Add FXIOS-13844 [Translations] language detection to middleware (#30407)

Author: cyndichin

firefox-ios/Client.xcodeproj/project.pbxproj

@@ -1406,6 +1406,7 @@
 		AAD861A82E9E748700F6E0E0 /* TranslationSetting.swift in Sources */ = {isa = PBXBuildFile; fileRef = AAD861A72E9E748100F6E0E0 /* TranslationSetting.swift */; };
 		AAD861AB2E9E75AB00F6E0E0 /* TranslationSettingsViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = AAD861AA2E9E75A100F6E0E0 /* TranslationSettingsViewController.swift */; };
 		AAD9D64B2EB25B3500BFECAF /* TranslationsMiddlewareTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = AAD9D64A2EB25B3200BFECAF /* TranslationsMiddlewareTests.swift */; };
+		AADBD0E42EBBA79B00F35E30 /* MockLanguageDetector.swift in Sources */ = {isa = PBXBuildFile; fileRef = AADBD0E32EBBA79700F35E30 /* MockLanguageDetector.swift */; };
 		AB2AC6632BCFD0A200022AAB /* X509 in Frameworks */ = {isa = PBXBuildFile; productRef = AB2AC6622BCFD0A200022AAB /* X509 */; };
 		AB2AC6662BD15E6300022AAB /* CertificatesHandler.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB2AC6652BD15E6300022AAB /* CertificatesHandler.swift */; };
 		AB3DB0C92B596739001D32CB /* AppStartupTelemetry.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB3DB0C82B596739001D32CB /* AppStartupTelemetry.swift */; };
@@ -9520,6 +9521,7 @@
 		AAD861A72E9E748100F6E0E0 /* TranslationSetting.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TranslationSetting.swift; sourceTree = "<group>"; };
 		AAD861AA2E9E75A100F6E0E0 /* TranslationSettingsViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TranslationSettingsViewController.swift; sourceTree = "<group>"; };
 		AAD9D64A2EB25B3200BFECAF /* TranslationsMiddlewareTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TranslationsMiddlewareTests.swift; sourceTree = "<group>"; };
+		AADBD0E32EBBA79700F35E30 /* MockLanguageDetector.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MockLanguageDetector.swift; sourceTree = "<group>"; };
 		AAF64ABAB8A585208603D45B /* dsb */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = dsb; path = dsb.lproj/LoginManager.strings; sourceTree = "<group>"; };
 		AB2AC6652BD15E6300022AAB /* CertificatesHandler.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CertificatesHandler.swift; sourceTree = "<group>"; };
 		AB2B45078A7F1E09F65ACEC5 /* cy */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = cy; path = cy.lproj/Shared.strings; sourceTree = "<group>"; };
@@ -14167,6 +14169,7 @@
 		AAD9D6492EB25B2700BFECAF /* TranslationsTests */ = {
 			isa = PBXGroup;
 			children = (
+				AADBD0E32EBBA79700F35E30 /* MockLanguageDetector.swift */,
 				C27EF61E2EBA395000BED719 /* MockLanguageSampleSource.swift */,
 				C27EF6142EBA2EDD00BED719 /* LanguageDetectorTests.swift */,
 				AAD9D64A2EB25B3200BFECAF /* TranslationsMiddlewareTests.swift */,
@@ -19369,6 +19372,7 @@
 				39BF0CD72EB512CD002064F5 /* ImpressionTrackingUtilityTests.swift in Sources */,
 				21FA8FB02AE856590013B815 /* RemoteTabsCoordinatorTests.swift in Sources */,
 				0E6557402D82232B00D7F017 /* DownloadProgressManagerTests.swift in Sources */,
+				AADBD0E42EBBA79B00F35E30 /* MockLanguageDetector.swift in Sources */,
 				AAB434062E82F0600075E47F /* MockTrendingSearchProvider.swift in Sources */,
 				C80C11F428B3CD580062922A /* MockUserDefaultsTests.swift in Sources */,
 				E14D6D342CCBA9FF0058B910 /* AddressBarStateTests.swift in Sources */,

