1use crate::{
   2    multi_buffer::MultiBufferRows, Anchor, AnchorRangeExt, MultiBufferChunks, MultiBufferSnapshot,
   3    ToOffset,
   4};
   5use language::{Chunk, Edit, Point, PointUtf16, TextSummary};
   6use parking_lot::Mutex;
   7use std::{
   8    cmp::{self, Ordering},
   9    iter,
  10    ops::{Range, Sub},
  11    sync::atomic::{AtomicUsize, Ordering::SeqCst},
  12};
  13use sum_tree::{Bias, Cursor, FilterCursor, SumTree};
  14
  15pub trait ToFoldPoint {
  16    fn to_fold_point(&self, snapshot: &FoldSnapshot, bias: Bias) -> FoldPoint;
  17}
  18
  19#[derive(Copy, Clone, Debug, Default, Eq, Ord, PartialOrd, PartialEq)]
  20pub struct FoldPoint(pub super::Point);
  21
  22impl FoldPoint {
  23    pub fn new(row: u32, column: u32) -> Self {
  24        Self(super::Point::new(row, column))
  25    }
  26
  27    pub fn row(self) -> u32 {
  28        self.0.row
  29    }
  30
  31    pub fn column(self) -> u32 {
  32        self.0.column
  33    }
  34
  35    pub fn row_mut(&mut self) -> &mut u32 {
  36        &mut self.0.row
  37    }
  38
  39    pub fn column_mut(&mut self) -> &mut u32 {
  40        &mut self.0.column
  41    }
  42
  43    pub fn to_buffer_point(&self, snapshot: &FoldSnapshot) -> Point {
  44        let mut cursor = snapshot.transforms.cursor::<(FoldPoint, Point)>();
  45        cursor.seek(self, Bias::Right, &());
  46        let overshoot = self.0 - cursor.start().0 .0;
  47        cursor.start().1 + overshoot
  48    }
  49
  50    pub fn to_buffer_offset(&self, snapshot: &FoldSnapshot) -> usize {
  51        let mut cursor = snapshot.transforms.cursor::<(FoldPoint, Point)>();
  52        cursor.seek(self, Bias::Right, &());
  53        let overshoot = self.0 - cursor.start().0 .0;
  54        snapshot
  55            .buffer_snapshot
  56            .point_to_offset(cursor.start().1 + overshoot)
  57    }
  58
  59    pub fn to_offset(&self, snapshot: &FoldSnapshot) -> FoldOffset {
  60        let mut cursor = snapshot
  61            .transforms
  62            .cursor::<(FoldPoint, TransformSummary)>();
  63        cursor.seek(self, Bias::Right, &());
  64        let overshoot = self.0 - cursor.start().1.output.lines;
  65        let mut offset = cursor.start().1.output.bytes;
  66        if !overshoot.is_zero() {
  67            let transform = cursor.item().expect("display point out of range");
  68            assert!(transform.output_text.is_none());
  69            let end_buffer_offset = snapshot
  70                .buffer_snapshot
  71                .point_to_offset(cursor.start().1.input.lines + overshoot);
  72            offset += end_buffer_offset - cursor.start().1.input.bytes;
  73        }
  74        FoldOffset(offset)
  75    }
  76}
  77
  78impl ToFoldPoint for Point {
  79    fn to_fold_point(&self, snapshot: &FoldSnapshot, bias: Bias) -> FoldPoint {
  80        let mut cursor = snapshot.transforms.cursor::<(Point, FoldPoint)>();
  81        cursor.seek(self, Bias::Right, &());
  82        if cursor.item().map_or(false, |t| t.is_fold()) {
  83            if bias == Bias::Left || *self == cursor.start().0 {
  84                cursor.start().1
  85            } else {
  86                cursor.end(&()).1
  87            }
  88        } else {
  89            let overshoot = *self - cursor.start().0;
  90            FoldPoint(cmp::min(
  91                cursor.start().1 .0 + overshoot,
  92                cursor.end(&()).1 .0,
  93            ))
  94        }
  95    }
  96}
  97
  98pub struct FoldMapWriter<'a>(&'a mut FoldMap);
  99
 100impl<'a> FoldMapWriter<'a> {
 101    pub fn fold<T: ToOffset>(
 102        &mut self,
 103        ranges: impl IntoIterator<Item = Range<T>>,
 104    ) -> (FoldSnapshot, Vec<FoldEdit>) {
 105        let mut edits = Vec::new();
 106        let mut folds = Vec::new();
 107        let buffer = self.0.buffer.lock().clone();
 108        for range in ranges.into_iter() {
 109            let range = range.start.to_offset(&buffer)..range.end.to_offset(&buffer);
 110            if range.start != range.end {
 111                let fold = Fold(buffer.anchor_after(range.start)..buffer.anchor_before(range.end));
 112                folds.push(fold);
 113                edits.push(text::Edit {
 114                    old: range.clone(),
 115                    new: range,
 116                });
 117            }
 118        }
 119
 120        folds.sort_unstable_by(|a, b| sum_tree::SeekTarget::cmp(a, b, &buffer));
 121
 122        self.0.folds = {
 123            let mut new_tree = SumTree::new();
 124            let mut cursor = self.0.folds.cursor::<Fold>();
 125            for fold in folds {
 126                new_tree.push_tree(cursor.slice(&fold, Bias::Right, &buffer), &buffer);
 127                new_tree.push(fold, &buffer);
 128            }
 129            new_tree.push_tree(cursor.suffix(&buffer), &buffer);
 130            new_tree
 131        };
 132
 133        consolidate_buffer_edits(&mut edits);
 134        let edits = self.0.sync(buffer.clone(), edits);
 135        let snapshot = FoldSnapshot {
 136            transforms: self.0.transforms.lock().clone(),
 137            folds: self.0.folds.clone(),
 138            buffer_snapshot: buffer,
 139            version: self.0.version.load(SeqCst),
 140        };
 141        (snapshot, edits)
 142    }
 143
 144    pub fn unfold<T: ToOffset>(
 145        &mut self,
 146        ranges: impl IntoIterator<Item = Range<T>>,
 147    ) -> (FoldSnapshot, Vec<FoldEdit>) {
 148        let mut edits = Vec::new();
 149        let mut fold_ixs_to_delete = Vec::new();
 150        let buffer = self.0.buffer.lock().clone();
 151        for range in ranges.into_iter() {
 152            // Remove intersecting folds and add their ranges to edits that are passed to sync.
