use std::marker::PhantomData;

use super::{Dimension, Ix, Ixs};
use super::{Elements, ElementsRepr, ElementsBase, ElementsBaseMut, ElementsMut, Indexed, IndexedMut};
use super::{
    ArrayBase,
    Data,
    ArrayView,
    ArrayViewMut,
    RemoveAxis,
};

/// Base for array iterators
///
/// Iterator element type is `&'a A`.
pub struct Baseiter<'a, A: 'a, D> {
    // Can have pub fields because it is not itself pub.
    pub ptr: *mut A,
    pub dim: D,
    pub strides: D,
    pub index: Option<D>,
    pub life: PhantomData<&'a A>,
}


impl<'a, A, D: Dimension> Baseiter<'a, A, D>
{
    /// Creating a Baseiter is unsafe, because it can
    /// have any lifetime, be immut or mut, and the
    /// boundary and stride parameters need to be correct to
    /// avoid memory unsafety.
    ///
    /// It must be placed in the correct mother iterator to be safe.
    ///
    /// NOTE: Mind the lifetime, it's arbitrary
    #[inline]
    pub unsafe fn new(ptr: *mut A, len: D, stride: D) -> Baseiter<'a, A, D>
    {
        Baseiter {
            ptr: ptr,
            index: len.first_index(),
            dim: len,
            strides: stride,
            life: PhantomData,
        }
    }
}

impl<'a, A, D: Dimension> Baseiter<'a, A, D>
{
    #[inline]
    pub fn next(&mut self) -> Option<*mut A>
    {
        let index = match self.index {
            None => return None,
            Some(ref ix) => ix.clone(),
        };
        let offset = Dimension::stride_offset(&index, &self.strides);
        self.index = self.dim.next_for(index);
        unsafe {
            Some(self.ptr.offset(offset))
        }
    }

    #[inline]
    fn next_ref(&mut self) -> Option<&'a A>
    {
        unsafe { self.next().map(|p| &*p) }
    }

    #[inline]
    fn next_ref_mut(&mut self) -> Option<&'a mut A>
    {
        unsafe { self.next().map(|p| &mut *p) }
    }

    fn size_hint(&self) -> usize
    {
        match self.index {
            None => 0,
            Some(ref ix) => {
                let gone = self.dim.default_strides().slice().iter()
                            .zip(ix.slice().iter())
                                 .fold(0, |s, (&a, &b)| s + a as usize * b as usize);
                self.dim.size() - gone
            }
        }
    }
}

impl<'a, A> Baseiter<'a, A, Ix>
{
    #[inline]
    fn next_back(&mut self) -> Option<*mut A>
    {
        let index = match self.index {
            None => return None,
            Some(ref ix) => ix.clone(),
        };
        self.dim -= 1;
        let offset = Dimension::stride_offset(&self.dim, &self.strides);
        if index == self.dim {
            self.index = None;
        }

        unsafe {
            Some(self.ptr.offset(offset))
        }
    }

    #[inline]
    fn next_back_ref(&mut self) -> Option<&'a A>
    {
        unsafe { self.next_back().map(|p| &*p) }
    }

    #[inline]
    fn next_back_ref_mut(&mut self) -> Option<&'a mut A>
    {
        unsafe { self.next_back().map(|p| &mut *p) }
    }
}

impl<'a, A, D: Clone> Clone for Baseiter<'a, A, D>
{
    fn clone(&self) -> Baseiter<'a, A, D>
    {
        Baseiter {
            ptr: self.ptr,
            dim: self.dim.clone(),
            strides: self.strides.clone(),
            index: self.index.clone(),
            life: self.life,
        }
    }
}

impl<'a, A, D: Clone> Clone for ElementsBase<'a, A, D>
{
    fn clone(&self) -> ElementsBase<'a, A, D> { ElementsBase{inner: self.inner.clone()} }
}

impl<'a, A, D: Dimension> Iterator for ElementsBase<'a, A, D>
{
    type Item = &'a A;
    #[inline]
    fn next(&mut self) -> Option<&'a A>
    {
        self.inner.next_ref()
    }

    fn size_hint(&self) -> (usize, Option<usize>)
    {
        let len = self.inner.size_hint();
        (len, Some(len))
    }
}

impl<'a, A> DoubleEndedIterator for ElementsBase<'a, A, Ix>
{
    #[inline]
    fn next_back(&mut self) -> Option<&'a A>
    {
        self.inner.next_back_ref()
    }
}

