use std::fs::File;
use std::io::{self, BufRead};
use std::path::Path;

fn main() {
	let mut sum = 0;
	let mut mus = 0;

	if let Ok(lines) = read_lines("./input") {
		for line in lines {
			if let Ok(text) = line {
				sum = sum + first_digit(&text);
				mus = mus + last_digit(&text);
			}
		}
	}

	println!("{}", 10*sum + mus);
}

// TODO: Switch to Option(i32) to allow not having a digit in text <https://doc.rust-lang.org/std/option/>.
fn first_digit(text: &String) -> i32 {
	for c in text.chars() {
		if c.is_digit(10) {
			return c.to_digit(10).unwrap() as i32;
		}
	}
	// TODO: What if there is no digit?
	0
}

fn last_digit(text: &String) -> i32 {
	let txet = &mut text.chars().rev().collect();
	first_digit(txet)
}

fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
where P: AsRef<Path>, {
    let file = File::open(filename)?;
    Ok(io::BufReader::new(file).lines())
}