Update RSC15a to new requirements

Source/ARTClientOptions.h

@@ -70,6 +70,11 @@ ART_ASSUME_NONNULL_BEGIN
  */
 @property (readwrite, assign, nonatomic) NSTimeInterval httpMaxRetryDuration;
 
+/**
+ If an array of custom fallback hosts are provided, then they will be used instead of default hosts.
+ */
+@property (nonatomic, copy, art_nullable) NSArray *fallbackHosts;
+
 - (BOOL)isBasicAuth;
 - (NSURL *)restUrl;
 - (NSURL *)realtimeUrl;

Source/ARTClientOptions.m

@@ -38,6 +38,7 @@ - (instancetype)initDefaults {
     _httpRequestTimeout = 15.0; //Seconds
     _httpMaxRetryDuration = 10.0; //Seconds
     _httpMaxRetryCount = 3;
+    _fallbackHosts = nil;
     return self;
 }
 
@@ -98,6 +99,7 @@ - (id)copyWithZone:(NSZone *)zone {
     options.httpMaxRetryDuration = self.httpMaxRetryDuration;
     options.httpOpenTimeout = self.httpOpenTimeout;
     options.httpRequestTimeout = self.httpRequestTimeout;
+    options.fallbackHosts = self.fallbackHosts;
 
     return options;
 }

Source/ARTFallback.h

@@ -26,6 +26,11 @@ extern int (^ARTFallback_getRandomHostIndex)(int count);
  */
 -(NSString *) popFallbackHost;
 
+/**
+ Init with fallback hosts array.
+ */
+-(instancetype)initWithFallbackHosts:(NSArray *)fallbackHosts;
+
 @end
 
 ART_ASSUME_NONNULL_END

Source/ARTFallback.m

@@ -26,10 +26,15 @@ @interface ARTFallback ()
 @implementation ARTFallback
 
 - (id)init {
+    self = [self initWithFallbackHosts:[ARTDefault fallbackHosts]];
+    return self;
+}
+
+-(instancetype)initWithFallbackHosts:(NSArray *)fallbackHosts {
     self = [super init];
     if(self) {
         self.hosts = [NSMutableArray array];
-        NSMutableArray * hostArray =[[NSMutableArray alloc] initWithArray: [ARTDefault fallbackHosts]];
+        NSMutableArray * hostArray = [[NSMutableArray alloc] initWithArray: [fallbackHosts copy]];
         size_t count = [hostArray count];
         for(int i=0; i <count; i++ ) {
             int randomIndex = ARTFallback_getRandomHostIndex((int)[hostArray count]);

Source/ARTRest.m

@@ -154,7 +154,11 @@ - (void)executeRequest:(NSMutableURLRequest *)request completion:(void (^)(NSHTT
         }
         if (retries < _options.httpMaxRetryCount && [self shouldRetryWithFallback:request response:response error:error]) {
             if (!blockFallbacks && [request.URL.host isEqualToString:(_prioritizedHost ? _prioritizedHost : [ARTDefault restHost])]) {
-                blockFallbacks = [[ARTFallback alloc] init];
+                if(self.options.fallbackHosts != nil) {
+                    blockFallbacks = [[ARTFallback alloc] initWithFallbackHosts:self.options.fallbackHosts];
+                } else {
+                    blockFallbacks = [[ARTFallback alloc] init];
+                }
             }
             if (blockFallbacks) {
                 NSString *host = [blockFallbacks popFallbackHost];

Spec/RestClient.swift

@@ -677,6 +677,37 @@ class RestClient: QuickSpec {
 
                         expect(resultFallbackHosts).to(equal(expectedFallbackHosts))
                     }
+
+                    it("use custom fallback hosts if set") {
+                        let options = ARTClientOptions(key: "xxxx:xxxx")
+                        options.httpMaxRetryCount = 10
+                        let customFallbackHosts = ["j.ably-realtime.com",
+                                                   "i.ably-realtime.com",
+                                                   "h.ably-realtime.com",
+                                                   "g.ably-realtime.com",
+                                                   "f.ably-realtime.com"]
+                        options.fallbackHosts = customFallbackHosts
+                        let client = ARTRest(options: options)
+                        client.httpExecutor = testHTTPExecutor
+                        testHTTPExecutor.http = MockHTTP(network: .HostUnreachable)
+                        let channel = client.channels.get("test")
+
+                        waitUntil(timeout: testTimeout) { done in
+                            channel.publish(nil, data: "nil") { _ in
+                                done()
+                            }
+                        }
+
+                        expect(testHTTPExecutor.requests).to(haveCount(customFallbackHosts.count + 1))
+
+                        let extractHostname = { (request: NSMutableURLRequest) in
+                            NSRegularExpression.extract(request.URL!.absoluteString, pattern: "[f-j].ably-realtime.com")
+                        }
+                        let resultFallbackHosts = testHTTPExecutor.requests.flatMap(extractHostname)
+                        let expectedFallbackHosts = expectedHostOrder.map { customFallbackHosts[$0] }
+
+                        expect(resultFallbackHosts).to(equal(expectedFallbackHosts))
+                    }
 
                     it("until all fallback hosts have been tried") {
                         let options = ARTClientOptions(key: "xxxx:xxxx")

Tests/ARTFallbackTest.m

@@ -43,4 +43,48 @@ - (void)testAllHostsIncludedOnce {
     }    
 }
 
+- (void)testCustomFallbackHosts {
+    NSArray *customHosts = @[@"test.ably.com",
+                             @"test2.ably.com",
+                             @"test3.ably.com",
+                             @"test4.ably.com",
+                             @"test5.ably.com",
+                             @"test6.ably.com",
+                             @"test7.ably.com",
+                             @"test8.ably.com",
+                             @"test9.ably.com",
+                             @"test10.ably.com",
+                             @"test11.ably.com",
+                             @"test12.ably.com",
+                             @"test13.ably.com",
+                             @"test14.ably.com"];
+    ARTFallback *f = [[ARTFallback alloc] initWithFallbackHosts:customHosts];
+
+    NSSet *customSet = [NSSet setWithArray:customHosts];
+    NSMutableArray *hostsRandomised = [NSMutableArray array];
+    for(int i=0;i < [customHosts count]; i++) {
+        [hostsRandomised addObject:[f popFallbackHost]];
+    }
+
+    //popping after all hosts are exhausted returns nil
+    XCTAssertTrue([f popFallbackHost] == nil);
+
+    // all fallback hosts are used in artfallback
+    XCTAssertEqual([hostsRandomised count], [customHosts count]);
+    bool inOrder = true;
+    for(int i=0;i < [customHosts count]; i++) {
+        if(![[customHosts objectAtIndex:i] isEqualToString:[hostsRandomised objectAtIndex:i]]) {
+            inOrder = false;
+            break;
+        }
+    }
+    //check artfallback randomises the order.
+    XCTAssertFalse(inOrder);
+
+    //every member of fallbacks hosts are in the list of custom hosts
+    for(int i=0;i < [hostsRandomised count]; i++) {
+        XCTAssertTrue([customSet containsObject:[hostsRandomised objectAtIndex:i]]);
+    }
+}
+
 @end