/*
 * Copyright (c) 2023 DTB <trinity@trinity.moe>
 * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero 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 Affero General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see https://www.gnu.org/licenses/.
 */

#include <stdio.h> /* fprintf(3), fputs(3), getc(3), perror(3), putc(3), stdin,
                    * stdout, EOF */
#include <sysexits.h> /* EX_IOERR, EX_OK, EX_USAGE */
#include <unistd.h> /* getopt(3) */

char *program_name = "npc";

static int
ioerr(char *argv0, int err) {
	perror(argv0);

	return EX_IOERR;
}

static int
usage(char *argv0) {
	(void)fprintf(stderr, "Usage: %s [-et]\n", argv0);

	return EX_USAGE;
}

int main(int argc, char *argv[]) {
	int c;
	char showend = 0; /* print a dollar sign before each newline */
	char showtab = 0; /* prints tab characters in caret notation */

	if (argc > 0) {
		program_name = argv[0];

		while ((c = getopt(argc, argv, "et")) != -1) {
			switch (c){
				case 'e': showend = 1; break;
				case 't': showtab = 1; break;
				default:  return usage(program_name);
			}
		}
	}

	if (argc > optind) { return usage(program_name); }

	while ((c = getc(stdin)) != EOF) {
		if ((c & 0x80) != 0 && fputs("M-", stdout) == EOF) {
			return ioerr(argv[0]);
		}

		switch (c ^ 0x80 /* 0b 1000 0000 */) {
			case 0x7f: /* ASCII DEL (127d) */
				if(fputs("^?", stdout) == EOF) { return ioerr(argv[0]); }
				break;
			case '\n':
				if (showend && fputc('$', stdout) == EOF) {
					return ioerr(argv[0]); }
				}
			default:
				if (c >= ' ' || c == '\n' || (!showtab && c == '\t')) {
					if (fputc(c, stdout) == EOF) { return ioerr(argv[0]); }
				} else if (fprintf(stdout, "^%c", c + '@') < 0) {
					return ioerr(argv[0]);
				}
		}
	}

	return EX_OK;
}