use hashbrown::Equivalent;
use hashbrown::HashMap;

use std::hash::Hash;

#[derive(Debug, Hash)]
pub struct Pair<A, B>(pub A, pub B);

impl<A, B, C, D> PartialEq<(A, B)> for Pair<C, D>
where
    C: PartialEq<A>,
    D: PartialEq<B>,
{
    fn eq(&self, rhs: &(A, B)) -> bool {
        self.0 == rhs.0 && self.1 == rhs.1
    }
}

impl<A, B, X> Equivalent<X> for Pair<A, B>
where
    Pair<A, B>: PartialEq<X>,
    A: Hash + Eq,
    B: Hash + Eq,
{
    fn equivalent(&self, other: &X) -> bool {
        *self == *other
    }
}

#[test]
fn test_lookup() {
    let s = String::from;
    let mut map = HashMap::new();
    map.insert((s("a"), s("b")), 1);
    map.insert((s("a"), s("x")), 2);

    assert!(map.contains_key(&Pair("a", "b")));
    assert!(!map.contains_key(&Pair("b", "a")));
}

#[test]
fn test_string_str() {
    let s = String::from;
    let mut map = HashMap::new();
    map.insert(s("a"), 1);
    map.insert(s("b"), 2);
    map.insert(s("x"), 3);
    map.insert(s("y"), 4);

    assert!(map.contains_key("a"));
    assert!(!map.contains_key("z"));
    assert_eq!(map.remove("b"), Some(2));
}