refactor findUserByDisplayName

src/shared/utils/__tests__/user.findByDisplayName.test.js

@@ -17,6 +17,19 @@ describe('findUserByDisplayName', () => {
         return map;
     }
 
+    function createDisplayNameIndex(entries) {
+        const index = new Map();
+        for (const entry of entries) {
+            let ids = index.get(entry.displayName);
+            if (!ids) {
+                ids = new Set();
+                index.set(entry.displayName, ids);
+            }
+            ids.add(entry.id);
+        }
+        return index;
+    }
+
     test('returns the user matching displayName', () => {
         const users = createCachedUsers([
             { id: 'usr_1', displayName: 'Alice' },
@@ -56,4 +69,31 @@ describe('findUserByDisplayName', () => {
         expect(findUserByDisplayName(users, 'alice')).toBeUndefined();
         expect(findUserByDisplayName(users, 'ALICE')).toBeUndefined();
     });
+
+    test('uses displayName index when provided', () => {
+        const entries = [
+            { id: 'usr_1', displayName: 'Alice' },
+            { id: 'usr_2', displayName: 'Bob' }
+        ];
+        const users = createCachedUsers(entries);
+        const index = createDisplayNameIndex(entries);
+
+        const result = findUserByDisplayName(users, 'Bob', index);
+
+        expect(result).toEqual({ id: 'usr_2', displayName: 'Bob' });
+    });
+
+    test('indexed lookup falls back to next duplicate when first user is missing', () => {
+        const entries = [
+            { id: 'usr_1', displayName: 'Alice' },
+            { id: 'usr_2', displayName: 'Alice' }
+        ];
+        const users = createCachedUsers(entries);
+        users.delete('usr_1');
+        const index = createDisplayNameIndex(entries);
+
+        const result = findUserByDisplayName(users, 'Alice', index);
+
+        expect(result).toEqual({ id: 'usr_2', displayName: 'Alice' });
+    });
 });

src/shared/utils/user.js

@@ -275,9 +275,23 @@ function userOnlineFor(ref) {
  * Find a user object from cachedUsers by displayName.
  * @param {Map} cachedUsers
  * @param {string} displayName
+ * @param {Map<string, Set<string>>} [cachedUserIdsByDisplayName]
  * @returns {object|undefined}
  */
-function findUserByDisplayName(cachedUsers, displayName) {
+function findUserByDisplayName(
+    cachedUsers,
+    displayName,
+    cachedUserIdsByDisplayName
+) {
+    const indexedUserIds = cachedUserIdsByDisplayName?.get(displayName);
+    if (indexedUserIds) {
+        for (const userId of indexedUserIds) {
+            const ref = cachedUsers.get(userId);
+            if (ref?.displayName === displayName) {
+                return ref;
+            }
+        }
+    }
     for (const ref of cachedUsers.values()) {
         if (ref.displayName === displayName) {
             return ref;