Extract WPUserAgent to WordPressShared

Modules/Sources/WordPressShared/WKWebView+UserAgent.swift

@@ -0,0 +1,24 @@
+import WebKit
+
+@objc
+public extension WKWebView {
+    static let userAgentKey = "_userAgent"
+
+    /// Call this method to get the user agent for the WKWebView
+    @objc
+    func userAgent() -> String {
+        guard let userAgent = value(forKey: WKWebView.userAgentKey) as? String, !userAgent.isEmpty else {
+            // TODO: Original implementation logged a message to Tracks/Sentry
+            print("This method for retrieveing the user agent seems to be no longer working. We need to figure out an alternative.")
+            return ""
+        }
+
+        return userAgent
+    }
+
+    /// Static version of the method that returns the current user agent.
+    @objc
+    static func userAgent() -> String {
+        return WKWebView().userAgent()
+    }
+}

Modules/Sources/WordPressShared/WPUserAgent.swift

@@ -0,0 +1,115 @@
+import Foundation
+import WebKit
+
+@objc
+public class WPUserAgent: NSObject {
+
+    public static let userAgentKey = "UserAgent"
+
+    @objc
+    public static func defaultUserAgent(userDefaults: UserDefaults) -> String {
+        // FIXME: What's the point of reading from user defaults then returning a possibly different value?
+        // See original Objective-C implementation at
+        // https://github.com/wordpress-mobile/WordPress-iOS/blob/a6eaa7aa8acb50828449df2d3fccaa50d7def821/WordPress/Classes/Utility/WPUserAgent.m#L10-L29
+
+        // 1. Extract current stored user agent
+        let registrationDomain = userDefaults.volatileDomain(forName: UserDefaults.registrationDomain)
+        let storedUserAgent = registrationDomain[userAgentKey] as? String
+
+        // 2. Flush stored user agent
+        userDefaults.register(defaults: [userAgentKey: ""])
+
+        // 3. Reset the stored user agent if there was one in the first place (why??)
+        if let storedUserAgent {
+            userDefaults.register(defaults: [userAgentKey: storedUserAgent])
+        }
+
+        let userAgent = WPUserAgent.webViewUserAgent
+        assert(!userAgent.isEmpty, "User agent should not be empty")
+        return userAgent
+    }
+
+    // The original impelmentation had logic to only read this once if not nil.
+    // But why? The performance hit should be negligible.
+    //
+    // See original implementation at
+    // https://github.com/wordpress-mobile/WordPress-iOS/blob/a6eaa7aa8acb50828449df2d3fccaa50d7def821/WordPress/Classes/Utility/WPUserAgent.m#L31-L41
+    @objc
+    public static func wordPressUserAgent(userDefaults: UserDefaults, bundle: Bundle = .main) -> String {
+        let appVersion = bundle.infoDictionary?["CFBundleShortVersionString"] as? String ?? "Unknown"
+        return "\(defaultUserAgent(userDefaults: userDefaults)) wp-iphone/\(appVersion)"
+    }
+
+    @objc
+    public static func useWordPressInWebViews(userDefaults: UserDefaults) {
+        // Cleanup unused UserDefaults keys from older WPUserAgent implementation
