use anyhow::Result;
use std::env::args;
use std::fs::File;
use std::io::{BufRead, BufReader};
use std::path::Path;

const SUM: usize = 2020;

fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<usize>> {
    let f = File::open(filename)?;
    let reader = BufReader::new(f);

    let values = reader.lines()
        .map(|v| v.unwrap().parse::<usize>().unwrap()).collect();

    Ok(values)
}

fn part1(input: &[usize]) -> Option<usize> {
    for first in input {
        for second in input {
            if first + second == SUM {
                return Some(first * second);
            }
        }
    }

    None
}

fn part2(input: &[usize]) -> Option<usize> {
    for first in input {
        for second in input {
            for third in input {
                if first + second + third == SUM {
                    return Some(first * second * third);
                }
            }
        }
    }

    None
}

fn main() {
    let ( do_part_1, do_part_2 ) = aoc::do_parts();

    let filename = match args().nth(1) {
        Some(f) => f,
        None => {
            eprintln!("Missing input filename");
            std::process::exit(1);
        },
    };
    match read_input(filename) {
        Ok(input) => {
            if do_part_1 {
                match part1(&input) {
                    Some(solution) => println!("Part1, product found to be: {}", solution),
                    None => {
                        eprintln!("Part1, no solution found");
                        std::process::exit(1);
                    }
                };
            }
            if do_part_2 {
                match part2(&input) {
                    Some(solution) => println!("Part2, product found to be: {}", solution),
                    None => {
                        eprintln!("Part2, no solution found");
                        std::process::exit(1);
                    }
                };
            }
        },
        Err(err) => eprintln!("Could not read input: {}", err),
    }
}