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use super::ConcurrentSlice;
use crate::elem::ConcurrentElement;
use orx_fixed_vec::IntoConcurrentPinnedVec;
impl<'a, T, P> ConcurrentSlice<'a, T, P>
where
P: IntoConcurrentPinnedVec<ConcurrentElement<T>>,
{
/// Divides one slice into two at an index:
/// * the first will contain elements in positions `[0, mid)`,
/// * the second will contain elements in positions `[mid, self.len())`.
///
/// # Panics
///
/// Panics if `mid > self.len()`.
///
/// # Examples
///
/// ```
/// use orx_concurrent_vec::*;
///
/// let vec = ConcurrentVec::from_iter(0..8);
///
/// let slice = vec.as_slice();
///
/// let (a, b) = slice.split_at(3);
/// assert_eq!(a, [0, 1, 2]);
/// assert_eq!(b, [3, 4, 5, 6, 7]);
/// ```
pub fn split_at(
&'a self,
mid: usize,
) -> (ConcurrentSlice<'a, T, P>, ConcurrentSlice<'a, T, P>) {
let len = self.len();
assert!(mid <= len);
(self.slice(0..mid), self.slice(mid..len))
}
/// Returns the first and all the rest of the elements of the slice, or None if it is empty.
///
/// # Examples
///
/// ```
/// use orx_concurrent_vec::*;
///
/// let vec = ConcurrentVec::from_iter(0..4);
/// let slice = vec.as_slice();
///
/// let (a, b) = slice.split_first().unwrap();
/// assert_eq!(a, &0);
/// assert_eq!(b, [1, 2, 3]);
///
/// // empty
/// let slice = vec.slice(0..0);
/// assert!(slice.split_first().is_none());
///
/// // single element
/// let slice = vec.slice(2..3);
/// let (a, b) = slice.split_first().unwrap();
/// assert_eq!(a, &2);
/// assert_eq!(b, []);
/// ```
pub fn split_first(&self) -> Option<(&ConcurrentElement<T>, ConcurrentSlice<'_, T, P>)> {
match self.get(0) {
Some(a) => {
let b = self.slice(1..self.len());
Some((a, b))
}
None => None,
}
}
/// Returns the last and all the rest of the elements of the slice, or None if it is empty.
///
/// # Examples
///
/// ```
/// use orx_concurrent_vec::*;
///
/// let vec = ConcurrentVec::from_iter(0..4);
/// let slice = vec.as_slice();
///
/// let (a, b) = slice.split_last().unwrap();
/// assert_eq!(a, &3);
/// assert_eq!(b, [0, 1, 2]);
///
/// // empty
/// let slice = vec.slice(0..0);
/// assert!(slice.split_last().is_none());
///
/// // single element
/// let slice = vec.slice(2..3);
/// let (a, b) = slice.split_last().unwrap();
/// assert_eq!(a, &2);
/// assert_eq!(b, []);
/// ```
pub fn split_last(&self) -> Option<(&ConcurrentElement<T>, ConcurrentSlice<'_, T, P>)> {
let len = self.len();
match len {
0 => None,
_ => {
let a = self.slice(0..(len - 1));
let b = &self[len - 1];
Some((b, a))
}
}
}
/// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the beginning of the slice.
///
/// The chunks are slices and do not overlap.
/// If chunk_size does not divide the length of the slice, then the last chunk will not have length chunk_size.
///
/// # Panics
///
/// Panics if chunk_size is 0.
///
/// # Examples
///
/// ```
/// use orx_concurrent_vec::*;
///
/// let vec: ConcurrentVec<_> = ['l', 'o', 'r', 'e', 'm'].into_iter().collect();
/// let slice = vec.as_slice();
///
/// let mut iter = slice.chunks(2);
/// assert_eq!(iter.next().unwrap(), ['l', 'o']);
/// assert_eq!(iter.next().unwrap(), ['r', 'e']);
/// assert_eq!(iter.next().unwrap(), ['m']);
/// assert!(iter.next().is_none());
/// ```
pub fn chunks(
&'a self,
chunk_size: usize,
) -> impl ExactSizeIterator<Item = ConcurrentSlice<'a, T, P>> {
assert!(chunk_size > 0);
let len = self.len();
let mut num_slices = len / chunk_size;
let remainder = len - num_slices * chunk_size;
if remainder > 0 {
num_slices += 1;
}
(0..num_slices).map(move |i| {
let a = i * chunk_size;
let b = a + match (i == num_slices - 1, remainder > 0) {
(true, true) => remainder,
_ => chunk_size,
};
self.slice(a..b)
})
}
}