 153            let mut folds_cursor = intersecting_folds(&buffer, &self.0.folds, range, true);
 154            while let Some(fold) = folds_cursor.item() {
 155                let offset_range = fold.0.start.to_offset(&buffer)..fold.0.end.to_offset(&buffer);
 156                if offset_range.end > offset_range.start {
 157                    edits.push(text::Edit {
 158                        old: offset_range.clone(),
 159                        new: offset_range,
 160                    });
 161                }
 162                fold_ixs_to_delete.push(*folds_cursor.start());
 163                folds_cursor.next(&buffer);
 164            }
 165        }
 166
 167        fold_ixs_to_delete.sort_unstable();
 168        fold_ixs_to_delete.dedup();
 169
 170        self.0.folds = {
 171            let mut cursor = self.0.folds.cursor::<usize>();
 172            let mut folds = SumTree::new();
 173            for fold_ix in fold_ixs_to_delete {
 174                folds.push_tree(cursor.slice(&fold_ix, Bias::Right, &buffer), &buffer);
 175                cursor.next(&buffer);
 176            }
 177            folds.push_tree(cursor.suffix(&buffer), &buffer);
 178            folds
 179        };
 180
 181        consolidate_buffer_edits(&mut edits);
 182        let edits = self.0.sync(buffer.clone(), edits);
 183        let snapshot = FoldSnapshot {
 184            transforms: self.0.transforms.lock().clone(),
 185            folds: self.0.folds.clone(),
 186            buffer_snapshot: buffer,
 187            version: self.0.version.load(SeqCst),
 188        };
 189        (snapshot, edits)
 190    }
 191}
 192
 193pub struct FoldMap {
 194    buffer: Mutex<MultiBufferSnapshot>,
 195    transforms: Mutex<SumTree<Transform>>,
 196    folds: SumTree<Fold>,
 197    version: AtomicUsize,
 198}
 199
 200impl FoldMap {
 201    pub fn new(buffer: MultiBufferSnapshot) -> (Self, FoldSnapshot) {
 202        let this = Self {
 203            buffer: Mutex::new(buffer.clone()),
 204            folds: Default::default(),
 205            transforms: Mutex::new(SumTree::from_item(
 206                Transform {
 207                    summary: TransformSummary {
 208                        input: buffer.text_summary(),
 209                        output: buffer.text_summary(),
 210                    },
 211                    output_text: None,
 212                },
 213                &(),
 214            )),
 215            version: Default::default(),
 216        };
 217
 218        let snapshot = FoldSnapshot {
 219            transforms: this.transforms.lock().clone(),
 220            folds: this.folds.clone(),
 221            buffer_snapshot: this.buffer.lock().clone(),
 222            version: this.version.load(SeqCst),
 223        };
 224        (this, snapshot)
 225    }
 226
 227    pub fn read(
 228        &self,
 229        buffer: MultiBufferSnapshot,
 230        edits: Vec<Edit<usize>>,
 231    ) -> (FoldSnapshot, Vec<FoldEdit>) {
 232        let edits = self.sync(buffer, edits);
 233        self.check_invariants();
 234        let snapshot = FoldSnapshot {
 235            transforms: self.transforms.lock().clone(),
 236            folds: self.folds.clone(),
 237            buffer_snapshot: self.buffer.lock().clone(),
 238            version: self.version.load(SeqCst),
 239        };
 240        (snapshot, edits)
 241    }
 242
 243    pub fn write(
 244        &mut self,
 245        buffer: MultiBufferSnapshot,
 246        edits: Vec<Edit<usize>>,
 247    ) -> (FoldMapWriter, FoldSnapshot, Vec<FoldEdit>) {
 248        let (snapshot, edits) = self.read(buffer, edits);
 249        (FoldMapWriter(self), snapshot, edits)
 250    }
 251
 252    fn check_invariants(&self) {
 253        if cfg!(test) {
 254            assert_eq!(
 255                self.transforms.lock().summary().input.bytes,
 256                self.buffer.lock().len(),
 257                "transform tree does not match buffer's length"
 258            );
 259        }
 260    }
 261
 262    fn sync(
 263        &self,
 264        new_buffer: MultiBufferSnapshot,
 265        buffer_edits: Vec<text::Edit<usize>>,
 266    ) -> Vec<FoldEdit> {
 267        if buffer_edits.is_empty() {
 268            let mut buffer = self.buffer.lock();
 269            if buffer.parse_count() != new_buffer.parse_count()
 270                || buffer.diagnostics_update_count() != new_buffer.diagnostics_update_count()
 271            {
 272                self.version.fetch_add(1, SeqCst);
 273            }
 274            *buffer = new_buffer;
 275            Vec::new()
 276        } else {
 277            let mut buffer_edits_iter = buffer_edits.iter().cloned().peekable();
 278
 279            let mut new_transforms = SumTree::new();
 280            let mut transforms = self.transforms.lock();
 281            let mut cursor = transforms.cursor::<usize>();
 282            cursor.seek(&0, Bias::Right, &());
 283
 284            while let Some(mut edit) = buffer_edits_iter.next() {
 285                new_transforms.push_tree(cursor.slice(&edit.old.start, Bias::Left, &()), &());
 286                edit.new.start -= edit.old.start - cursor.start();
 287                edit.old.start = *cursor.start();
 288
 289                cursor.seek(&edit.old.end, Bias::Right, &());
 290                cursor.next(&());
 291
 292                let mut delta = edit.new.len() as isize - edit.old.len() as isize;
 293                loop {
 294                    edit.old.end = *cursor.start();
 295
 296                    if let Some(next_edit) = buffer_edits_iter.peek() {
 297                        if next_edit.old.start > edit.old.end {
 298                            break;
 299                        }
 300
 301                        let next_edit = buffer_edits_iter.next().unwrap();
 302                        delta += next_edit.new.len() as isize - next_edit.old.len() as isize;
 303
 304                        if next_edit.old.end >= edit.old.end {
 305                            edit.old.end = next_edit.old.end;
 306                            cursor.seek(&edit.old.end, Bias::Right, &());
 307                            cursor.next(&());
 308                        }
 309                    } else {
 310                        break;
 311                    }
 312                }
 313
 314                edit.new.end = ((edit.new.start + edit.old.len()) as isize + delta) as usize;
 315
 316                let anchor = new_buffer.anchor_before(edit.new.start);
 317                let mut folds_cursor = self.folds.cursor::<Fold>();
 318                folds_cursor.seek(&Fold(anchor..Anchor::max()), Bias::Left, &new_buffer);
 319
 320                let mut folds = iter::from_fn({
 321                    let buffer = &new_buffer;
 322                    move || {
 323                        let item = folds_cursor
 324                            .item()
 325                            .map(|f| f.0.start.to_offset(buffer)..f.0.end.to_offset(buffer));
 326                        folds_cursor.next(buffer);
 327                        item
 328                    }
 329                })
 330                .peekable();
 331
 332                while folds.peek().map_or(false, |fold| fold.start < edit.new.end) {
 333                    let mut fold = folds.next().unwrap();
 334                    let sum = new_transforms.summary();
 335
 336                    assert!(fold.start >= sum.input.bytes);
 337
 338                    while folds
 339                        .peek()
 340                        .map_or(false, |next_fold| next_fold.start <= fold.end)
 341                    {
 342                        let next_fold = folds.next().unwrap();
 343                        if next_fold.end > fold.end {
 344                            fold.end = next_fold.end;
 345                        }
 346                    }
 347
 348                    if fold.start > sum.input.bytes {
 349                        let text_summary = new_buffer
 350                            .text_summary_for_range::<TextSummary, _>(sum.input.bytes..fold.start);
 351                        new_transforms.push(
 352                            Transform {
