WIP - maintain foldmap with Buffer::edits_since

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/text/src/patch.rs

@@ -0,0 +1,537 @@
+use crate::Edit;
+use std::{
+    cmp, mem,
+    ops::{Add, AddAssign, Sub},
+};
+
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
+pub struct Patch<T>(Vec<Edit<T>>);
+
+impl<T> Patch<T>
+where
+    T: Clone
+        + Copy
+        + Ord
+        + Sub<T, Output = T>
+        + Add<T, Output = T>
+        + AddAssign
+        + Default
+        + PartialEq,
+{
+    pub unsafe fn new_unchecked(edits: Vec<Edit<T>>) -> Self {
+        Self(edits)
+    }
+
+    pub fn new(edits: Vec<Edit<T>>) -> Self {
+        let mut last_edit: Option<&Edit<T>> = None;
+        for edit in &edits {
+            if let Some(last_edit) = last_edit {
+                assert!(edit.old.start > last_edit.old.end);
+                assert!(edit.new.start > last_edit.new.end);
+            }
+            last_edit = Some(edit);
+        }
+        Self(edits)
+    }
+
+    pub fn into_inner(self) -> Vec<Edit<T>> {
+        self.0
+    }
+
+    pub fn compose(&self, other: &Self) -> Self {
+        let mut old_edits_iter = self.0.iter().cloned().peekable();
+        let mut new_edits_iter = other.0.iter().cloned().peekable();
+        let mut composed = Patch(Vec::new());
+
+        let mut old_start = T::default();
+        let mut new_start = T::default();
+        loop {
+            let old_edit = old_edits_iter.peek_mut();
+            let new_edit = new_edits_iter.peek_mut();
+
+            // Push the old edit if its new end is before the new edit's old start.
+            if let Some(old_edit) = old_edit.as_ref() {
+                let new_edit = new_edit.as_ref();
+                if new_edit.map_or(true, |new_edit| old_edit.new.end < new_edit.old.start) {
+                    let catchup = old_edit.old.start - old_start;
+                    old_start += catchup;
+                    new_start += catchup;
+
+                    let old_end = old_start + old_edit.old_len();
+                    let new_end = new_start + old_edit.new_len();
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+                    old_start = old_end;
+                    new_start = new_end;
+                    old_edits_iter.next();
+                    continue;
+                }
+            }
+
+            // Push the new edit if its old end is before the old edit's new start.
+            if let Some(new_edit) = new_edit.as_ref() {
+                let old_edit = old_edit.as_ref();
+                if old_edit.map_or(true, |old_edit| new_edit.old.end < old_edit.new.start) {
+                    let catchup = new_edit.new.start - new_start;
+                    old_start += catchup;
+                    new_start += catchup;
+
+                    let old_end = old_start + new_edit.old_len();
+                    let new_end = new_start + new_edit.new_len();
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+                    old_start = old_end;
+                    new_start = new_end;
+                    new_edits_iter.next();
+                    continue;
+                }
+            }
+
+            // If we still have edits by this point then they must intersect, so we compose them.
