/*
 * Copyright 2022 Michael Drake <tlsa@netsurf-browser.org>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf 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; version 2 of the License.
 *
 * NetSurf 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, see <http://www.gnu.org/licenses/>.
 */

/** \file
 * Internal core bitmap interface.
 */

#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>

#include "utils/log.h"
#include "utils/errors.h"

#include "desktop/bitmap.h"
#include "desktop/gui_internal.h"

/** The client bitmap format. */
bitmap_fmt_t bitmap_fmt;

/** The client bitmap colour channel layout. */
struct bitmap_colour_layout bitmap_layout = {
	.r = 0,
	.g = 1,
	.b = 2,
	.a = 3,
};

/**
 * Get the colour layout for the given bitmap format.
 *
 * \param[in] fmt  Pixel format to get channel layout for,
 * \return channel layout structure.
 */
static struct bitmap_colour_layout bitmap__get_colour_layout(
		const bitmap_fmt_t *fmt)
{
	switch (fmt->layout) {
	default:
		/* Fall through. */
	case BITMAP_LAYOUT_R8G8B8A8:
		return (struct bitmap_colour_layout) {
			.r = 0,
			.g = 1,
			.b = 2,
			.a = 3,
		};

	case BITMAP_LAYOUT_B8G8R8A8:
		return (struct bitmap_colour_layout) {
			.b = 0,
			.g = 1,
			.r = 2,
			.a = 3,
		};

	case BITMAP_LAYOUT_A8R8G8B8:
		return (struct bitmap_colour_layout) {
			.a = 0,
			.r = 1,
			.g = 2,
			.b = 3,
		};

	case BITMAP_LAYOUT_A8B8G8R8:
		return (struct bitmap_colour_layout) {
			.a = 0,
			.b = 1,
			.g = 2,
			.r = 3,
		};
	}
}

/**
 * Get string for given pixel layout.
 *
 * \param[in] layout The pixel layout to get string for,
 * \return String for given layout.
 */
static const char *bitmap__layout_to_str(enum bitmap_layout layout)
{
	const char *const str[] = {
		[BITMAP_LAYOUT_R8G8B8A8] = "Byte-wise RGBA",
		[BITMAP_LAYOUT_B8G8R8A8] = "Byte-wise BGRA",
		[BITMAP_LAYOUT_A8R8G8B8] = "Byte-wise ARGB",
		[BITMAP_LAYOUT_A8B8G8R8] = "Byte-wise ABGR",
		[BITMAP_LAYOUT_RGBA8888] = "0xRRGGBBAA (native endian)",
		[BITMAP_LAYOUT_BGRA8888] = "0xBBGGRRAA (native endian)",
		[BITMAP_LAYOUT_ARGB8888] = "0xAARRGGBB (native endian)",
		[BITMAP_LAYOUT_ABGR8888] = "0xAABBGGRR (native endian)",
	};

	if ((size_t)layout >= (sizeof(str)) / sizeof(*str) ||
	    str[layout] == NULL) {
		return "Unknown";
	}

	return str[layout];
}

/* Exported function, documented in include/netsurf/bitmap.h */
void bitmap_set_format(const bitmap_fmt_t *bitmap_format)
{
	bitmap_fmt = *bitmap_format;

	NSLOG(netsurf, INFO, "Setting core bitmap format to: %s%s",
			bitmap__layout_to_str(bitmap_format->layout),
			bitmap_format->pma ? " pre multiplied alpha" : "");

	bitmap_fmt.layout = bitmap_sanitise_bitmap_layout(bitmap_fmt.layout);

	if (bitmap_format->layout != bitmap_fmt.layout) {
		NSLOG(netsurf, INFO, "Sanitised layout to: %s",
				bitmap__layout_to_str(bitmap_fmt.layout));
	}

	bitmap_layout = bitmap__get_colour_layout(&bitmap_fmt);
}

/**
 * Swap colour component order.
 *
 * \param[in] width      Bitmap width in pixels.
 * \param[in] height     Bitmap height in pixels.
 * \param[in] buffer     Pixel buffer.
 * \param[in] rowstride  Pixel buffer row stride in bytes.
 * \param[in] to         Pixel layout to convert to.
 * \param[in] from       Pixel layout to convert from.
 */
static inline void bitmap__format_convert(
		int width,
		int height,
		uint8_t *buffer,
		size_t rowstride,
		struct bitmap_colour_layout to,
		struct bitmap_colour_layout from)
{
	/* Just swapping the components around */
	for (int y = 0; y < height; y++) {
		uint8_t *row = buffer;

		for (int x = 0; x < width; x++) {
			const uint32_t px = *((uint32_t *)(void *) row);

			row[to.r] = ((const uint8_t *) &px)[from.r];
			row[to.g] = ((const uint8_t *) &px)[from.g];
			row[to.b] = ((const uint8_t *) &px)[from.b];
			row[to.a] = ((const uint8_t *) &px)[from.a];