 353                                summary: TransformSummary {
 354                                    output: text_summary.clone(),
 355                                    input: text_summary,
 356                                },
 357                                output_text: None,
 358                            },
 359                            &(),
 360                        );
 361                    }
 362
 363                    if fold.end > fold.start {
 364                        let output_text = "…";
 365                        let chars = output_text.chars().count() as u32;
 366                        let lines = Point::new(0, output_text.len() as u32);
 367                        let lines_utf16 =
 368                            PointUtf16::new(0, output_text.encode_utf16().count() as u32);
 369                        new_transforms.push(
 370                            Transform {
 371                                summary: TransformSummary {
 372                                    output: TextSummary {
 373                                        bytes: output_text.len(),
 374                                        lines,
 375                                        lines_utf16,
 376                                        first_line_chars: chars,
 377                                        last_line_chars: chars,
 378                                        longest_row: 0,
 379                                        longest_row_chars: chars,
 380                                    },
 381                                    input: new_buffer.text_summary_for_range(fold.start..fold.end),
 382                                },
 383                                output_text: Some(output_text),
 384                            },
 385                            &(),
 386                        );
 387                    }
 388                }
 389
 390                let sum = new_transforms.summary();
 391                if sum.input.bytes < edit.new.end {
 392                    let text_summary = new_buffer
 393                        .text_summary_for_range::<TextSummary, _>(sum.input.bytes..edit.new.end);
 394                    new_transforms.push(
 395                        Transform {
 396                            summary: TransformSummary {
 397                                output: text_summary.clone(),
 398                                input: text_summary,
 399                            },
 400                            output_text: None,
 401                        },
 402                        &(),
 403                    );
 404                }
 405            }
 406
 407            new_transforms.push_tree(cursor.suffix(&()), &());
 408            if new_transforms.is_empty() {
 409                let text_summary = new_buffer.text_summary();
 410                new_transforms.push(
 411                    Transform {
 412                        summary: TransformSummary {
 413                            output: text_summary.clone(),
 414                            input: text_summary,
 415                        },
 416                        output_text: None,
 417                    },
 418                    &(),
 419                );
 420            }
 421
 422            drop(cursor);
 423
 424            let mut fold_edits = Vec::with_capacity(buffer_edits.len());
 425            {
 426                let mut old_transforms = transforms.cursor::<(usize, FoldOffset)>();
 427                let mut new_transforms = new_transforms.cursor::<(usize, FoldOffset)>();
 428
 429                for mut edit in buffer_edits {
 430                    old_transforms.seek(&edit.old.start, Bias::Left, &());
 431                    if old_transforms.item().map_or(false, |t| t.is_fold()) {
 432                        edit.old.start = old_transforms.start().0;
 433                    }
 434                    let old_start =
 435                        old_transforms.start().1 .0 + (edit.old.start - old_transforms.start().0);
 436
 437                    old_transforms.seek_forward(&edit.old.end, Bias::Right, &());
 438                    if old_transforms.item().map_or(false, |t| t.is_fold()) {
 439                        old_transforms.next(&());
 440                        edit.old.end = old_transforms.start().0;
 441                    }
 442                    let old_end =
 443                        old_transforms.start().1 .0 + (edit.old.end - old_transforms.start().0);
 444
 445                    new_transforms.seek(&edit.new.start, Bias::Left, &());
 446                    if new_transforms.item().map_or(false, |t| t.is_fold()) {
 447                        edit.new.start = new_transforms.start().0;
 448                    }
 449                    let new_start =
 450                        new_transforms.start().1 .0 + (edit.new.start - new_transforms.start().0);
 451
 452                    new_transforms.seek_forward(&edit.new.end, Bias::Right, &());
 453                    if new_transforms.item().map_or(false, |t| t.is_fold()) {
 454                        new_transforms.next(&());
 455                        edit.new.end = new_transforms.start().0;
 456                    }
 457                    let new_end =
 458                        new_transforms.start().1 .0 + (edit.new.end - new_transforms.start().0);
 459
 460                    fold_edits.push(FoldEdit {
 461                        old: FoldOffset(old_start)..FoldOffset(old_end),
 462                        new: FoldOffset(new_start)..FoldOffset(new_end),
 463                    });
 464                }
 465
 466                consolidate_fold_edits(&mut fold_edits);
 467            }
 468
 469            *transforms = new_transforms;
 470            *self.buffer.lock() = new_buffer;
 471            self.version.fetch_add(1, SeqCst);
 472            fold_edits
 473        }
 474    }
 475}
 476
 477#[derive(Clone)]
 478pub struct FoldSnapshot {
 479    transforms: SumTree<Transform>,
 480    folds: SumTree<Fold>,
 481    buffer_snapshot: MultiBufferSnapshot,
 482    pub version: usize,
 483}
 484
 485impl FoldSnapshot {
 486    pub fn buffer_snapshot(&self) -> &MultiBufferSnapshot {
 487        &self.buffer_snapshot
 488    }
 489
 490    #[cfg(test)]
 491    pub fn text(&self) -> String {
 492        self.chunks(FoldOffset(0)..self.len())
 493            .map(|c| c.text)
 494            .collect()
 495    }
 496
 497    #[cfg(test)]
 498    pub fn fold_count(&self) -> usize {
 499        self.folds.items(&self.buffer_snapshot).len()
 500    }
 501
 502    pub fn text_summary_for_range(&self, range: Range<FoldPoint>) -> TextSummary {
 503        let mut summary = TextSummary::default();
 504
 505        let mut cursor = self.transforms.cursor::<(FoldPoint, Point)>();
 506        cursor.seek(&range.start, Bias::Right, &());
 507        if let Some(transform) = cursor.item() {
 508            let start_in_transform = range.start.0 - cursor.start().0 .0;
 509            let end_in_transform = cmp::min(range.end, cursor.end(&()).0).0 - cursor.start().0 .0;
 510            if let Some(output_text) = transform.output_text {
 511                summary = TextSummary::from(
 512                    &output_text
 513                        [start_in_transform.column as usize..end_in_transform.column as usize],
 514                );
 515            } else {
 516                let buffer_start = cursor.start().1 + start_in_transform;
 517                let buffer_end = cursor.start().1 + end_in_transform;
 518                summary = self
 519                    .buffer_snapshot
 520                    .text_summary_for_range(buffer_start..buffer_end);
 521            }
 522        }
 523
 524        if range.end > cursor.end(&()).0 {
 525            cursor.next(&());
 526            summary += &cursor
 527                .summary::<_, TransformSummary>(&range.end, Bias::Right, &())
 528                .output;
 529            if let Some(transform) = cursor.item() {
 530                let end_in_transform = range.end.0 - cursor.start().0 .0;
 531                if let Some(output_text) = transform.output_text {
