// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use {
    crate::{
        area::Area, entry::Entry, handle_iter::HandleIter, qtinner::QTInner, traversal::Traversal,
        types::StoreType,
    },
    num::PrimInt,
    std::iter::FusedIterator,
};

// d888888b d888888b d88888b d8888b.
//   `88'   `~~88~~' 88'     88  `8D
//    88       88    88ooooo 88oobY'
//    88       88    88~~~~~ 88`8b
//   .88.      88    88.     88 `88.
// Y888888P    YP    Y88888P 88   YD

/// An iterator over all regions and values of a [`Quadtree`].
///
/// This struct is created by the [`iter`] method on [`Quadtree`].
///
/// [`iter`]: ../struct.Quadtree.html#method.iter
/// [`Quadtree`]: ../struct.Quadtree.html
#[derive(Clone, Debug)]
pub struct Iter<'a, U, V>
where
    U: PrimInt + Default,
{
    store: &'a StoreType<U, V>,
    handle_iter: HandleIter<'a, U>,
}

impl<'a, U, V> Iter<'a, U, V>
where
    U: PrimInt + Default,
{
    pub(crate) fn new(qt: &'a QTInner<U>, store: &'a StoreType<U, V>) -> Iter<'a, U, V> {
        Iter {
            store,
            handle_iter: HandleIter::new(qt),
        }
    }
}

impl<'a, U, V> Iterator for Iter<'a, U, V>
where
    U: PrimInt + Default,
{
    type Item = &'a Entry<U, V>;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        match self.handle_iter.next() {
            Some(handle) => Some(
                self.store
                    .get(&handle)
                    .expect("Shouldn't have an handle in the tree which isn't in the store."),
            ),
            None => None,
        }
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, Some(self.store.len()))
    }
}

impl<U, V> FusedIterator for Iter<'_, U, V> where U: PrimInt + Default {}

// d888888b d8b   db d888888b  .d88b.  d888888b d888888b d88888b d8888b.
//   `88'   888o  88 `~~88~~' .8P  Y8.   `88'   `~~88~~' 88'     88  `8D
//    88    88V8o 88    88    88    88    88       88    88ooooo 88oobY'
//    88    88 V8o88    88    88    88    88       88    88~~~~~ 88`8b
//   .88.   88  V888    88    `8b  d8'   .88.      88    88.     88 `88.
// Y888888P VP   V8P    YP     `Y88P'  Y888888P    YP    Y88888P 88   YD

/// A consuming iterator over all region/value associations held in a [`Quadtree`].
///
/// This struct is created by the `into_iter()` method on the [`IntoIterator`] trait.
///
/// [`IntoIterator`]: ../struct.Quadtree.html#impl-IntoIterator
/// [`Quadtree`]: ../struct.Quadtree.html
#[derive(Debug)]
pub struct IntoIter<U, V>
where
    U: PrimInt + Default,
{
    pub(crate) entries: Vec<Entry<U, V>>,
}

impl<U, V> Iterator for IntoIter<U, V>
where
    U: PrimInt + Default,
{
    type Item = Entry<U, V>;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        self.entries.pop()
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, None)
    }
}

impl<U, V> FusedIterator for IntoIter<U, V> where U: PrimInt + Default {}

//  .d88b.  db    db d88888b d8888b. db    db
// .8P  Y8. 88    88 88'     88  `8D `8b  d8'
// 88    88 88    88 88ooooo 88oobY'  `8bd8'
// 88    88 88    88 88~~~~~ 88`8b      88
// `8P  d8' 88b  d88 88.     88 `88.    88
//  `Y88'Y8 ~Y8888P' Y88888P 88   YD    YP

