//! Traits defining different ways to access data from generic lattice maps.
//!
//! # Strided Iteration
//!
//! The fastest way to iterate over data in an Array is with a simple for loop over array indices, we call them "stride"s:
//! ```
//! use building_blocks_core::prelude::*;
//! use building_blocks_storage::prelude::*;
//!
//! let extent = Extent3i::from_min_and_shape(Point3i::ZERO, Point3i::fill(100));
//! let mut map = Array3x1::fill(extent, 0);
//!
//! for i in 0..extent.num_points() {
//!     // Use the `GetMut<Stride>` trait impl of the map.
//!     *map.get_mut(Stride(i)) = 1;
//! }
//! ```
//! But this may require understanding the array layout.
//!
//! # `ForEach` over Extent
//!
//! Often, you only want to iterate over a sub-extent of the map. This can also be done at similar speeds using the `ForEach`
//! and `ForEachMut` traits:
//! ```
//! # use building_blocks_core::prelude::*;
//! # use building_blocks_storage::prelude::*;
//! # let extent = Extent3i::from_min_and_shape(Point3i::ZERO, Point3i::fill(100));
//! # let mut map = Array3x1::fill(extent, 0);
//! let subextent = Extent3i::from_min_and_shape(Point3i::fill(1), Point3i::fill(98));
//! // Use the `ForEachMut<[i32; 3], Stride>` trait.
//! map.for_each_mut(&subextent, |_s: Stride, value| { *value = 2 });
//! ```
//! Arrays also implement `ForEach*<PointN<N>>` and `ForEach*<(PointN<N>, Stride)>`. `ChunkMap` only implements
//! `ForEach*<PointN<N>>`, because it's ambiguous which chunk a `Stride` would apply to.
//!
//! # Copy an Extent
//!
//! If you need to copy data between lattice maps, you should use the `copy_extent` function. Copies can be done efficiently
//! because the `ReadExtent` and `WriteExtent` traits allow lattice maps to define how they would like to be written to or read
//! from.
//! ```
//! # use building_blocks_core::prelude::*;
//! # use building_blocks_storage::prelude::*;
//! # let extent = Extent3i::from_min_and_shape(Point3i::ZERO, Point3i::fill(100));
//! # let mut map = Array3x1::fill(extent, 0);
//! # let subextent = Extent3i::from_min_and_shape(Point3i::fill(1), Point3i::fill(98));
//! // Create another map to copy to/from. We use a `ChunkHashMap`, but any map that implements
//! // `WriteExtent` can be a copy destination, and any map that implements `ReadExtent` can be a
//! // copy source.
//! let chunk_shape = Point3i::fill(16);
//! let builder = ChunkMapBuilder3x1::new(chunk_shape, 0);
//! let mut other_map = builder.build_with_hash_map_storage();
//! copy_extent(&subextent, &map, &mut other_map.lod_view_mut(0));
//! copy_extent(&subextent, &other_map.lod_view(0), &mut map);
//!
//! // You can even copy from a `Fn(Point3i) -> T`.
//! copy_extent(&subextent, &Func(|p: Point3i| p.x()), &mut map);
//!```

use building_blocks_core::ExtentN;

use auto_impl::auto_impl;

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// ██╔════╝ ██╔════╝╚══██╔══╝╚══██╔══╝██╔════╝██╔══██╗██╔════╝
// ██║  ███╗█████╗     ██║      ██║   █████╗  ██████╔╝███████╗
// ██║   ██║██╔══╝     ██║      ██║   ██╔══╝  ██╔══██╗╚════██║
// ╚██████╔╝███████╗   ██║      ██║   ███████╗██║  ██║███████║
//  ╚═════╝ ╚══════╝   ╚═╝      ╚═╝   ╚══════╝╚═╝  ╚═╝╚══════╝

#[auto_impl(&, &mut)]
pub trait Get<L> {
    type Item;

    /// Get an owned value at `location`.
    fn get(&self, location: L) -> Self::Item;
}

#[auto_impl(&, &mut)]
pub trait GetRef<'a, L> {
    type Item;

    /// Get an immutable reference to the value at `location`.
    fn get_ref(&'a self, location: L) -> Self::Item;
}

#[auto_impl(&mut)]
pub trait GetMut<'a, L> {
    type Item;

    /// Get a mutable reference to the value at `location`.
    fn get_mut(&'a mut self, location: L) -> Self::Item;
}

#[auto_impl(&mut)]
pub trait GetMutPtr<L> {
    type Item;

    /// Get a mutable pointer to the value at `location`.
    unsafe fn get_mut_ptr(&mut self, location: L) -> Self::Item;
}

// We need this macro because doing a blanket impl causes conflicts due to Rust's orphan rules.
macro_rules! impl_get_via_get_ref_and_clone {
    ($map:ty, $($type_params:ident),*) => {
        impl<L, $($type_params),*> $crate::Get<L> for $map
        where
            Self: for<'r> $crate::GetRef<'r, L, Item = &'r T>,
            T: Clone,
        {
            type Item = T;

            #[inline]
            fn get(&self, location: L) -> Self::Item {
                self.get_ref(location).clone()
            }
        }
    };
}

macro_rules! impl_get_for_tuple {
    ( $( $var:ident : $t:ident ),+ ) => {

        impl<Coord, $($t),+> Get<Coord> for ($($t,)+)
        where
            Coord: Copy,
            $($t: Get<Coord>),+
        {
            type Item = ($($t::Item,)+);

