Minimum implementation to handle global resume tokens

Author: wilhuff

packages/firestore/src/remote/watch_change.ts

@@ -297,7 +297,7 @@ export class WatchChangeAggregator {
 
   /** Processes and adds the WatchTargetChange to the current set of changes. */
   handleTargetChange(targetChange: WatchTargetChange): void {
-    targetChange.targetIds.forEach(targetId => {
+    this.forEachTargetId(targetChange, targetId => {
       const targetState = this.ensureTargetState(targetId);
       switch (targetChange.state) {
         case WatchTargetChangeState.NoChange:
@@ -352,6 +352,24 @@ export class WatchChangeAggregator {
     });
   }
 
+  /**
+   * Iterates over all targetIds that the watch change applies to: either the
+   * targetIds explicitly listed in the change or the targetIds of all currently
+   * active targets.
+   */
+  forEachTargetId(
+    targetChange: WatchTargetChange,
+    fn: (targetId: TargetId) => void
+  ): void {
+    if (targetChange.targetIds.length > 0) {
+      targetChange.targetIds.forEach(fn);
+    } else {
+      objUtils.forEachNumber(this.targetStates, (targetId, _) => {
+        fn(targetId);
+      });
+    }
+  }
+
   /**
    * Handles existence filters and synthesizes deletes for filter mismatches.
    * Targets that are invalidated by filter mismatches are added to