Merge pull request #500 from mynaparrot/improve

update reconciliation logic
mynaparrot · Aug 20, 2023 · 4d5980b · 4d5980b
2 parents a1f8d36 + 9a9c302
commit 4d5980b
Showing 1 changed file with 26 additions and 36 deletions.
diff --git a/src/components/whiteboard/helpers/reconciliation.ts b/src/components/whiteboard/helpers/reconciliation.ts
@@ -13,6 +13,14 @@ export type BroadcastedExcalidrawElement = ExcalidrawElement & {
   [PRECEDING_ELEMENT_KEY]?: string;
 };
 
+export const arrayToMapWithIndex = <T extends { id: string }>(
+  elements: readonly T[],
+) =>
+  elements.reduce((acc, element: T, idx) => {
+    acc.set(element.id, [element, idx]);
+    return acc;
+  }, new Map<string, [element: T, index: number]>());
+
 const shouldDiscardRemoteElement = (
   localAppState: AppState,
   local: ExcalidrawElement | undefined,
@@ -36,30 +44,13 @@ const shouldDiscardRemoteElement = (
   return false;
 };
 
-const getElementsMapWithIndex = <T extends ExcalidrawElement>(
-  elements: readonly T[],
-) =>
-  elements.reduce(
-    (
-      acc: {
-        [key: string]: [element: T, index: number] | undefined;
-      },
-      element: T,
-      idx,
-    ) => {
-      acc[element.id] = [element, idx];
-      return acc;
-    },
-    {},
-  );
-
 export const reconcileElements = (
   localElements: readonly ExcalidrawElement[],
   remoteElements: readonly BroadcastedExcalidrawElement[],
   localAppState: AppState,
 ): ReconciledElements => {
   const localElementsData =
-    getElementsMapWithIndex<ExcalidrawElement>(localElements);
+    arrayToMapWithIndex<ExcalidrawElement>(localElements);
 
   const reconciledElements: ExcalidrawElement[] = localElements.slice();
 
@@ -72,7 +63,7 @@ export const reconcileElements = (
   for (const remoteElement of remoteElements) {
     remoteElementIdx++;
 
-    const local = localElementsData[remoteElement.id];
+    const local = localElementsData.get(remoteElement.id);
 
     if (shouldDiscardRemoteElement(localAppState, local?.[0], remoteElement)) {
       if (remoteElement[PRECEDING_ELEMENT_KEY]) {
@@ -84,7 +75,7 @@ export const reconcileElements = (
 
     // Mark duplicate for removal as it'll be replaced with the remote element
     if (local) {
-      // Unless the ramote and local elements are the same element in which case
+      // Unless the remote and local elements are the same element in which case
       // we need to keep it as we'd otherwise discard it from the resulting
       // array.
       if (local[0] === remoteElement) {
@@ -108,61 +99,60 @@ export const reconcileElements = (
         offset++;
         if (cursor === 0) {
           reconciledElements.unshift(remoteElement);
-          localElementsData[remoteElement.id] = [
+          localElementsData.set(remoteElement.id, [
             remoteElement,
             cursor - offset,
-          ];
+          ]);
         } else {
           reconciledElements.splice(cursor + 1, 0, remoteElement);
-          localElementsData[remoteElement.id] = [
+          localElementsData.set(remoteElement.id, [
             remoteElement,
             cursor + 1 - offset,
-          ];
+          ]);
           cursor++;
         }
       } else {
-        let idx = localElementsData[parent]
-          ? //eslint-disable-next-line
-            localElementsData[parent]![1]
+        let idx = localElementsData.has(parent)
+          ? localElementsData.get(parent)![1]
           : null;
         if (idx != null) {
           idx += offset;
         }
         if (idx != null && idx >= cursor) {
           reconciledElements.splice(idx + 1, 0, remoteElement);
           offset++;
-          localElementsData[remoteElement.id] = [
+          localElementsData.set(remoteElement.id, [
             remoteElement,
             idx + 1 - offset,
-          ];
+          ]);
           cursor = idx + 1;
         } else if (idx != null) {
           reconciledElements.splice(cursor + 1, 0, remoteElement);
           offset++;
-          localElementsData[remoteElement.id] = [
+          localElementsData.set(remoteElement.id, [
             remoteElement,
             cursor + 1 - offset,
-          ];
+          ]);
           cursor++;
         } else {
           reconciledElements.push(remoteElement);
-          localElementsData[remoteElement.id] = [
+          localElementsData.set(remoteElement.id, [
             remoteElement,
             reconciledElements.length - 1 - offset,
-          ];
+          ]);
         }
       }
       // no parent z-index information, local element exists → replace in place
     } else if (local) {
       reconciledElements[local[1]] = remoteElement;
-      localElementsData[remoteElement.id] = [remoteElement, local[1]];
+      localElementsData.set(remoteElement.id, [remoteElement, local[1]]);
       // otherwise push to the end
     } else {
       reconciledElements.push(remoteElement);
-      localElementsData[remoteElement.id] = [
+      localElementsData.set(remoteElement.id, [
         remoteElement,
         reconciledElements.length - 1 - offset,
-      ];
+      ]);
     }
   }