/*
 * Xournal++
 *
 * Pixbuf utils
 *
 * Copied from F-Spot, part copied from GTK3
 */

/* f-pixbuf-utils.c
 *
 * Copyright (C) 2001, 2002, 2003 The Free Software Foundation, Inc.
 * Copyright (C) 2003 Ettore Perazzoli
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Author: Paolo Bacchilega <paolo.bacch@tin.it>
 *
 * Adapted by Ettore Perazzoli <ettore@perazzoli.org>
 */

/* Some bits are based upon the GIMP source code, the original copyright
 * note follows:
 *
 * The GIMP -- an image manipulation program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 */

#include "pixbuf-utils.h"

#include <cerrno>
#include <cmath>
#include <cstdio>

#include <gdk/gdk.h>

const cairo_user_data_key_t pixel_key = {0};
const cairo_user_data_key_t format_key = {0};

auto f_image_surface_create(cairo_format_t format, int width, int height) -> cairo_surface_t* {
    int size = 0;

    switch (format) {
        case CAIRO_FORMAT_ARGB32:
        case CAIRO_FORMAT_RGB24:
            size = 4;
            break;
        case CAIRO_FORMAT_A8:
            size = 8;
            break;
        case CAIRO_FORMAT_A1:
            size = 1;
            break;
        case CAIRO_FORMAT_INVALID:
        case CAIRO_FORMAT_RGB16_565:
        case CAIRO_FORMAT_RGB30:
        default:
            g_warning("Unsupported image format: %i\n", format);
            size = 1;
            break;
    }

    auto* pixels = static_cast<unsigned char*>(g_malloc(width * height * size));
    cairo_surface_t* surface = cairo_image_surface_create_for_data(pixels, format, width, height, width * size);

    cairo_surface_set_user_data(surface, &pixel_key, pixels, g_free);
    cairo_surface_set_user_data(surface, &format_key, GINT_TO_POINTER(format), nullptr);

    return surface;
}

auto f_image_surface_get_data(cairo_surface_t* surface) -> void* {
    return cairo_surface_get_user_data(surface, &pixel_key);
}

auto f_image_surface_get_format(cairo_surface_t* surface) -> cairo_format_t {
    return static_cast<cairo_format_t> GPOINTER_TO_INT(cairo_surface_get_user_data(surface, &format_key));
}

auto f_image_surface_get_width(cairo_surface_t* surface) -> int { return cairo_image_surface_get_width(surface); }

auto f_image_surface_get_height(cairo_surface_t* surface) -> int { return cairo_image_surface_get_height(surface); }

/* Public functions.  */

auto f_pixbuf_to_cairo_surface(GdkPixbuf* pixbuf) -> cairo_surface_t* {
    gint width = gdk_pixbuf_get_width(pixbuf);
    gint height = gdk_pixbuf_get_height(pixbuf);
    guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
    int gdk_rowstride = gdk_pixbuf_get_rowstride(pixbuf);
    int n_channels = gdk_pixbuf_get_n_channels(pixbuf);

    cairo_format_t format{};
    if (n_channels == 3) {
        format = CAIRO_FORMAT_RGB24;
    } else {
        format = CAIRO_FORMAT_ARGB32;
    }

    cairo_surface_t* surface = f_image_surface_create(format, width, height);
    auto* cairo_pixels = static_cast<guchar*>(f_image_surface_get_data(surface));

    for (int j = height; j; j--) {
        guchar* p = gdk_pixels;
        guchar* q = cairo_pixels;

        if (n_channels == 3) {
            guchar* end = p + 3 * width;

            while (p < end) {
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
                q[0] = p[2];
                q[1] = p[1];
                q[2] = p[0];
#else
                q[1] = p[0];
                q[2] = p[1];
                q[3] = p[2];
#endif
                p += 3;
                q += 4;
            }
        } else {
            guchar* end = p + 4 * width;
            guint t1 = 0, t2 = 0, t3 = 0;

            auto MULT = [](auto& d, auto c, auto a, auto& t) {
                t = c * a + 0x7f;
                d = ((t >> 8U) + t) >> 8U;
            };

            while (p < end) {
                if constexpr (G_BYTE_ORDER == G_LITTLE_ENDIAN) {
                    MULT(q[0], p[2], p[3], t1);
                    MULT(q[1], p[1], p[3], t2);
                    MULT(q[2], p[0], p[3], t3);
                    q[3] = p[3];
                } else {
                    q[0] = p[3];
                    MULT(q[1], p[0], p[3], t1);
                    MULT(q[2], p[1], p[3], t2);
                    MULT(q[3], p[2], p[3], t3);
                }

                p += 4;
                q += 4;
            }
        }

        gdk_pixels += gdk_rowstride;
        cairo_pixels += 4 * width;
    }

    return surface;
}

/**
 * Source GTK 3
 */

static auto gdk_cairo_format_for_content(cairo_content_t content) -> cairo_format_t {
    switch (content) {
        case CAIRO_CONTENT_COLOR:
            return CAIRO_FORMAT_RGB24;
        case CAIRO_CONTENT_ALPHA:
            return CAIRO_FORMAT_A8;
        case CAIRO_CONTENT_COLOR_ALPHA:
        default:
            return CAIRO_FORMAT_ARGB32;
    }
}

