// Copyright (c) 2021-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_WALLET_MIGRATE_H

#define BITCOIN_WALLET_MIGRATE_H

#include <wallet/db.h>

#include <optional>

namespace wallet {

using BerkeleyROData = std::map<SerializeData, SerializeData, std::less<>>;

/**

 * A class representing a BerkeleyDB file from which we can only read records.

 * This is used only for migration of legacy to descriptor wallets

 */

class BerkeleyRODatabase : public WalletDatabase

{

private:

    const fs::path m_filepath;

public:

    /** Create DB handle */

    BerkeleyRODatabase(const fs::path& filepath, bool open = true) : WalletDatabase(), m_filepath(filepath)

    {

        if (open) Open();

    }

    ~BerkeleyRODatabase() = default;

    BerkeleyROData m_records;

    /** Open the database if it is not already opened. */

    void Open() override;

    /** Rewrite the entire database on disk

     */

    bool Rewrite() override { return false; }

    /** Back up the entire database to a file.

     */

    bool Backup(const std::string& strDest) const override;

    /** Flush to the database file and close the database.

     *  Also close the environment if no other databases are open in it.

     */

    void Close() override {}

    /** Return path to main database file for logs and error messages. */

    std::string Filename() override { return fs::PathToString(m_filepath); }

    std::vector<fs::path> Files() override { return {m_filepath}; }

    std::string Format() override { return "bdb_ro"; }

    /** Make a DatabaseBatch connected to this database */

    std::unique_ptr<DatabaseBatch> MakeBatch() override;

};

class BerkeleyROCursor : public DatabaseCursor

{

private:

    const BerkeleyRODatabase& m_database;

    BerkeleyROData::const_iterator m_cursor;

    BerkeleyROData::const_iterator m_cursor_end;

public:

    explicit BerkeleyROCursor(const BerkeleyRODatabase& database, std::span<const std::byte> prefix = {});

    ~BerkeleyROCursor() = default;

    Status Next(DataStream& key, DataStream& value) override;

};

/** RAII class that provides access to a BerkeleyRODatabase */

class BerkeleyROBatch : public DatabaseBatch

{

private:

    const BerkeleyRODatabase& m_database;

    bool ReadKey(DataStream&& key, DataStream& value) override;

    // WriteKey returns true since various automatic upgrades for older wallets will expect writing to not fail.

    // It is okay for this batch type to not actually write anything as those automatic upgrades will occur again after migration.

    bool WriteKey(DataStream&& key, DataStream&& value, bool overwrite = true) override { return true; }

    bool EraseKey(DataStream&& key) override { return false; }

    bool HasKey(DataStream&& key) override;

    bool ErasePrefix(std::span<const std::byte> prefix) override { return false; }

public:

    explicit BerkeleyROBatch(const BerkeleyRODatabase& database) : m_database(database) {}

    ~BerkeleyROBatch() = default;

    BerkeleyROBatch(const BerkeleyROBatch&) = delete;

    BerkeleyROBatch& operator=(const BerkeleyROBatch&) = delete;

    void Close() override {}

    std::unique_ptr<DatabaseCursor> GetNewCursor() override { return std::make_unique<BerkeleyROCursor>(m_database); }

    std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(std::span<const std::byte> prefix) override;

    bool TxnBegin() override { return false; }

    bool TxnCommit() override { return false; }

    bool TxnAbort() override { return false; }

    bool HasActiveTxn() override { return false; }

};

//! Return object giving access to Berkeley Read Only database at specified path.

std::unique_ptr<BerkeleyRODatabase> MakeBerkeleyRODatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);

} // namespace wallet

#endif // BITCOIN_WALLET_MIGRATE_H