max / makenotwork

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1	//! Shared pagination helpers for the public page handlers.
2
3	use crate::constants;
4
5	/// Build a sliding window of page numbers for pagination controls.
6	///
7	/// One definition for every public list page (feed, discover, landing), they
8	/// previously each carried a byte-identical copy, so a tweak to the window
9	/// behavior had to be made in lockstep or silently drift.
10	pub(super) fn build_pagination_range(current_page: u32, total_pages: u32) -> Vec<u32> {
11	if total_pages <= constants::PAGINATION_WINDOW_SIZE {
12	(1..=total_pages).collect()
13	} else {
14	let start = current_page.saturating_sub(2).max(1);
15	let end = (start + 4).min(total_pages);
16	let start = end.saturating_sub(4).max(1);
17	(start..=end).collect()
18	}
19	}
20
21	#[cfg(test)]
22	mod tests {
23	use super::*;
24
25	#[test]
26	fn pagination_small_total() {
27	assert_eq!(build_pagination_range(1, 3), vec![1, 2, 3]);
28	assert_eq!(build_pagination_range(2, 5), vec![1, 2, 3, 4, 5]);
29	}
30
31	#[test]
32	fn pagination_large_at_start() {
33	assert_eq!(build_pagination_range(1, 20), vec![1, 2, 3, 4, 5]);
34	assert_eq!(build_pagination_range(2, 20), vec![1, 2, 3, 4, 5]);
35	}
36
37	#[test]
38	fn pagination_large_at_middle() {
39	assert_eq!(build_pagination_range(10, 20), vec![8, 9, 10, 11, 12]);
40	}
41
42	#[test]
43	fn pagination_large_at_end() {
44	assert_eq!(build_pagination_range(20, 20), vec![16, 17, 18, 19, 20]);
45	assert_eq!(build_pagination_range(19, 20), vec![16, 17, 18, 19, 20]);
46	}
47
48	#[test]
49	fn pagination_zero_pages() {
50	assert_eq!(build_pagination_range(1, 0), Vec::<u32>::new());
51	}
52
53	#[test]
54	fn pagination_single_page() {
55	assert_eq!(build_pagination_range(1, 1), vec![1]);
56	}
57	}
58