/*
 *  2ooM: The Master of Orion II Reverse Engineering Project
 *  Rendering routines for Cairo surfaces.
 *  Copyright © 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 <stdlib.h>
#include <string.h>
#include <assert.h>
#include <limits.h>
#include <cairo/cairo.h>
#include <glib.h>

#include "lbxgui.h"

static const cairo_user_data_key_t last_frame_key;

/*
 * Scale 6-bit colour values (0-63) to 8-bit (0-255) as evenly as possible.
 */
static inline guint32 scale6to8(unsigned x)
{
	assert(x <= 0x3f);

	return x*0xff / 0x3f;
}

/*
 * Output a single row of pixel data in cairo ARGB32 format.
 */
static void write_argb(unsigned char *argb, unsigned char *index,
                       unsigned n, unsigned x, unsigned y, unsigned stride,
                       const struct lbx_colour *palette)
{
	argb += (unsigned long) y * stride;
	argb += 4ul * x;

	for (unsigned i = 0; i < n; i++) {
		const struct lbx_colour *c;
		guint32 px = 0xffff00ff;

		c = palette+index[i];
		if (c->active) {
			px = 0xff000000
			   | (scale6to8(c->red)   << 16)
			   | (scale6to8(c->green) <<  8)
			   |  scale6to8(c->blue);
		}

		memcpy(argb + 4ul*i, &px, 4);
	}
}

/*
 * Update a cairo RGBA32 surface according to the drawing commands in the
 * specified frame.
 */
static int render_argb(cairo_surface_t *dst, struct lbx_image *img,
                       unsigned frame, const struct lbx_colour *palette)
{
	unsigned char *row, *sdata;
	unsigned x, y, stride;
	int ret = 0;
	long rc;

	g_return_val_if_fail(cairo_surface_get_type(dst) == CAIRO_SURFACE_TYPE_IMAGE, -1);
	g_return_val_if_fail(cairo_image_surface_get_format(dst) == CAIRO_FORMAT_ARGB32, -1);
	g_return_val_if_fail(cairo_image_surface_get_width(dst) == img->width, -1);
	g_return_val_if_fail(cairo_image_surface_get_height(dst) == img->height, -1);

	sdata = cairo_image_surface_get_data(dst);
	stride = cairo_image_surface_get_stride(dst);

	row = malloc(img->width);
	if (!row)
		return -1;

	rc = lbx_img_seek(img, frame);
	if (rc < 0) {
		ret = -1;
		goto out;
	}

	cairo_surface_flush(dst);
	while ((rc = lbx_img_read_row_header(img, &x, &y)) != 0) {
		if (rc < 0) {
			ret = -1;
			break;
		}

		rc = lbx_img_read_row_data(img, row);
		if (rc < 0) {
			ret = -1;
			break;
		}

		write_argb(sdata, row, rc, x, y, stride, palette);
	}
	cairo_surface_mark_dirty(dst);
out:
	free(row);
	return ret;
}

static int get_last_frame(cairo_surface_t *s)
{
	int *data = cairo_surface_get_user_data(s, &last_frame_key);

	return data ? *data : -1;
}

static void set_last_frame(cairo_surface_t *s, int frame)
{
	int *data = cairo_surface_get_user_data(s, &last_frame_key);

	if (!data) {
		cairo_status_t rc;

		data = malloc(sizeof *data);
		if (!data)
			return;

		rc = cairo_surface_set_user_data(s, &last_frame_key,
		                                 data, free);
		if (rc != CAIRO_STATUS_SUCCESS) {
			free(data);
			return;
		}
	}

	*data = frame;
}

/*
 * Render the specified frame onto a cairo surface.  If this is the first
 * time rendering a frame onto this surface, it is not assumed to contain
 * any particular data.  Otherwise, unless there was an intervening call to
 * lbxgui_render_restart, the surface is assumed to contain valid frame data
 * from the most recent call to this function.
 */
int lbxgui_render_argb(cairo_surface_t *dst, struct lbx_image *img,
                       unsigned frame, const struct lbx_colour *palette)
{
	int last_frame = get_last_frame(dst), ref_frame = 0;

	g_return_val_if_fail(frame < img->frames, -1);
	g_return_val_if_fail(dst, -1);

	if (img->chunk)
		ref_frame = (frame / img->chunk) * img->chunk;

	if (last_frame < ref_frame || last_frame > frame) {
		cairo_t *cr = cairo_create(dst);
		cairo_set_operator(cr, CAIRO_OPERATOR_CLEAR);
		cairo_paint(cr);
		cairo_destroy(cr);

		last_frame = -1;
	}

	for (unsigned i = MAX(last_frame+1, ref_frame); i <= frame; i++) {
		int rc = render_argb(dst, img, i, palette);
		if (rc < 0) {
			set_last_frame(dst, -1);
			return rc;
		}

		set_last_frame(dst, i);
	}

	return 0;
}

/*
 * "Forget" the last rendered frame on the specified surface so that the next
 * image will be redrawn from scratch.
 */
void lbxgui_render_restart(cairo_surface_t *dst)
{
	g_return_if_fail(dst);

	set_last_frame(dst, -1);
}

/*
 * Copies the active elements in the src palette over the corresponding
 * elements in the dst palette.
 */
void lbxgui_stack_palette(struct lbx_colour *dst, const struct lbx_colour *src)
{
	for (unsigned i = 0; i < 256; i++) {
		if (src[i].active)
			dst[i] = src[i];
	}
}