/*
 * 2ooM: The Master of Orion II Reverse Engineering Project
 * Library for working with LBX image files.
 * Copyright © 2006-2011, 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 <stdlib.h>
#include <string.h>
#include <assert.h>
#include <stdbool.h>
#include <inttypes.h>
#include <errno.h>

#include "pack.h"
#include "misc.h"
#include "lbx.h"
#include "error.h"
#include "image.h"

#define FLAG_RAW       0x0100 /* Image is stored as a flat array of bytes. */
#define FLAG_OVERWRITE 0x0400 /* Draw each frame on a clean slate (unsure). */
#define FLAG_BUILDING  0x0800 /* Buildings have this, related to shadow? */
#define FLAG_PALETTE   0x1000 /* Image contains embedded palette. */
#define FLAG_LOOPING   0x2000 /* Loop over all frames in the image (unsure). */

#define FLAG_ALL (FLAG_RAW|FLAG_OVERWRITE|FLAG_BUILDING|FLAG_PALETTE|FLAG_LOOPING)

#define HDR_LEN 12

/* States for image readout */
enum {
	READ_STATE_INIT,
	READ_STATE_HEADER,
	READ_STATE_DATA,
	READ_STATE_DONE,
};

struct lbx_image_priv {
	struct lbx_image pub;

	unsigned short wtf, flags;
	unsigned char  wtf2;

	const struct lbx_file_ops *fops;
	int (*dtor)(void *handle);
	void *f;

	/* State of frame readout */
	unsigned currentx, currenty, currentn;
	int read_state;

	unsigned long offsets[FLEXIBLE_ARRAY_MEMBER];
};

static struct lbx_image_priv *lbx_img_init(unsigned char *hdr)
{
	unsigned short nframes = unpack_16_le(hdr+6);
	struct lbx_image_priv *img;

	img = malloc(sizeof *img + sizeof img->offsets[0] * (nframes+1));
	if (!img) {
		lbx_error_raise(LBX_ENOMEM);
		return NULL;
	}

	*img = (struct lbx_image_priv) {
		.pub.width  = unpack_16_le(hdr+0),
		.pub.height = unpack_16_le(hdr+2),
		.wtf        = unpack_16_le(hdr+4),
		.pub.frames = hdr[6],
		.wtf2       = hdr[7],
		.pub.leadin = hdr[8],
		.pub.chunk  = hdr[9],
		.flags      = unpack_16_le(hdr+10),
	};

	if (img->flags & FLAG_OVERWRITE)
		img->pub.chunk = 1;

	if (img->flags & FLAG_LOOPING)
		img->pub.leadin = 0;

	if (img->pub.leadin >= img->pub.frames) {
		lbx_error_raise(LBX_EFORMAT);
		free(img);
		return NULL;
	}

	return img;
}

struct lbx_image *lbx_img_open(void *f, const struct lbx_file_ops *fops,
                               int (*destructor)(void *))
{
	unsigned char hdr_buf[HDR_LEN];
	struct lbx_image_priv *img;

	if (fops->read(hdr_buf, sizeof hdr_buf, f) != sizeof hdr_buf) {
		if (fops->eof(f))
			lbx_error_raise(LBX_EEOF);
		return NULL;
	}

	img = lbx_img_init(hdr_buf);
	if (!img)
		return NULL;

	img->f    = f;
	img->fops = fops;
	img->dtor = destructor;

	/*
	 * DEBUG ONLY.  These assertions exist to catch otherwise valid image
	 * files which differ from what I believe to be true of all LBX images.
	 * When we can decode every image, then these assertions should be
	 * replaced with constraints.
	 */
	_lbx_assert(img->wtf  == 0); /* version? */
	_lbx_assert(img->wtf2 == 0); /* very likely is simply reserved. */
	_lbx_assert(!(img->flags & ~FLAG_ALL));

	/* Read all offsets.  Should be merged with identical code in lbx.c */
	for (unsigned i = 0; i <= img->pub.frames; i++) {
		unsigned char buf[4];

		if (fops->read(buf, sizeof buf, f) != sizeof buf) {
			if (fops->eof(f))
				lbx_error_raise(LBX_EEOF);
			free(img);
			return NULL;
		}

		img->offsets[i] = unpack_32_le(buf);
	}

	return &img->pub;
}

static int pipe_close(void *f)
{
	struct lbx_pipe_state *p = f;
	int rc;

	rc = fclose(p->f);
	free(p);
	return rc;
}

static int file_close(void *f)
{
	return fclose((FILE *)f);
}

struct lbx_image *lbx_img_fopen(const char *file)
{
	struct lbx_pipe_state *p;
	FILE *f;

	f = fopen(file, "rb");
	if (!f) {
		lbx_error_raise(-errno);
		return NULL;
	}

	if (fseek(f, 0, SEEK_CUR) == 0)
		return lbx_img_open(f, &lbx_default_fops, file_close);

	p = malloc(sizeof *p);
	if (!p) {
		lbx_error_raise(LBX_ENOMEM);
		fclose(f);
		return NULL;
	}

	*p = (struct lbx_pipe_state) { .f = f };
	return lbx_img_open(p, &lbx_pipe_fops, pipe_close);
}

int lbx_img_seek(struct lbx_image *pub, unsigned frame)
{
	struct lbx_image_priv *img = (struct lbx_image_priv *)pub;

	if (frame >= pub->frames) {
		lbx_error_raise(LBX_EINVAL);
		return -1;
	}

	if (img->fops->seek(img->f, img->offsets[frame], SEEK_SET)) {
		return -1;
	}

	if (!(img->flags & FLAG_RAW)) {
		unsigned char buf[4];

