/*
 * Copyright (c) 2023 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/.
 */

use std::{
	env::args,
	io::{ Read, stdin, Write },
	process::{ Command, exit, Stdio },
};

fn main() {
	let argv = args().collect::<Vec<String>>();

	let index = match argv.get(1) {
		Some(i) => {
			i.parse::<usize>().unwrap_or_else(|_| {
				eprintln!("{}: {}: Not an integer.", argv[0], i);
				exit(1);
			})
		},
		None => {
			eprintln!("Usage: {} index command args...", argv[0]);
			exit(1);
		},
	};

	let mut buf = String::new();
	stdin().read_to_string(&mut buf).unwrap();
	let mut fields = buf.split('␞').collect::<Vec<&str>>();

	argv.get(2).unwrap_or_else(|| {
		eprintln!("Usage: {} index command args...", argv[0]);
		exit(1);
	});

	let opts = argv.iter().clone().skip(3).collect::<Vec<&String>>();

	let mut spawned = Command::new(argv.get(2).unwrap())
		.args(opts)
		.stdin(Stdio::piped())
		.stdout(Stdio::piped())
		.spawn()
		.unwrap();

	let field = fields.get(index).unwrap_or_else(|| {
		eprintln!("{}: {}: No such index in input.", argv[0], index.to_string());
		exit(1);
	});

	if let Some(mut child_stdin) = spawned.stdin.take() {
		child_stdin.write_all(field.as_bytes()).unwrap();
		drop(child_stdin);
	}

	let output = spawned.wait_with_output().unwrap();

	let new_field = String::from_utf8(output.stdout).unwrap();

	fields[index] = &new_field;

	print!("{}", fields.join("␞"));
}