use std::{
    collections::{HashMap, HashSet},
    hash::Hash,
};

pub trait HashLike<K, V>
where
    K: Hash + Eq,
{
    fn remove(&mut self, k: &K) -> Option<V>;
}

#[derive(Debug)]
pub struct MultiKeyMap<K, SK, V>
where
    K: Hash + Eq,
    SK: Hash + Eq,
{
    store: HashMap<K, V>,
    idx: HashMap<SK, HashSet<K>>,
}

impl<'a, 'b, K, SK, V> MultiKeyMap<K, SK, V>
where
    K: Hash + Eq + 'a,
    'b: 'a,
    &'a K: IntoIterator<Item = &'b SK>,
    SK: Hash + Eq + 'b,
{
    pub fn new() -> Self {
        MultiKeyMap {
            store: HashMap::new(),
            idx: HashMap::new(),
        }
    }

    pub fn remove(&mut self, k: &'a K) -> Option<V> {
        for sk in k {
            /* do stuff */
        }
        None
    }
}

impl<'a, 'b, K, SK, V> HashLike<K, V> for MultiKeyMap<K, SK, V>
where
    K: Hash + Eq + Clone + 'a,
    'b: 'a,
    &'a K: IntoIterator<Item = &'b SK>,
    SK: Hash + Eq + Clone + 'b,
{
    fn remove(&mut self, k: &K) -> Option<V> {
        self.remove(k)
    }
}