firefox-ios/Client/Frontend/Browser/Toolbars/Redux/AddressBarState.swift

@@ -1054,10 +1054,10 @@ struct AddressBarState: StateType, Sendable, Equatable {
         let shouldShowTranslationIcon = canTranslateFromAction || canTranslateFromState
         guard shouldShowTranslationIcon else { return nil }
         let configuration = action.translationConfiguration ?? addressBarState.translationConfiguration
-        guard let configuration else { return nil }
+        guard let state = configuration?.state else { return nil }
         return translateAction(
             enabled: isLoading == false,
-            configuration: configuration,
+            state: state,
             hasAlternativeLocationColor: hasAlternativeLocationColor
         )
     }
@@ -1308,22 +1308,22 @@ struct AddressBarState: StateType, Sendable, Equatable {
     // when switching from inactive icon to loading icon when user taps on it. Hence, `hasHighlightedColor: false`.
     private static func translateAction(
         enabled: Bool,
-        configuration: TranslationConfiguration,
+        state: TranslationConfiguration.IconState,
         hasAlternativeLocationColor: Bool
     ) -> ToolbarActionConfiguration {
         // We do not want to use template mode for translate active icon.
-        let isActiveState = configuration.state == .active
+        let isActiveState = state == .active
 
         return ToolbarActionConfiguration(
             actionType: .translate,
-            iconName: configuration.state.buttonImageName,
+            iconName: state.buttonImageName,
             templateModeForImage: !isActiveState,
-            shouldUseLoadingSpinner: configuration.state == .loading,
+            shouldUseLoadingSpinner: state == .loading,
             isEnabled: enabled,
             hasCustomColor: !hasAlternativeLocationColor,
             hasHighlightedColor: false,
             contextualHintType: ContextualHintType.translation.rawValue,
-            a11yLabel: configuration.state.buttonA11yLabel,
+            a11yLabel: state.buttonA11yLabel,
             a11yId: AccessibilityIdentifiers.Toolbar.translateButton
         )
     }

firefox-ios/Client/Frontend/Browser/Toolbars/Redux/TranslationsConfiguration.swift

@@ -41,9 +41,12 @@ struct TranslationConfiguration: Equatable, FeatureFlaggable {
     }
 
     let prefs: Prefs
-    let state: IconState
+    let state: IconState?
 
-    init(prefs: Prefs, state: IconState = .inactive) {
+    // We initially set icon state as nil until we can detect the
+    // web page and determine if we should show the translation icon
+    // and set the icon to .inactive state.
+    init(prefs: Prefs, state: IconState? = nil) {
         self.prefs = prefs
         self.state = state
     }

firefox-ios/Client/Frontend/Translations/LanguageDetector/LanguageDetector.swift

@@ -7,22 +7,31 @@ import NaturalLanguage
 
 /// A small utility for extracting a text sample from a web page and detecting its language.
 /// The sample is extracted using JS.
-final class LanguageDetector {
+protocol LanguageDetectorProvider: Sendable {
+    func detectLanguage(from source: LanguageSampleSource) async throws -> String?
+}
+
+final class LanguageDetector: LanguageDetectorProvider {
     /// JS function that is called to get a page sample back. The function is implemented in `Summarizer.js`.
     private let languageSampleScript =
         "return await window.__firefox__.Translations.getLanguageSampleWhenReady()"
 
+    func detectLanguage(from source: LanguageSampleSource) async throws -> String? {
+        let sample = try await extractSample(from: source)
+        guard let textSample = sample else { return nil }
+        return getDominantLanguage(of: textSample)
+    }
+
     /// Extracts a text sample from the page via the JS bridge.
     /// Returns `nil` if the bridge isn’t ready or no sample is available.
-    @MainActor
-    func extractSample(from source: LanguageSampleSource) async throws -> String? {
+    private func extractSample(from source: LanguageSampleSource) async throws -> String? {
         let sample = try await source.getLanguageSample(scriptEvalExpression: languageSampleScript)
         guard let sample = sample, !sample.isEmpty else { return nil }
         return sample
     }
 
     /// Detects the dominant language of a given text and returns its BCP-47 code (e.g. `"en"`, `"fr"`).
-    func detectLanguage(of text: String) -> String? {
+    private func getDominantLanguage(of text: String) -> String? {
         let trimmed = text.trimmingCharacters(in: .whitespacesAndNewlines)
         guard !trimmed.isEmpty else { return nil }
         return NLLanguageRecognizer.dominantLanguage(for: trimmed)?.rawValue

firefox-ios/Client/Frontend/Translations/LanguageDetector/LanguageSampleSource.swift

