Modify functions emulator to invoke RTDB emulator triggers

src/emulator/constants.ts

@@ -13,6 +13,7 @@ const DEFAULT_HOST = "localhost";
 
 export class Constants {
   static SERVICE_FIRESTORE = "firestore.googleapis.com";
+  static SERVICE_REALTIME_DATABASE = "firebaseio.com";
 
   static getDefaultHost(emulator: Emulators): string {
     return DEFAULT_HOST;

src/emulator/functionsEmulator.ts

@@ -490,6 +490,9 @@ You can probably fix this by running "npm install ${
             case Constants.SERVICE_FIRESTORE:
               await this.addFirestoreTrigger(this.projectId, definition);
               break;
+            case Constants.SERVICE_REALTIME_DATABASE:
+              await this.addRealtimeDatabaseTrigger(this.projectId, definition);
+              break;
             default:
               EmulatorLogger.log("DEBUG", `Unsupported trigger: ${JSON.stringify(definition)}`);
               EmulatorLogger.log(
@@ -514,6 +517,79 @@ You can probably fix this by running "npm install ${
     return loadTriggers();
   }
 
+  addRealtimeDatabaseTrigger(
+    projectId: string,
+    definition: EmulatedTriggerDefinition
+  ): Promise<any> {
+    const databasePort = EmulatorRegistry.getPort(Emulators.DATABASE);
+    if (!databasePort) {
+      EmulatorLogger.log(
+        "INFO",
+        `Ignoring trigger "${
+          definition.name
+        }" because the Realtime Database emulator is not running.`
+      );
+      return Promise.resolve();
+    }
+    if (definition.eventTrigger === undefined) {
+      EmulatorLogger.log(
+        "WARN",
+        `Event trigger "${definition.name}" has undefined "eventTrigger" member`
+      );
+      return Promise.reject();
+    }
+    /*
+     * The Realtime Database emulator expects the `path` field in its trigger
+     * definition to be relative to the database root.
+     */
+    const pathPattern = new RegExp("^projects/[^/]*/instances/[^/]*/refs(/.*)$");
+    const result: string[] | null = pathPattern.exec(definition.eventTrigger.resource);
+
+    if (result === null || result.length !== 2) {
+      EmulatorLogger.log(
+        "WARN",
+        `Event trigger "${definition.name}" has malformed "resource" member. ` +
+          `${definition.eventTrigger.resource}`
+      );
+      return Promise.reject();
+    }
+
+    const bundle = JSON.stringify([
+      {
+        name: `projects/${projectId}/locations/_/functions/${definition.name}`,
+        path: result[1], // path stored in the first capture group
+        event: definition.eventTrigger.eventType,
+        topic: `projects/${projectId}/topics/_`,
+      },
+    ]);
+
+    EmulatorLogger.logLabeled(
+      "BULLET",
+      "functions",
+      `Setting up Realtime Database trigger "${definition.name}"`
+    );
+    logger.debug(`addDatabaseTrigger`, JSON.stringify(bundle));
+    return new Promise((resolve, reject) => {
+      request.put(
+        `http://localhost:${databasePort}/.settings/functionTriggers.json`,
+        {
+          auth: {
+            bearer: "owner",
+          },
+          body: bundle,
+        },
+        (err, res, body) => {
+          if (err) {
+            EmulatorLogger.log("WARN", "Error adding trigger: " + err);
+            reject();
+            return;
+          }
+          resolve();
+        }
+      );
+    });
+  }
+
   addFirestoreTrigger(projectId: string, definition: EmulatedTriggerDefinition): Promise<any> {
     const firestorePort = EmulatorRegistry.getPort(Emulators.FIRESTORE);
     if (!firestorePort) {