// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Copyright (c) 2019-2021 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#pragma once

#include <fs.h>
#include <serialize.h>

#include <string>

struct FlatFilePos {
    int nFile;
    unsigned int nPos;

    SERIALIZE_METHODS(FlatFilePos, obj) { READWRITE(VARINT_MODE(obj.nFile, VarIntMode::NONNEGATIVE_SIGNED), VARINT(obj.nPos)); }

    FlatFilePos() : nFile(-1), nPos(0) {}

    FlatFilePos(int nFileIn, unsigned int nPosIn)
        : nFile(nFileIn), nPos(nPosIn) {}

    friend bool operator==(const FlatFilePos &a, const FlatFilePos &b) {
        return (a.nFile == b.nFile && a.nPos == b.nPos);
    }

    friend bool operator!=(const FlatFilePos &a, const FlatFilePos &b) {
        return !(a == b);
    }

    void SetNull() {
        nFile = -1;
        nPos = 0;
    }
    bool IsNull() const { return (nFile == -1); }

    std::string ToString() const;
};

/**
 * FlatFileSeq represents a sequence of numbered files storing raw data. This
 * class facilitates access to and efficient management of these files.
 */
class FlatFileSeq {
private:
    const fs::path m_dir;
    const char *const m_prefix;
    const size_t m_chunk_size;

public:
    /**
     * Constructor
     *
     * @param dir The base directory that all files live in.
     * @param prefix A short prefix given to all file names.
     * @param chunk_size Disk space is pre-allocated in multiples of this
     * amount.
     */
    FlatFileSeq(fs::path dir, const char *prefix, size_t chunk_size);

    /** Get the name of the file at the given position. */
    fs::path FileName(const FlatFilePos &pos) const;

    /** Open a handle to the file at the given position. */
    FILE *Open(const FlatFilePos &pos, bool read_only = false);

    /**
     * Allocate additional space in a file after the given starting position.
     * The amount allocated will be the minimum multiple of the sequence chunk
     * size greater than add_size.
     *
     * @param[in] pos The starting position that bytes will be allocated after.
     * @param[in] add_size The minimum number of bytes to be allocated.
     * @param[out] out_of_space Whether the allocation failed due to
     * insufficient disk space.
     * @return The number of bytes successfully allocated.
     */
    size_t Allocate(const FlatFilePos &pos, size_t add_size,
                    bool &out_of_space);

    /**
     * Commit a file to disk, and optionally truncate off extra pre-allocated
     * bytes if final.
     *
     * @param[in] pos The first unwritten position in the file to be flushed.
     * @param[in] finalize True if no more data will be written to this file.
     * @return true on success, false on failure.
     */
    bool Flush(const FlatFilePos &pos, bool finalize = false);
};
