use std::ops::{Index, IndexMut};

use crate::traits::GraphTopology;

pub struct VertexMap<V: Copy, T: Clone> {
    inner: EntityMap<V, T>,
}

impl<V: Copy, T: Clone> VertexMap<V, T> {
    pub fn new(default: T, to_index: fn(V) -> usize, capacity: usize) -> Self {
        Self {
            inner: EntityMap::new(default, to_index, capacity),
        }
    }

    // Reads beyond 'capacity' are valid and return the default value.
    pub fn capacity(&self) -> usize {
        self.inner.capacity()
    }

    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
    pub fn len(&self) -> usize {
        self.capacity()
    }


    pub fn sync<G: GraphTopology<Vertex = V>>(&mut self, graph: &G) {
        self.inner.resize(graph.vertex_capacity());
    }
}

impl<V: Copy, T: Clone> Index<V> for VertexMap<V, T> {
    type Output = T;

    fn index(&self, v: V) -> &T {
        &self.inner[v]
    }
}

impl<V: Copy, T: Clone> IndexMut<V> for VertexMap<V, T> {
    fn index_mut(&mut self, v: V) -> &mut T {
        &mut self.inner[v]
    }
}

pub struct EdgeMap<E: Copy, T: Clone> {
    inner: EntityMap<E, T>,
}

impl<E: Copy, T: Clone> EdgeMap<E, T> {
    pub fn new(default: T, to_index: fn(E) -> usize, capacity: usize) -> Self {
        Self {
            inner: EntityMap::new(default, to_index, capacity),
        }
    }

    // Reads beyond 'capacity' are valid and return the default value.
    pub fn capacity(&self) -> usize {
        self.inner.capacity()
    }

    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
    pub fn len(&self) -> usize {
        self.capacity()
    }

    pub fn sync<G: GraphTopology<Edge = E>>(&mut self, graph: &G) {
        self.inner.resize(graph.edge_capacity());
    }
}

impl<E: Copy, T: Clone> Index<E> for EdgeMap<E, T> {
    type Output = T;

    fn index(&self, e: E) -> &T {
        &self.inner[e]
    }
}

impl<E: Copy, T: Clone> IndexMut<E> for EdgeMap<E, T> {
    fn index_mut(&mut self, e: E) -> &mut T {
        &mut self.inner[e]
    }
}

struct EntityMap<E: Copy, T: Clone> {
    data: Vec<T>,
    default: T,
    to_index: fn(E) -> usize,
}

impl<E: Copy, T: Clone> EntityMap<E, T> {
    pub fn new(default: T, to_index: fn(E) -> usize, capacity: usize) -> Self {
        Self {
            data: vec![default.clone(); capacity],
            default,
            to_index,
        }
    }

    pub fn capacity(&self) -> usize {
        self.data.len()
    }

    pub fn resize(&mut self, capacity: usize) {
        if capacity > self.data.len() {
            self.data.resize(capacity, self.default.clone());
        }
    }
}

impl<E: Copy, T: Clone> Index<E> for EntityMap<E, T> {
    type Output = T;

    fn index(&self, e: E) -> &T {
        let i = (self.to_index)(e);
        if i < self.data.len() {
            &self.data[i]
        } else {
            &self.default
        }
    }
}

impl<E: Copy, T: Clone> IndexMut<E> for EntityMap<E, T> {
    fn index_mut(&mut self, e: E) -> &mut T {
        let i = (self.to_index)(e);
        if i >= self.data.len() {
            self.data.resize(i + 1, self.default.clone());
        }
        &mut self.data[i]
    }
}