#ifdef HAVE_CONFIG_H
#	include "config.h"
#endif

#include <stdlib.h>
#include <stdint.h>
#include <assert.h>
#include <errno.h>

#include "lbx.h"
#include "byteorder.h"

struct lbx_image {
	FILE *f;
	uint16_t width, height;
	uint16_t wtf1, wtf2;
	uint16_t offs, frames;
	uint32_t offsets[];
};

struct lbx_image *lbximg_fopen(FILE *f)
{
	struct lbx_image tmp = {.f = f}, *new;

	if (fread(&tmp.width,  sizeof tmp.width,   1, f) != 1) goto readerr;
	if (fread(&tmp.height, sizeof tmp.height,  1, f) != 1) goto readerr;
	if (fread(&tmp.wtf1,   sizeof tmp.wtf1,    1, f) != 1) goto readerr;
	if (fread(&tmp.offs,   sizeof tmp.offs,    1, f) != 1) goto readerr;
	if (fread(&tmp.frames, sizeof tmp.frames,  1, f) != 1) goto readerr;
	if (fread(&tmp.wtf2,   sizeof tmp.wtf2,    1, f) != 1) goto readerr;

	tmp.width  = letohs(tmp.width);
	tmp.height = letohs(tmp.height);
	tmp.wtf1   = letohs(tmp.wtf1);
	tmp.offs   = letohs(tmp.offs);
	tmp.frames = letohs(tmp.frames);
	tmp.wtf2   = letohs(tmp.wtf2);

	/*
	 * DEBUG ONLY.  These assertions exist to catch otherwise valid image
	 * files which differ from what I believe to be true of all LBX images.
	 * If we never find any exceptions, we can replace the assertions with
	 * assumptions.
	 */
	assert(tmp.wtf1 == 0);
	assert(tmp.offs == tmp.frames + 1);

	new = malloc(sizeof *new + tmp.offs * sizeof *new->offsets);
	if (!new) {
		lbx_errno = -errno;
		return NULL;
	}

	*new = tmp;

	if (fread(new->offsets, sizeof *new->offsets, new->offs, f) != new->offs)
		goto readerr;

	return new;
readerr:
	if (feof(f)) {
		lbx_errno = LBX_EEOF;
	} else {
		lbx_errno = -errno;
	}

	free(new);
	return NULL;
}

void lbximg_close(struct lbx_image *img)
{
	if (!img) return;

	if (img->f) {
		fclose(img->f);
	}

	free(img);
}