#include <optional>

namespace interfaces {

class Chain;

}

namespace txindex_tests {

class TxIndexTest;

}

inline constexpr bool DEFAULT_TXINDEX{false};

/// A found transaction and the hash of the block that contains it.

struct TxIndexResult {

    uint256 block_hash;

    CTransactionRef tx;

};

/**

 * TxIndex is used to look up transactions included in the blockchain by hash.

 * The index is written to a LevelDB database and records the block sequence

 * number and serialized block offset of each transaction by transaction hash.

 */

class TxIndex final : public BaseIndex

{

protected:

    class DB;

private:

    friend class txindex_tests::TxIndexTest;

    const std::unique_ptr<DB> m_db;

    bool AllowPrune() const override { return false; }

    /// Look up a transaction among the legacy (full-txid) entries.

    std::optional<TxIndexResult> FindLegacyTx(const Txid& tx_hash) const;

protected:

    bool CustomAppend(const interfaces::BlockInfo& block) override;

    BaseIndex::DB& GetDB() const override;

public:

    /// Constructs the index, which becomes available to be queried.

    explicit TxIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory = false, bool f_wipe = false);

    // Destructor is declared because this class contains a unique_ptr to an incomplete type.

    virtual ~TxIndex() override;

    /// Look up a transaction by hash.

    ///

    /// @param[in]   tx_hash  The hash of the transaction to be returned.

    /// @return  the transaction and containing block hash, or nullopt if it is not found

    std::optional<TxIndexResult> FindTx(const Txid& tx_hash) const;

};

/// The global transaction index, used in GetTransaction. May be null.

extern std::unique_ptr<TxIndex> g_txindex;

#endif // BITCOIN_INDEX_TXINDEX_H