Intercept iTunes links and open iTunes controller.

ios/chrome/browser/itunes_links/itunes_links_observer.mm

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/itunes_links/itunes_links_observer.h"
+
+#include <memory>
+
+#include "base/logging.h"
+#import "base/mac/scoped_nsobject.h"
+#include "base/strings/sys_string_conversions.h"
+#import "ios/chrome/browser/storekit_launcher.h"
+#import "ios/web/public/web_state/web_state_observer_bridge.h"
+#include "ios/web/public/web_state/web_state.h"
+#include "url/gurl.h"
+
+@interface ITunesLinksObserver ()
+
+// If |URL| points to a product on itunes.apple.com, returns the product ID.
+// Otherwise, returns nil.
+// Examples of URLs pointing to products on itunes.apple.com can be found in
+// itunes_links_observer_unittest.mm.
++ (NSString*)productIDFromURL:(const GURL&)URL;
+
+@end
+
+@implementation ITunesLinksObserver {
+  base::WeakNSProtocol<id<StoreKitLauncher>> _storeKitLauncher;
+  std::unique_ptr<web::WebStateObserverBridge> _webStateObserverBridge;
+}
+
+- (instancetype)initWithWebState:(web::WebState*)webState {
+  self = [super init];
+  if (self) {
+    _webStateObserverBridge.reset(
+        new web::WebStateObserverBridge(webState, self));
+  }
+  return self;
+}
+
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
++ (NSString*)productIDFromURL:(const GURL&)URL {
+  if (!URL.SchemeIsHTTPOrHTTPS() || !URL.DomainIs("itunes.apple.com"))
+    return nil;
+  std::string fileName = URL.ExtractFileName();
+  // The first 2 characters must be "id", followed by the app ID.
+  if (fileName.length() < 3 || fileName.substr(0, 2) != "id")
+    return nil;
+  std::string productID = fileName.substr(2);
+  return base::SysUTF8ToNSString(productID);
+}
+
+#pragma mark - CRWWebStateObserver
+
+- (void)webStateDidLoadPage:(web::WebState*)webState {
+  GURL URL = webState->GetLastCommittedURL();
+  NSString* productID = [ITunesLinksObserver productIDFromURL:URL];
+  if (productID)
+    [_storeKitLauncher openAppStore:productID];
+}
+
+- (void)setStoreKitLauncher:(id<StoreKitLauncher>)storeKitLauncher {
+  _storeKitLauncher.reset(storeKitLauncher);
+}
+
+@end