+        // FIXME: How old are those older implementations? Can we remove this code because "old enough"?
+        userDefaults.removeObject(forKey: "DefaultUserAgent")
+        userDefaults.removeObject(forKey: "AppUserAgent")
+
+        let userAgent = wordPressUserAgent(userDefaults: userDefaults)
+
+        userDefaults.register(defaults: [userAgentKey: userAgent])
+
+        print("User-Agent set to \(userAgent)")
+    }
+
+    /// Returns a user agent string similar to (but may not exactly match) the one used in `WKWebView`.
+    @objc static var webViewUserAgent: String {
+        // Examples user agent strings from `WKWebView` in iOS simulators:
+        //
+        // ## iPhone 15 Pro (iOS 17.2)
+        // Mozilla/5.0 (iPhone; CPU iPhone OS 17_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148
+        //
+        // ## iPad Pro (iOS 17.0.1)
+        // Mozilla/5.0 (iPad; CPU OS 17_0_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148
+        //
+        // Based on the WebKit implementation[^1], most of the components are hardcoded, and there are only a couple of dynamic components:
+        // 1. Device model. i.e. iPhone/iPad
+        // 2. OS name and version. i.e. iPhone OS 17_2
+        //
+        // Please note the "Mobile/15E148" part is WKWebView's default and hardcoded "application name"[^2].
+        //
+        // [^1]: https://github.com/WebKit/WebKit/blob/5fbb03ee1c6210c79779d6fa1a9e7290daa746d1/Source/WebCore/platform/ios/UserAgentIOS.mm#L88-L113
+        // [^2]: https://github.com/WebKit/WebKit/blob/492140d27dbe/Source/WebKit/UIProcess/API/Cocoa/WKWebViewConfiguration.mm#L612
+
+        let device = UIDevice.current
+
+        let deviceModel = device.model // Example: "iPhone"
+        var osName = device.systemName // Example: "iPhone OS"
+        let osVersion = device.systemVersion.replacingOccurrences(of: ".", with: "_") // Example: "17_2"
+
+        // WKWebView on iPad uses a static user agent.
+        // https://github.com/WebKit/WebKit/blob/6a053cfb431bd70d5017ba881a39f004e52effc2/Source/WebCore/platform/ios/UserAgentIOS.mm#L97
+        if device.userInterfaceIdiom == .pad {
+            osName = "OS"
+        }
+
+        // Use "iPhone OS" instead of "iOS", because that's what WKWebView uses.
+        if osName == "iOS" {
+            osName = "iPhone OS"
+        }
+
+        return "Mozilla/5.0 (\(deviceModel); CPU \(osName) \(osVersion) like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148"
+    }
+}
+
+public extension WPUserAgent {
+
+    private static let userDefaults = UserPersistentStoreFactory.userDefaultsInstance()
+
+    @objc
+    static func defaultUserAgent() -> String {
+        defaultUserAgent(userDefaults: userDefaults)
+    }
+
+    @objc(wordPressUserAgent)
+    static func wordPress() -> String {
+        wordPressUserAgent(userDefaults: userDefaults)
+    }
+
+    @objc
+    static func useWordPressInWebViews() {
+        useWordPressInWebViews(userDefaults: userDefaults)
+    }
+}