 532                    summary += TextSummary::from(&output_text[..end_in_transform.column as usize]);
 533                } else {
 534                    let buffer_start = cursor.start().1;
 535                    let buffer_end = cursor.start().1 + end_in_transform;
 536                    summary += self
 537                        .buffer_snapshot
 538                        .text_summary_for_range::<TextSummary, _>(buffer_start..buffer_end);
 539                }
 540            }
 541        }
 542
 543        summary
 544    }
 545
 546    pub fn len(&self) -> FoldOffset {
 547        FoldOffset(self.transforms.summary().output.bytes)
 548    }
 549
 550    pub fn line_len(&self, row: u32) -> u32 {
 551        let line_start = FoldPoint::new(row, 0).to_offset(self).0;
 552        let line_end = if row >= self.max_point().row() {
 553            self.len().0
 554        } else {
 555            FoldPoint::new(row + 1, 0).to_offset(self).0 - 1
 556        };
 557        (line_end - line_start) as u32
 558    }
 559
 560    pub fn buffer_rows(&self, start_row: u32) -> FoldBufferRows {
 561        if start_row > self.transforms.summary().output.lines.row {
 562            panic!("invalid display row {}", start_row);
 563        }
 564
 565        let fold_point = FoldPoint::new(start_row, 0);
 566        let mut cursor = self.transforms.cursor::<(FoldPoint, Point)>();
 567        cursor.seek(&fold_point, Bias::Left, &());
 568
 569        let overshoot = fold_point.0 - cursor.start().0 .0;
 570        let buffer_point = cursor.start().1 + overshoot;
 571        let input_buffer_rows = self.buffer_snapshot.buffer_rows(buffer_point.row);
 572
 573        FoldBufferRows {
 574            fold_point,
 575            input_buffer_rows,
 576            cursor,
 577        }
 578    }
 579
 580    pub fn max_point(&self) -> FoldPoint {
 581        FoldPoint(self.transforms.summary().output.lines)
 582    }
 583
 584    #[cfg(test)]
 585    pub fn longest_row(&self) -> u32 {
 586        self.transforms.summary().output.longest_row
 587    }
 588
 589    pub fn folds_in_range<'a, T>(
 590        &'a self,
 591        range: Range<T>,
 592    ) -> impl Iterator<Item = &'a Range<Anchor>>
 593    where
 594        T: ToOffset,
 595    {
 596        let mut folds = intersecting_folds(&self.buffer_snapshot, &self.folds, range, false);
 597        iter::from_fn(move || {
 598            let item = folds.item().map(|f| &f.0);
 599            folds.next(&self.buffer_snapshot);
 600            item
 601        })
 602    }
 603
 604    pub fn intersects_fold<T>(&self, offset: T) -> bool
 605    where
 606        T: ToOffset,
 607    {
 608        let offset = offset.to_offset(&self.buffer_snapshot);
 609        let mut cursor = self.transforms.cursor::<usize>();
 610        cursor.seek(&offset, Bias::Right, &());
 611        cursor.item().map_or(false, |t| t.output_text.is_some())
 612    }
 613
 614    pub fn is_line_folded(&self, output_row: u32) -> bool {
 615        let mut cursor = self.transforms.cursor::<FoldPoint>();
 616        cursor.seek(&FoldPoint::new(output_row, 0), Bias::Right, &());
 617        while let Some(transform) = cursor.item() {
 618            if transform.output_text.is_some() {
 619                return true;
 620            }
 621            if cursor.end(&()).row() == output_row {
 622                cursor.next(&())
 623            } else {
 624                break;
 625            }
 626        }
 627        false
 628    }
 629
 630    pub fn chars_at(&self, start: FoldPoint) -> impl '_ + Iterator<Item = char> {
 631        let start = start.to_offset(self);
 632        self.chunks(start..self.len())
 633            .flat_map(|chunk| chunk.text.chars())
 634    }
 635
 636    pub fn chunks<'a>(&'a self, range: Range<FoldOffset>) -> FoldChunks<'a> {
 637        let mut transform_cursor = self.transforms.cursor::<(FoldOffset, usize)>();
 638
 639        transform_cursor.seek(&range.end, Bias::Right, &());
 640        let overshoot = range.end.0 - transform_cursor.start().0 .0;
 641        let buffer_end = transform_cursor.start().1 + overshoot;
 642
 643        transform_cursor.seek(&range.start, Bias::Right, &());
 644        let overshoot = range.start.0 - transform_cursor.start().0 .0;
 645        let buffer_start = transform_cursor.start().1 + overshoot;
 646
 647        FoldChunks {
 648            transform_cursor,
 649            buffer_chunks: self.buffer_snapshot.chunks(buffer_start..buffer_end),
 650            buffer_chunk: None,
 651            buffer_offset: buffer_start,
 652            output_offset: range.start.0,
 653            max_output_offset: range.end.0,
 654        }
 655    }
 656
 657    #[cfg(test)]
 658    pub fn clip_offset(&self, offset: FoldOffset, bias: Bias) -> FoldOffset {
 659        let mut cursor = self.transforms.cursor::<(FoldOffset, usize)>();
 660        cursor.seek(&offset, Bias::Right, &());
 661        if let Some(transform) = cursor.item() {
 662            let transform_start = cursor.start().0 .0;
 663            if transform.output_text.is_some() {
 664                if offset.0 == transform_start || matches!(bias, Bias::Left) {
 665                    FoldOffset(transform_start)
 666                } else {
 667                    FoldOffset(cursor.end(&()).0 .0)
 668                }
 669            } else {
 670                let overshoot = offset.0 - transform_start;
 671                let buffer_offset = cursor.start().1 + overshoot;
 672                let clipped_buffer_offset = self.buffer_snapshot.clip_offset(buffer_offset, bias);
 673                FoldOffset(
 674                    (offset.0 as isize + (clipped_buffer_offset as isize - buffer_offset as isize))
 675                        as usize,
 676                )
 677            }
 678        } else {
 679            FoldOffset(self.transforms.summary().output.bytes)
 680        }
 681    }
 682
 683    pub fn clip_point(&self, point: FoldPoint, bias: Bias) -> FoldPoint {
 684        let mut cursor = self.transforms.cursor::<(FoldPoint, Point)>();
 685        cursor.seek(&point, Bias::Right, &());
 686        if let Some(transform) = cursor.item() {
 687            let transform_start = cursor.start().0 .0;
 688            if transform.output_text.is_some() {
 689                if point.0 == transform_start || matches!(bias, Bias::Left) {
 690                    FoldPoint(transform_start)
 691                } else {
 692                    FoldPoint(cursor.end(&()).0 .0)
 693                }
 694            } else {
 695                let overshoot = point.0 - transform_start;
 696                let buffer_position = cursor.start().1 + overshoot;
 697                let clipped_buffer_position =
 698                    self.buffer_snapshot.clip_point(buffer_position, bias);
 699                FoldPoint(cursor.start().0 .0 + (clipped_buffer_position - cursor.start().1))
 700            }
 701        } else {
 702            FoldPoint(self.transforms.summary().output.lines)
 703        }
 704    }
 705}
 706
 707fn intersecting_folds<'a, T>(
 708    buffer: &'a MultiBufferSnapshot,
 709    folds: &'a SumTree<Fold>,
 710    range: Range<T>,
 711    inclusive: bool,
 712) -> FilterCursor<'a, impl 'a + FnMut(&FoldSummary) -> bool, Fold, usize>
 713where
 714    T: ToOffset,
 715{
 716    let start = buffer.anchor_before(range.start.to_offset(buffer));
 717    let end = buffer.anchor_after(range.end.to_offset(buffer));
 718    folds.filter::<_, usize>(
 719        move |summary| {
 720            let start_cmp = start.cmp(&summary.max_end, buffer).unwrap();
 721            let end_cmp = end.cmp(&summary.min_start, buffer).unwrap();
 722
 723            if inclusive {
 724                start_cmp <= Ordering::Equal && end_cmp >= Ordering::Equal
 725            } else {
 726                start_cmp == Ordering::Less && end_cmp == Ordering::Greater
 727            }
 728        },
 729        buffer,
 730    )
 731}
 732
 733fn consolidate_buffer_edits(edits: &mut Vec<text::Edit<usize>>) {
 734    edits.sort_unstable_by(|a, b| {
 735        a.old
 736            .start
 737            .cmp(&b.old.start)
 738            .then_with(|| b.old.end.cmp(&a.old.end))
 739    });
