#![allow(non_snake_case)]
#![feature(allocator_api, alloc_layout_extra)]
//! Soa2, Soa3, ..SoaN are generic collections with an API similar to that of a Vec of tuples but which store
//! the data laid out as a separate slice per field. The advantage of this layout is that when
//! iterating over the data only a subset need be loaded from RAM.
//!
//! This approach is common to game engines, and entity component systems in particular but is
//! applicable anywhere that cache coherency and memory bandwidth are important for performance.
//!
//!
//! # Example
//! ```
//! # use soa_vec::Soa3;
//! /// Some 'entity' data.
//! # #[derive(Copy, Clone)]
//! struct Position { x: f64, y: f64 }
//! # #[derive(Copy, Clone)]
//! struct Velocity { dx: f64, dy: f64 }
//! struct ColdData { /* Potentially many fields omitted here */ }
//!
//! # use std::ops::Add;
//! # impl Add<Velocity> for Position { type Output=Self; fn add(self, other: Velocity) -> Self { Self { x: self.x + other.dx, y: self.y + other.dy } } }
//! // Create a vec of entities
//! let mut entities = Soa3::new();
//! entities.push((Position {x: 1.0, y: 2.0}, Velocity { dx: 0.0, dy: 0.5 }, ColdData {}));
//! entities.push((Position {x: 0.0, y: 2.0}, Velocity { dx: 0.5, dy: 0.5 }, ColdData {}));
//!
//! // Update entities. This loop only loads position and velocity data, while skipping over
//! // the ColdData which is not necessary for the physics simulation.
//! let (positions, velocities, _cold) = entities.iters_mut();
//! for (position, velocity) in positions.zip(velocities) {
//! 	*position = *position + *velocity;
//! }
//!
//! // Remove an entity
//! entities.swap_remove(0);
//!
//! // Sort entities by position on y axis
//! // The fields are passed by reference, so velocity and cold data are not loaded
//! // until such time as the items are being swapped which runs in O(N)
//! # use std::cmp;
//! entities.sort_unstable_by(
//! 	|(lh_pos, _, _), (rh_pos, _, _)| lh_pos.y.partial_cmp(&rh_pos.y).unwrap()
//! );
//!
//! // See individual structs for more methods.
//!
//! ```
//!
//!
//! # Nightly
//! This crate has strict requirements for allocations and memory layout and therefore requires the following nightly features:
//! * allocator_api
//! * alloc_layout_extra
//!
//! # Links:
//! * [Github source](https://github.com/That3Percent/soa-vec)
//! * [Crate](https://crates.io/crates/soa-vec)
//!
//! # License
//! [MIT](https://github.com/That3Percent/soa-vec/blob/master/LICENSE)




use second_stack::*;
use std::{alloc::*, cmp::*, marker::*, ptr::*, slice::*};

/// This macro defines a struct-of-arrays style struct.
/// It need not be called often, just once per count of generic parameters.
macro_rules! soa {
	($name:ident, $L:ident, $t1:ident, $($ts:ident),+) => {
		/// Struct of arrays storage with vec API. See module docs for more information.
		pub struct $name<$t1: Sized $(, $ts: Sized)*> {
			len: usize,
			capacity: usize,
			$t1: NonNull<$t1>,
			$($ts: NonNull<$ts>,)*
			_marker: (PhantomData<$t1> $(, PhantomData<$ts>)*),
		}

		impl<$t1: Sized $(, $ts: Sized)*> $name<$t1 $(, $ts)*> {
			/// Creates a new Soa with a capacity of 0
			pub fn new() -> $name<$t1 $(, $ts)*> {
				$name {
					len: 0,
					capacity: 0,
					$t1: NonNull::dangling(),
					$($ts: NonNull::dangling(),)*
					_marker: (PhantomData $(, PhantomData::<$ts>)*),
				}
			}

			fn dealloc(&mut self) {
				if self.capacity > 0 {
					let layout = Self::layout_for_capacity(self.capacity).layout;
					unsafe { Global.dealloc(self.$t1.cast::<u8>(), layout) }
				}
			}

