use std::borrow::Borrow;
use std::collections::hash_map::{
    Entry, IntoKeys, IntoValues, Iter, IterMut, Keys, Values, ValuesMut,
};
use std::fmt::{self, Write};
use std::hash::{Hash, Hasher};
use std::iter::FromIterator;
use std::ops::{Index, IndexMut};

use crate::fxhash::FxHashMap;
use crate::get_hash;
use crate::traits::Immutable;

#[macro_export]
macro_rules! dict {
    () => { $crate::dict::Dict::new() };
    ($($k: expr => $v: expr),+ $(,)?) => {{
        let mut dict = $crate::dict::Dict::new();
        $(dict.insert($k, $v);)+
        dict
    }};
}

#[derive(Debug, Clone)]
pub struct Dict<K, V> {
    dict: FxHashMap<K, V>,
}

impl<K: Hash + Eq + Immutable, V: Hash + Eq> PartialEq for Dict<K, V> {
    fn eq(&self, other: &Dict<K, V>) -> bool {
        self.dict == other.dict
    }
}

impl<K: Hash + Eq + Immutable, V: Hash + Eq> Eq for Dict<K, V> {}

impl<K: Hash, V: Hash> Hash for Dict<K, V> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        let len = self.len();
        len.hash(state);
        if len <= 1 {
            for (key, val) in self.iter() {
                key.hash(state);
                val.hash(state);
            }
        } else {
            let mut v = self
                .iter()
                .map(|(key, val)| (get_hash(key), val))
                .collect::<Vec<_>>();
            v.sort_unstable_by_key(|(h, _)| *h);
            for (h, val) in v.iter() {
                state.write_usize(*h);
                val.hash(state);
            }
        }
    }
}

impl<K: fmt::Display, V: fmt::Display> fmt::Display for Dict<K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut s = "".to_string();
        for (k, v) in self.dict.iter() {
            write!(s, "{k}: {v}, ")?;
        }
        s.pop();
        s.pop();
        write!(f, "{{{s}}}")
    }
}

impl<K: Hash + Eq, V> FromIterator<(K, V)> for Dict<K, V> {
    #[inline]
    fn from_iter<I: IntoIterator<Item = (K, V)>>(iter: I) -> Dict<K, V> {
        let mut dict = Dict::new();
        dict.extend(iter);
        dict
    }
}

impl<K: Hash + Eq, V> Extend<(K, V)> for Dict<K, V> {
    #[inline]
    fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iter: I) {
        self.guaranteed_extend(iter);
    }
}

impl<K: Hash + Eq, V> From<Vec<(K, V)>> for Dict<K, V> {
    #[inline]
    fn from(v: Vec<(K, V)>) -> Dict<K, V> {
        v.into_iter().collect()
    }
}

impl<K: Hash + Eq + Immutable, V, Q: ?Sized> Index<&Q> for Dict<K, V>
where
    K: Borrow<Q>,
    Q: Hash + Eq,
{
    type Output = V;
    #[inline]
    fn index(&self, index: &Q) -> &V {
        self.dict.get(index).unwrap()
    }
}

impl<K: Hash + Eq + Immutable, V, Q: ?Sized> IndexMut<&Q> for Dict<K, V>
where
    K: Borrow<Q>,
    Q: Hash + Eq,
{
    #[inline]
    fn index_mut(&mut self, index: &Q) -> &mut V {
        self.dict.get_mut(index).unwrap()
    }
}

impl<K, V> Default for Dict<K, V> {
    fn default() -> Dict<K, V> {
        Dict::new()
    }
}

impl<K: Clone + Hash + Eq, V: Clone> Dict<&K, &V> {
    pub fn cloned(&self) -> Dict<K, V> {
        self.dict
            .iter()
            .map(|(&k, &v)| (k.clone(), v.clone()))
            .collect()
    }
}

impl<K, V> Dict<K, V> {
    #[inline]
    pub fn new() -> Self {
        Self {
            dict: FxHashMap::default(),
        }
    }

    /// ```
    /// # use erg_common::dict;
    /// # use erg_common::dict::Dict;
    /// let mut dict = Dict::with_capacity(3);
    /// assert_eq!(dict.capacity(), 3);
    /// dict.insert("a", 1);
    /// assert_eq!(dict.capacity(), 3);
    /// dict.insert("b", 2);
    /// dict.insert("c", 3);
    /// dict.insert("d", 4);
    /// assert_ne!(dict.capacity(), 3);
    /// ```
    pub fn with_capacity(capacity: usize) -> Self {
        Self {
            dict: FxHashMap::with_capacity_and_hasher(capacity, Default::default()),
        }
    }

    #[inline]
    pub fn len(&self) -> usize {
        self.dict.len()
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.dict.is_empty()
    }

    #[inline]
    pub fn capacity(&self) -> usize {
        self.dict.capacity()
    }

    #[inline]
    pub fn keys(&self) -> Keys<K, V> {
        self.dict.keys()
    }

    #[inline]
    pub fn values(&self) -> Values<K, V> {
        self.dict.values()
    }

    #[inline]
    pub fn values_mut(&mut self) -> ValuesMut<K, V> {
        self.dict.values_mut()
    }

    #[inline]
    pub fn into_values(self) -> IntoValues<K, V> {
        self.dict.into_values()
    }

    #[inline]
    pub fn into_keys(self) -> IntoKeys<K, V> {
        self.dict.into_keys()
    }

