use std::collections::HashMap;
use std::hash::Hash;

pub struct HashList<K: Eq + Hash, V>(HashMap<K, Vec<V>>);

impl<K: Eq + Hash + core::fmt::Debug, V: core::fmt::Debug> core::fmt::Debug for HashList<K, V> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_tuple("HashList").field(&self.0).finish()
    }
}

impl<K: Eq + Hash + Clone, V: Clone> Clone for HashList<K, V> {
    fn clone(&self) -> Self {
        Self(self.0.clone())
    }
}

impl<K: Eq + Hash, V> HashList<K, V> {
    pub fn new() -> Self {
        Self(HashMap::new())
    }

    pub fn add(&mut self, key: K, value: V) {
        match self.0.get_mut(&key) {
            Some(values) => values.push(value),
            None => {
                self.0.insert(key, vec![value]);
            }
        }
    }
    pub fn decompose(&mut self) -> Box<[(K, Vec<V>)]> {
        let mut body = HashMap::new();
        core::mem::swap(&mut self.0, &mut body);
        body.into_iter().collect()
    }
}