1use crate::Edit;
2use std::{
3 cmp, mem,
4 ops::{Add, AddAssign, Sub},
5};
6
7#[derive(Clone, Default, Debug, PartialEq, Eq)]
8pub struct Patch<T>(Vec<Edit<T>>);
9
10impl<T> Patch<T>
11where
12 T: 'static + Clone + Copy + Ord + Default,
13{
14 pub fn new(edits: Vec<Edit<T>>) -> Self {
15 #[cfg(debug_assertions)]
16 {
17 let mut last_edit: Option<&Edit<T>> = None;
18 for edit in &edits {
19 if let Some(last_edit) = last_edit {
20 assert!(edit.old.start > last_edit.old.end);
21 assert!(edit.new.start > last_edit.new.end);
22 }
23 last_edit = Some(edit);
24 }
25 }
26 Self(edits)
27 }
28
29 pub fn edits(&self) -> &[Edit<T>] {
30 &self.0
31 }
32
33 pub fn into_inner(self) -> Vec<Edit<T>> {
34 self.0
35 }
36 pub fn invert(&mut self) -> &mut Self {
37 for edit in &mut self.0 {
38 mem::swap(&mut edit.old, &mut edit.new);
39 }
40 self
41 }
42
43 pub fn clear(&mut self) {
44 self.0.clear();
45 }
46
47 pub fn is_empty(&self) -> bool {
48 self.0.is_empty()
49 }
50
51 pub fn push(&mut self, edit: Edit<T>) {
52 if edit.is_empty() {
53 return;
54 }
55
56 if let Some(last) = self.0.last_mut() {
57 if last.old.end >= edit.old.start {
58 last.old.end = edit.old.end;
59 last.new.end = edit.new.end;
60 } else {
61 self.0.push(edit);
62 }
63 } else {
64 self.0.push(edit);
65 }
66 }
67}
68
69impl<T, TDelta> Patch<T>
70where
71 T: 'static
72 + Copy
73 + Ord
74 + Sub<T, Output = TDelta>
75 + Add<TDelta, Output = T>
76 + AddAssign<TDelta>
77 + Default,
78 TDelta: Ord + Copy,
79{
80 #[must_use]
81 pub fn compose(&self, new_edits_iter: impl IntoIterator<Item = Edit<T>>) -> Self {
82 let mut old_edits_iter = self.0.iter().cloned().peekable();
83 let mut new_edits_iter = new_edits_iter.into_iter().peekable();
84 let mut composed = Patch(Vec::new());
85
86 let mut old_start = T::default();
87 let mut new_start = T::default();
88 loop {
89 let old_edit = old_edits_iter.peek_mut();
90 let new_edit = new_edits_iter.peek_mut();
91
92 // Push the old edit if its new end is before the new edit's old start.
93 if let Some(old_edit) = old_edit.as_ref() {
94 let new_edit = new_edit.as_ref();
95 if new_edit.is_none_or(|new_edit| old_edit.new.end < new_edit.old.start) {
96 let catchup = old_edit.old.start - old_start;
97 old_start += catchup;
98 new_start += catchup;
99
100 let old_end = old_start + old_edit.old_len();
101 let new_end = new_start + old_edit.new_len();
102 composed.push(Edit {
103 old: old_start..old_end,
104 new: new_start..new_end,
105 });
106 old_start = old_end;
107 new_start = new_end;
108 old_edits_iter.next();
109 continue;
110 }
111 }
112
113 // Push the new edit if its old end is before the old edit's new start.
114 if let Some(new_edit) = new_edit.as_ref() {
115 let old_edit = old_edit.as_ref();
116 if old_edit.is_none_or(|old_edit| new_edit.old.end < old_edit.new.start) {
117 let catchup = new_edit.new.start - new_start;
118 old_start += catchup;
119 new_start += catchup;
120
121 let old_end = old_start + new_edit.old_len();
122 let new_end = new_start + new_edit.new_len();
123 composed.push(Edit {
124 old: old_start..old_end,
125 new: new_start..new_end,
126 });
127 old_start = old_end;
128 new_start = new_end;
129 new_edits_iter.next();
130 continue;
131 }
132 }
133
134 // If we still have edits by this point then they must intersect, so we compose them.