+            if let Some((old_edit, new_edit)) = old_edit.zip(new_edit) {
+                if old_edit.new.start < new_edit.old.start {
+                    let catchup = old_edit.old.start - old_start;
+                    old_start += catchup;
+                    new_start += catchup;
+
+                    let overshoot = new_edit.old.start - old_edit.new.start;
+                    let old_end = cmp::min(old_start + overshoot, old_edit.old.end);
+                    let new_end = new_start + overshoot;
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+
+                    old_edit.old.start += overshoot;
+                    old_edit.new.start += overshoot;
+                    old_start = old_end;
+                    new_start = new_end;
+                } else {
+                    let catchup = new_edit.new.start - new_start;
+                    old_start += catchup;
+                    new_start += catchup;
+
+                    let overshoot = old_edit.new.start - new_edit.old.start;
+                    let old_end = old_start + overshoot;
+                    let new_end = cmp::min(new_start + overshoot, new_edit.new.end);
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+
+                    new_edit.old.start += overshoot;
+                    new_edit.new.start += overshoot;
+                    old_start = old_end;
+                    new_start = new_end;
+                }
+
+                if old_edit.new.end > new_edit.old.end {
+                    let old_end = old_start + cmp::min(old_edit.old_len(), new_edit.old_len());
+                    let new_end = new_start + new_edit.new_len();
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+
+                    old_edit.old.start = old_end;
+                    old_edit.new.start = new_edit.old.end;
+                    old_start = old_end;
+                    new_start = new_end;
+                    new_edits_iter.next();
+                } else {
+                    let old_end = old_start + old_edit.old_len();
+                    let new_end = new_start + cmp::min(old_edit.new_len(), new_edit.new_len());
+                    composed.push(Edit {
+                        old: old_start..old_end,
+                        new: new_start..new_end,
+                    });
+
+                    new_edit.old.start = old_edit.new.end;
+                    new_edit.new.start = new_end;
+                    old_start = old_end;
+                    new_start = new_end;
+                    old_edits_iter.next();
+                }
+            } else {
+                break;
+            }
+        }
+
+        composed
+    }
+
+    pub fn invert(&mut self) -> &mut Self {
+        for edit in &mut self.0 {
+            mem::swap(&mut edit.old, &mut edit.new);
+        }
+        self
+    }
+
+    pub fn clear(&mut self) {
+        self.0.clear();
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    fn push(&mut self, edit: Edit<T>) {
+        if edit.is_empty() {
+            return;
+        }
+
+        if let Some(last) = self.0.last_mut() {
+            if last.old.end >= edit.old.start {
+                last.old.end = edit.old.end;
+                last.new.end = edit.new.end;
+            } else {
+                self.0.push(edit);
+            }
+        } else {
+            self.0.push(edit);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rand::prelude::*;
+    use std::env;
+
+    #[gpui::test]
+    fn test_one_disjoint_edit() {
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 1..3,
+                new: 1..4,
+            }]),
+            Patch(vec![Edit {
+                old: 0..0,
+                new: 0..4,
+            }]),
+            Patch(vec![
+                Edit {
+                    old: 0..0,
+                    new: 0..4,
+                },
+                Edit {
+                    old: 1..3,
+                    new: 5..8,
+                },
+            ]),
+        );
+
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 1..3,
+                new: 1..4,
+            }]),
+            Patch(vec![Edit {
+                old: 5..9,
+                new: 5..7,
+            }]),
+            Patch(vec![
+                Edit {
+                    old: 1..3,
+                    new: 1..4,
+                },
+                Edit {
+                    old: 4..8,
+                    new: 5..7,
+                },
+            ]),
+        );
+    }
+
+    #[gpui::test]
+    fn test_one_overlapping_edit() {
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 1..3,
+                new: 1..4,
+            }]),
+            Patch(vec![Edit {
+                old: 3..5,
+                new: 3..6,
+            }]),
+            Patch(vec![Edit {
+                old: 1..4,
+                new: 1..6,
+            }]),
+        );
+    }
+
+    #[gpui::test]
+    fn test_two_disjoint_and_overlapping() {
+        assert_patch_composition(
+            Patch(vec![
+                Edit {
+                    old: 1..3,
+                    new: 1..4,
+                },
+                Edit {
+                    old: 8..12,
+                    new: 9..11,
+                },
+            ]),
+            Patch(vec![
+                Edit {
+                    old: 0..0,
+                    new: 0..4,
+                },
+                Edit {
+                    old: 3..10,
+                    new: 7..9,
+                },
+            ]),
+            Patch(vec![
+                Edit {
+                    old: 0..0,
