/* See LICENSE file for copyright and license details. */
#include <arpa/inet.h>

#include <errno.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "arg.h"
#include "util.h"

static void
usage(void)
{
	fprintf(stderr, "usage: %s [-b #rrggbb]\n", argv0);
	exit(1);
}

int
main(int argc, char *argv[])
{
	size_t rowlen, rowoutlen;
	uint64_t a;
	uint32_t width, height, i, j, k, l;
	uint16_t *row, mask[3] = { 0xffff, 0xffff, 0xffff };
	uint8_t *rowout;

	/* arguments */
	ARGBEGIN {
	case 'b':
		if (parse_mask(EARGF(usage()), mask)) {
			usage();
		}
		break;
	default:
		usage();
	} ARGEND

	if (argc) {
		usage();
	}

	/* prepare */
	ff_read_header(&width, &height);
	row = ereallocarray(NULL, width, (sizeof("RGBA") - 1) * sizeof(uint16_t));
	rowout = ereallocarray(NULL, width, (sizeof("RGB") - 1) * sizeof(uint8_t));
	rowlen = width * (sizeof("RGBA") - 1);
	rowoutlen = width * (sizeof("RGB") - 1);

	/* write data */
	printf("P6\n%" PRIu32 " %" PRIu32 "\n255\n", width, height);

	for (i = 0; i < height; ++i) {
		if (fread(row, sizeof(uint16_t), rowlen, stdin) != rowlen) {
			if (ferror(stdin)) {
				fprintf(stderr, "%s: fread: %s\n", argv0,
				        strerror(errno));
			} else {
				fprintf(stderr, "%s: unexpected end of file\n",
				        argv0);
			}
			return 1;
		}
		for (j = 0, k = 0; j < rowlen; j += 4, k += 3) {
			a = ntohs(row[j + 3]);
			for (l = 0; l < 3; l++) {
				rowout[k + l] = (a * ntohs(row[j + l]) +
				                 (65535 - a) * mask[l]) /
				                (257 * 65535);
			}
		}
		if (fwrite(rowout, sizeof(uint8_t), rowoutlen, stdout) != rowoutlen) {
			fprintf(stderr, "%s: fwrite: %s\n", argv0, strerror(errno));
			return 1;
		}
	}

	return 0;
}