            #[inline]
            fn get(&self, offset: Coord) -> Self::Item {
                let ($($var,)+) = self;

                ($($var.get(offset),)+)
            }
        }

        impl<'a, Coord, $($t),+> GetRef<'a, Coord> for ($($t,)+)
        where
            Coord: Copy,
            $($t: GetRef<'a, Coord>),+
        {
            type Item = ($($t::Item,)+);

            #[inline]
            fn get_ref(&'a self, offset: Coord) -> Self::Item {
                let ($($var,)+) = self;

                ($($var.get_ref(offset),)+)
            }
        }

        impl<'a, Coord, $($t),+> GetMut<'a, Coord> for ($($t,)+)
        where
            Coord: Copy,
            $($t: GetMut<'a, Coord>),+
        {
            type Item = ($($t::Item,)+);

            #[inline]
            fn get_mut(&'a mut self, offset: Coord) -> Self::Item {
                let ($($var,)+) = self;

                ($($var.get_mut(offset),)+)
            }
        }

        impl<Coord, $($t),+> GetMutPtr<Coord> for ($($t,)+)
        where
            Coord: Copy,
            $($t: GetMutPtr<Coord>),+
        {
            type Item = ($($t::Item,)+);

            #[inline]
            unsafe fn get_mut_ptr(&mut self, offset: Coord) -> Self::Item {
                let ($($var,)+) = self;

                ($($var.get_mut_ptr(offset),)+)
            }
        }
    }
}

impl_get_for_tuple! { a: A }
impl_get_for_tuple! { a: A, b: B }
impl_get_for_tuple! { a: A, b: B, c: C }
impl_get_for_tuple! { a: A, b: B, c: C, d: D }
impl_get_for_tuple! { a: A, b: B, c: C, d: D, e: E }
impl_get_for_tuple! { a: A, b: B, c: C, d: D, e: E, f: F }

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// █████╗  ██║   ██║██████╔╝    █████╗  ███████║██║     ███████║
// ██╔══╝  ██║   ██║██╔══██╗    ██╔══╝  ██╔══██║██║     ██╔══██║
// ██║     ╚██████╔╝██║  ██║    ███████╗██║  ██║╚██████╗██║  ██║
// ╚═╝      ╚═════╝ ╚═╝  ╚═╝    ╚══════╝╚═╝  ╚═╝ ╚═════╝╚═╝  ╚═╝

#[auto_impl(&, &mut)]
pub trait ForEach<N, Coord> {
    type Item;

    fn for_each(&self, extent: &ExtentN<N>, f: impl FnMut(Coord, Self::Item));
}

/// An implementation detail of multichannel arrays that helps us get around compiler limitations w.r.t. HRTB.
#[doc(hidden)]
#[auto_impl(&mut)]
pub trait ForEachMutPtr<N, Coord> {
    type Item;

    /// # Safety
    /// `Self::Item` is intended to be a `*mut T` with the lifetime of `self`.
    unsafe fn for_each_mut_ptr(&mut self, extent: &ExtentN<N>, f: impl FnMut(Coord, Self::Item));
}

#[auto_impl(&mut)]
pub trait ForEachMut<'a, N, Coord> {
    // TODO: use GAT to remove unsafe lifetime workaround in impls
    type Item;

    fn for_each_mut(&'a mut self, extent: &ExtentN<N>, f: impl FnMut(Coord, Self::Item));
}

#[auto_impl(&mut)]
pub trait FillExtent<N> {
    type Item;

    fn fill_extent(&mut self, extent: &ExtentN<N>, value: Self::Item);
}

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// ██╔════╝██╔═══██╗██╔══██╗╚██╗ ██╔╝
// ██║     ██║   ██║██████╔╝ ╚████╔╝
// ██║     ██║   ██║██╔═══╝   ╚██╔╝
// ╚██████╗╚██████╔╝██║        ██║
//  ╚═════╝ ╚═════╝ ╚═╝        ╚═╝

/// A trait to facilitate the generic implementation of `copy_extent`.
///
/// Some lattice maps, like `ChunkMap`, have nonlinear layouts. This means that, in order for a writer to receive data
/// efficiently, it must come as an iterator over multiple extents.
#[auto_impl(&, &mut)]
pub trait ReadExtent<'a, N> {
    type Src;
    type SrcIter: Iterator<Item = (ExtentN<N>, Self::Src)>;

    /// `SrcIter` must return extents that are subsets of `extent`.
    fn read_extent(&'a self, extent: &ExtentN<N>) -> Self::SrcIter;
}

/// A trait to facilitate the generic implementation of `copy_extent`.
#[auto_impl(&mut)]
pub trait WriteExtent<N, Src> {
    fn write_extent(&mut self, extent: &ExtentN<N>, src: Src);
}

/// Copy all points in `extent` from the `src` map to the `dst` map.
pub fn copy_extent<'a, N, Src, Ms, Md>(extent: &ExtentN<N>, src_map: &'a Ms, dst_map: &mut Md)
where
    Ms: ReadExtent<'a, N, Src = Src>,
    Md: WriteExtent<N, Src>,
{
    for (sub_extent, extent_src) in src_map.read_extent(extent) {
        dst_map.write_extent(&sub_extent, extent_src);
    }
}