impl<'a, A, D> ExactSizeIterator for ElementsBase<'a, A, D>
    where D: Dimension,
{ }

macro_rules! either {
    ($value:expr, $inner:ident => $result:expr) => (
        match $value {
            ElementsRepr::Slice(ref $inner) => $result,
            ElementsRepr::Counted(ref $inner) => $result,
        }
    )
}

macro_rules! either_mut {
    ($value:expr, $inner:ident => $result:expr) => (
        match $value {
            ElementsRepr::Slice(ref mut $inner) => $result,
            ElementsRepr::Counted(ref mut $inner) => $result,
        }
    )
}

impl<'a, A, D: Clone> Clone for Elements<'a, A, D>
{
    fn clone(&self) -> Elements<'a, A, D> {
        Elements {
            inner: match self.inner {
                ElementsRepr::Slice(ref iter) => ElementsRepr::Slice(iter.clone()),
                ElementsRepr::Counted(ref iter) => ElementsRepr::Counted(iter.clone()),
            }
        }
    }
}

impl<'a, A, D: Dimension> Iterator for Elements<'a, A, D>
{
    type Item = &'a A;
    #[inline]
    fn next(&mut self) -> Option<&'a A> {
        either_mut!(self.inner, iter => iter.next())
    }

    fn size_hint(&self) -> (usize, Option<usize>)
    {
        either!(self.inner, iter => iter.size_hint())
    }
}

impl<'a, A> DoubleEndedIterator for Elements<'a, A, Ix>
{
    #[inline]
    fn next_back(&mut self) -> Option<&'a A> {
        either_mut!(self.inner, iter => iter.next_back())
    }
}

impl<'a, A, D> ExactSizeIterator for Elements<'a, A, D>
    where D: Dimension,
{ }


impl<'a, A, D: Dimension> Iterator for Indexed<'a, A, D>
{
    type Item = (D, &'a A);
    #[inline]
    fn next(&mut self) -> Option<(D, &'a A)>
    {
        let index = match self.0.inner.index {
            None => return None,
            Some(ref ix) => ix.clone()
        };
        match self.0.inner.next_ref() {
            None => None,
            Some(p) => Some((index, p))
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>)
    {
        let len = self.0.inner.size_hint();
        (len, Some(len))
    }
}

impl<'a, A, D: Dimension> Iterator for ElementsMut<'a, A, D>
{
    type Item = &'a mut A;
    #[inline]
    fn next(&mut self) -> Option<&'a mut A> {
        either_mut!(self.inner, iter => iter.next())
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        either!(self.inner, iter => iter.size_hint())
    }
}

impl<'a, A> DoubleEndedIterator for ElementsMut<'a, A, Ix>
{
    #[inline]
    fn next_back(&mut self) -> Option<&'a mut A> {
        either_mut!(self.inner, iter => iter.next_back())
    }
}

impl<'a, A, D> ExactSizeIterator for ElementsMut<'a, A, D>
    where D: Dimension,
{ }

impl<'a, A, D: Dimension> Iterator for ElementsBaseMut<'a, A, D>
{
    type Item = &'a mut A;
    #[inline]
    fn next(&mut self) -> Option<&'a mut A>
    {
        self.inner.next_ref_mut()
    }

    fn size_hint(&self) -> (usize, Option<usize>)
    {
        let len = self.inner.size_hint();
        (len, Some(len))
    }
}

impl<'a, A> DoubleEndedIterator for ElementsBaseMut<'a, A, Ix>
{
    #[inline]
    fn next_back(&mut self) -> Option<&'a mut A>
    {
        self.inner.next_back_ref_mut()
    }
}

impl<'a, A, D: Dimension> Iterator for IndexedMut<'a, A, D>
{
    type Item = (D, &'a mut A);
    #[inline]
    fn next(&mut self) -> Option<(D, &'a mut A)>
    {
        let index = match self.0.inner.index {
            None => return None,
            Some(ref ix) => ix.clone()
        };
        match self.0.inner.next_ref_mut() {
            None => None,
            Some(p) => Some((index, p))
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>)
    {
        let len = self.0.inner.size_hint();
        (len, Some(len))
    }
}

