use crate::avl::{Iter, Tree};
use std::{
    borrow::Borrow,
    cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd},
    default::Default,
    fmt::{self, Debug, Formatter},
    hash::{Hash, Hasher},
    iter::FromIterator,
    ops::{Bound, Index},
};

/// This Map uses a similar strategy to BTreeMap to ensure cache
/// efficient performance on modern hardware while still providing
/// log(N) get, insert, and remove operations.
///
/// For good performance, it is very important to understand
/// that clone is a fundamental operation, it needs to be fast
/// for your key and data types, because it's going to be
/// called a lot whenever you change the map.
///
/// # Why
///
/// 1. Multiple threads can read this structure even while one thread
/// is updating it. Using a library like arc_swap you can avoid ever
/// blocking readers.
///
/// 2. Snapshotting this structure is free.
///
/// # Examples
/// ```
/// use std::string::String;
/// use self::immutable_chunkmap::map::Map;
///
/// let m =
///    Map::new()
///    .insert(String::from("1"), 1).0
///    .insert(String::from("2"), 2).0
///    .insert(String::from("3"), 3).0;
///
/// assert_eq!(m.get("1"), Option::Some(&1));
/// assert_eq!(m.get("2"), Option::Some(&2));
/// assert_eq!(m.get("3"), Option::Some(&3));
/// assert_eq!(m.get("4"), Option::None);
///
/// for (k, v) in &m {
///   println!("key {}, val: {}", k, v)
/// }
/// ```
#[derive(Clone)]
pub struct Map<K: Ord + Clone, V: Clone>(Tree<K, V>);

impl<K, V> Hash for Map<K, V>
where
    K: Hash + Ord + Clone,
    V: Hash + Clone,
{
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.0.hash(state)
    }
}

impl<K, V> Default for Map<K, V>
where
    K: Ord + Clone,
    V: Clone,
{
    fn default() -> Map<K, V> {
        Map::new()
    }
}

impl<K, V> PartialEq for Map<K, V>
where
    K: PartialEq + Ord + Clone,
    V: PartialEq + Clone,
{
    fn eq(&self, other: &Map<K, V>) -> bool {
        self.0 == other.0
    }
}

impl<K, V> Eq for Map<K, V>
where
    K: Eq + Ord + Clone,
    V: Eq + Clone,
{
}

impl<K, V> PartialOrd for Map<K, V>
where
    K: Ord + Clone,
    V: PartialOrd + Clone,
{
    fn partial_cmp(&self, other: &Map<K, V>) -> Option<Ordering> {
        self.0.partial_cmp(&other.0)
    }
}

impl<K, V> Ord for Map<K, V>
where
    K: Ord + Clone,
    V: Ord + Clone,
{
    fn cmp(&self, other: &Map<K, V>) -> Ordering {
        self.0.cmp(&other.0)
    }
}

impl<K, V> Debug for Map<K, V>
where
    K: Debug + Ord + Clone,
    V: Debug + Clone,
{
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl<'a, Q, K, V> Index<&'a Q> for Map<K, V>
where
    Q: Ord,
    K: Ord + Clone + Borrow<Q>,
    V: Clone,
{
    type Output = V;
    fn index(&self, k: &Q) -> &V {
        self.get(k).expect("element not found for key")
    }
}

impl<K, V> FromIterator<(K, V)> for Map<K, V>
where
    K: Ord + Clone,
    V: Clone,
{
    fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
        Map::new().insert_many(iter)
    }
}

impl<'a, K, V> IntoIterator for &'a Map<K, V>
where
    K: 'a + Borrow<K> + Ord + Clone,
    V: 'a + Clone,
{
    type Item = (&'a K, &'a V);
    type IntoIter = Iter<'a, K, K, V>;
    fn into_iter(self) -> Self::IntoIter {
        self.0.into_iter()
    }
}

impl<K, V> Map<K, V>
where
    K: Ord + Clone,
    V: Clone,
{
    /// Create a new empty map
    pub fn new() -> Self {
        Map(Tree::new())
    }

    /// This will insert many elements at once, and is
    /// potentially a lot faster than inserting one by one,
    /// especially if the data is sorted. It is just a wrapper
    /// around the more general update_many method.
    ///
    /// #Examples
    ///```
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let mut v = vec![(1, 3), (10, 1), (-12, 2), (44, 0), (50, -1)];
    /// v.sort_unstable_by_key(|&(k, _)| k);
    ///
    /// let m = Map::new().insert_many(v.iter().map(|(k, v)| (*k, *v)));
    ///
    /// for (k, v) in &v {
    ///   assert_eq!(m.get(k), Option::Some(v))
    /// }
    /// ```
    pub fn insert_many<E: IntoIterator<Item = (K, V)>>(&self, elts: E) -> Self {
        Map(self.0.insert_many(elts))
    }

