Perf cache WASM text toDelta result (#378)

* refactor: make cursor transformation in undo/redo better

* chore: add release info

* perf: cache to_delta value in wasm

* chore: release msg

.changeset/strange-mirrors-visit.md

@@ -0,0 +1,6 @@
+---
+"loro-wasm": patch
+"loro-crdt": patch
+---
+
+Perf(wasm) cache text.toDelta

crates/loro-internal/src/event.rs

@@ -4,7 +4,6 @@ use itertools::Itertools;
 use loro_delta::{array_vec::ArrayVec, delta_trait::DeltaAttr, DeltaItem, DeltaRope};
 use serde::{Deserialize, Serialize};
 use smallvec::SmallVec;
-use tracing::trace;
 
 use crate::{
     container::richtext::richtext_state::RichtextStateChunk,
@@ -457,12 +456,11 @@ impl Diff {
 
     /// Transform the cursor based on this diff
     pub(crate) fn transform_cursor(&self, pos: usize, left_prior: bool) -> usize {
-        let ans = match self {
+        match self {
             Diff::List(list) => list.transform_pos(pos, left_prior),
             Diff::Text(text) => text.transform_pos(pos, left_prior),
             _ => pos,
-        };
-        ans
+        }
     }
 }
 

crates/loro-internal/src/handler.rs

@@ -1186,6 +1186,20 @@ impl TextHandler {
         }
     }
 
+    /// Get the version id of the richtext
+    ///
+    /// This can be used to detect whether the richtext is changed
+    pub fn version_id(&self) -> usize {
+        match &self.inner {
+            MaybeDetached::Detached(_) => {
+                unimplemented!("Detached text container does not have version id")
+            }
+            MaybeDetached::Attached(a) => {
+                a.with_state(|state| state.as_richtext_state_mut().unwrap().get_version_id())
+            }
+        }
+    }
+
     pub fn get_richtext_value(&self) -> LoroValue {
         match &self.inner {
             MaybeDetached::Detached(t) => {

crates/loro-internal/src/state/richtext_state.rs

@@ -37,7 +37,10 @@ use super::ContainerState;
 pub struct RichtextState {
     idx: ContainerIdx,
     config: Arc<RwLock<StyleConfigMap>>,
-    pub(crate) state: LazyLoad<RichtextStateLoader, InnerState>,
+    state: LazyLoad<RichtextStateLoader, InnerState>,
+    /// This is used to indicate whether the richtext state is changed, so the downstream has an easy way to cache
+    /// NOTE: We need to ensure the invariance that the version id is always increased when the richtext state is changed
+    version_id: usize,
 }
 
 struct Pos {
@@ -52,9 +55,23 @@ impl RichtextState {
             idx,
             config,
             state: LazyLoad::Src(Default::default()),
+            version_id: 0,
         }
     }
 
+    #[inline]
+    fn update_version(&mut self) {
+        self.version_id = self.version_id.wrapping_add(1);
+    }
+
+    /// Get the version id of the richtext
+    ///
+    /// This can be used to detect whether the richtext is changed
+    #[inline]
+    pub fn get_version_id(&self) -> usize {
+        self.version_id
+    }
+
     /// Get the text content of the richtext
     ///
     /// This uses `mut` because we may need to build the state from snapshot
@@ -84,6 +101,7 @@ impl RichtextState {
         style_starts: &mut FxHashMap<Arc<StyleOp>, Pos>,
         style: &Arc<StyleOp>,
     ) -> Pos {
+        self.update_version();
         match style_starts.remove(style) {
             Some(x) => x,
             None => {
@@ -213,6 +231,7 @@ impl Clone for RichtextState {
             idx: self.idx,
             config: self.config.clone(),
             state: self.state.clone(),
+            version_id: self.version_id,
         }
     }
 }
@@ -244,6 +263,7 @@ impl ContainerState for RichtextState {
         _txn: &Weak<Mutex<Option<Transaction>>>,
         _state: &Weak<Mutex<DocState>>,
     ) -> Diff {
+        self.update_version();
         let InternalDiff::RichtextRaw(richtext) = diff else {
             unreachable!()
         };
@@ -425,6 +445,7 @@ impl ContainerState for RichtextState {
         _txn: &Weak<Mutex<Option<Transaction>>>,
         _state: &Weak<Mutex<DocState>>,
     ) {
+        self.update_version();
         let InternalDiff::RichtextRaw(richtext) = diff else {
             unreachable!()
         };
@@ -511,6 +532,7 @@ impl ContainerState for RichtextState {
     }
 