Modules/Tests/WordPressSharedTests/WPUserAgentTests.swift

@@ -0,0 +1,115 @@
+import Foundation
+import Testing
+import WebKit
+import WordPressShared
+
+class WPWPUserAgentTests {
+
+    @Test
+    func userAgentFormat() throws {
+        let userAgent = WPUserAgent.defaultUserAgent(userDefaults: .standard)
+
+        #expect(
+            try webKitUserAgentRegExp().numberOfMatches(
+                in: userAgent,
+                options: [],
+                range: NSRange(location: 0, length: userAgent.utf16.count)
+            ) == 1
+        )
+    }
+
+    @Test
+    func wordPressUserAgentValue() throws {
+        let userDefaults = UserDefaults.standard
+        let appVersion = try #require(Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String)
+        let defaultUserAgent = WPUserAgent.defaultUserAgent(userDefaults: userDefaults)
+        let expectedUserAgent = String.init(format: "%@ wp-iphone/%@", defaultUserAgent, appVersion)
+
+        #expect(WPUserAgent.wordPressUserAgent(userDefaults: userDefaults) == expectedUserAgent)
+    }
+
+    @Test @MainActor
+    func usesWordPressUserAgentInWebViews() throws {
+        if #available(iOS 17, *) { // #available cannot go as an argument in @Test(.enabled(if: ..))
+            print("In iOS 17, WKWebView no longer reads User Agent from UserDefaults. Skipping while working on an alternative setup.")
+            return
+        }
+
+        let userDefaults = UserDefaults.standard
+        let defaultUserAgent = WPUserAgent.defaultUserAgent(userDefaults: userDefaults)
+        let wordPressUserAgent = WPUserAgent.wordPressUserAgent(userDefaults: userDefaults)
+
+        // FIXME: Is this necessary?
+        // See original implementation at
+        // https://github.com/wordpress-mobile/WordPress-iOS/blob/a6eaa7aa8acb50828449df2d3fccaa50d7def821/WordPress/WordPressTest/WPUserAgentTests.m#L57-L75
+        userDefaults.removeObject(forKey: WPUserAgent.userAgentKey)
+        userDefaults.register(defaults: [WPUserAgent.userAgentKey: defaultUserAgent])
+
+        WPUserAgent.useWordPressInWebViews(userDefaults: userDefaults)
+
+        #expect(try currentUserAgent(userDefaults: userDefaults) == wordPressUserAgent)
+        #expect(try currentUserAgentFromWebView() == wordPressUserAgent)
+    }
+
+    // FIXME: Is there even a point in testing for no throws when the method does not throw?
+    // See original implementation at
+    // https://github.com/wordpress-mobile/WordPress-iOS/blob/a6eaa7aa8acb50828449df2d3fccaa50d7def821/WordPress/WordPressTest/WPUserAgentTests.m#L102-L107
+    @Test
+    func accessingWordPressUserAgentOutsideMainThread() {
+        #expect(throws: Never.self, "Accessing outside the main thread should work") {
+            DispatchQueue.global(qos: .background).sync {
+                WPUserAgent.wordPressUserAgent(userDefaults: .standard)
+            }
+        }
+    }
+
+    func currentUserAgent(userDefaults: UserDefaults) throws -> String {
+        try #require(userDefaults.object(forKey: WPUserAgent.userAgentKey) as? String)
+    }
+
+    @MainActor
+    func currentUserAgentFromWebView() throws -> String {
+        try #require(WKWebView.userAgent())
+    }
+
+    func webKitUserAgentRegExp() throws -> NSRegularExpression {
+        try NSRegularExpression(
+            pattern: "^Mozilla/5\\.0 \\([a-zA-Z]+; CPU [\\sa-zA-Z]+ [_0-9]+ like Mac OS X\\) AppleWebKit/605\\.1\\.15 \\(KHTML, like Gecko\\) Mobile/15E148$"
+        )
+    }
+
+    // MARK: - Tests for underlying assumptions
+
+    @Test
+    func registerInUserDefaultsAdds() throws {
+        let userDefaults = UserDefaults.standard
+        let domainName = try #require(userDefaults.volatileDomainNames.first)
+        let originalDomain = userDefaults.volatileDomain(forName: domainName)
+
+        userDefaults.register(defaults: ["test-key": 0])
+
+        let updatedDomain = userDefaults.volatileDomain(forName: domainName)
+
+        // From the docs:
+        // Registered defaults are never stored between runs of an application, and are visible only to the application that registers them
+        //
+        // So we expect the count to be +1
+        #expect(updatedDomain.count == originalDomain.count + 1)
+    }
+
+    // If this test fails, it may mean `WKWebView` uses a user agent with an unexpected format (see `webKitUserAgentRegExp`)
+    // and we may need to adjust our implementation to match the new `WKWebView` user agent.
+    @Test @MainActor
+    func testWebKitUserAgentFormat() throws {
+        let regExp = try webKitUserAgentRegExp()
+        // Please note: WKWebView's user agent may be different on different test device types.
+        let userAgent = try currentUserAgentFromWebView()
+        #expect(
+            try webKitUserAgentRegExp().numberOfMatches(
+                in: userAgent,
+                options: [],
+                range: NSRange(location: 0, length: userAgent.utf16.count)
+            ) == 1
+        )
+    }
+}

WordPress/Classes/Login/WordPressDotComAuthenticator.swift

@@ -3,6 +3,7 @@ import AuthenticationServices
 import Foundation
 import UIKit
 import WordPressData
+import WordPressShared
 
 /// Log in or sign up a WordPress.com account via web.
 ///

WordPress/Classes/Models/Blog/Blog.m

@@ -2,7 +2,7 @@
 #import "WPAccount.h"
 #import "AccountService.h"
 @import WordPressDataObjC;
-#import "WPUserAgent.h"
+@import WordPressShared;
 #import "WordPress-Swift.h"
 @import SFHFKeychainUtils;
 