/// An iterator over the regions and values of a [`Quadtree`].
///
/// This struct is created by the [`query`] method on [`Quadtree`].
///
/// [`query`]: ../struct.Quadtree.html#method.query
/// [`Quadtree`]: ../struct.Quadtree.html
#[derive(Clone, Debug)]
pub struct Query<'a, U, V>
where
    U: PrimInt + Default,
{
    query_region: Area<U>,
    handle_iter: HandleIter<'a, U>,
    store: &'a StoreType<U, V>,
    traversal_method: Traversal,
}

impl<'a, U, V> Query<'a, U, V>
where
    U: PrimInt + Default,
{
    pub(crate) fn new(
        query_region: Area<U>,
        qt: &'a QTInner<U>,
        store: &'a StoreType<U, V>,
        traversal_method: Traversal,
    ) -> Query<'a, U, V>
    where
        U: PrimInt + Default,
    {
        // Construct the HandleIter first...
        let mut handle_iter = HandleIter::new(qt);

        // ...and descend it to the appropriate level. Depending on the type of @traversal_method,
        // this will potentially collect intersecting regions along the way. Avoiding combing the
        // entire Quadtree is essential for the efficiency of a query.
        handle_iter.query_optimization(query_region, traversal_method);

        Query {
            query_region,
            handle_iter,
            store,
            traversal_method,
        }
    }
}

impl<'a, U, V> Iterator for Query<'a, U, V>
where
    U: PrimInt + Default,
{
    type Item = &'a Entry<U, V>;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        if let Some(handle) = self.handle_iter.next() {
            if let Some(entry) = self.store.get(&handle) {
                if self.traversal_method.eval(entry.area(), self.query_region) {
                    return Some(entry);
                }
            }
            return self.next();
        }
        None
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, Some(self.store.len()))
    }
}

impl<U, V> FusedIterator for Query<'_, U, V> where U: PrimInt + Default {}

// db    db  .d8b.  db      db    db d88888b .d8888.
// 88    88 d8' `8b 88      88    88 88'     88'  YP
// Y8    8P 88ooo88 88      88    88 88ooooo `8bo.
// `8b  d8' 88~~~88 88      88    88 88~~~~~   `Y8b.
//  `8bd8'  88   88 88booo. 88b  d88 88.     db   8D
//    YP    YP   YP Y88888P ~Y8888P' Y88888P `8888Y'

/// An iterator over the values held within a [`Quadtree`].
///
/// This struct is created by the [`values`] method on [`Quadtree`].
///
/// [`values`]: ../struct.Quadtree.html#method.values
/// [`Quadtree`]: ../struct.Quadtree.html
#[derive(Clone, Debug)]
pub struct Values<'a, U, V>
where
    U: PrimInt + Default,
{
    pub(crate) inner: Iter<'a, U, V>,
}

impl<'a, U, V> Iterator for Values<'a, U, V>
where
    U: PrimInt + Default,
{
    type Item = (&'a V);

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        self.inner.next().and_then(|e| Some(e.value_ref()))
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, None)
    }
}

impl<U, V> FusedIterator for Values<'_, U, V> where U: PrimInt + Default {}

// d8888b. d88888b  d888b  d888888b  .d88b.  d8b   db .d8888.
// 88  `8D 88'     88' Y8b   `88'   .8P  Y8. 888o  88 88'  YP
// 88oobY' 88ooooo 88         88    88    88 88V8o 88 `8bo.
// 88`8b   88~~~~~ 88  ooo    88    88    88 88 V8o88   `Y8b.
// 88 `88. 88.     88. ~8~   .88.   `8b  d8' 88  V888 db   8D
// 88   YD Y88888P  Y888P  Y888888P  `Y88P'  VP   V8P `8888Y'

/// An iterator over the regions held within a [`Quadtree`].
///
/// This struct is created by the [`regions`] method on [`Quadtree`].
///
/// [`regions`]: ../struct.Quadtree.html#method.regions
/// [`Quadtree`]: ../struct.Quadtree.html
#[derive(Clone, Debug)]
pub struct Regions<'a, U, V>
where
    U: PrimInt + Default,
{
    pub(crate) inner: Iter<'a, U, V>,
}

impl<'a, U, V> Iterator for Regions<'a, U, V>
where
    U: PrimInt + Default,
{
    type Item = Area<U>;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        self.inner.next().and_then(|e| Some(e.area()))
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, None)
    }
}

impl<U, V> FusedIterator for Regions<'_, U, V> where U: PrimInt + Default {}