use super::plumbing::*;
use super::*;

use std::fmt::{self, Debug};

/// `MapWith` is an iterator that transforms the elements of an underlying iterator.
///
/// This struct is created by the [`map_with()`] method on [`ParallelIterator`]
///
/// [`map_with()`]: trait.ParallelIterator.html#method.map_with
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct MapWith<I: ParallelIterator, T, F> {
    base: I,
    item: T,
    map_op: F,
}

impl<I: ParallelIterator + Debug, T: Debug, F> Debug for MapWith<I, T, F> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("MapWith")
            .field("base", &self.base)
            .field("item", &self.item)
            .finish()
    }
}

impl<I, T, F> MapWith<I, T, F>
where
    I: ParallelIterator,
{
    /// Create a new `MapWith` iterator.
    pub(super) fn new(base: I, item: T, map_op: F) -> Self {
        MapWith { base, item, map_op }
    }
}

impl<I, T, F, R> ParallelIterator for MapWith<I, T, F>
where
    I: ParallelIterator,
    T: Send + Clone,
    F: Fn(&mut T, I::Item) -> R + Sync + Send,
    R: Send,
{
    type Item = R;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        let consumer1 = MapWithConsumer::new(consumer, self.item, &self.map_op);
        self.base.drive_unindexed(consumer1)
    }

    fn opt_len(&self) -> Option<usize> {
        self.base.opt_len()
    }
}

impl<I, T, F, R> IndexedParallelIterator for MapWith<I, T, F>
where
    I: IndexedParallelIterator,
    T: Send + Clone,
    F: Fn(&mut T, I::Item) -> R + Sync + Send,
    R: Send,
{
    fn drive<C>(self, consumer: C) -> C::Result
    where
        C: Consumer<Self::Item>,
    {
        let consumer1 = MapWithConsumer::new(consumer, self.item, &self.map_op);
        self.base.drive(consumer1)
    }

    fn len(&self) -> usize {
        self.base.len()
    }

    fn with_producer<CB>(self, callback: CB) -> CB::Output
    where
        CB: ProducerCallback<Self::Item>,
    {
        return self.base.with_producer(Callback {
            callback,
            item: self.item,
            map_op: self.map_op,
        });

        struct Callback<CB, U, F> {
            callback: CB,
            item: U,
            map_op: F,
        }

        impl<T, U, F, R, CB> ProducerCallback<T> for Callback<CB, U, F>
        where
            CB: ProducerCallback<R>,
            U: Send + Clone,
            F: Fn(&mut U, T) -> R + Sync,
            R: Send,
        {
            type Output = CB::Output;

            fn callback<P>(self, base: P) -> CB::Output
            where
                P: Producer<Item = T>,
            {
                let producer = MapWithProducer {
                    base,
                    item: self.item,
                    map_op: &self.map_op,
                };
                self.callback.callback(producer)
            }
        }
    }
}

/// ////////////////////////////////////////////////////////////////////////

struct MapWithProducer<'f, P, U, F: 'f> {
    base: P,
    item: U,
    map_op: &'f F,
}

impl<'f, P, U, F, R> Producer for MapWithProducer<'f, P, U, F>
where
    P: Producer,
    U: Send + Clone,
    F: Fn(&mut U, P::Item) -> R + Sync,
    R: Send,
{
    type Item = R;
    type IntoIter = MapWithIter<'f, P::IntoIter, U, F>;

    fn into_iter(self) -> Self::IntoIter {
        MapWithIter {
            base: self.base.into_iter(),
            item: self.item,
            map_op: self.map_op,
        }
    }

    fn min_len(&self) -> usize {
        self.base.min_len()
    }
    fn max_len(&self) -> usize {
        self.base.max_len()
    }

    fn split_at(self, index: usize) -> (Self, Self) {
        let (left, right) = self.base.split_at(index);
        (
            MapWithProducer {
                base: left,
                item: self.item.clone(),
                map_op: self.map_op,
            },
            MapWithProducer {
                base: right,
                item: self.item,
                map_op: self.map_op,
            },
        )
    }

    fn fold_with<G>(self, folder: G) -> G
    where
        G: Folder<Self::Item>,
    {
        let folder1 = MapWithFolder {
            base: folder,
            item: self.item,
            map_op: self.map_op,
        };
        self.base.fold_with(folder1).base
    }
}

struct MapWithIter<'f, I, U, F: 'f> {
    base: I,
    item: U,
    map_op: &'f F,
}

impl<'f, I, U, F, R> Iterator for MapWithIter<'f, I, U, F>
where
    I: Iterator,
    F: Fn(&mut U, I::Item) -> R + Sync,
    R: Send,
{
    type Item = R;

    fn next(&mut self) -> Option<R> {
        let item = self.base.next()?;
        Some((self.map_op)(&mut self.item, item))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.base.size_hint()
    }
}

impl<'f, I, U, F, R> DoubleEndedIterator for MapWithIter<'f, I, U, F>
where
    I: DoubleEndedIterator,
    F: Fn(&mut U, I::Item) -> R + Sync,
    R: Send,
{
    fn next_back(&mut self) -> Option<R> {
        let item = self.base.next_back()?;
        Some((self.map_op)(&mut self.item, item))
    }
}

impl<'f, I, U, F, R> ExactSizeIterator for MapWithIter<'f, I, U, F>
where
    I: ExactSizeIterator,
    F: Fn(&mut U, I::Item) -> R + Sync,
    R: Send,
{
}