    /// This method updates multiple bindings in one call. Given an
    /// iterator of an arbitrary type (Q, D), where Q is any borrowed
    /// form of K, an update function taking Q, D, the current binding
    /// in the map, if any, and producing the new binding, if any,
    /// this method will produce a new map with updated bindings of
    /// many elements at once. It will skip intermediate node
    /// allocations where possible. If the data in elts is sorted, it
    /// will be able to skip many more intermediate allocations, and
    /// can produce a speedup of about 10x compared to
    /// inserting/updating one by one. In any case it should always be
    /// faster than inserting elements one by one, even with random
    /// unsorted keys.
    ///
    /// #Examples
    /// ```
    /// use std::iter::FromIterator;
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let m = Map::from_iter((0..4).map(|k| (k, k)));
    /// let m = m.update_many(
    ///     (0..4).map(|x| (x, ())),
    ///     |k, (), cur| cur.map(|(_, c)| (k, c + 1))
    /// );
    /// assert_eq!(
    ///     m.into_iter().map(|(k, v)| (*k, *v)).collect::<Vec<_>>(),
    ///     vec![(0, 1), (1, 2), (2, 3), (3, 4)]
    /// );
    /// ```
    pub fn update_many<Q, D, E, F>(&self, elts: E, mut f: F) -> Self
    where
        E: IntoIterator<Item = (Q, D)>,
        Q: Ord,
        K: Borrow<Q>,
        F: FnMut(Q, D, Option<(&K, &V)>) -> Option<(K, V)>,
    {
        Map(self.0.update_many(elts, &mut f))
    }

    /// return a new map with (k, v) inserted into it. If k
    /// already exists in the old map, the old binding will be
    /// returned, and the new map will contain the new
    /// binding. In fact this method is just a wrapper around
    /// update.
    pub fn insert(&self, k: K, v: V) -> (Self, Option<V>) {
        let (root, prev) = self.0.insert(k, v);
        (Map(root), prev)
    }

    /// return a new map with the binding for q, which can be any
    /// borrowed form of k, updated to the result of f. If f returns
    /// None, the binding will be removed from the new map, otherwise
    /// it will be inserted. This function is more efficient than
    /// calling `get` and then `insert`, since it makes only one tree
    /// traversal instead of two. This method runs in log(N) time and
    /// space where N is the size of the map.
    ///
    /// # Examples
    /// ```
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let (m, _) = Map::new().update(0, 0, |k, d, _| Some((k, d)));
    /// let (m, _) = m.update(1, 1, |k, d, _| Some((k, d)));
    /// let (m, _) = m.update(2, 2, |k, d, _| Some((k, d)));
    /// assert_eq!(m.get(&0), Some(&0));
    /// assert_eq!(m.get(&1), Some(&1));
    /// assert_eq!(m.get(&2), Some(&2));
    ///
    /// let (m, _) = m.update(0, (), |k, (), v| v.map(move |(_, v)| (k, v + 1)));
    /// assert_eq!(m.get(&0), Some(&1));
    /// assert_eq!(m.get(&1), Some(&1));
    /// assert_eq!(m.get(&2), Some(&2));
    ///
    /// let (m, _) = m.update(1, (), |_, (), _| None);
    /// assert_eq!(m.get(&0), Some(&1));
    /// assert_eq!(m.get(&1), None);
    /// assert_eq!(m.get(&2), Some(&2));
    /// ```
    pub fn update<Q, D, F>(&self, q: Q, d: D, mut f: F) -> (Self, Option<V>)
    where
        Q: Ord,
        K: Borrow<Q>,
        F: FnMut(Q, D, Option<(&K, &V)>) -> Option<(K, V)>,
    {
        let (root, prev) = self.0.update(q, d, &mut f);
        (Map(root), prev)
    }

    /// Merge two maps together. Bindings that exist in both maps will
    /// be passed to f, which may elect to remove the binding by
    /// returning None. This function runs in O(log(n) + m) time and
    /// space, where n is the size of the largest map, and m is the
    /// number of intersecting chunks. It will never be slower than
    /// calling update_many on the first map with an iterator over the
    /// second, and will be significantly faster if the intersection
    /// is minimal or empty.
    ///
    /// # Examples
    /// ```
    /// use std::iter::FromIterator;
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let m0 = Map::from_iter((0..10).map(|k| (k, 1)));
    /// let m1 = Map::from_iter((10..20).map(|k| (k, 1)));
    /// let m2 = m0.union(&m1, |_k, _v0, _v1| panic!("no intersection expected"));
    ///
    /// for i in 0..20 {
    ///     assert!(m2.get(&i).is_some())
    /// }
    ///
    /// let m3 = Map::from_iter((5..9).map(|k| (k, 1)));
    /// let m4 = m3.union(&m2, |_k, v0, v1| Some(v0 + v1));
    ///
    /// for i in 0..20 {
    ///    assert!(
    ///        *m4.get(&i).unwrap() ==
    ///        *m3.get(&i).unwrap_or(&0) + *m2.get(&i).unwrap_or(&0)
    ///    )
    /// }
    /// ```
    pub fn union<F>(&self, other: &Map<K, V>, mut f: F) -> Self
    where
        F: FnMut(&K, &V, &V) -> Option<V>,
    {
        Map(Tree::union(&self.0, &other.0, &mut f))
    }

