bp3d-util 2.3.0

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//! A map with the key stored as part of the value.

use std::borrow::Borrow;
use std::collections::HashSet;
use std::hash::{Hash, Hasher};
use std::rc::Rc;
use std::sync::Arc;

/// The main index type to implement for each type to be stored in an IndexMap.
pub trait Index {
    /// The type of the key.
    type Key: ?Sized + Hash + PartialEq + Eq;

    /// The index function which returns a reference to the key stored in the object.
    fn index(&self) -> &Self::Key;
}

impl<T: Index> Index for Rc<T> {
    type Key = T::Key;

    fn index(&self) -> &Self::Key {
        (**self).index()
    }
}

impl<T: Index> Index for Arc<T> {
    type Key = T::Key;

    fn index(&self) -> &Self::Key {
        (**self).index()
    }
}

#[derive(Clone, Debug)]
struct Item<V>(V);

impl<V: Index> Hash for Item<V> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.0.index().hash(state);
    }
}

impl<V: Index> PartialEq for Item<V> {
    fn eq(&self, other: &Self) -> bool {
        self.0.index().eq(other.0.index())
    }
}

impl<V: Index> Eq for Item<V> {}

impl<V: Index<Key = str>> Borrow<str> for Item<V> {
    fn borrow(&self) -> &V::Key {
        self.0.index()
    }
}

impl<V: Index<Key = usize>> Borrow<usize> for Item<V> {
    fn borrow(&self) -> &V::Key {
        self.0.index()
    }
}

/// The main IndexMap data-structure type.
///
/// This map type uses a [HashSet] to store the underlying items.
/// The underlying items are wrapped in a custom struct, hidden from the public API, to workaround
/// Rust broken coherence and WTF other stupid similar rules.
#[derive(Default, Clone, Debug)]
pub struct IndexMap<V>(HashSet<Item<V>>);

impl<V> IndexMap<V> {
    /// Creates a new instance of an [IndexMap].
    pub fn new() -> IndexMap<V> {
        IndexMap(HashSet::new())
    }

    /// Returns the number of items in this [IndexMap].
    pub fn len(&self) -> usize {
        self.0.len()
    }

    /// Returns true when this [IndexMap] is empty.
    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }

    /// Creates a new instance of an [IndexMap] with a given capacity.
    ///
    /// # Arguments
    ///
    /// * `capacity`: the capacity of the new [IndexMap].
    pub fn with_capacity(capacity: usize) -> IndexMap<V> {
        Self(HashSet::with_capacity(capacity))
    }

    /// Returns an iterator over all elements contained in the map.
    pub fn iter(&self) -> impl Iterator<Item = &V> {
        self.0.iter().map(|v| &v.0)
    }
}

impl<V: Index> IndexMap<V> {
    /// Inserts a new item in this [IndexMap].
    ///
    /// # Arguments
    ///
    /// * `value`: the value to be inserted.
    ///
    /// returns: ()
    pub fn insert(&mut self, value: V) {
        self.0.insert(Item(value));
    }

    /// Gets an element stored in this [IndexMap] from its key.
    ///
    /// # Arguments
    ///
    /// * `key`: the key of the element to look for.
    #[allow(private_bounds)] // Because Rust is a piece of shit!!
    pub fn get(&self, key: &V::Key) -> Option<&V>
    where
        Item<V>: Borrow<V::Key>,
    {
        self.0.get(key).map(|v| &v.0)
    }
}

impl<'a, V: Index> std::ops::Index<&'a V::Key> for IndexMap<V>
where
    Item<V>: Borrow<V::Key>,
{
    type Output = V;

    fn index(&self, index: &'a V::Key) -> &Self::Output {
        self.get(index).unwrap()
    }
}