#[path = "../lib.rs"]
mod lib;

fn parse_input() -> Vec<(usize, usize)> {
    let mut start = (0, 0);
    let mut map = vec![];
    for (y, line) in lib::iter_input().enumerate() {
        let mut row = vec![];
        for (x, c) in line.bytes().enumerate() {
            row.push(match c {
                b'#' => false,
                b'.' => true,
                b'S' => {
                    start = (x, y);
                    true
                },
                b'E' => true,
                _ => unreachable!(),
            });
        }
        map.push(row);
    }

    let mut path = vec![];
    let (mut x, mut y) = start;
    loop {
        path.push((x, y));
        map[y][x] = false;
        if map[y - 1][x] {
            y -= 1;
        } else if map[y + 1][x] {
            y += 1;
        } else if map[y][x - 1] {
            x -= 1;
        } else if map[y][x + 1] {
            x += 1;
        } else {
            break;
        }
    }

    return path;
}

fn main() {
    let path = parse_input();
    let mut count1 = 0;
    let mut count2 = 0;

    for t1 in 0..path.len() {
        let (x1, y1) = path[t1];

        for t2 in (t1 + 102)..(t1 + 121).min(path.len()) {
            let (x2, y2) = path[t2];
            let d = x1.abs_diff(x2) + y1.abs_diff(y2);
            if t2 >= t1 + d + 100 {
                if d <= 2 {
                    count1 += 1;
                }
                if d <= 20 {
                    count2 += 1;
                }
            }
        }

        // perf: check t2 >= t1 + d + 100 if we already know it is true
        // saves ~33%
        for t2 in (t1 + 121)..path.len() {
            let (x2, y2) = path[t2];
            let d = x1.abs_diff(x2) + y1.abs_diff(y2);
            if d <= 2 {
                count1 += 1;
            }
            if d <= 20 {
                count2 += 1;
            }
        }
    }

    println!("part1: {}", count1);
    println!("part2: {}", count2);
}