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

pub fn map_drain_filter<K : Eq + Hash, V>(map : &mut HashMap<K, V>, filter : impl Fn(&K, &V) -> bool) -> Vec<(K, V)> {
    let mut removed = vec![];
    let mut retain = vec![];
    for (k, v) in map.drain() {
        if filter(&k, &v) {
            removed.push((k, v));
        } else {
            retain.push((k, v));
        }
    }
    map.extend(retain);
    removed
}

pub trait KVVecToKeysOrValues<K, V> {
    fn keys(self) -> Vec<K>;
    fn values(self) -> Vec<V>;
}

impl<K, V> KVVecToKeysOrValues<K, V> for Vec<(K,V)> {
    fn keys(self) -> Vec<K> {
        self.into_iter().map(|(k, _v)| k).collect()
    }

    fn values(self) -> Vec<V> {
        self.into_iter().map(|(_k, v)| v).collect()
    }
}