/*

 * Copyright (c) 2020-2022, the SerenityOS developers.

 * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/NonnullOwnPtr.h>

#include <AK/OwnPtr.h>

#include <AK/Stream.h>

#include <LibCompress/Deflate.h>

#include <LibCrypto/Checksum/CRC32.h>

namespace Compress {

constexpr u8 gzip_magic_1 = 0x1f;

constexpr u8 gzip_magic_2 = 0x8b;

struct [[gnu::packed]] BlockHeader {

    u8 identification_1;

    u8 identification_2;

    u8 compression_method;

    u8 flags;

    LittleEndian<u32> modification_time;

    u8 extra_flags;

    u8 operating_system;

    bool valid_magic_number() const;

    bool supported_by_implementation() const;

};

struct Flags {

    static constexpr u8 FTEXT = 1 << 0;

    static constexpr u8 FHCRC = 1 << 1;

    static constexpr u8 FEXTRA = 1 << 2;

    static constexpr u8 FNAME = 1 << 3;

    static constexpr u8 FCOMMENT = 1 << 4;

    static constexpr u8 MAX = FTEXT | FHCRC | FEXTRA | FNAME | FCOMMENT;

};

class GzipDecompressor final : public Stream {

public:

    GzipDecompressor(MaybeOwned<Stream>);

    ~GzipDecompressor();

    virtual ErrorOr<Bytes> read_some(Bytes) override;

    virtual ErrorOr<size_t> write_some(ReadonlyBytes) override;

    virtual bool is_eof() const override;

    virtual bool is_open() const override { return true; }

    virtual void close() override { }

    static ErrorOr<ByteBuffer> decompress_all(ReadonlyBytes);

    static ErrorOr<Optional<String>> describe_header(ReadonlyBytes);

    static bool is_likely_compressed(ReadonlyBytes bytes);

private:

    class Member {

    public:

        static ErrorOr<NonnullOwnPtr<Member>> construct(BlockHeader header, LittleEndianInputBitStream&);

        BlockHeader m_header;

        NonnullOwnPtr<DeflateDecompressor> m_stream;

        Crypto::Checksum::CRC32 m_checksum;

        size_t m_nread { 0 };

    private:

        Member(BlockHeader, NonnullOwnPtr<DeflateDecompressor>);

    };

    Member const& current_member() const { return *m_current_member; }

    Member& current_member() { return *m_current_member; }

    NonnullOwnPtr<LittleEndianInputBitStream> m_input_stream;

    u8 m_partial_header[sizeof(BlockHeader)];

    size_t m_partial_header_offset { 0 };

    OwnPtr<Member> m_current_member {};

    bool m_eof { false };

};

class GzipCompressor final : public Stream {

public:

    GzipCompressor(MaybeOwned<Stream>);

    virtual ErrorOr<Bytes> read_some(Bytes) override;

    virtual ErrorOr<size_t> write_some(ReadonlyBytes) override;

    virtual bool is_eof() const override;

    virtual bool is_open() const override;

    virtual void close() override;

    static ErrorOr<ByteBuffer> compress_all(ReadonlyBytes bytes);

private:

    MaybeOwned<Stream> m_output_stream;

};

}