/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation

struct MapWithConsumer<'f, C, U, F: 'f> {
    base: C,
    item: U,
    map_op: &'f F,
}

impl<'f, C, U, F> MapWithConsumer<'f, C, U, F> {
    fn new(base: C, item: U, map_op: &'f F) -> Self {
        MapWithConsumer { base, item, map_op }
    }
}

impl<'f, T, U, R, C, F> Consumer<T> for MapWithConsumer<'f, C, U, F>
where
    C: Consumer<R>,
    U: Send + Clone,
    F: Fn(&mut U, T) -> R + Sync,
    R: Send,
{
    type Folder = MapWithFolder<'f, C::Folder, U, F>;
    type Reducer = C::Reducer;
    type Result = C::Result;

    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
        let (left, right, reducer) = self.base.split_at(index);
        (
            MapWithConsumer::new(left, self.item.clone(), self.map_op),
            MapWithConsumer::new(right, self.item, self.map_op),
            reducer,
        )
    }

    fn into_folder(self) -> Self::Folder {
        MapWithFolder {
            base: self.base.into_folder(),
            item: self.item,
            map_op: self.map_op,
        }
    }

    fn full(&self) -> bool {
        self.base.full()
    }
}

impl<'f, T, U, R, C, F> UnindexedConsumer<T> for MapWithConsumer<'f, C, U, F>
where
    C: UnindexedConsumer<R>,
    U: Send + Clone,
    F: Fn(&mut U, T) -> R + Sync,
    R: Send,
{
    fn split_off_left(&self) -> Self {
        MapWithConsumer::new(self.base.split_off_left(), self.item.clone(), self.map_op)
    }

    fn to_reducer(&self) -> Self::Reducer {
        self.base.to_reducer()
    }
}

struct MapWithFolder<'f, C, U, F: 'f> {
    base: C,
    item: U,
    map_op: &'f F,
}

impl<'f, T, U, R, C, F> Folder<T> for MapWithFolder<'f, C, U, F>
where
    C: Folder<R>,
    F: Fn(&mut U, T) -> R,
{
    type Result = C::Result;

    fn consume(mut self, item: T) -> Self {
        let mapped_item = (self.map_op)(&mut self.item, item);
        self.base = self.base.consume(mapped_item);
        self
    }

    fn consume_iter<I>(mut self, iter: I) -> Self
    where
        I: IntoIterator<Item = T>,
    {
        fn with<'f, T, U, R>(
            item: &'f mut U,
            map_op: impl Fn(&mut U, T) -> R + 'f,
        ) -> impl FnMut(T) -> R + 'f {
            move |x| map_op(item, x)
        }

        {
            let mapped_iter = iter.into_iter().map(with(&mut self.item, self.map_op));
            self.base = self.base.consume_iter(mapped_iter);
        }
        self
    }

    fn complete(self) -> C::Result {
        self.base.complete()
    }

    fn full(&self) -> bool {
        self.base.full()
    }
}

// ------------------------------------------------------------------------------------------------

/// `MapInit` is an iterator that transforms the elements of an underlying iterator.
///
/// This struct is created by the [`map_init()`] method on [`ParallelIterator`]
///
/// [`map_init()`]: trait.ParallelIterator.html#method.map_init
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct MapInit<I: ParallelIterator, INIT, F> {
    base: I,
    init: INIT,
    map_op: F,
}

impl<I: ParallelIterator + Debug, INIT, F> Debug for MapInit<I, INIT, F> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("MapInit").field("base", &self.base).finish()
    }
}

impl<I, INIT, F> MapInit<I, INIT, F>
where
    I: ParallelIterator,
{
    /// Create a new `MapInit` iterator.
    pub(super) fn new(base: I, init: INIT, map_op: F) -> Self {
        MapInit { base, init, map_op }
    }
}

impl<I, INIT, T, F, R> ParallelIterator for MapInit<I, INIT, F>
where
    I: ParallelIterator,
    INIT: Fn() -> T + Sync + Send,
    F: Fn(&mut T, I::Item) -> R + Sync + Send,
    R: Send,
{
    type Item = R;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        let consumer1 = MapInitConsumer::new(consumer, &self.init, &self.map_op);
        self.base.drive_unindexed(consumer1)
    }

