/*
 * 2ooM: The Master of Orion II Reverse Engineering Project
 * PNG output routines for lbximg extration.
 * Copyright © 2013-2014 Nick Bowler
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdbool.h>
#include <setjmp.h>
#include <assert.h>

#include <png.h>

#include "image.h"
#include "tools.h"

#include "imgoutput.h"

struct file_info {
	const char *filename;
	FILE *f;
};

static void fatal(png_structp png, int err, const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	tool_verr(err, fmt, ap);
	va_end(ap);

	png_longjmp(png, 1);
}

static void warning_fn(png_structp png, const char *msg)
{
	tool_err(-1, "libpng warning: %s", msg);
}

static void error_fn(png_structp png, const char *msg)
{
	fatal(png, -1, "libpng error: %s", msg);
}

/*
 * We implement our own I/O routines because libpng's internal stdio calls do
 * not handle errors particularly well.
 */
static void write_data(png_structp png, png_bytep data, png_size_t len)
{
	struct file_info *file = png_get_io_ptr(png);
	size_t ret;

	ret = fwrite(data, 1, len, file->f);
	if (ret < len) {
		fatal(png, 0, "error writing %s", file->filename);
	}
}

static void flush_data(png_structp png)
{
	struct file_info *file = png_get_io_ptr(png);

	if (fflush(file->f) == EOF) {
		fatal(png, 0, "error writing %s", file->filename);
	}
}

static inline unsigned scale6to8(unsigned x)
{
	assert(x <= 0x3f);

	return x*0xff / 0x3f;
}

/* Scale the 18-bit LBX palette into a 24-bit PNG palette. */
static void fill_png_palette(png_color *out, const struct lbx_colour *in)
{
	for (unsigned i = 0; i < 256; i++) {
		out[i] = (struct png_color_struct) {
			.red   = scale6to8(in[i].red),
			.green = scale6to8(in[i].green),
			.blue  = scale6to8(in[i].blue),
		};
	}
}

static void
write_rgba_frame(png_structp png, png_infop info,
                 unsigned char *pixels, unsigned char *mask,
                 struct lbx_colour *lbx_palette)
{
	png_uint_32 width = png_get_image_width(png, info);
	png_uint_32 height = png_get_image_height(png, info);
	png_color png_palette[256];
	unsigned char (*row)[4];
	jmp_buf parent;

	if (width >= PNG_UINT_32_MAX / sizeof *row)
		fatal(png, -1, "image too wide to allocate row buffer");

	row = png_malloc(png, width * sizeof *row);

	/*
	 * We need to establish our own error handler to free the row buffer.
	 * Some care must be taken to save/restore the caller's handler.
	 */
	memcpy(&parent, &png_jmpbuf(png), sizeof parent);
	if (setjmp(png_jmpbuf(png))) {
		png_free(png, row);

		memcpy(&png_jmpbuf(png), &parent, sizeof parent);
		png_longjmp(png, 1);
	}

	png_write_info(png, info);
	fill_png_palette(png_palette, lbx_palette);
	for (png_uint_32 y = 0; y < height; y++) {
		for (png_uint_32 x = 0; x < width; x++) {
			unsigned long offset = (unsigned long) y * width + x;
			png_color *c = &png_palette[pixels[offset]];
			bool vis;

			vis = mask[offset/CHAR_BIT] & (1u << offset%CHAR_BIT);
			row[x][0] = c->red;
			row[x][1] = c->green;
			row[x][2] = c->blue;
			row[x][3] = -vis;
		}
		png_write_row(png, (void *)row);
	}
	png_write_end(png, NULL);

	memcpy(&png_jmpbuf(png), &parent, sizeof parent);
}

static void
write_masked_index_frame(png_structp png, png_infop info,
                         unsigned char *pixels, unsigned char *mask)
{
	png_uint_32 width = png_get_image_width(png, info);
	png_uint_32 height = png_get_image_height(png, info);
	unsigned char (*row)[2];
	jmp_buf parent;

	if (width >= PNG_UINT_32_MAX / sizeof *row)
		fatal(png, -1, "image too wide to allocate row buffer");

	row = png_malloc(png, width * sizeof *row);

