/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD 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.
 * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file png.cpp Reading sprites from png files. */

#ifdef WITH_PNG

#include "../stdafx.h"
#include "../fileio_func.h"
#include "../debug.h"
#include "png.hpp"
#include <png.h>

#define PNG_SLOT 62

static void PNGAPI png_my_read(png_structp png_ptr, png_bytep data, png_size_t length)
{
	FioReadBlock(data, length);
}

static void PNGAPI png_my_error(png_structp png_ptr, png_const_charp message)
{
	DEBUG(sprite, 0, "ERROR (libpng): %s - %s", message, (char *)png_get_error_ptr(png_ptr));
	longjmp(png_jmpbuf(png_ptr), 1);
}

static void PNGAPI png_my_warning(png_structp png_ptr, png_const_charp message)
{
	DEBUG(sprite, 0, "WARNING (libpng): %s - %s", message, (char *)png_get_error_ptr(png_ptr));
}

static bool OpenPNGFile(const char *filename, uint32 id, bool mask)
{
	char png_file[MAX_PATH];

	/* Add path separator after 'sprites' if not present */
	const char *sep = (filename[0] == PATHSEPCHAR) ? "" : PATHSEP;
	snprintf(png_file, sizeof(png_file), "sprites%s%s" PATHSEP "%d%s.png", sep, filename, id, mask ? "m" : "");
	if (FioCheckFileExists(png_file, NEWGRF_DIR)) {
		FioOpenFile(PNG_SLOT, png_file, NEWGRF_DIR);
		return true;
	}

	/* TODO -- Add TAR support */
	return false;
}

static bool LoadPNG(SpriteLoader::Sprite *sprite, const char *filename, uint32 id, volatile bool mask)
{
	png_byte header[8];
	png_structp png_ptr;
	png_infop info_ptr, end_info;
	uint bit_depth, colour_type;
	uint i, pixelsize;
	SpriteLoader::CommonPixel *dst;

	if (!OpenPNGFile(filename, id, mask)) return mask; // If mask is true, and file not found, continue true anyway, as it isn't a show-stopper

	/* Check the header */
	FioReadBlock(header, 8);
	if (png_sig_cmp(header, 0, 8) != 0) return false;

	/* Create the reader */
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL, png_my_error, png_my_warning);
	if (png_ptr == NULL) return false;

	/* Create initial stuff */
	info_ptr = png_create_info_struct(png_ptr);
	if (info_ptr == NULL) {
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		return false;
	}
	end_info = png_create_info_struct(png_ptr);
	if (end_info == NULL) {
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		return false;
	}

	/* Make sure that upon error, we can clean up graceful */
	if (setjmp(png_jmpbuf(png_ptr))) {
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return false;
	}

	/* Read the file */
	png_set_read_fn(png_ptr, NULL, png_my_read);
	png_set_sig_bytes(png_ptr, 8);

	png_read_info(png_ptr, info_ptr);

	if (!mask) {
		/* Read the text chunks */
		png_textp text_ptr;
		int num_text = 0;
		png_get_text(png_ptr, info_ptr, &text_ptr, &num_text);
		if (num_text == 0) DEBUG(misc, 0, "Warning: PNG Sprite '%s/%d.png' doesn't have x_offs and y_offs; expect graphical problems", filename, id);
		for (int i = 0; i < num_text; i++) {
			/* x_offs and y_offs are in the text-chunk of PNG */
			if (strcmp("x_offs", text_ptr[i].key) == 0) sprite->x_offs = strtol(text_ptr[i].text, NULL, 0);
			if (strcmp("y_offs", text_ptr[i].key) == 0) sprite->y_offs = strtol(text_ptr[i].text, NULL, 0);
		}

		uint height = png_get_image_height(png_ptr, info_ptr);
		uint width  = png_get_image_width(png_ptr, info_ptr);
		/* Check if sprite dimensions aren't larger than what is allowed in GRF-files. */
		if (height > UINT8_MAX || width > UINT16_MAX) {
			png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
			return false;
		}
		sprite->height = height;
		sprite->width  = width;
		sprite->AllocateData(sprite->width * sprite->height * ZOOM_LVL_BASE * ZOOM_LVL_BASE);
	} else if (sprite->height != png_get_image_height(png_ptr, info_ptr) || sprite->width != png_get_image_width(png_ptr, info_ptr)) {
		/* Make sure the mask image isn't larger than the sprite image. */
		DEBUG(misc, 0, "Ignoring mask for SpriteID %d as it isn't the same dimension as the masked sprite", id);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return true;
	}

