[js][database] _handleCancelEvent completed - now correctly handles cancellation events from .on()

lib/modules/database/index.js

@@ -8,6 +8,7 @@ import Reference from './reference';
 import Snapshot from './snapshot';
 import TransactionHandler from './transaction';
 import ModuleBase from './../../utils/ModuleBase';
+import { nativeToJSError } from './../../utils';
 
 /**
  * @class Database
@@ -36,8 +37,15 @@ export default class Database extends ModuleBase {
     );
   }
 
+  /**
+   * Routes native database 'on' events to their js equivalent counterpart.
+   * If there is no longer any listeners remaining for this event we internally
+   * call the native unsub method to prevent further events coming through.
+   *
+   * @param event
+   * @private
+   */
   _handleOnEvent(event) {
-    console.log('>>>ON-event>>>', event);
     const { queryKey, body, refId } = event;
     const { snapshot, previousChildName } = body;
 
@@ -64,8 +72,21 @@ export default class Database extends ModuleBase {
     }
   }
 
+
+  /**
+   * Routes native database query listener cancellation events to their js counterparts.
+   *
+   * @param event
+   * @private
+   */
   _handleCancelEvent(event) {
-    console.log('>>>CANCEL-event>>>', event);
+    const { queryKey, code, message, path, refId, appName } = event;
+    const remainingListeners = this.listeners(`${queryKey}:cancelled`);
+
+    if (remainingListeners && remainingListeners.length) {
+      const error = nativeToJSError(code, message, { path, queryKey, refId, appName });
+      this.emit(`${queryKey}:cancelled`, error);
+    }
   }
 
   /**
@@ -98,14 +119,6 @@ export default class Database extends ModuleBase {
   ref(path: string) {
     return new Reference(this, path);
   }
-
-
-  /**
-   * INTERNALS
-   */
-
-  // todo handleDbEvent
-  // todo handleDbError
 }
 
 export const statics = {