use std::collections::HashMap;

fn main() {
    print_all(&vec![7, 3, 2, 4, 4, 5, 5, 6]);
    print_all(&vec![7, 3, 2, 4, 5, 4, 5, 5, 6]);
    print_all(&vec![]);
}

fn print_all(list: &Vec<u32>) {
    println!("{:?}", list);

    println!("Average: {:?}", average(&list));
    println!("Media: {:?}", median(&list));
    println!("Mode: {:?}", mode(&list));
}

fn average(list: &Vec<u32>) -> Option<f64> {
    let sum = list.iter().sum::<u32>() as f64;
    let average = sum / list.len() as f64;

    if average.is_nan() {
        None
    } else {
        Some(average)
    }
}

fn median(list: &Vec<u32>) -> Option<f64> {
    let mut list = list.clone();
    list.sort_unstable();

    let start = list.len().checked_sub(1).unwrap_or(0) / 2;
    let end = list.len().checked_add(1).unwrap_or(0) / 2;

    let slice = Vec::from(&list[start..end]);
    average(&slice)
}

fn mode(list: &Vec<u32>) -> Option<Vec<u32>> {
    if list.is_empty() {
        return None;
    }

    let mut bins = HashMap::new();

    let mut largest = 0;
    for e in list.iter() {
        let count = bins.entry(*e).or_insert(0);
        *count += 1;
        if *count > largest {
            largest = *count;
        }
    }

    Some(
        bins.iter()
            .filter_map(|(k, v)| if v == &largest { Some(k.clone()) } else { None })
            .collect(),
    )
}