use {
    anyhow::{
        anyhow,
        Context,
        Result,
    },
    std::{
        env::args,
        fs::read_to_string,
        path::Path,
    },
};

fn read_input<T: AsRef<Path>>(filename: T) -> Result<String> {
    read_to_string(filename).context("Could not read {filename}")
}

fn find_sequence(input: &str, len: usize) -> Option<usize> {
    input.as_bytes().windows(len).enumerate().find_map(|(pos, win)| {
        for i in 0..len {
            if win[(i + 1)..].contains(&win[i]) {
                return None
            }
        }
        Some(pos + len)
    })
}

fn part1(input: &str) -> Result<usize> {
    find_sequence(input, 4).ok_or_else(|| anyhow!("No match found"))
}

fn part2(input: &str) -> Result<usize> {
    find_sequence(input, 14).ok_or_else(|| anyhow!("No match found"))
}

fn main() -> Result<()> {
    let ( do_part_1, do_part_2 ) = aoc::do_parts();

    let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
    let input = read_input(filename).context("Could not read input")?;
    if do_part_1 {
        let solution = part1(&input).context("No solution for part 1")?;
        println!("Part1, solution found to be: {}", solution);
    }
    if do_part_2 {
        let solution = part2(&input).context("No solution for part 2")?;
        println!("Part2, solution found to be: {}", solution);
    }
    Ok(())
}