 740
 741    let mut i = 1;
 742    while i < edits.len() {
 743        let edit = edits[i].clone();
 744        let prev_edit = &mut edits[i - 1];
 745        if prev_edit.old.end >= edit.old.start {
 746            prev_edit.old.end = prev_edit.old.end.max(edit.old.end);
 747            prev_edit.new.start = prev_edit.new.start.min(edit.new.start);
 748            prev_edit.new.end = prev_edit.new.end.max(edit.new.end);
 749            edits.remove(i);
 750            continue;
 751        }
 752        i += 1;
 753    }
 754}
 755
 756fn consolidate_fold_edits(edits: &mut Vec<FoldEdit>) {
 757    edits.sort_unstable_by(|a, b| {
 758        a.old
 759            .start
 760            .cmp(&b.old.start)
 761            .then_with(|| b.old.end.cmp(&a.old.end))
 762    });
 763
 764    let mut i = 1;
 765    while i < edits.len() {
 766        let edit = edits[i].clone();
 767        let prev_edit = &mut edits[i - 1];
 768        if prev_edit.old.end >= edit.old.start {
 769            prev_edit.old.end = prev_edit.old.end.max(edit.old.end);
 770            prev_edit.new.start = prev_edit.new.start.min(edit.new.start);
 771            prev_edit.new.end = prev_edit.new.end.max(edit.new.end);
 772            edits.remove(i);
 773            continue;
 774        }
 775        i += 1;
 776    }
 777}
 778
 779#[derive(Clone, Debug, Default, Eq, PartialEq)]
 780struct Transform {
 781    summary: TransformSummary,
 782    output_text: Option<&'static str>,
 783}
 784
 785impl Transform {
 786    fn is_fold(&self) -> bool {
 787        self.output_text.is_some()
 788    }
 789}
 790
 791#[derive(Clone, Debug, Default, Eq, PartialEq)]
 792struct TransformSummary {
 793    output: TextSummary,
 794    input: TextSummary,
 795}
 796
 797impl sum_tree::Item for Transform {
 798    type Summary = TransformSummary;
 799
 800    fn summary(&self) -> Self::Summary {
 801        self.summary.clone()
 802    }
 803}
 804
 805impl sum_tree::Summary for TransformSummary {
 806    type Context = ();
 807
 808    fn add_summary(&mut self, other: &Self, _: &()) {
 809        self.input += &other.input;
 810        self.output += &other.output;
 811    }
 812}
 813
 814#[derive(Clone, Debug)]
 815struct Fold(Range<Anchor>);
 816
 817impl Default for Fold {
 818    fn default() -> Self {
 819        Self(Anchor::min()..Anchor::max())
 820    }
 821}
 822
 823impl sum_tree::Item for Fold {
 824    type Summary = FoldSummary;
 825
 826    fn summary(&self) -> Self::Summary {
 827        FoldSummary {
 828            start: self.0.start.clone(),
 829            end: self.0.end.clone(),
 830            min_start: self.0.start.clone(),
 831            max_end: self.0.end.clone(),
 832            count: 1,
 833        }
 834    }
 835}
 836
 837#[derive(Clone, Debug)]
 838struct FoldSummary {
 839    start: Anchor,
 840    end: Anchor,
 841    min_start: Anchor,
 842    max_end: Anchor,
 843    count: usize,
 844}
 845
 846impl Default for FoldSummary {
 847    fn default() -> Self {
 848        Self {
 849            start: Anchor::min(),
 850            end: Anchor::max(),
 851            min_start: Anchor::max(),
 852            max_end: Anchor::min(),
 853            count: 0,
 854        }
 855    }
 856}
 857
 858impl sum_tree::Summary for FoldSummary {
 859    type Context = MultiBufferSnapshot;
 860
 861    fn add_summary(&mut self, other: &Self, buffer: &MultiBufferSnapshot) {
 862        if other.min_start.cmp(&self.min_start, buffer).unwrap() == Ordering::Less {
 863            self.min_start = other.min_start.clone();
 864        }
 865        if other.max_end.cmp(&self.max_end, buffer).unwrap() == Ordering::Greater {
 866            self.max_end = other.max_end.clone();
 867        }
 868
 869        #[cfg(debug_assertions)]
 870        {
 871            let start_comparison = self.start.cmp(&other.start, buffer).unwrap();
 872            assert!(start_comparison <= Ordering::Equal);
 873            if start_comparison == Ordering::Equal {
 874                assert!(self.end.cmp(&other.end, buffer).unwrap() >= Ordering::Equal);
 875            }
 876        }
 877
 878        self.start = other.start.clone();
 879        self.end = other.end.clone();
 880        self.count += other.count;
 881    }
 882}
 883
 884impl<'a> sum_tree::Dimension<'a, FoldSummary> for Fold {
 885    fn add_summary(&mut self, summary: &'a FoldSummary, _: &MultiBufferSnapshot) {
 886        self.0.start = summary.start.clone();
 887        self.0.end = summary.end.clone();
 888    }
 889}
 890
 891impl<'a> sum_tree::SeekTarget<'a, FoldSummary, Fold> for Fold {
 892    fn cmp(&self, other: &Self, buffer: &MultiBufferSnapshot) -> Ordering {
 893        self.0.cmp(&other.0, buffer).unwrap()
 894    }
 895}
 896
 897impl<'a> sum_tree::Dimension<'a, FoldSummary> for usize {
 898    fn add_summary(&mut self, summary: &'a FoldSummary, _: &MultiBufferSnapshot) {
 899        *self += summary.count;
 900    }
 901}
 902
 903pub struct FoldBufferRows<'a> {
 904    cursor: Cursor<'a, Transform, (FoldPoint, Point)>,
 905    input_buffer_rows: MultiBufferRows<'a>,
 906    fold_point: FoldPoint,
 907}
 908
 909impl<'a> Iterator for FoldBufferRows<'a> {
 910    type Item = Option<u32>;
 911
 912    fn next(&mut self) -> Option<Self::Item> {
 913        let mut traversed_fold = false;
 914        while self.fold_point > self.cursor.end(&()).0 {
 915            self.cursor.next(&());
 916            traversed_fold = true;
 917            if self.cursor.item().is_none() {
 918                break;
 919            }
 920        }
 921
 922        if self.cursor.item().is_some() {
 923            if traversed_fold {
 924                self.input_buffer_rows.seek(self.cursor.start().1.row);
 925                self.input_buffer_rows.next();
 926            }
 927            *self.fold_point.row_mut() += 1;
 928            self.input_buffer_rows.next()
 929        } else {
 930            None
 931        }
 932    }
 933}
 934
 935pub struct FoldChunks<'a> {
 936    transform_cursor: Cursor<'a, Transform, (FoldOffset, usize)>,
 937    buffer_chunks: MultiBufferChunks<'a>,
 938    buffer_chunk: Option<(usize, Chunk<'a>)>,
 939    buffer_offset: usize,
 940    output_offset: usize,
 941    max_output_offset: usize,
 942}
 943
 944impl<'a> Iterator for FoldChunks<'a> {
 945    type Item = Chunk<'a>;
 946
 947    fn next(&mut self) -> Option<Self::Item> {
 948        if self.output_offset >= self.max_output_offset {
 949            return None;
 950        }
 951
 952        let transform = if let Some(item) = self.transform_cursor.item() {
 953            item
 954        } else {
 955            return None;
 956        };
 957
 958        // If we're in a fold, then return the fold's display text and
 959        // advance the transform and buffer cursors to the end of the fold.
 960        if let Some(output_text) = transform.output_text {
 961            self.buffer_chunk.take();
 962            self.buffer_offset += transform.summary.input.bytes;
 963            self.buffer_chunks.seek(self.buffer_offset);
 964
 965            while self.buffer_offset >= self.transform_cursor.end(&()).1
 966                && self.transform_cursor.item().is_some()
 967            {
 968                self.transform_cursor.next(&());
 969            }
 970
 971            self.output_offset += output_text.len();
 972            return Some(Chunk {
 973                text: output_text,
 974                highlight_id: None,
 975                diagnostic: None,
 976            });
 977        }
 978
 979        // Retrieve a chunk from the current location in the buffer.
 980        if self.buffer_chunk.is_none() {
 981            let chunk_offset = self.buffer_chunks.offset();
 982            self.buffer_chunk = self.buffer_chunks.next().map(|chunk| (chunk_offset, chunk));
 983        }
 984
 985        // Otherwise, take a chunk from the buffer's text.
 986        if let Some((chunk_offset, mut chunk)) = self.buffer_chunk {
 987            let offset_in_chunk = self.buffer_offset - chunk_offset;
 988            chunk.text = &chunk.text[offset_in_chunk..];
 989
 990            // Truncate the chunk so that it ends at the next fold.