135 if let Some((old_edit, new_edit)) = old_edit.zip(new_edit) {
136 if old_edit.new.start < new_edit.old.start {
137 let catchup = old_edit.old.start - old_start;
138 old_start += catchup;
139 new_start += catchup;
140
141 let overshoot = new_edit.old.start - old_edit.new.start;
142 let old_end = cmp::min(old_start + overshoot, old_edit.old.end);
143 let new_end = new_start + overshoot;
144 composed.push(Edit {
145 old: old_start..old_end,
146 new: new_start..new_end,
147 });
148
149 old_edit.old.start = old_end;
150 old_edit.new.start += overshoot;
151 old_start = old_end;
152 new_start = new_end;
153 } else {
154 let catchup = new_edit.new.start - new_start;
155 old_start += catchup;
156 new_start += catchup;
157
158 let overshoot = old_edit.new.start - new_edit.old.start;
159 let old_end = old_start + overshoot;
160 let new_end = cmp::min(new_start + overshoot, new_edit.new.end);
161 composed.push(Edit {
162 old: old_start..old_end,
163 new: new_start..new_end,
164 });
165
166 new_edit.old.start += overshoot;
167 new_edit.new.start = new_end;
168 old_start = old_end;
169 new_start = new_end;
170 }
171
172 if old_edit.new.end > new_edit.old.end {
173 let old_end = old_start + cmp::min(old_edit.old_len(), new_edit.old_len());
174 let new_end = new_start + new_edit.new_len();
175 composed.push(Edit {
176 old: old_start..old_end,
177 new: new_start..new_end,
178 });
179
180 old_edit.old.start = old_end;
181 old_edit.new.start = new_edit.old.end;
182 old_start = old_end;
183 new_start = new_end;
184 new_edits_iter.next();
185 } else {
186 let old_end = old_start + old_edit.old_len();
187 let new_end = new_start + cmp::min(old_edit.new_len(), new_edit.new_len());
188 composed.push(Edit {
189 old: old_start..old_end,
190 new: new_start..new_end,
191 });
192
193 new_edit.old.start = old_edit.new.end;
194 new_edit.new.start = new_end;
195 old_start = old_end;
196 new_start = new_end;
197 old_edits_iter.next();
198 }
199 } else {
200 break;
201 }
202 }
203
204 composed
205 }
206
207 pub fn old_to_new(&self, old: T) -> T {
208 let ix = match self.0.binary_search_by(|probe| probe.old.start.cmp(&old)) {
209 Ok(ix) => ix,
210 Err(ix) => {
211 if ix == 0 {
212 return old;
213 } else {
214 ix - 1
215 }
216 }
217 };
218 if let Some(edit) = self.0.get(ix) {
219 if old >= edit.old.end {
220 edit.new.end + (old - edit.old.end)
221 } else {
222 edit.new.start
223 }
224 } else {
225 old
226 }
227 }
228}
229
230impl<T> Patch<T> {
231 pub fn retain_mut<F>(&mut self, f: F)
232 where
233 F: FnMut(&mut Edit<T>) -> bool,
234 {
235 self.0.retain_mut(f);
236 }
237}
238
239impl<T: Clone> IntoIterator for Patch<T> {
240 type Item = Edit<T>;
241 type IntoIter = std::vec::IntoIter<Edit<T>>;
242
243 fn into_iter(self) -> Self::IntoIter {
244 self.0.into_iter()
245 }
246}
247
248impl<'a, T: Clone> IntoIterator for &'a Patch<T> {
249 type Item = Edit<T>;
250 type IntoIter = std::iter::Cloned<std::slice::Iter<'a, Edit<T>>>;
251
252 fn into_iter(self) -> Self::IntoIter {
253 self.0.iter().cloned()
254 }
255}
256
257impl<'a, T: Clone> IntoIterator for &'a mut Patch<T> {
258 type Item = Edit<T>;
259 type IntoIter = std::iter::Cloned<std::slice::Iter<'a, Edit<T>>>;
260
261 fn into_iter(self) -> Self::IntoIter {
262 self.0.iter().cloned()
263 }
264}
265
266#[cfg(test)]
267mod tests {
268 use super::*;
269 use rand::prelude::*;
270 use std::env;
271