/// An iterator that traverses over all dimensions but the innermost,
/// and yields each inner row.
///
/// See [`.inner_iter()`](struct.ArrayBase.html#method.inner_iter) for more information.
pub struct InnerIter<'a, A: 'a, D> {
    inner_len: Ix,
    inner_stride: Ixs,
    iter: Baseiter<'a, A, D>,
}

pub fn new_inner_iter<A, D>(mut v: ArrayView<A, D>) -> InnerIter<A, D>
    where D: Dimension,
{
    if v.shape().len() == 0 {
        InnerIter {
            inner_len: 1,
            inner_stride: 1,
            iter: v.into_base_iter(),
        }
    } else {
        // Set length of innerest dimension to 1, start iteration
        let ndim = v.shape().len();
        let len = v.shape()[ndim - 1];
        let stride = v.strides()[ndim - 1];
        v.dim.slice_mut()[ndim - 1] = 1;
        InnerIter {
            inner_len: len,
            inner_stride: stride,
            iter: v.into_base_iter(),
        }
    }
}

impl<'a, A, D> Iterator for InnerIter<'a, A, D>
    where D: Dimension,
{
    type Item = ArrayView<'a, A, Ix>;
    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|ptr| {
            unsafe {
                ArrayView::new_(ptr, self.inner_len, self.inner_stride as Ix)
            }
        })
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.iter.size_hint();
        (len, Some(len))
    }
}

impl<'a, A, D> ExactSizeIterator for InnerIter<'a, A, D>
    where D: Dimension,
{ }

// NOTE: InnerIterMut is a mutable iterator and must not expose aliasing
// pointers. Due to this we use an empty slice for the raw data (it's unused
// anyway).
/// An iterator that traverses over all dimensions but the innermost,
/// and yields each inner row (mutable).
///
/// See [`.inner_iter_mut()`](struct.ArrayBase.html#method.inner_iter_mut)
/// for more information.
pub struct InnerIterMut<'a, A: 'a, D> {
    inner_len: Ix,
    inner_stride: Ixs,
    iter: Baseiter<'a, A, D>,
}

pub fn new_inner_iter_mut<A, D>(mut v: ArrayViewMut<A, D>) -> InnerIterMut<A, D>
    where D: Dimension,
{
    if v.shape().len() == 0 {
        InnerIterMut {
            inner_len: 1,
            inner_stride: 1,
            iter: v.into_base_iter(),
        }
    } else {
        // Set length of innerest dimension to 1, start iteration
        let ndim = v.shape().len();
        let len = v.shape()[ndim - 1];
        let stride = v.strides()[ndim - 1];
        v.dim.slice_mut()[ndim - 1] = 1;
        InnerIterMut {
            inner_len: len,
            inner_stride: stride,
            iter: v.into_base_iter(),
        }
    }
}

impl<'a, A, D> Iterator for InnerIterMut<'a, A, D>
    where D: Dimension,
{
    type Item = ArrayViewMut<'a, A, Ix>;
    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|ptr| {
            unsafe {
                ArrayViewMut::new_(ptr, self.inner_len, self.inner_stride as Ix)
            }
        })
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.iter.size_hint();
        (len, Some(len))
    }
}

impl<'a, A, D> ExactSizeIterator for InnerIterMut<'a, A, D>
    where D: Dimension,
{ }

pub struct OuterIterCore<A, D> {
    index: Ix,
    len: Ix,
    stride: Ixs,
    inner_dim: D,
    inner_strides: D,
    ptr: *mut A,
}

fn new_outer_core<A, S, D>(v: ArrayBase<S, D>,
                           axis: usize
                           ) -> OuterIterCore<A, D::Smaller>
    where D: RemoveAxis,
          S: Data<Elem=A>,
{
    let shape = v.shape()[axis];
    let stride = v.strides()[axis];

    OuterIterCore {
        index: 0,
        len: shape,
        stride: stride,
        inner_dim: v.dim.remove_axis(axis),
        inner_strides: v.strides.remove_axis(axis),
        ptr: v.ptr,
    }
}

impl<A, D> Iterator for OuterIterCore<A, D>
    where D: Dimension,
{
    type Item = *mut A;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index >= self.len {
            None
        } else {
            let ptr = unsafe {
                self.ptr.offset(self.index as isize * self.stride)
            };
            self.index += 1;
            Some(ptr)
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len - self.index;
        (len, Some(len))
    }
}

impl<A, D> DoubleEndedIterator for OuterIterCore<A, D>
    where D: Dimension,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        if self.index >= self.len {
            None
        } else {
            self.len -= 1;
            let ptr = unsafe {
                self.ptr.offset(self.len as isize * self.stride)
            };
            Some(ptr)
        }
    }
}

