1 files changed, 145 insertions, 0 deletions
diff --git a/Firebase/Database/Utilities/FEventEmitter.m b/Firebase/Database/Utilities/FEventEmitter.m
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+++ b/Firebase/Database/Utilities/FEventEmitter.m
@@ -0,0 +1,145 @@
+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+#import "FEventEmitter.h"
+#import "FUtilities.h"
+#import "FRepoManager.h"
+#import "FIRDatabaseQuery_Private.h"
+
+@interface FEventListener : NSObject
+
+@property (nonatomic, copy) fbt_void_id userCallback;
+@property (nonatomic) FIRDatabaseHandle handle;
+
+@end
+
+@implementation FEventListener
+
+@synthesize userCallback;
+@synthesize handle;
+
+@end
+
+
+@interface FEventEmitter ()
+
+@property (nonatomic, strong) NSArray *allowedEvents;
+@property (nonatomic, strong) NSMutableDictionary *listeners;
+@property (nonatomic, strong) dispatch_queue_t queue;
+
+@end
+
+
+@implementation FEventEmitter
+
+@synthesize allowedEvents;
+@synthesize listeners;
+
+- (id) initWithAllowedEvents:(NSArray *)theAllowedEvents queue:(dispatch_queue_t)queue {
+    if (theAllowedEvents == nil || [theAllowedEvents count] == 0) {
+        @throw [NSException exceptionWithName:@"AllowedEventsValidation" reason:@"FEventEmitters must be initialized with at least one valid event." userInfo:nil];
+    }
+
+    self = [super init];
+
+    if (self) {
+        self.allowedEvents = [theAllowedEvents copy];
+        self.listeners = [[NSMutableDictionary alloc] init];
+        self.queue = queue;
+    }
+
+    return self;
+}
+
+- (id) getInitialEventForType:(NSString *)eventType {
+    @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:@"You must override getInitialEvent: when subclassing FEventEmitter" userInfo:nil];
+}
+
+- (void) triggerEventType:(NSString *)eventType data:(id)data {
+    [self validateEventType:eventType];
+    NSMutableDictionary *eventTypeListeners = [self.listeners objectForKey:eventType];
+    for (FEventListener *listener in eventTypeListeners) {
+        [self triggerListener:listener withData:data];
+    }
+}
+
+- (void) triggerListener:(FEventListener *)listener withData:(id)data {
+    // TODO, should probably get this from FRepo or something although it ends up being the same. (Except maybe for testing)
+    if (listener.userCallback) {
+        dispatch_async(self.queue, ^{
+            listener.userCallback(data);
+        });
+    }
+}
+
+- (FIRDatabaseHandle)observeEventType:(NSString *)eventType withBlock:(fbt_void_id)block {
+    [self validateEventType:eventType];
+
+    // Create listener
+    FEventListener *listener = [[FEventListener alloc] init];
+    listener.handle = [[FUtilities LUIDGenerator] integerValue];
+    listener.userCallback = block; // copies block automatically
+
+    dispatch_async([FIRDatabaseQuery sharedQueue], ^{
+        [self addEventListener:listener forEventType:eventType];
+    });
+
+    return listener.handle;
+}
+
+- (void) addEventListener:(FEventListener *)listener forEventType:(NSString *)eventType {
+    // Get or initializer listeners map [FIRDatabaseHandle -> callback block] for eventType
+    NSMutableArray *eventTypeListeners = [self.listeners objectForKey:eventType];
+    if (eventTypeListeners == nil) {
+        eventTypeListeners = [[NSMutableArray alloc] init];
+        [self.listeners setObject:eventTypeListeners forKey:eventType];
+    }
+
+    // Add listener and fire the current event for this listener
+    [eventTypeListeners addObject:listener];
+    id initialData = [self getInitialEventForType:eventType];
+    [self triggerListener:listener withData:initialData];
+}
+
+- (void) removeObserverForEventType:(NSString *)eventType withHandle:(FIRDatabaseHandle)handle {
+    [self validateEventType:eventType];
+
+    dispatch_async([FIRDatabaseQuery sharedQueue], ^{
+        [self removeEventListenerWithHandle:handle forEventType:eventType];
+    });
+}
+
+- (void)removeEventListenerWithHandle:(FIRDatabaseHandle)handle forEventType:(NSString *)eventType {
+    NSMutableArray *eventTypeListeners = [self.listeners objectForKey:eventType];
+    for (FEventListener *listener in [eventTypeListeners copy]) {
+        if (handle == NSNotFound || handle == listener.handle) {
+            [eventTypeListeners removeObject:listener];
+        }
+    }
+}
+
+
+- (void) validateEventType:(NSString *)eventType {
+    if ([self.allowedEvents indexOfObject:eventType] == NSNotFound) {
+        @throw [NSException exceptionWithName:@"InvalidEventType"
+                                         reason:[NSString stringWithFormat:@"%@ is not a valid event type. %@ is the list of valid events.",
+                                                         eventType, self.allowedEvents]
+                                       userInfo:nil];
+    }
+}
+
+@end