 991            let region_end = self.transform_cursor.end(&()).1 - self.buffer_offset;
 992            if chunk.text.len() >= region_end {
 993                chunk.text = &chunk.text[0..region_end];
 994                self.transform_cursor.next(&());
 995            } else {
 996                self.buffer_chunk.take();
 997            }
 998
 999            self.buffer_offset += chunk.text.len();
1000            self.output_offset += chunk.text.len();
1001            return Some(chunk);
1002        }
1003
1004        None
1005    }
1006}
1007
1008impl<'a> sum_tree::Dimension<'a, TransformSummary> for FoldPoint {
1009    fn add_summary(&mut self, summary: &'a TransformSummary, _: &()) {
1010        self.0 += &summary.output.lines;
1011    }
1012}
1013
1014#[derive(Copy, Clone, Debug, Default, Eq, Ord, PartialOrd, PartialEq)]
1015pub struct FoldOffset(pub usize);
1016
1017impl FoldOffset {
1018    pub fn to_point(&self, snapshot: &FoldSnapshot) -> FoldPoint {
1019        let mut cursor = snapshot
1020            .transforms
1021            .cursor::<(FoldOffset, TransformSummary)>();
1022        cursor.seek(self, Bias::Right, &());
1023        let overshoot = if cursor.item().map_or(true, |t| t.is_fold()) {
1024            Point::new(0, (self.0 - cursor.start().0 .0) as u32)
1025        } else {
1026            let buffer_offset = cursor.start().1.input.bytes + self.0 - cursor.start().0 .0;
1027            let buffer_point = snapshot.buffer_snapshot.offset_to_point(buffer_offset);
1028            buffer_point - cursor.start().1.input.lines
1029        };
1030        FoldPoint(cursor.start().1.output.lines + overshoot)
1031    }
1032}
1033
1034impl Sub for FoldOffset {
1035    type Output = Self;
1036
1037    fn sub(self, rhs: Self) -> Self::Output {
1038        Self(self.0 - rhs.0)
1039    }
1040}
1041
1042impl<'a> sum_tree::Dimension<'a, TransformSummary> for FoldOffset {
1043    fn add_summary(&mut self, summary: &'a TransformSummary, _: &()) {
1044        self.0 += &summary.output.bytes;
1045    }
1046}
1047
1048impl<'a> sum_tree::Dimension<'a, TransformSummary> for Point {
1049    fn add_summary(&mut self, summary: &'a TransformSummary, _: &()) {
1050        *self += &summary.input.lines;
1051    }
1052}
1053
1054impl<'a> sum_tree::Dimension<'a, TransformSummary> for usize {
1055    fn add_summary(&mut self, summary: &'a TransformSummary, _: &()) {
1056        *self += &summary.input.bytes;
1057    }
1058}
1059
1060pub type FoldEdit = Edit<FoldOffset>;
1061
1062#[cfg(test)]
1063mod tests {
1064    use super::*;
1065    use crate::{MultiBuffer, ToPoint};
1066    use rand::prelude::*;
1067    use std::{env, mem};
1068    use text::RandomCharIter;
1069    use util::test::sample_text;
1070    use Bias::{Left, Right};
1071
1072    #[gpui::test]
1073    fn test_basic_folds(cx: &mut gpui::MutableAppContext) {
1074        let buffer = MultiBuffer::build_simple(&sample_text(5, 6, 'a'), cx);
1075        let subscription = buffer.update(cx, |buffer, _| buffer.subscribe());
1076        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1077        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1078
1079        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1080        let (snapshot2, edits) = writer.fold(vec![
1081            Point::new(0, 2)..Point::new(2, 2),
1082            Point::new(2, 4)..Point::new(4, 1),
1083        ]);
1084        assert_eq!(snapshot2.text(), "aa…cc…eeeee");
1085        assert_eq!(
1086            edits,
1087            &[
1088                FoldEdit {
1089                    old: FoldOffset(2)..FoldOffset(16),
1090                    new: FoldOffset(2)..FoldOffset(5),
1091                },
1092                FoldEdit {
1093                    old: FoldOffset(18)..FoldOffset(29),
1094                    new: FoldOffset(7)..FoldOffset(10)
1095                },
1096            ]
1097        );
1098
1099        let buffer_snapshot = buffer.update(cx, |buffer, cx| {
1100            buffer.edit(
1101                vec![
1102                    Point::new(0, 0)..Point::new(0, 1),
1103                    Point::new(2, 3)..Point::new(2, 3),
1104                ],
1105                "123",
1106                cx,
1107            );
1108            buffer.snapshot(cx)
1109        });
1110        let (snapshot3, edits) =
1111            map.read(buffer_snapshot.clone(), subscription.consume().into_inner());
1112        assert_eq!(snapshot3.text(), "123a…c123c…eeeee");
1113        assert_eq!(
1114            edits,
1115            &[
1116                FoldEdit {
1117                    old: FoldOffset(0)..FoldOffset(1),
1118                    new: FoldOffset(0)..FoldOffset(3),
1119                },
1120                FoldEdit {
1121                    old: FoldOffset(6)..FoldOffset(6),
1122                    new: FoldOffset(8)..FoldOffset(11),
1123                },
1124            ]
1125        );
1126
1127        let buffer_snapshot = buffer.update(cx, |buffer, cx| {
1128            buffer.edit(vec![Point::new(2, 6)..Point::new(4, 3)], "456", cx);
1129            buffer.snapshot(cx)
1130        });
1131        let (snapshot4, _) = map.read(buffer_snapshot.clone(), subscription.consume().into_inner());
1132        assert_eq!(snapshot4.text(), "123a…c123456eee");
1133
1134        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1135        writer.unfold(Some(Point::new(0, 4)..Point::new(0, 5)));
1136        let (snapshot5, _) = map.read(buffer_snapshot.clone(), vec![]);
1137        assert_eq!(snapshot5.text(), "123aaaaa\nbbbbbb\nccc123456eee");
1138    }
1139
1140    #[gpui::test]
1141    fn test_adjacent_folds(cx: &mut gpui::MutableAppContext) {
1142        let buffer = MultiBuffer::build_simple("abcdefghijkl", cx);
1143        let subscription = buffer.update(cx, |buffer, _| buffer.subscribe());
1144        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1145
1146        {
1147            let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1148
1149            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1150            writer.fold(vec![5..8]);
1151            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1152            assert_eq!(snapshot.text(), "abcde…ijkl");
1153
1154            // Create an fold adjacent to the start of the first fold.
1155            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1156            writer.fold(vec![0..1, 2..5]);
1157            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1158            assert_eq!(snapshot.text(), "…b…ijkl");
1159
1160            // Create an fold adjacent to the end of the first fold.
1161            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1162            writer.fold(vec![11..11, 8..10]);
1163            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1164            assert_eq!(snapshot.text(), "…b…kl");
1165        }
1166
1167        {
1168            let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1169
1170            // Create two adjacent folds.
1171            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1172            writer.fold(vec![0..2, 2..5]);
1173            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1174            assert_eq!(snapshot.text(), "…fghijkl");
1175
1176            // Edit within one of the folds.