@@ -7,7 +7,7 @@ import Foundation
 /// A small abstraction for obtaining a language sample from webpage content.
 /// This is done to allow `LanguageDetector` to request text from a page without knowing
 /// whether the source is a real `WKWebView` running JavaScript or a test mock.
-protocol LanguageSampleSource {
+protocol LanguageSampleSource: Sendable {
     /// `scriptEvalExpression` is the JavaScript expression that should be evaluated
     /// by the underlying implementation.
     @MainActor

firefox-ios/Client/Frontend/Translations/TranslationsMiddleware.swift

@@ -10,11 +10,18 @@ import Common
 final class TranslationsMiddleware {
     private let profile: Profile
     private let logger: Logger
+    private let languageDetector: LanguageDetectorProvider
+    private let windowManager: WindowManager
 
     init(profile: Profile = AppContainer.shared.resolve(),
-         logger: Logger = DefaultLogger.shared) {
+         languageDetector: LanguageDetectorProvider = LanguageDetector(),
+         logger: Logger = DefaultLogger.shared,
+         windowManager: WindowManager = AppContainer.shared.resolve()
+    ) {
         self.profile = profile
+        self.languageDetector = languageDetector
         self.logger = logger
+        self.windowManager = windowManager
     }
 
     lazy var translationsProvider: Middleware<AppState> = { state, action in
@@ -104,21 +111,31 @@ final class TranslationsMiddleware {
         store.dispatch(toolbarAction)
     }
 
-    // TODO: FXIOS-13844 - Check if we can translate a page based on certain eligibility
-    @MainActor
+    /// Checks whether the current page in the active tab is eligible for translation,
+    /// and if so, dispatches a toolbar action to update the translation state.
     private func checkTranslationsAreEligible(for action: ToolbarAction) {
-        // We dispatch an action for now, but eventually we want to inject a script
-        // to check if the page language differs from our locale language.
-        guard action.translationConfiguration?.canTranslate == true else { return }
-        let toolbarAction = ToolbarAction(
-            translationConfiguration: TranslationConfiguration(
-                prefs: profile.prefs,
-                state: .inactive
-            ),
-            windowUUID: action.windowUUID,
-            actionType: ToolbarActionType.receivedTranslationLanguage
-        )
-        store.dispatch(toolbarAction)
+        Task { @MainActor in
+            guard action.translationConfiguration?.canTranslate == true else { return }
+
+            guard let selectedTab = self.windowManager.tabManager(for: action.windowUUID).selectedTab,
+                  let webView = selectedTab.webView
+            else { return }
+
+            let languageSampleSource = WebViewLanguageSampleSource(webView: webView)
+            let pageLanguage = try await languageDetector.detectLanguage(from: languageSampleSource)
+
+            guard let pageLanguage, pageLanguage != Locale.current.languageCode else { return }
+
+            let toolbarAction = ToolbarAction(
+                translationConfiguration: TranslationConfiguration(
+                    prefs: profile.prefs,
+                    state: .inactive
+                ),
+                windowUUID: action.windowUUID,
+                actionType: ToolbarActionType.receivedTranslationLanguage
+            )
+            store.dispatch(toolbarAction)
+        }
     }
 
     // TODO: FXIOS-13844 - Start translation a page and dispatch action after completion

firefox-ios/firefox-ios-tests/Tests/ClientTests/Toolbar/AddressBarStateTests.swift

@@ -391,7 +391,10 @@ final class AddressBarStateTests: XCTestCase, StoreTestUtility {
             initialState,
             ToolbarAction(
                 url: URL(string: "http://mozilla.com"),
-                translationConfiguration: TranslationConfiguration(prefs: mockProfile.prefs),
+                translationConfiguration: TranslationConfiguration(
+                    prefs: mockProfile.prefs,
+                    state: .inactive
+                ),
                 windowUUID: windowUUID,
                 actionType: ToolbarActionType.urlDidChange
             )

firefox-ios/firefox-ios-tests/Tests/ClientTests/TranslationsTests/LanguageDetectorTests.swift

@@ -9,61 +9,80 @@ import XCTest
 final class LanguageDetectorTests: XCTestCase {
     var mockLanguageSampleSource = MockLanguageSampleSource()
 
-    func testExtractSampleReturnsTextSample() async throws {
+    func test_detectLanguage_withFrench_returnsProperLanguageCode() async throws {
         mockLanguageSampleSource.mockResult = "Bonjour le monde"
         let subject = createSubject()
-        let result = try await subject.extractSample(from: mockLanguageSampleSource)
-        XCTAssertEqual(result, "Bonjour le monde")
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "fr")
     }
 