	/*
	 * We need to establish our own error handler to free the row buffer.
	 * Some care must be taken to save/restore the caller's handler.
	 */
	memcpy(&parent, &png_jmpbuf(png), sizeof parent);
	if (setjmp(png_jmpbuf(png))) {
		png_free(png, row);

		memcpy(&png_jmpbuf(png), &parent, sizeof parent);
		png_longjmp(png, 1);
	}

	png_write_info(png, info);
	for (png_uint_32 y = 0; y < height; y++) {
		for (png_uint_32 x = 0; x < width; x++) {
			unsigned long offset = (unsigned long) y * width + x;
			bool vis;

			vis = mask[offset/CHAR_BIT] & (1u << offset%CHAR_BIT);
			row[x][0] = pixels[offset];
			row[x][1] = -vis;
		}
		png_write_row(png, (void *)row);
	}
	png_write_end(png, NULL);

	memcpy(&png_jmpbuf(png), &parent, sizeof parent);
}

static void
write_index_frame(png_structp png, png_infop info, unsigned char *pixels)
{
	png_uint_32 width = png_get_image_width(png, info);
	png_uint_32 height = png_get_image_height(png, info);

	png_write_info(png, info);
	for (png_uint_32 y = 0; y < height; y++) {
		unsigned long offset = (unsigned long) y * width;

		png_write_row(png, (void *)(pixels+offset));
	}
	png_write_end(png, NULL);
}

static void
write_palette_frame(png_structp png, png_infop info,
                    unsigned char *pixels, struct lbx_colour *lbx_palette)
{
	png_color png_palette[256];
	fill_png_palette(png_palette, lbx_palette);
	png_set_PLTE(png, info, png_palette, 256);

	write_index_frame(png, info, pixels);
}

int img_output_png(FILE *f, const char *filename,
                   unsigned width, unsigned height,
                   unsigned char *pixels, unsigned char *mask,
                   struct lbx_colour *palette)
{
	bool masked = img_is_masked(mask, width, height);
	struct file_info file = { filename, f };
	png_structp png;
	png_infop info;

	png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	if (!png) {
		tool_err(-1, "failed to init libpng.");
		return -1;
	}

	info = png_create_info_struct(png);
	if (!info) {
		tool_err(-1, "failed to init libpng.");
		png_destroy_write_struct(&png, NULL);
		return -1;
	}

	if (setjmp(png_jmpbuf(png))) {
		png_destroy_write_struct(&png, &info);
		return -1;
	}

	png_set_error_fn(png, NULL, error_fn, warning_fn);
	png_set_write_fn(png, &file, write_data, flush_data);

	if (palette && masked) {
		/*
		 * Indexed colour mode can only be used for images without
		 * transparency, since indexed PNG requires sacrificing one or
		 * more palette colours to indicate transparency, while LBX
		 * does not.  So we use full-up RGBA in this case.
		 */
		png_set_IHDR(png, info, width, height, 8,
		             PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
		             PNG_COMPRESSION_TYPE_DEFAULT,
		             PNG_FILTER_TYPE_DEFAULT);

		write_rgba_frame(png, info, pixels, mask, palette);
	} else if (palette) {
		png_set_IHDR(png, info, width, height, 8,
		             PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
		             PNG_COMPRESSION_TYPE_DEFAULT,
		             PNG_FILTER_TYPE_DEFAULT);

		write_palette_frame(png, info, pixels, palette);
	} else if (masked) {
		png_set_IHDR(png, info, width, height, 8,
		             PNG_COLOR_TYPE_GRAY_ALPHA, PNG_INTERLACE_NONE,
			     PNG_COMPRESSION_TYPE_DEFAULT,
			     PNG_FILTER_TYPE_DEFAULT);

		write_masked_index_frame(png, info, pixels, mask);
	} else {
		png_set_IHDR(png, info, width, height, 8,
		             PNG_COLOR_TYPE_GRAY, PNG_INTERLACE_NONE,
			     PNG_COMPRESSION_TYPE_DEFAULT,
			     PNG_FILTER_TYPE_DEFAULT);

		write_index_frame(png, info, pixels);
	}

	png_destroy_write_struct(&png, &info);
	return 0;
}