Support Inbox for iOS (#2)

* Add Batch push notification interface

* Start implementing fetchNewNotifications on ios

* Suppose date is already a timestamp

* Fix timestamp

* Add payload

* timeIntervalSince1970 is a double

* Update README

* Use milliseconds for timestamp

Author: chdeps

README.md

@@ -84,8 +84,6 @@ BatchPush.logoutUser(); // when the user logs out
 ```
 
 ### Inbox
-Only on Android at the moment. See the [Batch's docs](https://batch.com/doc/ios/inbox.html) if you want to do a PR!
-
 ```js
 import BatchPush from 'react-native-batch-push';
 

ios/RNBatchPush.m

@@ -39,4 +39,30 @@ - (id)init {
     [editor save];
 }
 
+RCT_REMAP_METHOD(fetchNewNotifications,
+                 fetchNewNotificationsWithUserID:(NSString*)userID authKey:(NSString*)authKey resolver:(RCTPromiseResolveBlock)resolve rejecter:(RCTPromiseRejectBlock)reject)
+{
+    BatchInboxFetcher* inboxFetcher = [BatchInbox fetcherForUserIdentifier:userID authenticationKey:authKey];
+    [inboxFetcher fetchNewNotifications:^(NSError * _Nullable error, NSArray<BatchInboxNotificationContent *> * _Nullable notifications, BOOL foundNewNotifications, BOOL endReached) {
+
+        if(error) {
+            reject(@"BATCH_ERROR", @"Error fetching new notifications", error);
+            return;
+        }
+
+        NSMutableArray* jsNotifications = [[NSMutableArray alloc] init];
+        
+        for (BatchInboxNotificationContent* notification in notifications) {
+            NSMutableDictionary* jsNotification = [NSMutableDictionary new];
+            [jsNotification setObject:notification.title forKey:@"title"];
+            [jsNotification setObject:notification.body forKey:@"body"];
+            [jsNotification setObject:@([notification.date timeIntervalSince1970] * 1000.0) forKey:@"timestamp"];
+            [jsNotification setObject:notification.payload forKey:@"payload"];
+            [jsNotifications addObject:jsNotification];
+        }
+
+        resolve(jsNotifications);
+    }];
+}
+
 @end