use std::error::Error;
use std::fs;


pub fn both(filename: &str) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(filename)?;
    let lines = contents.lines().collect();

    let trees01 = calc_trees(&lines, 3, 1);
    println!("Encountered {} trees while going down", trees01);

    let trees02 = calc_trees(&lines, 1, 1) * trees01 * calc_trees(&lines, 5, 1) *
        calc_trees(&lines, 7, 1) * calc_trees(&lines, 1, 2);

    println!("Part 2: {}", trees02);
    Ok(())
}

fn calc_trees(contents: &Vec<&str>, right: usize, down: usize) -> u64 {
    let mut trees = 0;
    for height in 0..contents.len() {
        if height % down != 0 {
            continue;
        }

        let x = height/down * right;
        let row = contents[height].repeat(  x / contents[height].len() + 1);
        if row.as_bytes()[x] == "#".as_bytes()[0] {
            trees += 1;
        }
    }

    return trees
}