			row += sizeof(uint32_t);
		}

		buffer += rowstride;
	}
}

/**
 * Convert plain alpha to premultiplied alpha.
 *
 * \param[in] width      Bitmap width in pixels.
 * \param[in] height     Bitmap height in pixels.
 * \param[in] buffer     Pixel buffer.
 * \param[in] rowstride  Pixel buffer row stride in bytes.
 * \param[in] to         Pixel layout to convert to.
 * \param[in] from       Pixel layout to convert from.
 */
static inline void bitmap__format_convert_to_pma(
		int width,
		int height,
		uint8_t *buffer,
		size_t rowstride,
		struct bitmap_colour_layout to,
		struct bitmap_colour_layout from)
{
	for (int y = 0; y < height; y++) {
		uint8_t *row = buffer;

		for (int x = 0; x < width; x++) {
			const uint32_t px = *((uint32_t *)(void *) row);
			uint32_t a, r, g, b;

			r = ((const uint8_t *) &px)[from.r];
			g = ((const uint8_t *) &px)[from.g];
			b = ((const uint8_t *) &px)[from.b];
			a = ((const uint8_t *) &px)[from.a];

			if (a != 0) {
				r = ((r * (a + 1)) >> 8) & 0xff;
				g = ((g * (a + 1)) >> 8) & 0xff;
				b = ((b * (a + 1)) >> 8) & 0xff;
			} else {
				r = g = b = 0;
			}

			row[to.r] = r;
			row[to.g] = g;
			row[to.b] = b;
			row[to.a] = a;

			row += sizeof(uint32_t);
		}

		buffer += rowstride;
	}
}

/**
 * Convert from premultiplied alpha to plain alpha.
 *
 * \param[in] width      Bitmap width in pixels.
 * \param[in] height     Bitmap height in pixels.
 * \param[in] buffer     Pixel buffer.
 * \param[in] rowstride  Pixel buffer row stride in bytes.
 * \param[in] to         Pixel layout to convert to.
 * \param[in] from       Pixel layout to convert from.
 */
static inline void bitmap__format_convert_from_pma(
		int width,
		int height,
		uint8_t *buffer,
		size_t rowstride,
		struct bitmap_colour_layout to,
		struct bitmap_colour_layout from)
{
	for (int y = 0; y < height; y++) {
		uint8_t *row = buffer;

		for (int x = 0; x < width; x++) {
			const uint32_t px = *((uint32_t *)(void *) row);
			uint32_t a, r, g, b;

			r = ((const uint8_t *) &px)[from.r];
			g = ((const uint8_t *) &px)[from.g];
			b = ((const uint8_t *) &px)[from.b];
			a = ((const uint8_t *) &px)[from.a];

			if (a != 0) {
				r = (r << 8) / a;
				g = (g << 8) / a;
				b = (b << 8) / a;

				r = (r > 255) ? 255 : r;
				g = (g > 255) ? 255 : g;
				b = (b > 255) ? 255 : b;
			} else {
				r = g = b = 0;
			}

			row[to.r] = r;
			row[to.g] = g;
			row[to.b] = b;
			row[to.a] = a;

			row += sizeof(uint32_t);
		}

		buffer += rowstride;
	}
}

/* Exported function, documented in desktop/bitmap.h */
void bitmap_format_convert(void *bitmap,
		const bitmap_fmt_t *fmt_from,
		const bitmap_fmt_t *fmt_to)
{
	int width = guit->bitmap->get_width(bitmap);
	int height = guit->bitmap->get_height(bitmap);
	bool opaque = guit->bitmap->get_opaque(bitmap);
	uint8_t *buffer = guit->bitmap->get_buffer(bitmap);
	size_t rowstride = guit->bitmap->get_rowstride(bitmap);
	struct bitmap_colour_layout to = bitmap__get_colour_layout(fmt_to);
	struct bitmap_colour_layout from = bitmap__get_colour_layout(fmt_from);

	NSLOG(netsurf, DEEPDEBUG, "%p: format conversion (%u%s --> %u%s)",
			bitmap,
			fmt_from->layout, fmt_from->pma ? " pma" : "",
			fmt_to->layout, fmt_to->pma ? " pma" : "");

	if (fmt_from->pma == fmt_to->pma) {
		/* Just component order to switch. */
		bitmap__format_convert(
				width, height, buffer,
				rowstride, to, from);

	} else if (opaque == false) {
		/* Need to do conversion to/from premultiplied alpha. */
		if (fmt_to->pma) {
			bitmap__format_convert_to_pma(
					width, height, buffer,
					rowstride, to, from);
		} else {
			bitmap__format_convert_from_pma(
					width, height, buffer,
					rowstride, to, from);
		}
	}
}

/* Exported function, documented in desktop/bitmap.h */
bool bitmap_test_opaque(void *bitmap)
{
	int width = guit->bitmap->get_width(bitmap);
	int height = guit->bitmap->get_height(bitmap);
	size_t rowstride = guit->bitmap->get_rowstride(bitmap);
	const uint8_t *buffer = guit->bitmap->get_buffer(bitmap);

	width *= sizeof(uint32_t);

	for (int y = 0; y < height; y++) {
		const uint8_t *row = buffer;

		for (int x = bitmap_layout.a; x < width; x += 4) {
			if (row[x] != 0xff) {
				return false;
			}
		}

		buffer += rowstride;
	}

	return true;
}