Adds mailto: URL support to app launching.

ios/chrome/browser/web/mailto_url_rewriter.mm

Index: ios/chrome/browser/web/mailto_url_rewriter.mm
diff --git a/ios/chrome/browser/web/mailto_url_rewriter.mm b/ios/chrome/browser/web/mailto_url_rewriter.mm
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+// Copyright 2017 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/web/mailto_url_rewriter.h"
+
+#import "base/logging.h"
+#import "ios/chrome/browser/web/mailto_handler.h"
+#import "ios/chrome/browser/web/mailto_handler_gmail.h"
+#import "ios/chrome/browser/web/mailto_handler_system_mail.h"
+
+#import <UIKit/UIKit.h>
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+// The key for NSUserDefaults to store the Mail client selected to handle
+// mailto: URL scheme.
+NSString* const kMailtoDefaultHandlerKey = @"MailtoHandlerDefault";
+}  // namespace
+
+@interface MailtoURLRewriter ()
+
+// Dictionary keyed by the App Store ID of the Mail client and the value is
+// the MailtoHandler object that can rewrite a mailto: URL.
+@property(nonatomic, strong)
+    NSMutableDictionary<NSString*, MailtoHandler*>* handlers;
+
+// Private method for testing to clear the default state.
++ (void)resetDefaultHandlerID;
+
+// Private method to add |handlerApp| to the list of know Mail client apps.
+- (void)addMailtoApp:(MailtoHandler*)handlerApp;
+
+// Custom logic to handle the migration from Google Native App Launcher options
+// to this simplified mailto: URL only system. This must be called after
+// -addMailtoApp: has been called to add all the known Mail client apps.
+// TODO(crbug.com/718601): At some point in the future when almost all users
+// have upgraded, this method can be removed.
+- (void)convertLegacyOptions;
+
+@end
+
+@implementation MailtoURLRewriter
+@synthesize handlers = _handlers;
+
++ (NSString*)systemMailApp {
+  // This is the App Store ID for Apple Mail app.
+  // See https://itunes.apple.com/us/app/mail/id1108187098?mt=8
+  return @"1108187098";
+}
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    _handlers = [NSMutableDictionary dictionary];
+  }
+  return self;
+}
+
+- (instancetype)initWithStandardHandlers {
+  self = [self init];
+  if (self) {
+    [self addMailtoApp:[[MailtoHandlerSystemMail alloc] init]];
+    [self addMailtoApp:[[MailtoHandlerGmail alloc] init]];
+    [self convertLegacyOptions];
+  }
+  return self;
+}
+
+- (NSArray<MailtoHandler*>*)defaultHandlers {
+  return [_handlers allValues];
+}
+
+- (NSString*)defaultHandlerID {
+  NSString* value = [[NSUserDefaults standardUserDefaults]
+      stringForKey:kMailtoDefaultHandlerKey];
+  return value ? value : [[self class] systemMailApp];
+}
+
+- (void)setDefaultHandlerID:(NSString*)appStoreID {
+  DCHECK([appStoreID length]);
+  [[NSUserDefaults standardUserDefaults] setObject:appStoreID
+                                            forKey:kMailtoDefaultHandlerKey];
+}
+
+- (NSString*)rewriteMailtoURL:(const GURL&)gURL {
+  NSString* value = [self defaultHandlerID];
+  if ([value length]) {
+    MailtoHandler* handler = _handlers[value];
+    if (handler) {
+      return [handler rewriteMailtoURL:gURL];
+    }
+  }
+  return nil;
+}
+
+#pragma mark - Private
+
++ (void)resetDefaultHandlerID {
+  [[NSUserDefaults standardUserDefaults]
+      removeObjectForKey:kMailtoDefaultHandlerKey];
+}
+
+- (void)addMailtoApp:(MailtoHandler*)handlerApp {
+  if ([handlerApp isAvailable])
+    [_handlers setObject:handlerApp forKey:[handlerApp appStoreID]];
+}
+
+// Implements the migration logic for users of previous versions of Google
+// Chrome which supports Google Native App Launcher. The goal is to preserve
+// the previous behavior and support user choice of non-system provided Mail
+// client apps. System-provided Mail client app will be referred to as
+// "System Mail". The migration goals are:
+// - If a user has not made a choice for preferred mailto: handler in the past,
+//   the behavior after upgrading to this version should not change.
+// - If a user had disabled Gmail app as the preferred mailto: handler in the
+//   past, System Mail should be selected as the default mailto: handler.
+// - If a user installs Gmail app after the installation of Chrome, Gmail app
+//   will be chosen as the default mailto: handler, preserving the previous
+//   behavior.
+// - If a user installs another 3rd party mail client app, assuming that the
+//   3rd party mail client app is explicitly supported in Chrome, the new 3rd
+//   party mail client app can be set as the default mailto: handler through
+//   Tools > Settings > Content Settings.
+- (void)convertLegacyOptions {
+  // If a default handler for mailto: has already been registered, this is not
+  // an upgrade case that needs to take legacy options into account.
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  if ([defaults objectForKey:kMailtoDefaultHandlerKey])
+    return;
+
+  // The key used in NSUserDefaults is from legacy code when Native App
+  // Launcher was still in use. The general format is a string prefix,
+  // underscore, then followed by the App Store ID of the application.
+  NSString* const kGmailAppStoreID = @"422689480";
+  NSString* const kLegacyShouldAutoOpenKey =
+      [NSString stringWithFormat:@"ShouldAutoOpenLinks_%@", kGmailAppStoreID];
+
+  // If Gmail app is not installed, there is nothing to migrate.
+  MailtoHandler* gmailHandler = _handlers[kGmailAppStoreID];
+  if (!gmailHandler) {
+    // There is a stale legacy key around. This may mean that the user was using
+    // Gmail  some time in the past but later uninstalled Gmail app. This clears
+    // the stale entry to start user from a clean slate again.
+    [defaults removeObjectForKey:kLegacyShouldAutoOpenKey];
+    return;
+  }
+
+  // If Gmail app is not installed or otherwise unavailable, do not make it the
+  // default mailto: handler app.
+  if (![gmailHandler isAvailable])
+    [defaults removeObjectForKey:kMailtoDefaultHandlerKey];
+
+  // User previously had a selection made for opening mailto: links with Gmail,
+  // upgrade will set Gmail app to be the default mailto: handler. If user had
+  // opted out to using Gmail app (even when it was installed), migrate user
+  // to use system-provided Mail client.
+  NSNumber* legacyValue = [defaults objectForKey:kLegacyShouldAutoOpenKey];
+  if (legacyValue) {
+    switch ([legacyValue intValue]) {
+      case 0:  // kAutoOpenLinksNotSet
+      case 2:  // kAutoOpenLinksYes
+        [defaults setObject:kGmailAppStoreID forKey:kMailtoDefaultHandlerKey];
+        break;
+      case 1:  // kAutoOpenLinksNo
+        [defaults removeObjectForKey:kMailtoDefaultHandlerKey];
+        break;
+      default:
+        NOTREACHED();
+        break;
+    }
+    [defaults removeObjectForKey:kLegacyShouldAutoOpenKey];
+  } else {
+    // This is an unlikely (if not impossible) case of user not having the
+    // legacy key set at all. In this case, set the default to use Gmail app
+    // for mailto: handling.
+    [defaults setObject:kGmailAppStoreID forKey:kMailtoDefaultHandlerKey];
+  }
+}
+
+@end