-    func testExtractSampleReturnsNilForEmptyString() async throws {
+    func test_detectLanguage_withEnglish_returnsProperLanguageCode() async throws {
+        mockLanguageSampleSource.mockResult = "Hello world"
+        let subject = createSubject()
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "en")
+    }
+
+    func test_detectLanguage_withSpanish_returnsProperLanguageCode() async throws {
+        mockLanguageSampleSource.mockResult = "Hola mundo"
+        let subject = createSubject()
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "es")
+    }
+
+    func test_detectLanguage_withJapanese_returnsProperLanguageCode() async throws {
+        mockLanguageSampleSource.mockResult = "こんにちは世界"
+        let subject = createSubject()
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "ja")
+    }
+
+    func test_detectLanguage_withKorean_returnsProperLanguageCode() async throws {
+        mockLanguageSampleSource.mockResult = "안녕하세요 세계"
+        let subject = createSubject()
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "ko")
+    }
+
+    func test_detectLanguage_withEmptyString_returnsNil() async throws {
         mockLanguageSampleSource.mockResult = ""
         let subject = createSubject()
-        let result = try await subject.extractSample(from: mockLanguageSampleSource)
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
         XCTAssertNil(result)
     }
 
-    func testExtractSampleReturnsNilForNonString() async throws {
+    func test_detectLanguage_withWhitespaces_returnsNil() async throws {
+        mockLanguageSampleSource.mockResult = " \n\t "
+        let subject = createSubject()
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertNil(result)
+    }
+
+    func test_detectLanguage_returnsNilForNonString() async throws {
         mockLanguageSampleSource.mockResult = 42
         let subject = createSubject()
-        let result = try await subject.extractSample(from: mockLanguageSampleSource)
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
         XCTAssertNil(result)
     }
 
-    func testExtractSamplePropagatesError() async {
+    func test_detectLanguage_propagatesError() async {
         enum FakeError: Error, Equatable { case foo }
         mockLanguageSampleSource.mockError = FakeError.foo
         let subject = createSubject()
 
         do {
-            _ = try await subject.extractSample(from: mockLanguageSampleSource)
+            _ = try await subject.detectLanguage(from: mockLanguageSampleSource)
             XCTFail("expected error")
         } catch {
             XCTAssertEqual(error as? FakeError, .foo)
         }
     }
 
-    func testDetectLanguageReturnsLanguageCode() {
-        let subject = createSubject()
-
-        XCTAssertEqual(subject.detectLanguage(of: "Hello world"), "en")
-        XCTAssertEqual(subject.detectLanguage(of: "Bonjour le monde"), "fr")
-        XCTAssertEqual(subject.detectLanguage(of: "Hola mundo"), "es")
-        XCTAssertEqual(subject.detectLanguage(of: "こんにちは世界"), "ja")
-        XCTAssertEqual(subject.detectLanguage(of: "안녕하세요 세계"), "ko")
-    }
-
-    func testDetectLanguageReturnsNilForEmptyOrWhitespace() {
-        let subject = createSubject()
-
-        XCTAssertNil(subject.detectLanguage(of: ""))
-        XCTAssertNil(subject.detectLanguage(of: " \n\t "))
-    }
-
-    func testDetectLanguagePrefersDominantLanguage() {
+    func test_detectLanguage_prefersDominantLanguage() async throws {
         let subject = createSubject()
-        let text = "Hello, bonjour, hello, hello"
-        XCTAssertEqual(subject.detectLanguage(of: text), "en")
+        mockLanguageSampleSource.mockResult = "Hello, bonjour, hello, hello"
+        let result = try await subject.detectLanguage(from: mockLanguageSampleSource)
+        XCTAssertEqual(result, "en")
     }
 
     private func createSubject() -> LanguageDetector {

firefox-ios/firefox-ios-tests/Tests/ClientTests/TranslationsTests/MockLanguageDetector.swift

@@ -0,0 +1,14 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/
+import Foundation
+@testable import Client
+
+/// Test helper that simulates language detection.
+final class MockLanguageDetector: LanguageDetectorProvider, @unchecked Sendable {
+    var detectLanguageCallCount = 0
+    func detectLanguage(from source: LanguageSampleSource) async throws -> String? {
+        detectLanguageCallCount += 1
+        return "ja"
+    }
+}

firefox-ios/firefox-ios-tests/Tests/ClientTests/TranslationsTests/MockLanguageSampleSource.swift

@@ -6,7 +6,7 @@ import Foundation
 @testable import Client
 
 /// Test helper that simulates JS evaluation for language sample extraction.
-final class MockLanguageSampleSource: LanguageSampleSource {
+final class MockLanguageSampleSource: LanguageSampleSource, @unchecked Sendable {
     var mockResult: Any?
     var mockError: Error?