[ios] Use enum for IncognitoModeAvailability pref

Use enum to avoid meaningless decision like "kprefValue == 0" and
improve the readability.

Add an util class to help check the value of the incognito pref.

Change-Id: I005891908e261c8d292e2a861c7b5950a4f526d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586104Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Tina Wang <tinazwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836644}

ios/chrome/browser/prefs/BUILD.gn

@@ -29,6 +29,8 @@ source_set("browser_prefs") {
   sources = [
     "browser_prefs.h",
     "browser_prefs.mm",
+    "prefs_util.h",
+    "prefs_util.mm",
   ]
   deps = [
     "//components/autofill/core/browser",
@@ -78,6 +80,7 @@ source_set("browser_prefs") {
     "//ios/chrome/browser/memory",
     "//ios/chrome/browser/metrics",
     "//ios/chrome/browser/net",
+    "//ios/chrome/browser/policy:feature_flags",
     "//ios/chrome/browser/prerender:prerender_pref",
     "//ios/chrome/browser/signin",
     "//ios/chrome/browser/ui/authentication",

ios/chrome/browser/prefs/browser_prefs.h

@@ -12,6 +12,18 @@ namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
+enum class IncognitoModePrefs {
+  // Incognito mode enabled. Users may open pages in both Incognito mode and
+  // normal mode (usually the default behaviour).
+  kEnabled = 0,
+  // Incognito mode disabled. Users may not open pages in Incognito mode.
+  // Only normal mode is available for browsing.
+  kDisabled,
+  // Incognito mode forced. Users may open pages *ONLY* in Incognito mode.
+  // Normal mode is not available for browsing.
+  kForced,
+};
+
 // Registers all prefs that will be used via the local state PrefService.
 void RegisterLocalStatePrefs(PrefRegistrySimple* registry);
 

ios/chrome/browser/prefs/browser_prefs.mm

@@ -233,8 +233,8 @@ void RegisterBrowserStatePrefs(user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterIntegerPref(kGCMChannelPollIntervalSeconds, 0);
   registry->RegisterInt64Pref(kGCMChannelLastCheckTime, 0);
 
-  // Register kIncognitoModeAvailability to available.
-  registry->RegisterIntegerPref(prefs::kIncognitoModeAvailability, 0);
+  registry->RegisterIntegerPref(prefs::kIncognitoModeAvailability,
+                                static_cast<int>(IncognitoModePrefs::kEnabled));
 
   registry->RegisterListPref(kInvalidatorSavedInvalidations);
   registry->RegisterStringPref(kInvalidatorInvalidationState, std::string());

ios/chrome/browser/prefs/prefs_util.h

+// Copyright 2020 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.
+
+#ifndef IOS_CHROME_BROWSER_PREFS_PREFS_UTIL_H_
+#define IOS_CHROME_BROWSER_PREFS_PREFS_UTIL_H_
+
+class PrefService;
+
+// Returns true if incognito mode is disabled by enterprise policy.
+bool IsIncognitoModeDisabled(PrefService* pref_service);
+
+// Returns true if incognito mode is forced by enterprise policy.
+bool IsIncognitoModeForced(PrefService* pref_service);
+
+#endif  // IOS_CHROME_BROWSER_PREFS_PREFS_UTIL_H_

ios/chrome/browser/prefs/prefs_util.mm

+// Copyright 2020 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/prefs/prefs_util.h"
+
+#include "components/prefs/pref_service.h"
+#include "ios/chrome/browser/policy/policy_features.h"
+#include "ios/chrome/browser/pref_names.h"
+#include "ios/chrome/browser/prefs/browser_prefs.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+bool IsIncognitoModeDisabled(PrefService* pref_service) {
+  return IsEnterprisePolicyEnabled() &&
+         pref_service->IsManagedPreference(prefs::kIncognitoModeAvailability) &&
+         pref_service->GetInteger(prefs::kIncognitoModeAvailability) ==
+             static_cast<int>(IncognitoModePrefs::kDisabled);
+}
+
+bool IsIncognitoModeForced(PrefService* pref_service) {
+  return IsEnterprisePolicyEnabled() &&
+         pref_service->IsManagedPreference(prefs::kIncognitoModeAvailability) &&
+         pref_service->GetInteger(prefs::kIncognitoModeAvailability) ==
+             static_cast<int>(IncognitoModePrefs::kForced);
+}