+                    new: 0..4,
+                },
+                Edit {
+                    old: 1..12,
+                    new: 5..10,
+                },
+            ]),
+        );
+    }
+
+    #[gpui::test]
+    fn test_two_new_edits_overlapping_one_old_edit() {
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 0..0,
+                new: 0..3,
+            }]),
+            Patch(vec![
+                Edit {
+                    old: 0..0,
+                    new: 0..1,
+                },
+                Edit {
+                    old: 1..2,
+                    new: 2..2,
+                },
+            ]),
+            Patch(vec![Edit {
+                old: 0..0,
+                new: 0..3,
+            }]),
+        );
+
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 2..3,
+                new: 2..4,
+            }]),
+            Patch(vec![
+                Edit {
+                    old: 0..2,
+                    new: 0..1,
+                },
+                Edit {
+                    old: 3..3,
+                    new: 2..5,
+                },
+            ]),
+            Patch(vec![Edit {
+                old: 0..3,
+                new: 0..6,
+            }]),
+        );
+
+        assert_patch_composition(
+            Patch(vec![Edit {
+                old: 0..0,
+                new: 0..2,
+            }]),
+            Patch(vec![
+                Edit {
+                    old: 0..0,
+                    new: 0..2,
+                },
+                Edit {
+                    old: 2..5,
+                    new: 4..4,
+                },
+            ]),
+            Patch(vec![Edit {
+                old: 0..3,
+                new: 0..4,
+            }]),
+        );
+    }
+
+    // #[test]
+    // fn test_compose_edits() {
+    //     assert_eq!(
+    //         compose_edits(
+    //             &Edit {
+    //                 old: 3..3,
+    //                 new: 3..6,
+    //             },
+    //             &Edit {
+    //                 old: 2..7,
+    //                 new: 2..4,
+    //             },
+    //         ),
+    //         Edit {
+    //             old: 2..4,
+    //             new: 2..4
+    //         }
+    //     );
+    // }
+
+    #[gpui::test]
+    fn test_two_new_edits_touching_one_old_edit() {
+        assert_patch_composition(
+            Patch(vec![
+                Edit {
+                    old: 2..3,
+                    new: 2..4,
+                },
+                Edit {
+                    old: 7..7,
+                    new: 8..11,
+                },
+            ]),
+            Patch(vec![
+                Edit {
+                    old: 2..3,
+                    new: 2..2,
+                },
+                Edit {
+                    old: 4..4,
+                    new: 3..4,
+                },
+            ]),
+            Patch(vec![
+                Edit {
+                    old: 2..3,
+                    new: 2..4,
+                },
+                Edit {
+                    old: 7..7,
+                    new: 8..11,
+                },
+            ]),
+        );
+    }
+
+    #[gpui::test(iterations = 100)]
+    fn test_random_patch_compositions(mut rng: StdRng) {
+        let operations = env::var("OPERATIONS")
+            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
+            .unwrap_or(20);
+
+        let initial_chars = (0..rng.gen_range(0..=100))
+            .map(|_| rng.gen_range(b'a'..=b'z') as char)
+            .collect::<Vec<_>>();
+        log::info!("initial chars: {:?}", initial_chars);
+
+        // Generate two sequential patches
+        let mut patches = Vec::new();
+        let mut expected_chars = initial_chars.clone();
+        for i in 0..2 {
+            log::info!("patch {}:", i);
+
+            let mut delta = 0i32;
+            let mut last_edit_end = 0;
+            let mut edits = Vec::new();
+
+            for _ in 0..operations {
+                if last_edit_end >= expected_chars.len() {
+                    break;
+                }
+
+                let end = rng.gen_range(last_edit_end..=expected_chars.len());
+                let start = rng.gen_range(last_edit_end..=end);
+                let old_len = end - start;
+
+                let mut new_len = rng.gen_range(0..=3);
+                if start == end && new_len == 0 {
+                    new_len += 1;
+                }
+
+                last_edit_end = start + new_len + 1;
+
+                let new_chars = (0..new_len)
+                    .map(|_| rng.gen_range(b'A'..=b'Z') as char)
+                    .collect::<Vec<_>>();
+                log::info!(
+                    "  editing {:?}: {:?}",
+                    start..end,
+                    new_chars.iter().collect::<String>()
+                );
+                edits.push(Edit {
+                    old: (start as i32 - delta) as u32..(end as i32 - delta) as u32,
+                    new: start as u32..(start + new_len) as u32,
+                });
+                expected_chars.splice(start..end, new_chars);
+
+                delta += new_len as i32 - old_len as i32;
+            }
+
+            patches.push(Patch(edits));
+        }
+
+        log::info!("old patch: {:?}", &patches[0]);
+        log::info!("new patch: {:?}", &patches[1]);
+        log::info!("initial chars: {:?}", initial_chars);
+        log::info!("final chars: {:?}", expected_chars);
+
+        // Compose the patches, and verify that it has the same effect as applying the
+        // two patches separately.