WordPress/Classes/Models/ReaderListTopic+Creation.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 
 extension ReaderListTopic {
 

WordPress/Classes/Models/WPAccount+RestApi.swift

@@ -1,5 +1,5 @@
-
 import Foundation
+import WordPressShared
 import WordPressKit
 
 extension WPAccount {

WordPress/Classes/Networking/WordPressOrgRestApi+WordPress.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 import WordPressKit
 
 private func apiBase(blog: Blog) -> URL? {

WordPress/Classes/Services/AuthenticationService.swift

@@ -1,5 +1,6 @@
 import AutomatticTracks
 import Foundation
+import WordPressShared
 
 class AuthenticationService {
 

WordPress/Classes/Services/BloggingPrompts/BloggingPromptsService.swift

@@ -1,6 +1,7 @@
 import CoreData
 import WordPressData
 import WordPressKit
+import WordPressShared
 
 class BloggingPromptsService {
     let siteID: NSNumber

WordPress/Classes/Services/Page Layouts/PageLayoutService.swift

@@ -2,6 +2,7 @@ import UIKit
 import CoreData
 import Gutenberg
 import WordPressKit
+import WordPressShared
 
 class PageLayoutService {
     private struct Parameters {

WordPress/Classes/Services/PostServiceRemoteFactory.swift

@@ -1,6 +1,6 @@
-
 import Foundation
 import WordPressKit
+import WordPressShared
 
 @objc class PostServiceRemoteFactory: NSObject {
     @objc func forBlog(_ blog: Blog) -> PostServiceRemote? {

WordPress/Classes/Services/PushAuthenticationService.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 
 /// The purpose of this service is to encapsulate the Restful API that performs Mobile 2FA
 /// Code Verification.

WordPress/Classes/Services/ReaderCardService.swift

@@ -1,5 +1,6 @@
 import Foundation
 import WordPressKit
+import WordPressShared
 
 protocol ReaderCardServiceRemote {
     func fetchStreamCards(stream: ReaderStream,

WordPress/Classes/Services/ReaderSiteSearchService.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 
 typealias ReaderSiteSearchSuccessBlock = (_ feeds: [ReaderFeed], _ hasMore: Bool, _ feedCount: Int) -> Void
 typealias ReaderSiteSearchFailureBlock = (_ error: Error?) -> Void

WordPress/Classes/Services/ReaderTopicService+FollowedInterests.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 
 // MARK: - ReaderFollowedInterestsService
 

WordPress/Classes/Services/ReaderTopicService+FollowedSites.swift

@@ -1,3 +1,4 @@
+import WordPressShared
 
 extension ReaderTopicService {
 

WordPress/Classes/Services/ReaderTopicService+Interests.swift

@@ -1,5 +1,6 @@
 import Foundation
 import WordPressKit
+import WordPressShared
 
 // MARK: - ReaderInterestsService
 

WordPress/Classes/Services/ReaderTopicService+SiteInfo.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressShared
 
 /// Protocol representing a service that retrieves the users followed interests/tags
 protocol ReaderSiteInfoService: AnyObject {

WordPress/Classes/Services/ReaderTopicService+Subscriptions.swift

@@ -1,5 +1,6 @@
 import Foundation
 import WordPressKit
+import WordPressShared
 
 private enum SubscriptionAction {
     case notifications(siteId: Int)

WordPress/Classes/Services/SiteAddressService.swift

@@ -1,4 +1,5 @@
 import WordPressKit
+import WordPressShared
 
 // MARK: - SiteAddressService
 

WordPress/Classes/Services/SiteAssemblyService.swift

@@ -1,5 +1,6 @@
 import Foundation
 import WordPressData
+import WordPressShared
 
 /// Site Creation Notification
 ///

WordPress/Classes/Services/SiteSegmentsService.swift

@@ -1,6 +1,6 @@
-
 import Foundation
 import WordPressKit
+import WordPressShared
 
 /// Abstracts the service to obtain site types
 typealias SiteSegmentsServiceCompletion = (SiteSegmentsResult) -> Void