/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2024 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

// mapnik
#include <mapnik/image_reader.hpp>
#include <mapnik/util/char_array_buffer.hpp>
#include <mapnik/color.hpp>

// jpeg
extern "C" {
#include <jpeglib.h>
}

// std
#include <cstdio>
#include <memory>
#include <fstream>

namespace mapnik {

template<typename T>
class jpeg_reader : public image_reader
{
  public:
    using source_type = T;
    using input_stream = std::iostream;
    const static unsigned BUF_SIZE = 4096;

  private:
    struct jpeg_stream_wrapper
    {
        jpeg_source_mgr manager;
        input_stream* stream;
        JOCTET buffer[BUF_SIZE];
    };

    struct jpeg_info_guard
    {
        jpeg_info_guard(jpeg_decompress_struct* cinfo)
            : i_(cinfo)
        {}

        ~jpeg_info_guard() { jpeg_destroy_decompress(i_); }
        jpeg_decompress_struct* i_;
    };

  private:
    source_type source_;
    input_stream stream_;
    unsigned width_;
    unsigned height_;

  public:
    explicit jpeg_reader(std::string const& filename);
    explicit jpeg_reader(char const* data, size_t size);
    ~jpeg_reader();
    unsigned width() const final;
    unsigned height() const final;
    std::optional<box2d<double>> bounding_box() const override final;
    inline bool has_alpha() const final { return false; }
    void read(unsigned x, unsigned y, image_rgba8& image) final;
    image_any read(unsigned x, unsigned y, unsigned width, unsigned height) final;

  private:
    void init();
    static void on_error(j_common_ptr cinfo);
    static void on_error_message(j_common_ptr cinfo);
    static void init_source(j_decompress_ptr cinfo);
    static boolean fill_input_buffer(j_decompress_ptr cinfo);
    static void skip(j_decompress_ptr cinfo, long count);
    static void term(j_decompress_ptr cinfo);
    static void attach_stream(j_decompress_ptr cinfo, input_stream* in);
};

image_reader* create_jpeg_reader(std::string const& filename)
{
    return new jpeg_reader<std::filebuf>(filename);
}

image_reader* create_jpeg_reader2(char const* data, size_t size)
{
    return new jpeg_reader<mapnik::util::char_array_buffer>(data, size);
}
void register_jpeg_reader()
{
    const bool registered = register_image_reader("jpeg", create_jpeg_reader);
    const bool registered2 = register_image_reader("jpeg", create_jpeg_reader2);
}

// ctors
template<typename T>
jpeg_reader<T>::jpeg_reader(std::string const& filename)
    : source_()
    , stream_(&source_)
    , width_(0)
    , height_(0)
{
    source_.open(filename, std::ios_base::in | std::ios_base::binary);
    if (!stream_)
        throw image_reader_exception("cannot open image file " + filename);
    init();
}

template<typename T>
jpeg_reader<T>::jpeg_reader(char const* data, size_t size)
    : source_(data, size)
    , stream_(&source_)
    , width_(0)
    , height_(0)
{
    if (!stream_)
        throw image_reader_exception("cannot open image stream");
    init();
}

// dtor
template<typename T>
jpeg_reader<T>::~jpeg_reader()
{}

// jpeg stream wrapper
template<typename T>
void jpeg_reader<T>::init_source(j_decompress_ptr cinfo)
{
    jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);
    wrap->stream->seekg(0, std::ios_base::beg);
}

template<typename T>
boolean jpeg_reader<T>::fill_input_buffer(j_decompress_ptr cinfo)
{
    jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);
    wrap->stream->read(reinterpret_cast<char*>(&wrap->buffer[0]), BUF_SIZE);
    std::streamsize size = wrap->stream->gcount();
    wrap->manager.next_input_byte = wrap->buffer;
    wrap->manager.bytes_in_buffer = BUF_SIZE;
    return (size > 0) ? TRUE : FALSE;
}

template<typename T>
void jpeg_reader<T>::skip(j_decompress_ptr cinfo, long count)
{
    if (count <= 0)
        return; // A zero or negative skip count should be treated as a no-op.
    jpeg_stream_wrapper* wrap = reinterpret_cast<jpeg_stream_wrapper*>(cinfo->src);

    if (wrap->manager.bytes_in_buffer > 0 && count < static_cast<long>(wrap->manager.bytes_in_buffer))
    {
        wrap->manager.bytes_in_buffer -= count;
        wrap->manager.next_input_byte = &wrap->buffer[BUF_SIZE - wrap->manager.bytes_in_buffer];
    }
    else
    {
        wrap->stream->seekg(count - wrap->manager.bytes_in_buffer, std::ios_base::cur);
        // trigger buffer fill
        wrap->manager.next_input_byte = 0;
        wrap->manager.bytes_in_buffer = 0; // bytes_in_buffer may be zero on return.
    }
}

template<typename T>
void jpeg_reader<T>::term(j_decompress_ptr /*cinfo*/)
{
    // no-op
}

