// SPDX-License-Identifier: WTFPL
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

extern char *optarg;

#define WIDTH 1500

struct header {
	char signature[7];
	char unknown[4];
} __attribute__((packed));

__attribute__((unused)) const static char sig[] = "SynFax2";

static char *loadfile(char *filename, int *size)
{
	FILE *fp;
	char *buf = NULL;
	int filesize;

	if ((fp = fopen(filename, "r")) == NULL) {
		printf("loadfile: %s open error\n", filename);
		goto fin0;
	}

	fseek(fp, 0, SEEK_END);
	filesize = ftell(fp) - sizeof(struct header);
	fseek(fp, sizeof(struct header), SEEK_SET);

	*size = ((filesize + WIDTH - 1) / WIDTH) * WIDTH;
	if (*size < WIDTH || (buf = calloc(*size, 1)) == NULL)
		goto fin1;

	fread(buf, filesize, 1, fp);
fin1:
	fclose(fp);
fin0:
	return buf;
}

static int savefile(char *filename, char *buf, int x, int y)
{
	int result;
	FILE *fp;

	if ((fp = fopen(filename, "w")) == NULL) {
		printf("savefile: %s open error\n", filename);
		result = -1;
		goto fin0;
	}

	fprintf(fp, "P5\n%d %d\n255\n", x, y);
	fwrite(buf, x * y, 1, fp);

	result = 0;
	fclose(fp);
fin0:
	return result;
}

static void do_rotate(char *outbuf, char *inbuf, int in_x, int in_y)
{
	int x, y;

	for (y = 0; y < in_y; y++) {
		for (x = 0; x < in_x; x++) {
			outbuf[(in_x - x - 1) * in_y + y] =
				inbuf[y * in_x + x];
		}
	}
}

int main(int argc, char *argv[])
{
	int ch, size, x, y, rotate = 0;
	char *infile = NULL, *outfile = NULL, *inbuf, *outbuf;
	
	while ((ch = getopt(argc, argv, "i:o:r")) != -1) {
		switch (ch) {
		case 'i':
			infile = optarg;
			break;
		case 'o':
			outfile = optarg;
			break;
		case 'r':
			rotate = 1;
			break;
		}
	}

	if (infile == NULL || outfile == NULL) {
		printf("usage: %s -i [infile] -o [outfile]\n", argv[0]);
		goto fin0;
	}

	if ((inbuf = loadfile(infile, &size)) == NULL)
		goto fin0;

	if (rotate) {
		x = size / WIDTH; 
		y = WIDTH;
		if ((outbuf = malloc(size)) == NULL)
			goto fin1;
		do_rotate(outbuf, inbuf, y, x);
	} else {
		x = WIDTH;
		y = size / WIDTH;
		outbuf = inbuf;
		inbuf = NULL;
	}

	if (savefile(outfile, outbuf, x, y))
		goto fin2;

fin2:
	free(outbuf);
fin1:
	free(inbuf);
fin0:
	return 0;
}