use crate::iter::plumbing::*;
use crate::iter::Either::{Left, Right};
use crate::iter::*;

/// `Either<L, R>` is a parallel iterator if both `L` and `R` are parallel iterators.
impl<L, R> ParallelIterator for Either<L, R>
where
    L: ParallelIterator,
    R: ParallelIterator<Item = L::Item>,
{
    type Item = L::Item;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        match self {
            Left(iter) => iter.drive_unindexed(consumer),
            Right(iter) => iter.drive_unindexed(consumer),
        }
    }

    fn opt_len(&self) -> Option<usize> {
        self.as_ref().either(L::opt_len, R::opt_len)
    }
}

impl<L, R> IndexedParallelIterator for Either<L, R>
where
    L: IndexedParallelIterator,
    R: IndexedParallelIterator<Item = L::Item>,
{
    fn drive<C>(self, consumer: C) -> C::Result
    where
        C: Consumer<Self::Item>,
    {
        match self {
            Left(iter) => iter.drive(consumer),
            Right(iter) => iter.drive(consumer),
        }
    }

    fn len(&self) -> usize {
        self.as_ref().either(L::len, R::len)
    }

    fn with_producer<CB>(self, callback: CB) -> CB::Output
    where
        CB: ProducerCallback<Self::Item>,
    {
        match self {
            Left(iter) => iter.with_producer(callback),
            Right(iter) => iter.with_producer(callback),
        }
    }
}

/// `Either<L, R>` can be extended if both `L` and `R` are parallel extendable.
impl<L, R, T> ParallelExtend<T> for Either<L, R>
where
    L: ParallelExtend<T>,
    R: ParallelExtend<T>,
    T: Send,
{
    fn par_extend<I>(&mut self, par_iter: I)
    where
        I: IntoParallelIterator<Item = T>,
    {
        match self.as_mut() {
            Left(collection) => collection.par_extend(par_iter),
            Right(collection) => collection.par_extend(par_iter),
        }
    }
}