    /// Produce a map containing the mapping over F of the
    /// intersection (by key) of two maps. The function f runs on each
    /// intersecting element, and has the option to omit elements from
    /// the intersection by returning None, or change the value any
    /// way it likes. Runs in O(log(N) + M) time and space where N is
    /// the size of the smallest map, and M is the number of
    /// intersecting chunks.
    ///
    /// # Examples
    ///```
    /// use std::iter::FromIterator;
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let m0 = Map::from_iter((0..100000).map(|k| (k, 1)));
    /// let m1 = Map::from_iter((50..30000).map(|k| (k, 1)));
    /// let m2 = m0.intersect(&m1, |_k, v0, v1| Some(v0 + v1));
    ///
    /// for i in 0..100000 {
    ///     if i >= 30000 || i < 50 {
    ///         assert!(m2.get(&i).is_none());
    ///     } else {
    ///         assert!(*m2.get(&i).unwrap() == 2);
    ///     }
    /// }
    /// ```
    pub fn intersect<F>(&self, other: &Map<K, V>, mut f: F) -> Self
    where
        F: FnMut(&K, &V, &V) -> Option<V>,
    {
        Map(Tree::intersect(&self.0, &other.0, &mut f))
    }

    /// Produce a map containing the second map subtracted from the
    /// first. The function F is called for each intersecting element,
    /// and ultimately decides whether it appears in the result, for
    /// example, to compute a classical set diff, the function should
    /// always return None.
    ///
    /// # Examples
    ///```
    /// use std::iter::FromIterator;
    /// use self::immutable_chunkmap::map::Map;
    ///
    /// let m0 = Map::from_iter((0..10000).map(|k| (k, 1)));
    /// let m1 = Map::from_iter((50..3000).map(|k| (k, 1)));
    /// let m2 = m0.diff(&m1, |_k, _v0, _v1| None);
    ///
    /// m2.invariant();
    /// dbg!(m2.len());
    /// assert!(m2.len() == 10000 - 2950);
    /// for i in 0..10000 {
    ///     if i >= 3000 || i < 50 {
    ///         assert!(*m2.get(&i).unwrap() == 1);
    ///     } else {
    ///         assert!(m2.get(&i).is_none());
    ///     }
    /// }
    /// ```
    pub fn diff<F>(&self, other: &Map<K, V>, mut f: F) -> Self
    where F: FnMut(&K, &V, &V) -> Option<V>, K: Debug, V: Debug
    {
        Map(Tree::diff(&self.0, &other.0, &mut f))
    }

    /// lookup the mapping for k. If it doesn't exist return
    /// None. Runs in log(N) time and constant space. where N
    /// is the size of the map.
    pub fn get<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<&'a V>
    where
        K: Borrow<Q>,
    {
        self.0.get(k)
    }

    /// lookup the mapping for k. Return the key. If it doesn't exist
    /// return None. Runs in log(N) time and constant space. where N
    /// is the size of the map.
    pub fn get_key<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<&'a K>
    where
        K: Borrow<Q>,
    {
        self.0.get_key(k)
    }

    /// lookup the mapping for k. Return both the key and the
    /// value. If it doesn't exist return None. Runs in log(N) time
    /// and constant space. where N is the size of the map.
    pub fn get_full<'a, Q: ?Sized + Ord>(&'a self, k: &Q) -> Option<(&'a K, &'a V)>
    where
        K: Borrow<Q>,
    {
        self.0.get_full(k)
    }

    /// return a new map with the mapping under k removed. If
    /// the binding existed in the old map return it. Runs in
    /// log(N) time and log(N) space, where N is the size of
    /// the map.
    pub fn remove<Q: Sized + Ord>(&self, k: &Q) -> (Self, Option<V>)
    where
        K: Borrow<Q>,
    {
        let (t, prev) = self.0.remove(k);
        (Map(t), prev)
    }

    /// get the number of elements in the map O(1) time and space
    pub fn len(&self) -> usize {
        self.0.len()
    }

    /// return an iterator over the subset of elements in the
    /// map that are within the specified range.
    ///
    /// The returned iterator runs in O(log(N) + M) time, and
    /// constant space. N is the number of elements in the
    /// tree, and M is the number of elements you examine.
    ///
    /// if lbound >= ubound the returned iterator will be empty
    pub fn range<'a, Q>(&'a self, lbound: Bound<Q>, ubound: Bound<Q>) -> Iter<'a, Q, K, V>
    where
        Q: Ord,
        K: Borrow<Q>,
    {
        self.0.range(lbound, ubound)
    }
}

impl<K, V> Map<K, V>
where
    K: Ord + Clone + Debug,
    V: Clone + Debug,
{
    #[allow(dead_code)]
    pub fn invariant(&self) -> () {
        self.0.invariant()
    }
}