1177            let buffer_snapshot = buffer.update(cx, |buffer, cx| {
1178                buffer.edit(vec![0..1], "12345", cx);
1179                buffer.snapshot(cx)
1180            });
1181            let (snapshot, _) =
1182                map.read(buffer_snapshot.clone(), subscription.consume().into_inner());
1183            assert_eq!(snapshot.text(), "12345…fghijkl");
1184        }
1185    }
1186
1187    #[gpui::test]
1188    fn test_overlapping_folds(cx: &mut gpui::MutableAppContext) {
1189        let buffer = MultiBuffer::build_simple(&sample_text(5, 6, 'a'), cx);
1190        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1191        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1192        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1193        writer.fold(vec![
1194            Point::new(0, 2)..Point::new(2, 2),
1195            Point::new(0, 4)..Point::new(1, 0),
1196            Point::new(1, 2)..Point::new(3, 2),
1197            Point::new(3, 1)..Point::new(4, 1),
1198        ]);
1199        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1200        assert_eq!(snapshot.text(), "aa…eeeee");
1201    }
1202
1203    #[gpui::test]
1204    fn test_merging_folds_via_edit(cx: &mut gpui::MutableAppContext) {
1205        let buffer = MultiBuffer::build_simple(&sample_text(5, 6, 'a'), cx);
1206        let subscription = buffer.update(cx, |buffer, _| buffer.subscribe());
1207        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1208        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1209
1210        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1211        writer.fold(vec![
1212            Point::new(0, 2)..Point::new(2, 2),
1213            Point::new(3, 1)..Point::new(4, 1),
1214        ]);
1215        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1216        assert_eq!(snapshot.text(), "aa…cccc\nd…eeeee");
1217
1218        let buffer_snapshot = buffer.update(cx, |buffer, cx| {
1219            buffer.edit(Some(Point::new(2, 2)..Point::new(3, 1)), "", cx);
1220            buffer.snapshot(cx)
1221        });
1222        let (snapshot, _) = map.read(buffer_snapshot.clone(), subscription.consume().into_inner());
1223        assert_eq!(snapshot.text(), "aa…eeeee");
1224    }
1225
1226    #[gpui::test]
1227    fn test_folds_in_range(cx: &mut gpui::MutableAppContext) {
1228        let buffer = MultiBuffer::build_simple(&sample_text(5, 6, 'a'), cx);
1229        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1230        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1231
1232        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1233        writer.fold(vec![
1234            Point::new(0, 2)..Point::new(2, 2),
1235            Point::new(0, 4)..Point::new(1, 0),
1236            Point::new(1, 2)..Point::new(3, 2),
1237            Point::new(3, 1)..Point::new(4, 1),
1238        ]);
1239        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1240        let fold_ranges = snapshot
1241            .folds_in_range(Point::new(1, 0)..Point::new(1, 3))
1242            .map(|fold| fold.start.to_point(&buffer_snapshot)..fold.end.to_point(&buffer_snapshot))
1243            .collect::<Vec<_>>();
1244        assert_eq!(
1245            fold_ranges,
1246            vec![
1247                Point::new(0, 2)..Point::new(2, 2),
1248                Point::new(1, 2)..Point::new(3, 2)
1249            ]
1250        );
1251    }
1252
1253    #[gpui::test(iterations = 100)]
1254    fn test_random_folds(cx: &mut gpui::MutableAppContext, mut rng: StdRng) {
1255        let operations = env::var("OPERATIONS")
1256            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
1257            .unwrap_or(10);
1258
1259        let len = rng.gen_range(0..10);
1260        let text = RandomCharIter::new(&mut rng).take(len).collect::<String>();
1261        let buffer = if rng.gen() {
1262            MultiBuffer::build_simple(&text, cx)
1263        } else {
1264            MultiBuffer::build_random(&mut rng, cx)
1265        };
1266        let mut buffer_snapshot = buffer.read(cx).snapshot(cx);
1267        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1268
1269        let (mut initial_snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1270        let mut snapshot_edits = Vec::new();
1271
1272        for _ in 0..operations {
1273            log::info!("text: {:?}", buffer_snapshot.text());
1274            let mut buffer_edits = Vec::new();
1275            match rng.gen_range(0..=100) {
1276                0..=59 => {
1277                    snapshot_edits.extend(map.randomly_mutate(&mut rng));
1278                }
1279                _ => buffer.update(cx, |buffer, cx| {
1280                    let subscription = buffer.subscribe();
1281                    let edit_count = rng.gen_range(1..=5);
1282                    buffer.randomly_edit(&mut rng, edit_count, cx);
1283                    buffer_snapshot = buffer.snapshot(cx);
1284                    let edits = subscription.consume().into_inner();
1285                    log::info!("editing {:?}", edits);
1286                    buffer_edits.extend(edits);
1287                }),
1288            };
1289
1290            let (snapshot, edits) = map.read(buffer_snapshot.clone(), buffer_edits);
1291            snapshot_edits.push((snapshot.clone(), edits));
1292
1293            let mut expected_text: String = buffer_snapshot.text().to_string();
1294            for fold_range in map.merged_fold_ranges().into_iter().rev() {
1295                expected_text.replace_range(fold_range.start..fold_range.end, "…");
1296            }
1297
1298            assert_eq!(snapshot.text(), expected_text);
1299            log::info!(
1300                "fold text {:?} ({} lines)",
1301                expected_text,
1302                expected_text.matches('\n').count() + 1
1303            );
1304
1305            let mut prev_row = 0;
1306            let mut expected_buffer_rows = Vec::new();
1307            for fold_range in map.merged_fold_ranges().into_iter() {
1308                let fold_start = buffer_snapshot.offset_to_point(fold_range.start).row;
1309                let fold_end = buffer_snapshot.offset_to_point(fold_range.end).row;
1310                expected_buffer_rows.extend(
1311                    buffer_snapshot
1312                        .buffer_rows(prev_row)
1313                        .take((1 + fold_start - prev_row) as usize),
1314                );
1315                prev_row = 1 + fold_end;
1316            }
1317            expected_buffer_rows.extend(buffer_snapshot.buffer_rows(prev_row));
1318
1319            assert_eq!(
1320                expected_buffer_rows.len(),
1321                expected_text.matches('\n').count() + 1,
1322                "wrong expected buffer rows {:?}. text: {:?}",
1323                expected_buffer_rows,
1324                expected_text
1325            );
1326
1327            for (output_row, line) in expected_text.lines().enumerate() {
1328                let line_len = snapshot.line_len(output_row as u32);
1329                assert_eq!(line_len, line.len() as u32);
1330            }
1331
1332            let longest_row = snapshot.longest_row();
1333            let longest_char_column = expected_text
1334                .split('\n')
1335                .nth(longest_row as usize)
1336                .unwrap()
1337                .chars()
1338                .count();
1339            let mut fold_point = FoldPoint::new(0, 0);
1340            let mut fold_offset = FoldOffset(0);
1341            let mut char_column = 0;
1342            for c in expected_text.chars() {
1343                let buffer_point = fold_point.to_buffer_point(&snapshot);
1344                let buffer_offset = buffer_point.to_offset(&buffer_snapshot);
1345                assert_eq!(
1346                    buffer_point.to_fold_point(&snapshot, Right),
1347                    fold_point,
1348                    "{:?} -> fold point",
1349                    buffer_point,
1350                );
1351                assert_eq!(
1352                    fold_point.to_buffer_offset(&snapshot),
1353                    buffer_offset,
1354                    "fold_point.to_buffer_offset({:?})",
1355                    fold_point,
1356                );
1357                assert_eq!(
1358                    fold_point.to_offset(&snapshot),
1359                    fold_offset,
1360                    "fold_point.to_offset({:?})",
1361                    fold_point,
1362                );
1363
1364                if c == '\n' {
1365                    *fold_point.row_mut() += 1;
1366                    *fold_point.column_mut() = 0;
1367                    char_column = 0;
1368                } else {
1369                    *fold_point.column_mut() += c.len_utf8() as u32;
1370                    char_column += 1;
1371                }
1372                fold_offset.0 += c.len_utf8();
1373                if char_column > longest_char_column {
1374                    panic!(
1375                        "invalid longest row {:?} (chars {}), found row {:?} (chars: {})",
1376                        longest_row,
1377                        longest_char_column,
1378                        fold_point.row(),
1379                        char_column