		/* Read frame header */
		if (img->fops->read(buf, 4, img->f) != 4) {
			if (img->fops->eof(img->f))
				lbx_error_raise(LBX_EEOF);
			return -1;
		}

		if (unpack_16_le(buf) != 1) {
			lbx_error_raise(LBX_EFORMAT);
			return -1;
		}

		img->currentx = 0;
		img->currenty = unpack_16_le(buf+2);
		if (img->currenty > img->pub.height) {
			lbx_error_raise(LBX_EFORMAT);
			return -1;
		}
	}

	img->read_state = READ_STATE_HEADER;
	return 0;
}

long lbx_img_read_row_header(struct lbx_image *pub, unsigned *x, unsigned *y)
{
	struct lbx_image_priv *img = (struct lbx_image_priv *)pub;
	unsigned short length, offset;
	unsigned char buf[4];

	if (img->read_state != READ_STATE_HEADER) {
		lbx_error_raise(LBX_EINVAL);
		return -1;
	}

	/* Raw images have no row headers */
	if (img->flags & FLAG_RAW) {
		img->currentn = img->pub.width;
		*y = img->currenty++;
		*x = 0;

		if (*y < img->pub.height) {
			img->read_state = READ_STATE_DATA;
			return img->currentn;
		} else {
			img->read_state = READ_STATE_DONE;
			return 0;
		}
	}

	do {
		if (img->fops->read(buf, sizeof buf, img->f) != sizeof buf) {
			if (img->fops->eof(img->f))
				lbx_error_raise(LBX_EEOF);
			return -1;
		}

		length = unpack_16_le(buf+0);
		offset = unpack_16_le(buf+2);

		if (length == 0) {
			if (offset == 1000) {
				img->read_state = READ_STATE_DONE;
				return 0;
			} else if (offset > img->pub.height - img->currenty) {
				lbx_error_raise(LBX_EFORMAT);
				return -1;
			}

			img->currenty += offset;
			img->currentx  = 0;
		}
	} while (length == 0);

	if (offset > img->pub.width - img->currentx) {
		lbx_error_raise(LBX_EFORMAT);
		return -1;
	}
	img->currentx += offset;

	if (length > img->pub.width - img->currentx) {
		lbx_error_raise(LBX_EFORMAT);
		return -1;
	}
	img->currentn = length;

	img->read_state = READ_STATE_DATA;
	*x = img->currentx;
	*y = img->currenty;

	return img->currentn;
}

long lbx_img_read_row_data(struct lbx_image *pub, void *buf)
{
	struct lbx_image_priv *img = (struct lbx_image_priv *)pub;

	if (img->read_state != READ_STATE_DATA) {
		lbx_error_raise(LBX_EINVAL);
		return -1;
	}

	if (img->fops->read(buf, img->currentn, img->f) != img->currentn) {
		if (img->fops->eof(img->f))
			lbx_error_raise(LBX_EEOF);
		return -1;
	}

	if (!(img->flags & FLAG_RAW) && img->currentn % 2) {
		unsigned char c;

		/* Skip padding byte */
		if (img->fops->read(&c, 1, img->f) != 1) {
			if (img->fops->eof(img->f))
				lbx_error_raise(LBX_EEOF);
			return -1;
		}
	}

	img->read_state = READ_STATE_HEADER;
	img->currentx += img->currentn;

	return img->currentn;
}

static int read_palette(void *f, const struct lbx_file_ops *fops,
                        struct lbx_colour *palette, unsigned count,
			bool external)
{
	assert(count <= 256);
	for (unsigned i = 0; i < count; i++) {
		unsigned char buf[4];

		if (fops->read(buf, 4, f) != 4) {
			if (fops->eof(f))
				lbx_error_raise(LBX_EEOF);
			return -1;
		}

		if (buf[0] != external) {
			lbx_error_raise(LBX_EFORMAT);
			return -1;
		}

		palette[i] = (struct lbx_colour) {
			.red    = buf[1] & 0x3f,
			.green  = buf[2] & 0x3f,
			.blue   = buf[3] & 0x3f,
			.active = 1,
		};
	}

	return 0;
}

int lbx_img_loadpalette(void *f, const struct lbx_file_ops *fops,
                        struct lbx_colour *palette)
{
	return read_palette(f, fops, palette, 256, true);
}

int lbx_img_getpalette(struct lbx_image *pub, struct lbx_colour *out)
{
	struct lbx_image_priv *img = (struct lbx_image_priv *)pub;
	unsigned long palette_start, palette_count, palette_offset;
	unsigned char buf[4];
	int rc;

	/* Do nothing if the image doesn't have embedded palette data. */
	if (!(img->flags & FLAG_PALETTE))
		return 0;

	palette_offset = 16 + 4ul * img->pub.frames;
	if (img->fops->seek(img->f, palette_offset, SEEK_SET)) {
		return -1;
	}

	/* Read embedded palette header */
	if (img->fops->read(buf, 4, img->f) < 4)
		goto readerr;

	palette_start = unpack_16_le(buf+0);
	palette_count = unpack_16_le(buf+2);
	if (palette_start + palette_count > 256) {
		lbx_error_raise(LBX_EFORMAT);
		return -1;
	}

	if (out) {
		rc = read_palette(img->f, img->fops,
		                  out+palette_start, palette_count,
		                  false);
		if (rc < 0)
			return -1;
	}

	return palette_count;
readerr:
	if (img->fops->eof(img->f))
		lbx_error_raise(LBX_EEOF);
	return -1;
}

int lbx_img_close(struct lbx_image *pub)
{
	struct lbx_image_priv *img = (struct lbx_image_priv *)pub;
	int rc = 0;

	if (img && img->dtor) {
		rc = img->dtor(img->f);
	}
	free(img);

	return rc;
}