+        let composed = patches[0].compose(&patches[1]);
+        log::info!("composed patch: {:?}", &composed);
+
+        let mut actual_chars = initial_chars.clone();
+        for edit in composed.0 {
+            actual_chars.splice(
+                edit.new.start as usize..edit.new.start as usize + edit.old.len(),
+                expected_chars[edit.new.start as usize..edit.new.end as usize]
+                    .iter()
+                    .copied(),
+            );
+        }
+
+        assert_eq!(actual_chars, expected_chars);
+    }
+
+    #[track_caller]
+    fn assert_patch_composition(old: Patch<u32>, new: Patch<u32>, composed: Patch<u32>) {
+        let original = ('a'..'z').collect::<Vec<_>>();
+        let inserted = ('A'..'Z').collect::<Vec<_>>();
+
+        let mut expected = original.clone();
+        apply_patch(&mut expected, &old, &inserted);
+        apply_patch(&mut expected, &new, &inserted);
+
+        let mut actual = original.clone();
+        apply_patch(&mut actual, &composed, &expected);
+        assert_eq!(
+            actual.into_iter().collect::<String>(),
+            expected.into_iter().collect::<String>(),
+            "expected patch is incorrect"
+        );
+
+        assert_eq!(old.compose(&new), composed);
+    }
+
+    fn apply_patch(text: &mut Vec<char>, patch: &Patch<u32>, new_text: &[char]) {
+        for edit in patch.0.iter().rev() {
+            text.splice(
+                edit.old.start as usize..edit.old.end as usize,
+                new_text[edit.new.start as usize..edit.new.end as usize]
+                    .iter()
+                    .copied(),
+            );
+        }
+    }
+}

crates/text/src/text.rs

@@ -1,5 +1,6 @@
 mod anchor;
 mod operation_queue;
+mod patch;
 mod point;
 mod point_utf16;
 #[cfg(any(test, feature = "test-support"))]
@@ -14,6 +15,7 @@ use anyhow::{anyhow, Result};
 use clock::ReplicaId;
 use collections::{HashMap, HashSet};
 use operation_queue::OperationQueue;
+pub use patch::Patch;
 pub use point::*;
 pub use point_utf16::*;
 #[cfg(any(test, feature = "test-support"))]
@@ -24,7 +26,7 @@ pub use selection::*;
 use std::{
     cmp::{self, Reverse},
     iter::Iterator,
-    ops::{self, Deref, Range},
+    ops::{self, Deref, Range, Sub},
     str,
     sync::Arc,
     time::{Duration, Instant},
@@ -307,6 +309,23 @@ pub struct Edit<D> {
     pub new: Range<D>,
 }
 
+impl<D> Edit<D>
+where
+    D: Sub<D, Output = D> + PartialEq + Copy,
+{
+    pub fn old_len(&self) -> D {
+        self.old.end - self.old.start
+    }
+
+    pub fn new_len(&self) -> D {
+        self.new.end - self.new.start
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.old.start == self.old.end && self.new.start == self.new.end
+    }
+}
+
 impl<D1, D2> Edit<(D1, D2)> {
     pub fn flatten(self) -> (Edit<D1>, Edit<D2>) {
         (