use std::cmp;

fn abs_diff(a: u32, b: u32) -> u32 { cmp::max(a, b) - cmp::min(a, b) }

fn fuel_required_constant(positions: &[u32], destination: u32) -> u32
{
    positions.iter().fold(0, |fuel_total, pos| {
        fuel_total + abs_diff(*pos, destination)
    })
}

fn fuel_required_linear(positions: &[u32], destination: u32) -> u32
{
    let fuel_required = |pos, dest| {
        let distance = abs_diff(pos, dest);
        // Get total fuel cost by adding all integers until distance on top of each
        // other
        (distance * (distance + 1)) / 2
    };

    positions.iter().fold(0, |fuel_total, pos| {
        fuel_total + fuel_required(*pos, destination)
    })
}

fn part1(positions: &[u32])
{
    // Stupid approach: Try all positions out
    let mut min_required = fuel_required_constant(positions, 0);
    for pos in 1..positions.len() {
        min_required = cmp::min(fuel_required_constant(positions, pos as u32), min_required);
    }

    println!("Solution to part 1: {}", min_required);
}

fn part2(positions: &[u32])
{
    // Stupid approach: Try all positions out
    let mut min_required = fuel_required_linear(positions, 0);
    for pos in 1..positions.len() {
        min_required = cmp::min(fuel_required_linear(positions, pos as u32), min_required);
    }

    println!("Solution to part 2: {}", min_required);
}

pub fn run(input: Vec<String>)
{
    let positions: Vec<u32> = input
        .iter()
        .map(|s| s.split(',').map(|s| s.parse().unwrap()))
        .flatten()
        .collect();

    part1(&positions);
    part2(&positions);
}