    #[inline]
    pub fn iter(&self) -> Iter<K, V> {
        self.dict.iter()
    }

    #[inline]
    pub fn iter_mut(&mut self) -> IterMut<K, V> {
        self.dict.iter_mut()
    }

    pub fn clear(&mut self) {
        self.dict.clear();
    }

    /// remove all elements for which the predicate returns false
    pub fn retain<F>(&mut self, f: F)
    where
        F: FnMut(&K, &mut V) -> bool,
    {
        self.dict.retain(f);
    }

    pub fn retained(mut self, f: impl FnMut(&K, &mut V) -> bool) -> Self {
        self.retain(f);
        self
    }

    pub fn get_by(&self, k: &K, cmp: impl Fn(&K, &K) -> bool) -> Option<&V> {
        for (k_, v) in self.dict.iter() {
            if cmp(k, k_) {
                return Some(v);
            }
        }
        None
    }
}

impl<K, V> IntoIterator for Dict<K, V> {
    type Item = (K, V);
    type IntoIter = <FxHashMap<K, V> as IntoIterator>::IntoIter;
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.dict.into_iter()
    }
}

impl<'a, K, V> IntoIterator for &'a Dict<K, V> {
    type Item = (&'a K, &'a V);
    type IntoIter = Iter<'a, K, V>;
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.dict.iter()
    }
}

impl<K: Eq, V> Dict<K, V> {
    /// K: interior-mutable
    pub fn linear_get<Q>(&self, key: &Q) -> Option<&V>
    where
        K: Borrow<Q>,
        Q: Eq + ?Sized,
    {
        self.dict
            .iter()
            .find(|(k, _)| (*k).borrow() == key)
            .map(|(_, v)| v)
    }

    pub fn linear_get_mut<Q>(&mut self, key: &Q) -> Option<&mut V>
    where
        K: Borrow<Q>,
        Q: Eq + ?Sized,
    {
        self.dict
            .iter_mut()
            .find(|(k, _)| (*k).borrow() == key)
            .map(|(_, v)| v)
    }
}

impl<K: Eq, V: Eq> Dict<K, V> {
    /// K: interior-mutable
    pub fn linear_eq(&self, other: &Self) -> bool {
        if self.len() != other.len() {
            return false;
        }
        for (k, v) in self.iter() {
            if other.linear_get(k) != Some(v) {
                return false;
            }
        }
        true
    }
}

impl<K: Hash + Eq + Immutable, V> Dict<K, V> {
    #[inline]
    pub fn get<Q>(&self, k: &Q) -> Option<&V>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.get(k)
    }

    #[inline]
    pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.get_mut(k)
    }

    pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.get_key_value(k)
    }

    #[inline]
    pub fn contains_key<Q>(&self, k: &Q) -> bool
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.contains_key(k)
    }

    #[inline]
    pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.remove(k)
    }

    pub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized,
    {
        self.dict.remove_entry(k)
    }

    pub fn remove_entries<'q, Q>(&mut self, keys: impl IntoIterator<Item = &'q Q>)
    where
        K: Borrow<Q>,
        Q: Hash + Eq + ?Sized + 'q,
    {
        for k in keys {
            self.remove_entry(k);
        }
    }
}

impl<K: Hash + Eq, V> Dict<K, V> {
    #[inline]
    pub fn insert(&mut self, k: K, v: V) -> Option<V> {
        self.dict.insert(k, v)
    }

    /// NOTE: This method does not consider pairing with values and keys. That is, a value may be paired with a different key (can be considered equal).
    /// If you need to consider the pairing of the keys and values, use `guaranteed_extend` instead.
    #[inline]
    pub fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iter: I) {
        self.dict.extend(iter);
    }

    /// If the key already exists, the value will not be updated.
    #[inline]
    pub fn guaranteed_extend<I: IntoIterator<Item = (K, V)>>(&mut self, other: I) {
        for (k, v) in other {
            self.dict.entry(k).or_insert(v);
        }
    }

    #[inline]
    pub fn merge(&mut self, other: Self) {
        self.dict.extend(other.dict);
    }

    #[inline]
    pub fn concat(mut self, other: Self) -> Self {
        self.merge(other);
        self
    }

    #[inline]
    pub fn diff(mut self, other: &Self) -> Self {
        for k in other.dict.keys() {
            self.dict.remove(k);
        }
        self
    }

    pub fn entry(&mut self, k: K) -> Entry<K, V> {
        self.dict.entry(k)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use crate::str::Str;

    #[test]
    fn test_dict() {
        let mut dict = Dict::new();
        dict.insert(Str::from("a"), 1);
        dict.insert(Str::from("b"), 2);
        dict.insert(Str::from("c"), 3);
        assert_eq!(dict.len(), 3);
        assert_eq!(dict.get(&Str::from("a")), Some(&1));
        assert_eq!(dict.get(&Str::from("b")), Some(&2));
        assert_eq!(dict.get(&Str::from("c")), Some(&3));
        assert_eq!(dict.get(&Str::from("d")), None);
        assert_eq!(dict.get("a"), Some(&1));
        assert_eq!(dict.get("b"), Some(&2));
        assert_eq!(dict.get("c"), Some(&3));
        assert_eq!(dict.get("d"), None);
        assert_eq!(dict.remove(&Str::from("a")), Some(1));
        assert_eq!(dict.remove(&Str::from("a")), None);
        assert_eq!(dict.len(), 2);
        assert_eq!(dict.get(&Str::from("a")), None);
        assert_eq!(dict.get(&Str::from("b")), Some(&2));
        assert_eq!(dict.get(&Str::from("c")), Some(&3));
        assert_eq!(dict.get(&Str::from("d")), None);
        dict.clear();
        assert_eq!(dict.len(), 0);
        assert_eq!(dict.get(&Str::from("a")), None);
        assert_eq!(dict.get(&Str::from("b")), None);
        assert_eq!(dict.get(&Str::from("c")), None);
        assert_eq!(dict.get(&Str::from("d")), None);
    }
}