From 425dfbcc43679965a81f4cd712332f4dc8933088 Mon Sep 17 00:00:00 2001
From: Salakar <mike.diarmid@gmail.com>
Date: Mon, 7 Aug 2017 09:46:05 +0100
Subject: [PATCH] [js][database] once now supports passing context - as per the
 web sdk

---
 lib/modules/database/reference.js | 34 +++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/lib/modules/database/reference.js b/lib/modules/database/reference.js
index cadf987f..7a95aa46 100644
--- a/lib/modules/database/reference.js
+++ b/lib/modules/database/reference.js
@@ -172,7 +172,11 @@ export default class Reference extends ReferenceBase {
    * @param onComplete
    * @param applyLocally
    */
-  transaction(transactionUpdate: Function, onComplete: (error: ?Error, committed: boolean, snapshot: ?Snapshot) => *, applyLocally: boolean = false) {
+  transaction(
+    transactionUpdate: Function,
+    onComplete: (error: ?Error, committed: boolean, snapshot: ?Snapshot) => *,
+    applyLocally: boolean = false,
+  ) {
     if (!isFunction(transactionUpdate)) {
       return Promise.reject(
         new Error('Missing transactionUpdate function argument.'),
@@ -190,6 +194,7 @@ export default class Reference extends ReferenceBase {
         return resolve({ committed, snapshot: new Snapshot(this, snapshotData) });
       };
 
+      // start the transaction natively
       this._database._transactionHandler.add(this, transactionUpdate, onCompleteWrapper, applyLocally);
     });
   }
@@ -199,19 +204,30 @@ export default class Reference extends ReferenceBase {
    *
    * @param eventName
    * @param successCallback
-   * @param failureCallback
-   * TODO @param context
+   * @param cancelOrContext
+   * @param context
    * @returns {Promise.<any>}
    */
-  once(eventName: string = 'value', successCallback: (snapshot: Object) => void, failureCallback: (error: FirebaseError) => void) {
+  once(
+    eventName: string = 'value',
+    successCallback: (snapshot: Object) => void,
+    cancelOrContext: (error: FirebaseError) => void,
+    context?: Object,
+  ) {
     return this._database._native.once(this._refId, this.path, this._query.getModifiers(), eventName)
-      .then(({ snapshot }) => new Snapshot(this, snapshot))
-      .then((snapshot) => {
-        if (isFunction(successCallback)) successCallback(snapshot);
-        return snapshot;
+      .then(({ snapshot }) => {
+        const _snapshot = new Snapshot(this, snapshot);
+
+        if (isFunction(successCallback)) {
+          if (isObject(cancelOrContext)) successCallback.bind(cancelOrContext)(_snapshot);
+          if (context && isObject(context)) successCallback.bind(context)(_snapshot);
+          successCallback(_snapshot);
+        }
+
+        return _snapshot;
       })
       .catch((error) => {
-        if (isFunction(failureCallback)) return failureCallback(error);
+        if (isFunction(cancelOrContext)) return cancelOrContext(error);
         return error;
       });
   }