    fn opt_len(&self) -> Option<usize> {
        self.base.opt_len()
    }
}

impl<I, INIT, T, F, R> IndexedParallelIterator for MapInit<I, INIT, F>
where
    I: IndexedParallelIterator,
    INIT: Fn() -> T + Sync + Send,
    F: Fn(&mut T, I::Item) -> R + Sync + Send,
    R: Send,
{
    fn drive<C>(self, consumer: C) -> C::Result
    where
        C: Consumer<Self::Item>,
    {
        let consumer1 = MapInitConsumer::new(consumer, &self.init, &self.map_op);
        self.base.drive(consumer1)
    }

    fn len(&self) -> usize {
        self.base.len()
    }

    fn with_producer<CB>(self, callback: CB) -> CB::Output
    where
        CB: ProducerCallback<Self::Item>,
    {
        return self.base.with_producer(Callback {
            callback,
            init: self.init,
            map_op: self.map_op,
        });

        struct Callback<CB, INIT, F> {
            callback: CB,
            init: INIT,
            map_op: F,
        }

        impl<T, INIT, U, F, R, CB> ProducerCallback<T> for Callback<CB, INIT, F>
        where
            CB: ProducerCallback<R>,
            INIT: Fn() -> U + Sync,
            F: Fn(&mut U, T) -> R + Sync,
            R: Send,
        {
            type Output = CB::Output;

            fn callback<P>(self, base: P) -> CB::Output
            where
                P: Producer<Item = T>,
            {
                let producer = MapInitProducer {
                    base,
                    init: &self.init,
                    map_op: &self.map_op,
                };
                self.callback.callback(producer)
            }
        }
    }
}

/// ////////////////////////////////////////////////////////////////////////

struct MapInitProducer<'f, P, INIT: 'f, F: 'f> {
    base: P,
    init: &'f INIT,
    map_op: &'f F,
}

impl<'f, P, INIT, U, F, R> Producer for MapInitProducer<'f, P, INIT, F>
where
    P: Producer,
    INIT: Fn() -> U + Sync,
    F: Fn(&mut U, P::Item) -> R + Sync,
    R: Send,
{
    type Item = R;
    type IntoIter = MapWithIter<'f, P::IntoIter, U, F>;

    fn into_iter(self) -> Self::IntoIter {
        MapWithIter {
            base: self.base.into_iter(),
            item: (self.init)(),
            map_op: self.map_op,
        }
    }

    fn min_len(&self) -> usize {
        self.base.min_len()
    }
    fn max_len(&self) -> usize {
        self.base.max_len()
    }

    fn split_at(self, index: usize) -> (Self, Self) {
        let (left, right) = self.base.split_at(index);
        (
            MapInitProducer {
                base: left,
                init: self.init,
                map_op: self.map_op,
            },
            MapInitProducer {
                base: right,
                init: self.init,
                map_op: self.map_op,
            },
        )
    }

    fn fold_with<G>(self, folder: G) -> G
    where
        G: Folder<Self::Item>,
    {
        let folder1 = MapWithFolder {
            base: folder,
            item: (self.init)(),
            map_op: self.map_op,
        };
        self.base.fold_with(folder1).base
    }
}

/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation

struct MapInitConsumer<'f, C, INIT: 'f, F: 'f> {
    base: C,
    init: &'f INIT,
    map_op: &'f F,
}

impl<'f, C, INIT, F> MapInitConsumer<'f, C, INIT, F> {
    fn new(base: C, init: &'f INIT, map_op: &'f F) -> Self {
        MapInitConsumer { base, init, map_op }
    }
}

impl<'f, T, INIT, U, R, C, F> Consumer<T> for MapInitConsumer<'f, C, INIT, F>
where
    C: Consumer<R>,
    INIT: Fn() -> U + Sync,
    F: Fn(&mut U, T) -> R + Sync,
    R: Send,
{
    type Folder = MapWithFolder<'f, C::Folder, U, F>;
    type Reducer = C::Reducer;
    type Result = C::Result;

    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
        let (left, right, reducer) = self.base.split_at(index);
        (
            MapInitConsumer::new(left, self.init, self.map_op),
            MapInitConsumer::new(right, self.init, self.map_op),
            reducer,
        )
    }

    fn into_folder(self) -> Self::Folder {
        MapWithFolder {
            base: self.base.into_folder(),
            item: (self.init)(),
            map_op: self.map_op,
        }
    }

    fn full(&self) -> bool {
        self.base.full()
    }
}

impl<'f, T, INIT, U, R, C, F> UnindexedConsumer<T> for MapInitConsumer<'f, C, INIT, F>
where
    C: UnindexedConsumer<R>,
    INIT: Fn() -> U + Sync,
    F: Fn(&mut U, T) -> R + Sync,
    R: Send,
{
    fn split_off_left(&self) -> Self {
        MapInitConsumer::new(self.base.split_off_left(), self.init, self.map_op)
    }

    fn to_reducer(&self) -> Self::Reducer {
        self.base.to_reducer()
    }
}