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use std::{
    collections::HashSet,
    hash::{BuildHasher, Hash, Hasher, RandomState},
    ops::{Deref, DerefMut},
};

#[derive(Clone, Debug, Default)]
pub struct HashableSet<T, S = RandomState>(HashSet<T, S>);

impl<T> HashableSet<T> {
    pub fn new() -> Self {
        Self(HashSet::new())
    }

    pub fn with_capacity(capacity: usize) -> Self {
        Self(HashSet::with_capacity(capacity))
    }
}

impl<T, S> HashableSet<T, S> {
    pub fn with_hasher(hash_builder: S) -> Self {
        Self(HashSet::with_hasher(hash_builder))
    }

    pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self {
        Self(HashSet::with_capacity_and_hasher(capacity, hash_builder))
    }
}

impl<T, S> Deref for HashableSet<T, S> {
    type Target = HashSet<T, S>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T, S> DerefMut for HashableSet<T, S> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl<T, S> From<HashSet<T, S>> for HashableSet<T, S> {
    fn from(value: HashSet<T, S>) -> Self {
        Self(value)
    }
}

impl<T, S> From<HashableSet<T, S>> for HashSet<T, S> {
    fn from(value: HashableSet<T, S>) -> HashSet<T, S> {
        value.0
    }
}

impl<T, S, D> Hash for HashableSet<T, S>
where
    T: Hash,
    S: BuildHasher<Hasher = D>,
    D: Hasher + Default,
{
    fn hash<H: Hasher>(&self, state: &mut H) {
        let hash = self
            .iter()
            .map(|t| {
                let mut hasher = D::default();
                t.hash(&mut hasher);
                hasher.finish()
            })
            .fold(0, u64::wrapping_add);

        state.write_u64(hash);
    }
}

impl<T, S> PartialEq for HashableSet<T, S>
where
    T: Eq + Hash,
    S: BuildHasher,
{
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
}

impl<T, S> Eq for HashableSet<T, S>
where
    T: Eq + Hash,
    S: BuildHasher,
{
}

#[cfg(test)]
pub(crate) mod tests {
    use std::hash::BuildHasherDefault;

    use super::*;

    use crate::map::tests::*;

    #[test]
    fn insertion_order_random_state() {
        insertion_order::<RandomState, _>()
    }

    #[test]
    fn insertion_order_fx_build_hasher() {
        insertion_order::<fxhash::FxBuildHasher, _>()
    }

    #[cfg(all(target_feature = "aes", feature = "sse2"))]
    #[test]
    fn insertion_order_gx_build_hasher() {
        insertion_order::<gxhash::GxBuildHasher, _>()
    }

    #[test]
    fn insertion_order_fnv_build_hasher() {
        insertion_order::<fnv::FnvBuildHasher, _>()
    }

    #[test]
    fn insertion_order_ahash_build_hasher() {
        insertion_order::<BuildHasherDefault<ahash::AHasher>, _>()
    }

    fn insertion_order<B: BuildHasher<Hasher = H> + Default, H: Hasher + Default>() {
        let values = generate_random_values::<i32, 128>();
        let values_shuffled = shuffle(&values);
        let values_other = generate_random_values::<i32, 128>();

        assert_ne!(values, values_shuffled);
        assert_ne!(values, values_other);
        assert_ne!(values_shuffled, values_other);

        let mut a = HashableSet::<_, B>::default();
        a.extend(values.iter().copied());
        let mut b = HashableSet::<_, B>::default();
        b.extend(values_shuffled.iter().copied());
        let mut c = HashableSet::<_, B>::default();
        c.extend(values_other.iter().copied());

        assert_hash_eq(&a, &b);
        assert_hash_ne(&a, &c);
        assert_hash_ne(&b, &c)
    }
}