WIP

crates/editor/src/display_map.rs

@@ -1,5 +1,6 @@
 mod block_map;
 mod fold_map;
+mod patch;
 mod tab_map;
 mod wrap_map;
 

crates/editor/src/display_map/patch.rs

@@ -0,0 +1,138 @@
+use std::mem;
+
+type Edit = buffer::Edit<u32>;
+
+#[derive(Default, Debug)]
+struct Patch(Vec<Edit>);
+
+impl Patch {
+    fn compose(&self, new: &Self) -> Patch {
+        let mut composed = Vec::new();
+        let mut new_edits = new.0.iter().cloned().peekable();
+        let mut old_delta = 0;
+        let mut new_delta = 0;
+        for mut old_edit in self.0.iter().cloned() {
+            let mut next_new_delta = new_delta;
+            while let Some(mut new_edit) = new_edits.peek().cloned() {
+                let new_edit_delta = new_edit.new.len() as i32 - new_edit.old.len() as i32;
+                if new_edit.old.end < old_edit.new.start {
+                    new_edit.old.start = (new_edit.old.start as i32 - old_delta) as u32;
+                    new_edit.old.end = (new_edit.old.end as i32 - old_delta) as u32;
+                    new_edits.next();
+                    new_delta += new_edit_delta;
+                    next_new_delta += new_edit_delta;
+                    composed.push(new_edit);
+                } else if new_edit.old.start <= old_edit.new.end {
+                    if new_edit.old.start < old_edit.new.start {
+                        old_edit.old.start -= old_edit.new.start - new_edit.old.start;
+                        old_edit.new.start = new_edit.new.start;
+                    }
+                    if new_edit.old.end > old_edit.new.end {
+                        old_edit.old.end += new_edit.old.end - old_edit.new.end;
+                        old_edit.new.end = new_edit.old.end;
+                    }
+
+                    old_edit.new.end = (old_edit.new.end as i32 + new_edit_delta) as u32;
+                    new_edits.next();
+                    next_new_delta += new_edit_delta;
+                } else {
+                    break;
+                }
+            }
+
+            old_edit.new.start = (old_edit.new.start as i32 + new_delta) as u32;
+            old_edit.new.end = (old_edit.new.end as i32 + new_delta) as u32;
+            old_delta += old_edit.new.len() as i32 - old_edit.old.len() as i32;
+            new_delta = next_new_delta;
+            composed.push(old_edit);
+        }
+        composed.extend(new_edits.map(|mut new_edit| {
+            new_edit.old.start = (new_edit.old.start as i32 - old_delta) as u32;
+            new_edit.old.end = (new_edit.old.end as i32 - old_delta) as u32;
+            new_edit
+        }));
+
+        Patch(composed)
+    }
+
+    fn invert(&mut self) -> &mut Self {
+        for edit in &mut self.0 {
+            mem::swap(&mut edit.old, &mut edit.new);
+        }
+        self
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rand::prelude::*;
+    use std::env;
+
+    #[gpui::test(iterations = 1000, seed = 28)]
+    fn test_random(mut rng: StdRng) {
+        let operations = env::var("OPERATIONS")
+            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
+            .unwrap_or(3);
+
+        let initial_chars = (0..rng.gen_range(0..=5))
+            .map(|_| rng.gen_range(b'a'..=b'z') as char)
+            .collect::<Vec<_>>();
+        let mut final_chars = initial_chars.clone();
+        let mut patches = Vec::new();
+
+        println!("initial chars: {:?}", initial_chars);
+        for _ in 0..operations {
+            let end = rng.gen_range(0..=final_chars.len());
+            let start = rng.gen_range(0..=end);
+            let mut len = rng.gen_range(0..=3);
+            if start == end && len == 0 {
+                len += 1;
+            }
+            let new_chars = (0..len)
+                .map(|_| rng.gen_range(b'a'..=b'z') as char)
+                .collect::<Vec<_>>();
+            println!(
+                "editing {:?}: {:?}",
+                start..end,
+                new_chars.iter().collect::<String>()
+            );
+
+            let patch = Patch(vec![Edit {
+                old: start as u32..end as u32,
+                new: start as u32..start as u32 + new_chars.len() as u32,
+            }]);
+            if patches.is_empty() || rng.gen() {
+                println!("pushing singleton patch: {:?}", patch.0);
+                patches.push(patch);
+            } else {
+                let patch = patches.pop().unwrap().compose(&patch);
+                println!("composed patches: {:?}", patch.0);
+                patches.push(patch);
+            }
+            final_chars.splice(start..end, new_chars);
+        }
+
+        println!("final chars: {:?}", final_chars);
+        println!("final patches: {:?}", patches);
+
+        let mut composed = Patch::default();
+        for patch in patches {
+            println!("composing patches {:?} and {:?}", composed, patch);
+            composed = composed.compose(&patch);
+            println!("composed {:?}", composed);
+        }
+        println!("composed edits: {:?}", composed);
+        let mut chars = initial_chars.clone();
+        for edit in composed.0 {
+            chars.splice(
+                edit.new.start as usize..edit.new.start as usize + edit.old.len(),
+                final_chars[edit.new.start as usize..edit.new.end as usize]
+                    .iter()
+                    .copied(),
+            );
+        }
+
+        assert_eq!(chars, final_chars);
+    }
+}