272 #[gpui::test]
273 fn test_one_disjoint_edit() {
274 assert_patch_composition(
275 Patch(vec![Edit {
276 old: 1..3,
277 new: 1..4,
278 }]),
279 Patch(vec![Edit {
280 old: 0..0,
281 new: 0..4,
282 }]),
283 Patch(vec![
284 Edit {
285 old: 0..0,
286 new: 0..4,
287 },
288 Edit {
289 old: 1..3,
290 new: 5..8,
291 },
292 ]),
293 );
294
295 assert_patch_composition(
296 Patch(vec![Edit {
297 old: 1..3,
298 new: 1..4,
299 }]),
300 Patch(vec![Edit {
301 old: 5..9,
302 new: 5..7,
303 }]),
304 Patch(vec![
305 Edit {
306 old: 1..3,
307 new: 1..4,
308 },
309 Edit {
310 old: 4..8,
311 new: 5..7,
312 },
313 ]),
314 );
315 }
316
317 #[gpui::test]
318 fn test_one_overlapping_edit() {
319 assert_patch_composition(
320 Patch(vec![Edit {
321 old: 1..3,
322 new: 1..4,
323 }]),
324 Patch(vec![Edit {
325 old: 3..5,
326 new: 3..6,
327 }]),
328 Patch(vec![Edit {
329 old: 1..4,
330 new: 1..6,
331 }]),
332 );
333 }
334
335 #[gpui::test]
336 fn test_two_disjoint_and_overlapping() {
337 assert_patch_composition(
338 Patch(vec![
339 Edit {
340 old: 1..3,
341 new: 1..4,
342 },
343 Edit {
344 old: 8..12,
345 new: 9..11,
346 },
347 ]),
348 Patch(vec![
349 Edit {
350 old: 0..0,
351 new: 0..4,
352 },
353 Edit {
354 old: 3..10,
355 new: 7..9,
356 },
357 ]),
358 Patch(vec![
359 Edit {
360 old: 0..0,
361 new: 0..4,
362 },
363 Edit {
364 old: 1..12,
365 new: 5..10,
366 },
367 ]),
368 );
369 }
370
371 #[gpui::test]
372 fn test_two_new_edits_overlapping_one_old_edit() {
373 assert_patch_composition(
374 Patch(vec![Edit {
375 old: 0..0,
376 new: 0..3,
377 }]),
378 Patch(vec![
379 Edit {
380 old: 0..0,
381 new: 0..1,
382 },
383 Edit {
384 old: 1..2,
385 new: 2..2,
386 },
387 ]),
388 Patch(vec![Edit {
389 old: 0..0,
390 new: 0..3,
391 }]),
392 );
393
394 assert_patch_composition(
395 Patch(vec![Edit {
396 old: 2..3,
397 new: 2..4,
398 }]),
399 Patch(vec![
400 Edit {
401 old: 0..2,
402 new: 0..1,
403 },
404 Edit {
405 old: 3..3,
406 new: 2..5,
407 },
408 ]),
409 Patch(vec![Edit {
410 old: 0..3,
411 new: 0..6,
412 }]),
413 );
414
415 assert_patch_composition(
416 Patch(vec![Edit {
417 old: 0..0,
418 new: 0..2,
419 }]),
420 Patch(vec![
421 Edit {
422 old: 0..0,
423 new: 0..2,
424 },
425 Edit {
426 old: 2..5,
427 new: 4..4,
428 },
429 ]),
430 Patch(vec![Edit {
431 old: 0..3,
432 new: 0..4,
433 }]),
434 );
435 }
436
437 #[gpui::test]
438 fn test_two_new_edits_touching_one_old_edit() {
439 assert_patch_composition(
440 Patch(vec![
441 Edit {
442 old: 2..3,
443 new: 2..4,
444 },
445 Edit {
446 old: 7..7,
447 new: 8..11,
448 },
449 ]),
450 Patch(vec![
451 Edit {
452 old: 2..3,
453 new: 2..2,
454 },
455 Edit {
456 old: 4..4,
457 new: 3..4,
458 },
459 ]),
460 Patch(vec![
461 Edit {
462 old: 2..3,
463 new: 2..4,
464 },
465 Edit {
466 old: 7..7,
467 new: 8..11,
468 },
469 ]),
470 );
471 }
472
473 #[gpui::test]
474 fn test_old_to_new() {
475 let patch = Patch(vec![
476 Edit {
477 old: 2..4,
478 new: 2..4,
479 },
480 Edit {
481 old: 7..8,
482 new: 7..11,
483 },
484 ]);
485 assert_eq!(patch.old_to_new(0), 0);
486 assert_eq!(patch.old_to_new(1), 1);
487 assert_eq!(patch.old_to_new(2), 2);
488 assert_eq!(patch.old_to_new(3), 2);
489 assert_eq!(patch.old_to_new(4), 4);
490 assert_eq!(patch.old_to_new(5), 5);
491 assert_eq!(patch.old_to_new(6), 6);
492 assert_eq!(patch.old_to_new(7), 7);
493 assert_eq!(patch.old_to_new(8), 11);
494 assert_eq!(patch.old_to_new(9), 12);
495 }