/// An iterator that traverses over the outermost dimension
/// and yields each subview.
///
/// For example, in a 2 × 2 × 3 array, the iterator element
/// is a 2 × 3 subview (and there are 2 in total).
///
/// Iterator element type is `ArrayView<'a, A, D>`.
///
/// See [`.outer_iter()`](struct.ArrayBase.html#method.outer_iter)
/// for more information.
pub struct OuterIter<'a, A: 'a, D> {
    iter: OuterIterCore<A, D>,
    life: PhantomData<&'a A>,
}

impl<'a, A, D> Iterator for OuterIter<'a, A, D>
    where D: Dimension,
{
    type Item = ArrayView<'a, A, D>;

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|ptr| {
            unsafe {
                ArrayView::new_(ptr, self.iter.inner_dim.clone(), self.iter.inner_strides.clone())
            }
        })
    }

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

impl<'a, A, D> DoubleEndedIterator for OuterIter<'a, A, D>
    where D: Dimension,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        self.iter.next_back().map(|ptr| {
            unsafe {
                ArrayView::new_(ptr, self.iter.inner_dim.clone(), self.iter.inner_strides.clone())
            }
        })
    }
}

impl<'a, A, D> ExactSizeIterator for OuterIter<'a, A, D>
    where D: Dimension,
{ }

pub fn new_outer_iter<A, D>(v: ArrayView<A, D>) -> OuterIter<A, D::Smaller>
    where D: RemoveAxis,
{
    OuterIter {
        iter: new_outer_core(v, 0),
        life: PhantomData,
    }
}

pub fn new_axis_iter<A, D>(v: ArrayView<A, D>, axis: usize) -> OuterIter<A, D::Smaller>
    where D: RemoveAxis,
{
    OuterIter {
        iter: new_outer_core(v, axis),
        life: PhantomData,
    }
}


/// An iterator that traverses over the outermost dimension
/// and yields each subview (mutable).
///
/// For example, in a 2 × 2 × 3 array, the iterator element
/// is a 2 × 3 subview (and there are 2 in total).
///
/// Iterator element type is `ArrayViewMut<'a, A, D>`.
///
/// See [`.outer_iter_mut()`](struct.ArrayBase.html#method.outer_iter_mut)
/// for more information.
pub struct OuterIterMut<'a, A: 'a, D> {
    iter: OuterIterCore<A, D>,
    life: PhantomData<&'a mut A>,
}

impl<'a, A, D> Iterator for OuterIterMut<'a, A, D>
    where D: Dimension,
{
    type Item = ArrayViewMut<'a, A, D>;

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|ptr| {
            unsafe {
                ArrayViewMut::new_(ptr, self.iter.inner_dim.clone(),
                                   self.iter.inner_strides.clone())
            }
        })
    }

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

impl<'a, A, D> DoubleEndedIterator for OuterIterMut<'a, A, D>
    where D: Dimension,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        self.iter.next_back().map(|ptr| {
            unsafe {
                ArrayViewMut::new_(ptr, self.iter.inner_dim.clone(),
                                   self.iter.inner_strides.clone())
            }
        })
    }
}

impl<'a, A, D> ExactSizeIterator for OuterIterMut<'a, A, D>
    where D: Dimension,
{ }

pub fn new_outer_iter_mut<A, D>(v: ArrayViewMut<A, D>) -> OuterIterMut<A, D::Smaller>
    where D: RemoveAxis,
{
    OuterIterMut {
        iter: new_outer_core(v, 0),
        life: PhantomData,
    }
}

pub fn new_axis_iter_mut<A, D>(v: ArrayViewMut<A, D>, axis: usize)
    -> OuterIterMut<A, D::Smaller>
    where D: RemoveAxis,
{
    OuterIterMut {
        iter: new_outer_core(v, axis),
        life: PhantomData,
    }
}