			/// Allocates and partitions a new region of uninitialized memory
			fn alloc(capacity: usize) -> (NonNull<$t1> $(, NonNull<$ts>)*) {
				unsafe {
					let layouts = Self::layout_for_capacity(capacity);
					let bytes = Global.alloc(layouts.layout).unwrap();
					(
						bytes.cast::<$t1>()
						$(, NonNull::new_unchecked(bytes.as_ptr().add(layouts.$ts) as *mut $ts))*
					)
				}
			}

			fn check_grow(&mut self) {
				unsafe {
					if self.len == self.capacity {
						let capacity = (self.capacity * 2).max(4);
						let ($t1 $(, $ts)*) = Self::alloc(capacity);

						copy_nonoverlapping(self.$t1.as_ptr(), $t1.as_ptr(), self.len);
						$(
							copy_nonoverlapping(self.$ts.as_ptr(), $ts.as_ptr(), self.len);
						)*

						self.dealloc();

						// Assign
						self.$t1 = $t1;
						$(self.$ts = $ts;)*
						self.capacity = capacity;

					}
				}
			}

			/// Returns the number of tuples in the soa, also referred to as its 'length'.
			#[inline(always)]
			pub fn len(&self) -> usize { self.len }

			/// Clears the soa, removing all values.
			/// Note that this method has no effect on the allocated capacity of the soa.
			pub fn clear(&mut self) {
				while self.len > 0 {
					self.pop();
				}
			}

			/// Appends a tuple to the back of a soa.
			pub fn push(&mut self, value: ($t1 $(, $ts)*)) {
				unsafe {
					self.check_grow();
					let ($t1 $(, $ts)*) = value;
					write(self.$t1.as_ptr().add(self.len), $t1);
					$(write(self.$ts.as_ptr().add(self.len), $ts);)*
					self.len += 1;
				}
			}

			/// Removes the last tuple from a soa and returns it, or None if it is empty.
			pub fn pop(&mut self) -> Option<($t1 $(, $ts)*)> {
				if self.len == 0 {
					None
				} else {
					self.len -= 1;
					unsafe {
						Some((
							read(self.$t1.as_ptr().add(self.len))
							$(, read(self.$ts.as_ptr().add(self.len)))*
						))
					}
				}
			}

			/// Removes a tuple from the soa and returns it.
			/// The removed tuple is replaced by the last tuple of the soa.
			/// This does not preserve ordering, but is O(1).
			///
			/// # Panics:
			///  * Must panic if index is out of bounds
			pub fn swap_remove(&mut self, index: usize) -> ($t1 $(, $ts)*) {
				if index >= self.len {
					panic!("Index out of bounds");
				}

				unsafe {
					let $t1 = self.$t1.as_ptr().add(index);
					$(let $ts = self.$ts.as_ptr().add(index);)*

					let v = (
						read($t1)
						$(, read($ts))*
					);

					self.len -= 1;

					if self.len != index {
						copy_nonoverlapping(self.$t1.as_ptr().add(self.len), $t1, 1);
						$(copy_nonoverlapping(self.$ts.as_ptr().add(self.len), $ts, 1);)*
					}

					v
				}
			}

			fn layout_for_capacity(capacity: usize) -> $L {
				let layout = Layout::array::<$t1>(capacity).unwrap();

				$(let (layout, $ts) = layout.extend(Layout::array::<$ts>(capacity).unwrap()).unwrap();)*

				$L {
					layout
					$(, $ts)*
				}
			}

			/// Returns a tuple of all the destructured tuples added to this soa.
			#[inline(always)] // Inline for dead code elimination
			pub fn slices<'a>(&self) -> (&'a [$t1] $(, &'a [$ts])*) {
				unsafe {
					(
						from_raw_parts::<'a>(self.$t1.as_ptr(), self.len),
						$(from_raw_parts::<'a>(self.$ts.as_ptr(), self.len),)*
					)
				}
			}