496
497 #[gpui::test(iterations = 100)]
498 fn test_random_patch_compositions(mut rng: StdRng) {
499 let operations = env::var("OPERATIONS")
500 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
501 .unwrap_or(20);
502
503 let initial_chars = (0..rng.random_range(0..=100))
504 .map(|_| rng.random_range(b'a'..=b'z') as char)
505 .collect::<Vec<_>>();
506 log::info!("initial chars: {:?}", initial_chars);
507
508 // Generate two sequential patches
509 let mut patches = Vec::new();
510 let mut expected_chars = initial_chars.clone();
511 for i in 0..2 {
512 log::info!("patch {}:", i);
513
514 let mut delta = 0i32;
515 let mut last_edit_end = 0;
516 let mut edits = Vec::new();
517
518 for _ in 0..operations {
519 if last_edit_end >= expected_chars.len() {
520 break;
521 }
522
523 let end = rng.random_range(last_edit_end..=expected_chars.len());
524 let start = rng.random_range(last_edit_end..=end);
525 let old_len = end - start;
526
527 let mut new_len = rng.random_range(0..=3);
528 if start == end && new_len == 0 {
529 new_len += 1;
530 }
531
532 last_edit_end = start + new_len + 1;
533
534 let new_chars = (0..new_len)
535 .map(|_| rng.random_range(b'A'..=b'Z') as char)
536 .collect::<Vec<_>>();
537 log::info!(
538 " editing {:?}: {:?}",
539 start..end,
540 new_chars.iter().collect::<String>()
541 );
542 edits.push(Edit {
543 old: (start as i32 - delta) as u32..(end as i32 - delta) as u32,
544 new: start as u32..(start + new_len) as u32,
545 });
546 expected_chars.splice(start..end, new_chars);
547
548 delta += new_len as i32 - old_len as i32;
549 }
550
551 patches.push(Patch(edits));
552 }
553
554 log::info!("old patch: {:?}", &patches[0]);
555 log::info!("new patch: {:?}", &patches[1]);
556 log::info!("initial chars: {:?}", initial_chars);
557 log::info!("final chars: {:?}", expected_chars);
558
559 // Compose the patches, and verify that it has the same effect as applying the
560 // two patches separately.
561 let composed = patches[0].compose(&patches[1]);
562 log::info!("composed patch: {:?}", &composed);
563
564 let mut actual_chars = initial_chars;
565 for edit in composed.0 {
566 actual_chars.splice(
567 edit.new.start as usize..edit.new.start as usize + edit.old.len(),
568 expected_chars[edit.new.start as usize..edit.new.end as usize]
569 .iter()
570 .copied(),
571 );
572 }
573
574 assert_eq!(actual_chars, expected_chars);
575 }
576
577 #[track_caller]
578 #[allow(clippy::almost_complete_range)]
579 fn assert_patch_composition(old: Patch<u32>, new: Patch<u32>, composed: Patch<u32>) {
580 let original = ('a'..'z').collect::<Vec<_>>();
581 let inserted = ('A'..'Z').collect::<Vec<_>>();
582
583 let mut expected = original.clone();
584 apply_patch(&mut expected, &old, &inserted);
585 apply_patch(&mut expected, &new, &inserted);
586
587 let mut actual = original;
588 apply_patch(&mut actual, &composed, &expected);
589 assert_eq!(
590 actual.into_iter().collect::<String>(),
591 expected.into_iter().collect::<String>(),
592 "expected patch is incorrect"
593 );
594
595 assert_eq!(old.compose(&new), composed);
596 }
597
598 fn apply_patch(text: &mut Vec<char>, patch: &Patch<u32>, new_text: &[char]) {
599 for edit in patch.0.iter().rev() {
600 text.splice(
601 edit.old.start as usize..edit.old.end as usize,
602 new_text[edit.new.start as usize..edit.new.end as usize]
603 .iter()
604 .copied(),
605 );
606 }
607 }
608}