/// An iterator that traverses over the specified axis
/// and yields views of the specified size on this axis.
///
/// For example, in a 2 × 8 × 3 array, if the axis of iteration
/// is 1 and the chunk size is 2, the yielded elements
/// are 2 × 2 × 3 views (and there are 4 in total).
///
/// Iterator element type is `ArrayView<'a, A, D>`.
///
/// See [`.axis_chunks_iter()`](struct.ArrayBase.html#method.axis_chunks_iter) for more information.
pub struct AxisChunksIter<'a, A: 'a, D> {
    iter: OuterIterCore<A, D>,
    last_ptr: *mut A,
    last_dim: D,
    life: PhantomData<&'a A>,
}

fn chunk_iter_parts<A, D: Dimension>(v: ArrayView<A, D>, axis: usize, size: usize)
    -> (OuterIterCore<A, D>, *mut A, D)
{
    let axis_len = v.shape()[axis];
    let size = if size > axis_len { axis_len } else { size };
    let last_index = axis_len / size;
    let rem = axis_len % size;
    let shape = if rem == 0 { last_index } else { last_index + 1 };
    let stride = v.strides()[axis] * size as isize;

    let mut inner_dim = v.dim.clone();
    inner_dim.slice_mut()[axis] = size;

    let mut last_dim = v.dim.clone();
    last_dim.slice_mut()[axis] = if rem == 0 { size } else { rem };

    let last_ptr = if rem != 0 {
        unsafe {
            v.ptr.offset(stride * last_index as isize)
        }
    }
    else {
        v.ptr
    };
    let iter = OuterIterCore {
        index: 0,
        len: shape,
        stride: stride,
        inner_dim: inner_dim,
        inner_strides: v.strides.clone(),
        ptr: v.ptr,
    };

    (iter, last_ptr, last_dim)
}

pub fn new_chunk_iter<A, D>(v: ArrayView<A, D>, axis: usize, size: usize)
    -> AxisChunksIter<A, D>
    where D: Dimension
{
    let (iter, last_ptr, last_dim) = chunk_iter_parts(v.view(), axis, size);

    AxisChunksIter {
        iter: iter,
        last_ptr: last_ptr,
        last_dim: last_dim,
        life: PhantomData,
    }
}

macro_rules! chunk_iter_impl {
    ($iter:ident, $array:ident) => (
        impl<'a, A, D> $iter<'a, A, D>
            where D: Dimension
        {
            fn get_subview(&self, iter_item: Option<*mut A>)
                -> Option<$array<'a, A, D>>
            {
                iter_item.map(|ptr| {
                    if ptr != self.last_ptr {
                        unsafe {
                            $array::new_(ptr,
                                         self.iter.inner_dim.clone(),
                                         self.iter.inner_strides.clone())
                        }
                    }
                    else {
                        unsafe {
                            $array::new_(ptr,
                                         self.last_dim.clone(),
                                         self.iter.inner_strides.clone())
                        }
                    }
                })
            }
        }

        impl<'a, A, D> Iterator for $iter<'a, A, D>
            where D: Dimension,
        {
            type Item = $array<'a, A, D>;

            fn next(&mut self) -> Option<Self::Item> {
                let res = self.iter.next();
                self.get_subview(res)
            }

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

        impl<'a, A, D> DoubleEndedIterator for $iter<'a, A, D>
            where D: Dimension,
        {
            fn next_back(&mut self) -> Option<Self::Item> {
                let res = self.iter.next_back();
                self.get_subview(res)
            }
        }

        impl<'a, A, D> ExactSizeIterator for $iter<'a, A, D>
            where D: Dimension,
        { }
    )
}

/// An iterator that traverses over the specified axis
/// and yields mutable views of the specified size on this axis.
///
/// For example, in a 2 × 8 × 3 array, if the axis of iteration
/// is 1 and the chunk size is 2, the yielded elements
/// are 2 × 2 × 3 views (and there are 4 in total).
///
/// Iterator element type is `ArrayViewMut<'a, A, D>`.
///
/// See [`.axis_chunks_iter_mut()`](struct.ArrayBase.html#method.axis_chunks_iter_mut)
/// for more information.
pub struct AxisChunksIterMut<'a, A: 'a, D> {
    iter: OuterIterCore<A, D>,
    last_ptr: *mut A,
    last_dim: D,
    life: PhantomData<&'a mut A>,
}

pub fn new_chunk_iter_mut<A, D>(v: ArrayViewMut<A, D>, axis: usize, size: usize)
    -> AxisChunksIterMut<A, D>
    where D: Dimension
{
    let (iter, last_ptr, last_dim) = chunk_iter_parts(v.view(), axis, size);

    AxisChunksIterMut {
        iter: iter,
        last_ptr: last_ptr,
        last_dim: last_dim,
        life: PhantomData,
    }
}

chunk_iter_impl!(AxisChunksIter, ArrayView);
chunk_iter_impl!(AxisChunksIterMut, ArrayViewMut);