     fn apply_local_op(&mut self, r_op: &RawOp, op: &Op) -> LoroResult<()> {
+        self.update_version();
         match &op.content {
             crate::op::InnerContent::List(l) => match l {
                 list_op::InnerListOp::Insert { slice: _, pos: _ } => {
@@ -634,6 +656,7 @@ impl ContainerState for RichtextState {
 
     #[doc = " Restore the state to the state represented by the ops that exported by `get_snapshot_ops`"]
     fn import_from_snapshot_ops(&mut self, ctx: StateSnapshotDecodeContext) {
+        self.update_version();
         assert_eq!(ctx.mode, EncodeMode::Snapshot);
         let mut loader = RichtextStateLoader::default();
         let mut id_to_style = FxHashMap::default();

crates/loro-internal/src/undo.rs

@@ -735,7 +735,7 @@ pub(crate) fn undo(
                 let next = if i + 1 < spans.len() {
                     spans[i + 1].0.id_last().into()
                 } else {
-                    match last_frontiers_or_last_bi.clone() {
+                    match last_frontiers_or_last_bi {
                         Either::Left(last_frontiers) => last_frontiers.clone(),
                         Either::Right(right) => break 'block right,
                     }

crates/loro-wasm/src/convert.rs

@@ -316,7 +316,12 @@ fn map_delta_to_js(value: &ResolvedMapDelta, doc: &Arc<LoroDoc>) -> JsValue {
 
 pub(crate) fn handler_to_js_value(handler: Handler, doc: Option<Arc<LoroDoc>>) -> JsValue {
     match handler {
-        Handler::Text(t) => LoroText { handler: t, doc }.into(),
+        Handler::Text(t) => LoroText {
+            handler: t,
+            doc,
+            delta_cache: None,
+        }
+        .into(),
         Handler::Map(m) => LoroMap { handler: m, doc }.into(),
         Handler::List(l) => LoroList { handler: l, doc }.into(),
         Handler::Tree(t) => LoroTree { handler: t, doc }.into(),

crates/loro-wasm/src/lib.rs

@@ -588,6 +588,7 @@ impl Loro {
         Ok(LoroText {
             handler: text,
             doc: Some(self.0.clone()),
+            delta_cache: None,
         })
     }
 
@@ -721,6 +722,7 @@ impl Loro {
                 LoroText {
                     handler: richtext,
                     doc: Some(self.0.clone()),
+                    delta_cache: None,
                 }
                 .into()
             }
@@ -1348,6 +1350,7 @@ fn convert_container_path_to_js_value(path: &[(ContainerID, Index)]) -> JsValue
 pub struct LoroText {
     handler: TextHandler,
     doc: Option<Arc<LoroDoc>>,
+    delta_cache: Option<(usize, JsValue)>,
 }
 
 #[derive(Serialize, Deserialize)]
@@ -1367,6 +1370,7 @@ impl LoroText {
         Self {
             handler: TextHandler::new_detached(),
             doc: None,
+            delta_cache: None,
         }
     }
 
@@ -1480,10 +1484,19 @@ impl LoroText {
     /// console.log(text.toDelta());  // [ { insert: 'Hello', attributes: { bold: true } } ]
     /// ```
     #[wasm_bindgen(js_name = "toDelta")]
-    pub fn to_delta(&self) -> JsStringDelta {
+    pub fn to_delta(&mut self) -> JsStringDelta {
+        let version = self.handler.version_id();
+        if let Some((v, delta)) = self.delta_cache.as_ref() {
+            if *v == version {
+                return delta.clone().into();
+            }
+        }
+
         let delta = self.handler.get_richtext_value();
         let value: JsValue = delta.into();
-        value.into()
+        let ans: JsStringDelta = value.clone().into();
+        self.delta_cache = Some((version, value));
+        ans
     }
 
     /// Get the container id of the text.