AoC2019/src/main.rs

#[macro_use]
extern crate clap;
use clap::{Arg, App};
use std::fs::File;
use std::io::BufReader;

mod day1;

fn main() {
    let matches = App::new("Advent of Code 2019")
        .version("0.1")
        .arg(Arg::with_name("challenge")
            .short("c")
            .long("challenge")
            .value_name("CHALLENGE")
            .help("Challenge id from 1 (1st day, 1st part) to 50 (25th day, 2nd part).")
            .required(true)
            .takes_value(true)
            .min_values(1)
            .max_values(50))
        .arg(Arg::with_name("input")
            .short("i")
            .long("input")
            .value_name("INPUT")
            .help("Input file, ex `input/day1`.")
            .required(true)
            .takes_value(true))
        .get_matches();

    let input = matches.value_of("input").unwrap();
    let challenge = value_t!(matches, "challenge", usize).unwrap() - 1;

    let input_file = File::open(input).expect("Unable to open input file");
    let reader = BufReader::new(input_file);

    let challenges = [
        day1::part1, day1::part2
    ];

    if let Some(f) = challenges.get(challenge) {
        f(reader);
    } else {
        println!("Challenge {}, part {} not unimplemented", challenge / 2 + 1, challenge % 2 +1)
    }
}