	bit_depth  = png_get_bit_depth(png_ptr, info_ptr);
	colour_type = png_get_color_type(png_ptr, info_ptr);

	if (mask && (bit_depth != 8 || colour_type != PNG_COLOR_TYPE_PALETTE)) {
		DEBUG(misc, 0, "Ignoring mask for SpriteID %d as it isn't a 8 bit palette image", id);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return true;
	}

	bool win_palette = false;
	if (!mask) {
		if (bit_depth == 16) png_set_strip_16(png_ptr);

		if (colour_type == PNG_COLOR_TYPE_PALETTE) {
			png_set_palette_to_rgb(png_ptr);
			colour_type = PNG_COLOR_TYPE_RGB;
		}
		if (colour_type == PNG_COLOR_TYPE_GRAY || colour_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
			png_set_gray_to_rgb(png_ptr);
			colour_type = PNG_COLOR_TYPE_RGB;
		}

		if (colour_type == PNG_COLOR_TYPE_RGB) {
			if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
				/* Create an alpha channel when there is a tRNS chunk */
				png_set_tRNS_to_alpha(png_ptr);
			} else {
				png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER);
			}
		}

		pixelsize = sizeof(uint32);
	} else {
		pixelsize = sizeof(uint8);

		/* Check whether the DOS greyscale is in place. If not, we assume WIN palette */
		png_colorp palette;
		int num_palette;
		if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette) && num_palette == 256) {
			for (uint i = 3; i <= 5; i++) {
				/* Allow differences between -4 and +4 */
				uint8 intensity = i * 16 - 4;
				uint8 diff_r = palette[i].red - intensity;
				uint8 diff_g = palette[i].green - intensity;
				uint8 diff_b = palette[i].blue - intensity;
				if (diff_r > 8 || diff_g > 8 || diff_b > 8) {
					win_palette = true;
					break;
				}
			}
		}
	}

	png_bytep row_pointer = AllocaM(png_byte, png_get_image_width(png_ptr, info_ptr) * pixelsize);

	for (i = 0; i < png_get_image_height(png_ptr, info_ptr); i++) {
		png_read_row(png_ptr, row_pointer, NULL);

		dst = sprite->data + i * png_get_image_width(png_ptr, info_ptr);

		for (uint x = 0; x < png_get_image_width(png_ptr, info_ptr); x++) {
			if (mask) {
				if (row_pointer[x * sizeof(uint8)] != 0) {
					/* Alpha channel is used from the original image (to allow transparency in remap colours) */
					extern const byte _palmap_w2d[];
					byte colour = row_pointer[x * sizeof(uint8)];
					dst[x].m = win_palette ? _palmap_w2d[colour] : colour;
				}
			} else {
				dst[x].r = row_pointer[x * sizeof(uint32) + 0];
				dst[x].g = row_pointer[x * sizeof(uint32) + 1];
				dst[x].b = row_pointer[x * sizeof(uint32) + 2];
				dst[x].a = row_pointer[x * sizeof(uint32) + 3];
				dst[x].m = 0;
			}
		}
	}

	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);

	return true;
}

bool SpriteLoaderPNG::LoadSprite(SpriteLoader::Sprite *sprite, uint8 file_slot, size_t file_pos, SpriteType sprite_type)
{
	const char *filename = FioGetFilename(file_slot);
	if (!LoadPNG(sprite, filename, (uint32)file_pos, false)) return false;
	if (!LoadPNG(sprite, filename, (uint32)file_pos, true)) return false;

	if (ZOOM_LVL_BASE != 1 && sprite_type == ST_NORMAL) {
		/* Simple scaling, back-to-front so that no intermediate buffers are needed. */
		int width  = sprite->width  * ZOOM_LVL_BASE;
		int height = sprite->height * ZOOM_LVL_BASE;
		for (int y = height - 1; y >= 0; y--) {
			for (int x = width - 1; x >= 0; x--) {
				sprite->data[y * width + x] = sprite->data[y / ZOOM_LVL_BASE * sprite->width + x / ZOOM_LVL_BASE];
			}
		}

		sprite->width  *= ZOOM_LVL_BASE;
		sprite->height *= ZOOM_LVL_BASE;
		sprite->x_offs *= ZOOM_LVL_BASE;
		sprite->y_offs *= ZOOM_LVL_BASE;
	}

	return true;
}

#endif /* WITH_PNG */