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use std::collections::VecDeque;
use super::{CellValue, MapExt, ScanExt, Watchable};
use crate::{
cell::{Cell, CellImmutable},
pipeline::{Definite, MaterializeDefinite, Pipeline, PipelineSeed},
};
#[allow(private_bounds)]
pub trait WindowExt<T: CellValue>: Pipeline<T, Definite> + PipelineSeed<T> + Watchable<T> {
/// Collect values into a sliding window of size `count`.
///
/// Emits a `Vec<T>` containing the most recent `count` values each time
/// a new value arrives. Before `count` values are collected, emits the
/// values collected so far.
///
/// # Example
///
/// ```
/// use hyphae::{Cell, Mutable, Gettable, WindowExt};
///
/// let source = Cell::new(0);
/// let windowed = source.window(3);
///
/// assert_eq!(windowed.get(), vec![0]); // Initial value
///
/// source.set(1);
/// assert_eq!(windowed.get(), vec![0, 1]); // Growing window
///
/// source.set(2);
/// assert_eq!(windowed.get(), vec![0, 1, 2]); // Full window
///
/// source.set(3);
/// assert_eq!(windowed.get(), vec![1, 2, 3]); // Sliding window
/// ```
#[track_caller]
fn window(&self, count: usize) -> Cell<Vec<T>, CellImmutable>
where
T: CellValue,
Self: Clone + Send + Sync + 'static,
{
assert!(count > 0, "window size must be positive");
self.clone()
.scan(VecDeque::with_capacity(count), move |acc, value| {
let mut new_acc = acc.clone();
new_acc.push_back(value.clone());
if new_acc.len() > count {
new_acc.pop_front();
}
new_acc
})
.map(|deque| deque.iter().cloned().collect())
.materialize()
}
}
impl<T: CellValue, W: Pipeline<T, Definite> + PipelineSeed<T> + Watchable<T>> WindowExt<T> for W {}
#[cfg(test)]
mod tests {
use super::*;
use crate::{Gettable, Mutable};
#[test]
fn test_window_sliding() {
let source = Cell::new(0);
let windowed = source.window(3);
assert_eq!(windowed.get(), vec![0]); // Initial
source.set(1);
assert_eq!(windowed.get(), vec![0, 1]);
source.set(2);
assert_eq!(windowed.get(), vec![0, 1, 2]); // Full window
source.set(3);
assert_eq!(windowed.get(), vec![1, 2, 3]); // Slides
source.set(4);
assert_eq!(windowed.get(), vec![2, 3, 4]); // Slides
}
#[test]
fn test_window_size_one() {
let source = Cell::new(10);
let windowed = source.window(1);
assert_eq!(windowed.get(), vec![10]);
source.set(20);
assert_eq!(windowed.get(), vec![20]);
source.set(30);
assert_eq!(windowed.get(), vec![30]);
}
}