static auto gdk_cairo_surface_coerce_to_image(cairo_surface_t* surface, cairo_content_t content, int src_x, int src_y,
                                              int width, int height) -> cairo_surface_t* {
    cairo_surface_t* copy = cairo_image_surface_create(gdk_cairo_format_for_content(content), width, height);

    cairo_t* cr = cairo_create(copy);
    cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_surface(cr, surface, -src_x, -src_y);
    cairo_paint(cr);
    cairo_destroy(cr);

    return copy;
}

static void convert_alpha(guchar* dest_data, int dest_stride, guchar* src_data, int src_stride, int src_x, int src_y,
                          int width, int height) {
    src_data += src_stride * src_y + src_x * 4;

    for (int y = 0; y < height; y++) {
        auto* src = reinterpret_cast<guint32*>(src_data);

        for (int x = 0; x < width; x++) {
            guint alpha = src[x] >> 24;

            if (alpha == 0) {
                dest_data[x * 4 + 0] = 0;
                dest_data[x * 4 + 1] = 0;
                dest_data[x * 4 + 2] = 0;
            } else {
                dest_data[x * 4 + 0] = (((src[x] & 0xff0000U) >> 16U) * 255 + alpha / 2) / alpha;
                dest_data[x * 4 + 1] = (((src[x] & 0x00ff00U) >> 8U) * 255 + alpha / 2) / alpha;
                dest_data[x * 4 + 2] = (((src[x] & 0x0000ffU) >> 0U) * 255 + alpha / 2) / alpha;
            }
            dest_data[x * 4 + 3] = alpha;
        }

        src_data += src_stride;
        dest_data += dest_stride;
    }
}

static void convert_no_alpha(guchar* dest_data, int dest_stride, guchar* src_data, int src_stride, int src_x, int src_y,
                             int width, int height) {
    src_data += src_stride * src_y + src_x * 4;

    for (int y = 0; y < height; y++) {
        auto* src = reinterpret_cast<guint32*>(src_data);

        for (int x = 0; x < width; x++) {
            dest_data[x * 3 + 0] = src[x] >> 16U;
            dest_data[x * 3 + 1] = src[x] >> 8U;
            dest_data[x * 3 + 2] = src[x];
        }

        src_data += src_stride;
        dest_data += dest_stride;
    }
}

/**
 * gdk_pixbuf_get_from_surface:
 * @surface: surface to copy from
 * @src_x: Source X coordinate within @surface
 * @src_y: Source Y coordinate within @surface
 * @width: Width in pixels of region to get
 * @height: Height in pixels of region to get
 *
 * Transfers image data from a #cairo_surface_t and converts it to an RGB(A)
 * representation inside a #GdkPixbuf. This allows you to efficiently read
 * individual pixels from cairo surfaces. For #GdkWindows, use
 * gdk_pixbuf_get_from_window() instead.
 *
 * This function will create an RGB pixbuf with 8 bits per channel.
 * The pixbuf will contain an alpha channel if the @surface contains one.
 *
 * Return value: (transfer full): A newly-created pixbuf with a reference
 *     count of 1, or %nullptr on error
 */
auto xoj_pixbuf_get_from_surface(cairo_surface_t* surface, gint src_x, gint src_y, gint width, gint height)
        -> GdkPixbuf* {
    /* General sanity checks */
    g_return_val_if_fail(surface != nullptr, nullptr);
    g_return_val_if_fail(width > 0 && height > 0, nullptr);

    auto content = static_cast<cairo_content_t>(cairo_surface_get_content(surface) | CAIRO_CONTENT_COLOR);
    GdkPixbuf* dest = gdk_pixbuf_new(GDK_COLORSPACE_RGB, !!(content & CAIRO_CONTENT_ALPHA), 8, width, height);

    surface = gdk_cairo_surface_coerce_to_image(surface, content, src_x, src_y, width, height);
    cairo_surface_flush(surface);
    if (cairo_surface_status(surface) || dest == nullptr) {
        cairo_surface_destroy(surface);
        return nullptr;
    }

    if (gdk_pixbuf_get_has_alpha(dest)) {
        convert_alpha(gdk_pixbuf_get_pixels(dest), gdk_pixbuf_get_rowstride(dest),
                      cairo_image_surface_get_data(surface), cairo_image_surface_get_stride(surface), 0, 0, width,
                      height);
    } else {
        convert_no_alpha(gdk_pixbuf_get_pixels(dest), gdk_pixbuf_get_rowstride(dest),
                         cairo_image_surface_get_data(surface), cairo_image_surface_get_stride(surface), 0, 0, width,
                         height);
    }

    cairo_surface_destroy(surface);
    return dest;
}