template<typename T>
void jpeg_reader<T>::attach_stream(j_decompress_ptr cinfo, input_stream* in)
{
    if (cinfo->src == 0)
    {
        cinfo->src = (struct jpeg_source_mgr*)(*cinfo->mem->alloc_small)((j_common_ptr)cinfo,
                                                                         JPOOL_PERMANENT,
                                                                         sizeof(jpeg_stream_wrapper));
    }
    jpeg_reader::jpeg_stream_wrapper* src = reinterpret_cast<jpeg_reader::jpeg_stream_wrapper*>(cinfo->src);
    src->manager.init_source = init_source;
    src->manager.fill_input_buffer = fill_input_buffer;
    src->manager.skip_input_data = skip;
    src->manager.resync_to_restart = jpeg_resync_to_restart;
    src->manager.term_source = term;
    src->manager.bytes_in_buffer = 0;
    src->manager.next_input_byte = 0;
    src->stream = in;
}

template<typename T>
void jpeg_reader<T>::on_error(j_common_ptr cinfo)
{
    char buffer[JMSG_LENGTH_MAX];
    (*cinfo->err->format_message)(cinfo, buffer);
    throw image_reader_exception(std::string("JPEG Reader: libjpeg could not read image: ") + buffer);
}

template<typename T>
void jpeg_reader<T>::on_error_message(j_common_ptr cinfo)
{
    char buffer[JMSG_LENGTH_MAX];
    (*cinfo->err->format_message)(cinfo, buffer);
    throw image_reader_exception(std::string("JPEG Reader: libjpeg could not read image: ") + buffer);
}

template<typename T>
void jpeg_reader<T>::init()
{
    jpeg_decompress_struct cinfo;
    jpeg_info_guard iguard(&cinfo);
    jpeg_error_mgr jerr;
    cinfo.err = jpeg_std_error(&jerr);
    jerr.error_exit = on_error;
    jerr.output_message = on_error_message;
    jpeg_create_decompress(&cinfo);
    attach_stream(&cinfo, &stream_);
    int ret = jpeg_read_header(&cinfo, TRUE);
    if (ret != JPEG_HEADER_OK)
        throw image_reader_exception("JPEG Reader: failed to read header");
    jpeg_start_decompress(&cinfo);
    width_ = cinfo.output_width;
    height_ = cinfo.output_height;

    if (cinfo.out_color_space == JCS_UNKNOWN)
    {
        throw image_reader_exception("JPEG Reader: failed to read unknown color space");
    }
    if (cinfo.output_width == 0 || cinfo.output_height == 0)
    {
        throw image_reader_exception("JPEG Reader: failed to read image size of");
    }
}

template<typename T>
unsigned jpeg_reader<T>::width() const
{
    return width_;
}

template<typename T>
unsigned jpeg_reader<T>::height() const
{
    return height_;
}

template<typename T>
std::optional<box2d<double>> jpeg_reader<T>::bounding_box() const
{
    return std::nullopt;
}

template<typename T>
void jpeg_reader<T>::read(unsigned x0, unsigned y0, image_rgba8& image)
{
    stream_.clear();
    stream_.seekg(0, std::ios_base::beg);

    jpeg_decompress_struct cinfo;
    jpeg_info_guard iguard(&cinfo);
    jpeg_error_mgr jerr;
    cinfo.err = jpeg_std_error(&jerr);
    jerr.error_exit = on_error;
    jerr.output_message = on_error_message;
    jpeg_create_decompress(&cinfo);
    attach_stream(&cinfo, &stream_);
    int ret = jpeg_read_header(&cinfo, TRUE);
    if (ret != JPEG_HEADER_OK)
        throw image_reader_exception("JPEG Reader read(): failed to read header");
    jpeg_start_decompress(&cinfo);
    JSAMPARRAY buffer;
    int row_stride;
    unsigned char a, r, g, b;
    row_stride = cinfo.output_width * cinfo.output_components;
    buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo, JPOOL_IMAGE, row_stride, 1);

    const unsigned w = std::min(unsigned(image.width()), width_ - x0);
    const unsigned h = std::min(unsigned(image.height()), height_ - y0);

    const std::unique_ptr<unsigned int[]> out_row(new unsigned int[w]);
    unsigned row = 0;
    while (cinfo.output_scanline < cinfo.output_height)
    {
        jpeg_read_scanlines(&cinfo, buffer, 1);
        if (row >= y0 && row < y0 + h)
        {
            for (unsigned int x = 0; x < w; ++x)
            {
                unsigned col = x + x0;
                a = 255; // alpha not supported in jpg
                r = buffer[0][cinfo.output_components * col];
                if (cinfo.output_components > 2)
                {
                    g = buffer[0][cinfo.output_components * col + 1];
                    b = buffer[0][cinfo.output_components * col + 2];
                }
                else
                {
                    g = r;
                    b = r;
                }
                out_row[x] = color(r, g, b, a).rgba();
            }
            image.set_row(row - y0, out_row.get(), w);
        }
        ++row;
    }
    jpeg_finish_decompress(&cinfo);
}

template<typename T>
image_any jpeg_reader<T>::read(unsigned x, unsigned y, unsigned width, unsigned height)
{
    image_rgba8 data(width, height, true, true);
    read(x, y, data);
    return image_any(std::move(data));
}

} // namespace mapnik