			/// Returns a tuple of iterators over each field in the soa.
			#[inline(always)] // Inline for dead code elimination
			pub fn iters<'a>(&self) -> (Iter<'a, $t1> $(, Iter<'a, $ts>)*) {
				unsafe {
					(
						from_raw_parts::<'a>(self.$t1.as_ptr(), self.len).iter()
						$(, from_raw_parts::<'a>(self.$ts.as_ptr(), self.len).iter())*
					)
				}
			}

			/// Returns a tuple of mutable iterators over each field in the soa.
			#[inline(always)] // Inline for dead code elimination
			pub fn iters_mut<'a>(&mut self) -> (IterMut<'a, $t1> $(, IterMut<'a, $ts>)*) {
				unsafe {
					(
						from_raw_parts_mut::<'a>(self.$t1.as_ptr(), self.len).iter_mut()
						$(, from_raw_parts_mut::<'a>(self.$ts.as_ptr(), self.len).iter_mut())*
					)
				}
			}

			/// Returns a tuple of all the destructured mutable tuples added to this soa.
			#[inline(always)] // Inline for dead code elimination
			pub fn slices_mut<'a>(&self) -> (&'a mut [$t1] $(, &'a mut [$ts])*) {
				unsafe {
					(
						from_raw_parts_mut::<'a>(self.$t1.as_ptr(), self.len),
						$(from_raw_parts_mut::<'a>(self.$ts.as_ptr(), self.len),)*
					)
				}
			}

			/// This is analogous to the index operator in vec, but returns a tuple of references.
			/// ## Panics
			/// * If index is >= len
			pub fn get<'a>(&self, index: usize) -> (&'a $t1 $(, &'a $ts)*) {
				unsafe {
					if index >= self.len {
						panic!("Index out of range");
					}

					(
						&*self.$t1.as_ptr().add(index)
						$(, &*self.$ts.as_ptr().add(index))*
					)
				}
			}

			/// Sorts the soa keeping related data together.
			pub fn sort_unstable_by<F: FnMut((&$t1 $(, &$ts)*), (&$t1 $(, &$ts)*))->Ordering>(&mut self, mut f: F) {
				if self.len < 2 {
					return;
				}
				let mut indices = acquire(0..self.len);

				indices.sort_unstable_by(|a, b| unsafe {
					f(
						(&*self.$t1.as_ptr().add(*a) $(, &*self.$ts.as_ptr().add(*a))*, ),
						(&*self.$t1.as_ptr().add(*b) $(, &*self.$ts.as_ptr().add(*b))*, ),
					)});

				// Example
				// c b d e a
				// 4 1 0 2 3 // indices
				// 2 1 3 4 0 // lookup

				let mut lookup = unsafe { acquire_uninitialized(self.len) };
				for (i, index) in indices.iter().enumerate() {
					lookup[*index] = i;
				}

				let ($t1 $(, $ts)*) = self.slices_mut();

				for i in 0..indices.len() {
					let dest = indices[i]; // The index that should go here
					if i != dest {
						// Swap
						$t1.swap(i, dest);
						$($ts.swap(i, dest);)*

						// Account for swaps that already happened
						indices[lookup[i]] = dest;
						lookup[dest] = lookup[i];
					}
				}
			}
		}

		struct $L {
			layout: Layout,
			$($ts: usize,)*
		}


		impl<$t1: Sized $(, $ts: Sized)*> Drop for $name<$t1 $(, $ts)*> {
			fn drop(&mut self) {
				self.clear(); // Drop owned items
				self.dealloc()
			}
		}


		impl<$t1: Clone + Sized $(, $ts: Clone + Sized)*> Clone for $name<$t1 $(, $ts)*> {
			fn clone(&self) -> Self {
				let capacity = self.len;
				if capacity == 0 {
					Self::new()
				} else {
					let ($t1 $(,$ts)*) = Self::alloc(capacity);

					unsafe {
						for i in 0..self.len {
							write($t1.as_ptr().add(i), (&*(self.$t1.as_ptr().add(i))).clone());
						}
						$(
							for i in 0..self.len {
								write($ts.as_ptr().add(i), (&*(self.$ts.as_ptr().add(i))).clone());
							}
						)*
					}