crates/editor/src/display_map/wrap_map.rs

@@ -361,6 +361,55 @@ impl Patch {
         // self.ranges = new_ranges;
     }
 
+    fn compose2(&self, new: &Self) -> Patch {
+        let mut composed = Vec::new();
+        let mut new_edits = new.0.iter().cloned().peekable();
+        let mut old_delta = 0;
+        let mut new_delta = 0;
+        for mut old_edit in self.0.iter().cloned() {
+            let mut next_new_delta = new_delta;
+            while let Some(mut new_edit) = new_edits.peek().cloned() {
+                let new_edit_delta = new_edit.new.len() as i32 - new_edit.old.len() as i32;
+                if new_edit.old.end < old_edit.new.start {
+                    new_edit.old.start = (new_edit.old.start as i32 - old_delta) as u32;
+                    new_edit.old.end = (new_edit.old.end as i32 - old_delta) as u32;
+                    new_edits.next();
+                    new_delta += new_edit_delta;
+                    next_new_delta += new_edit_delta;
+                    composed.push(new_edit);
+                } else if new_edit.old.start <= old_edit.new.end {
+                    if new_edit.old.start < old_edit.new.start {
+                        old_edit.old.start -= old_edit.new.start - new_edit.old.start;
+                        old_edit.new.start = new_edit.new.start;
+                    }
+                    if new_edit.old.end > old_edit.new.end {
+                        old_edit.old.end += new_edit.old.end - old_edit.new.end;
+                        old_edit.new.end = new_edit.old.end;
+                    }
+
+                    old_edit.new.end = (old_edit.new.end as i32 + new_edit_delta) as u32;
+                    new_edits.next();
+                    next_new_delta += new_edit_delta;
+                } else {
+                    break;
+                }
+            }
+
+            old_edit.new.start = (old_edit.new.start as i32 + new_delta) as u32;
+            old_edit.new.end = (old_edit.new.end as i32 + new_delta) as u32;
+            old_delta += old_edit.new.len() as i32 - old_edit.old.len() as i32;
+            new_delta = next_new_delta;
+            composed.push(old_edit);
+        }
+        composed.extend(new_edits.map(|mut new_edit| {
+            new_edit.old.start = (new_edit.old.start as i32 - old_delta) as u32;
+            new_edit.old.end = (new_edit.old.end as i32 - old_delta) as u32;
+            new_edit
+        }));
+
+        Patch(composed)
+    }
+
     fn invert(&mut self) -> &mut Self {
         for edit in &mut self.0 {
             mem::swap(&mut edit.old, &mut edit.new);