1380                    );
1381                }
1382            }
1383
1384            for _ in 0..5 {
1385                let mut start = snapshot
1386                    .clip_offset(FoldOffset(rng.gen_range(0..=snapshot.len().0)), Bias::Left);
1387                let mut end = snapshot
1388                    .clip_offset(FoldOffset(rng.gen_range(0..=snapshot.len().0)), Bias::Right);
1389                if start > end {
1390                    mem::swap(&mut start, &mut end);
1391                }
1392
1393                let text = &expected_text[start.0..end.0];
1394                assert_eq!(
1395                    snapshot
1396                        .chunks(start..end)
1397                        .map(|c| c.text)
1398                        .collect::<String>(),
1399                    text,
1400                );
1401            }
1402
1403            let mut fold_row = 0;
1404            while fold_row < expected_buffer_rows.len() as u32 {
1405                fold_row = snapshot
1406                    .clip_point(FoldPoint::new(fold_row, 0), Bias::Right)
1407                    .row();
1408                eprintln!("fold_row: {} of {}", fold_row, expected_buffer_rows.len());
1409                assert_eq!(
1410                    snapshot.buffer_rows(fold_row).collect::<Vec<_>>(),
1411                    expected_buffer_rows[(fold_row as usize)..],
1412                    "wrong buffer rows starting at fold row {}",
1413                    fold_row,
1414                );
1415                fold_row += 1;
1416            }
1417
1418            for fold_range in map.merged_fold_ranges() {
1419                let fold_point = fold_range
1420                    .start
1421                    .to_point(&buffer_snapshot)
1422                    .to_fold_point(&snapshot, Right);
1423                assert!(snapshot.is_line_folded(fold_point.row()));
1424            }
1425
1426            for _ in 0..5 {
1427                let end =
1428                    buffer_snapshot.clip_offset(rng.gen_range(0..=buffer_snapshot.len()), Right);
1429                let start = buffer_snapshot.clip_offset(rng.gen_range(0..=end), Left);
1430                let expected_folds = map
1431                    .folds
1432                    .items(&buffer_snapshot)
1433                    .into_iter()
1434                    .filter(|fold| {
1435                        let start = buffer_snapshot.anchor_before(start);
1436                        let end = buffer_snapshot.anchor_after(end);
1437                        start.cmp(&fold.0.end, &buffer_snapshot).unwrap() == Ordering::Less
1438                            && end.cmp(&fold.0.start, &buffer_snapshot).unwrap()
1439                                == Ordering::Greater
1440                    })
1441                    .map(|fold| fold.0)
1442                    .collect::<Vec<_>>();
1443
1444                assert_eq!(
1445                    snapshot
1446                        .folds_in_range(start..end)
1447                        .cloned()
1448                        .collect::<Vec<_>>(),
1449                    expected_folds
1450                );
1451            }
1452
1453            let text = snapshot.text();
1454            for _ in 0..5 {
1455                let start_row = rng.gen_range(0..=snapshot.max_point().row());
1456                let start_column = rng.gen_range(0..=snapshot.line_len(start_row));
1457                let end_row = rng.gen_range(0..=snapshot.max_point().row());
1458                let end_column = rng.gen_range(0..=snapshot.line_len(end_row));
1459                let mut start =
1460                    snapshot.clip_point(FoldPoint::new(start_row, start_column), Bias::Left);
1461                let mut end = snapshot.clip_point(FoldPoint::new(end_row, end_column), Bias::Right);
1462                if start > end {
1463                    mem::swap(&mut start, &mut end);
1464                }
1465
1466                let lines = start..end;
1467                let bytes = start.to_offset(&snapshot)..end.to_offset(&snapshot);
1468                assert_eq!(
1469                    snapshot.text_summary_for_range(lines),
1470                    TextSummary::from(&text[bytes.start.0..bytes.end.0])
1471                )
1472            }
1473
1474            let mut text = initial_snapshot.text();
1475            for (snapshot, edits) in snapshot_edits.drain(..) {
1476                let new_text = snapshot.text();
1477                for edit in edits {
1478                    let old_bytes = edit.new.start.0..edit.new.start.0 + edit.old_len().0;
1479                    let new_bytes = edit.new.start.0..edit.new.end.0;
1480                    text.replace_range(old_bytes, &new_text[new_bytes]);
1481                }
1482
1483                assert_eq!(text, new_text);
1484                initial_snapshot = snapshot;
1485            }
1486        }
1487    }
1488
1489    #[gpui::test]
1490    fn test_buffer_rows(cx: &mut gpui::MutableAppContext) {
1491        let text = sample_text(6, 6, 'a') + "\n";
1492        let buffer = MultiBuffer::build_simple(&text, cx);
1493
1494        let buffer_snapshot = buffer.read(cx).snapshot(cx);
1495        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
1496
1497        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
1498        writer.fold(vec![
1499            Point::new(0, 2)..Point::new(2, 2),
1500            Point::new(3, 1)..Point::new(4, 1),
1501        ]);
1502
1503        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
1504        assert_eq!(snapshot.text(), "aa…cccc\nd…eeeee\nffffff\n");
1505        assert_eq!(
1506            snapshot.buffer_rows(0).collect::<Vec<_>>(),
1507            [Some(0), Some(3), Some(5), Some(6)]
1508        );
1509        assert_eq!(snapshot.buffer_rows(3).collect::<Vec<_>>(), [Some(6)]);
1510    }
1511
1512    impl FoldMap {
1513        fn merged_fold_ranges(&self) -> Vec<Range<usize>> {
1514            let buffer = self.buffer.lock().clone();
1515            let mut folds = self.folds.items(&buffer);
1516            // Ensure sorting doesn't change how folds get merged and displayed.
1517            folds.sort_by(|a, b| a.0.cmp(&b.0, &buffer).unwrap());
1518            let mut fold_ranges = folds
1519                .iter()
1520                .map(|fold| fold.0.start.to_offset(&buffer)..fold.0.end.to_offset(&buffer))
1521                .peekable();
1522
1523            let mut merged_ranges = Vec::new();
1524            while let Some(mut fold_range) = fold_ranges.next() {
1525                while let Some(next_range) = fold_ranges.peek() {
1526                    if fold_range.end >= next_range.start {
1527                        if next_range.end > fold_range.end {
1528                            fold_range.end = next_range.end;
1529                        }
1530                        fold_ranges.next();
1531                    } else {
1532                        break;
1533                    }
1534                }
1535                if fold_range.end > fold_range.start {
1536                    merged_ranges.push(fold_range);
1537                }
1538            }
1539            merged_ranges
1540        }
1541
1542        pub fn randomly_mutate(
1543            &mut self,
1544            rng: &mut impl Rng,
1545        ) -> Vec<(FoldSnapshot, Vec<FoldEdit>)> {
1546            let mut snapshot_edits = Vec::new();
1547            match rng.gen_range(0..=100) {
1548                0..=39 if !self.folds.is_empty() => {
1549                    let buffer = self.buffer.lock().clone();
1550                    let mut to_unfold = Vec::new();
1551                    for _ in 0..rng.gen_range(1..=3) {
1552                        let end = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Right);
1553                        let start = buffer.clip_offset(rng.gen_range(0..=end), Left);
1554                        to_unfold.push(start..end);
1555                    }
1556                    log::info!("unfolding {:?}", to_unfold);
1557                    let (mut writer, snapshot, edits) = self.write(buffer, vec![]);
1558                    snapshot_edits.push((snapshot, edits));
1559                    let (snapshot, edits) = writer.fold(to_unfold);
1560                    snapshot_edits.push((snapshot, edits));
1561                }
1562                _ => {
1563                    let buffer = self.buffer.lock().clone();
1564                    let mut to_fold = Vec::new();
1565                    for _ in 0..rng.gen_range(1..=2) {
1566                        let end = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Right);
1567                        let start = buffer.clip_offset(rng.gen_range(0..=end), Left);
1568                        to_fold.push(start..end);
1569                    }
1570                    log::info!("folding {:?}", to_fold);
1571                    let (mut writer, snapshot, edits) = self.write(buffer, vec![]);
1572                    snapshot_edits.push((snapshot, edits));
1573                    let (snapshot, edits) = writer.fold(to_fold);
1574                    snapshot_edits.push((snapshot, edits));
1575                }
1576            }
1577            snapshot_edits
1578        }
1579    }
1580}