					Self {
						capacity,
						len: self.len,
						$t1: $t1,
						$($ts: $ts,)*
						_marker: (PhantomData $(, PhantomData::<$ts>)*),
					}
				}
			}
		}

		impl<$t1: Sized $(, $ts: Sized)*> Default for $name<$t1 $(, $ts)*> {
			fn default() -> Self { Self::new() }
		}
	};
}

soa!(Soa2, _2, T1, T2);
soa!(Soa3, _3, T1, T2, T3);
soa!(Soa4, _4, T1, T2, T3, T4);
soa!(Soa5, _5, T1, T2, T3, T4, T5);
soa!(Soa6, _6, T1, T2, T3, T4, T5, T6);
soa!(Soa7, _7, T1, T2, T3, T4, T5, T6, T7);
soa!(Soa8, _8, T1, T2, T3, T4, T5, T6, T7, T8);

#[cfg(test)]
mod tests {
    use super::*;
    use testdrop::TestDrop;

    #[test]
    fn layouts_do_not_overlap() {
        // Trying with both (small, large) and (large, small) to ensure nothing bleeds into anything else.
        // This verifies we correctly chunk the slices from the larger allocations.
        let mut soa_ab = Soa2::new();
        let mut soa_ba = Soa2::new();

        fn ab(v: usize) -> (u8, f64) {
            (v as u8, 200.0 + ((v as f64) / 200.0))
        }

        fn ba(v: usize) -> (f64, u8) {
            (15.0 + ((v as f64) / 16.0), (200 - v) as u8)
        }

        // Combined with the tests inside, also verifies that we are copying the data on grow correctly.
        for i in 0..100 {
            soa_ab.push(ab(i));
            let (a, b) = soa_ab.slices();
            assert_eq!(i + 1, a.len());
            assert_eq!(i + 1, b.len());
            assert_eq!(ab(0).0, a[0]);
            assert_eq!(ab(0).1, b[0]);
            assert_eq!(ab(i).0, a[i]);
            assert_eq!(ab(i).1, b[i]);

            soa_ba.push(ba(i));
            let (b, a) = soa_ba.slices();
            assert_eq!(i + 1, a.len());
            assert_eq!(i + 1, b.len());
            assert_eq!(ba(0).0, b[0]);
            assert_eq!(ba(0).1, a[0]);
            assert_eq!(ba(i).0, b[i]);
            assert_eq!(ba(i).1, a[i]);
        }
    }

    #[test]
    fn sort() {
        let mut soa = Soa3::new();

        soa.push((3, 'a', 4.0));
        soa.push((1, 'b', 5.0));
        soa.push((2, 'c', 6.0));

        soa.sort_unstable_by(|(a1, _, _), (a2, _, _)| a1.cmp(a2));

        assert_eq!(soa.get(0), (&1, &('b'), &5.0));
        assert_eq!(soa.get(1), (&2, &('c'), &6.0));
        assert_eq!(soa.get(2), (&3, &('a'), &4.0));
    }

    #[test]
    fn drops() {
        let td = TestDrop::new();
        let (id, item) = td.new_item();
        {
            let mut soa = Soa2::new();
            soa.push((1.0, item));

            // Did not drop when moved into the vec
            td.assert_no_drop(id);

            // Did not drop through resizing the vec.
            for _ in 0..50 {
                soa.push((2.0, td.new_item().1));
            }
            td.assert_no_drop(id);
        }
        // Dropped with the vec
        td.assert_drop(id);
    }

    #[test]
    fn clones() {
        let mut src = Soa2::new();
        src.push((1.0, 2.0));
        src.push((3.0, 4.0));

        let dst = src.clone();
        assert_eq!(dst.len(), 2);
        assert_eq!(dst.get(0), (&1.0, &2.0));
        assert_eq!(dst.get(1), (&3.0, &4.0));
    }
}