feat: Warn the user if the posting language might be incorrect

PRIVACY.md

@@ -28,8 +28,22 @@ You can not delete your Mastodon account using the application. Deleting your ac
 
 ## Data sharing
 
+### If you have installed Pachli from F-Droid or GitHub releases
+
 **None of the data used by the application is shared with the application developers or unrelated third parties.** Your data is only ever sent to your server, and handled in accordance with your server's privacy policy.
 
+### If you have installed Pachli from Google Play
+
+Pachli uses Google's [ML Kit](https://developers.google.com/ml-kit) to provide features that:
+
+- Warn you if the language you have selected when editing a post appears to be different from the language you used
+
+When Pachli does this all of the data you have provided (e.g., the content you are posting) is processed on your device, and **ML Kit does not send that data to Google servers**.
+
+The ML Kit APIs may contact Google servers from time to time in order to receive things like bug fixes, updated models and hardware accelerator compatibility information. The ML Kit APIs also send metrics about the performance and utilization of the APIs in your app to Google. Google uses this metrics data to measure performance, debug, maintain and improve the APIs, and detect misuse or abuse, as further described in Google's [Privacy Policy](https://policies.google.com/privacy).
+
+The specific data collected by ML Kit is in Google's [data disclosure](https://developers.google.com/ml-kit/android-data-disclosure) description.
+
 ## Data types
 
 The application processes the following types of data.

app/build.gradle.kts

@@ -179,6 +179,11 @@ dependencies {
     googleImplementation(libs.app.update)
     googleImplementation(libs.app.update.ktx)
 
+    // Language detection
+    googleImplementation(libs.play.services.base)
+    googleImplementation(libs.mlkit.language.id)
+    googleImplementation(libs.kotlinx.coroutines.play.services)
+
     implementation(libs.semver)
 
     debugImplementation(libs.leakcanary)

app/src/fdroid/kotlin/app/pachli/di/LanguageIdentifierFactoryModule.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 Pachli Association
+ *
+ * This file is a part of Pachli.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Pachli is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Pachli; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package app.pachli.di
+
+import android.content.Context
+import app.pachli.core.common.di.ApplicationScope
+import app.pachli.languageidentification.DefaultLanguageIdentifierFactory
+import app.pachli.languageidentification.LanguageIdentifier
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import kotlinx.coroutines.CoroutineScope
+
+@InstallIn(SingletonComponent::class)
+@Module
+object LanguageIdentifierFactoryModule {
+    @Provides
+    @Singleton
+    fun providesLanguageIdentifierFactory(
+        @ApplicationScope externalScope: CoroutineScope,
+        @ApplicationContext context: Context,
+    ): LanguageIdentifier.Factory = DefaultLanguageIdentifierFactory(externalScope, context)
+}

app/src/github/kotlin/app/pachli/di/LanguageIdentifierFactoryModule.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 Pachli Association
+ *
+ * This file is a part of Pachli.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Pachli is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Pachli; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package app.pachli.di
+
+import android.content.Context
+import app.pachli.core.common.di.ApplicationScope
+import app.pachli.languageidentification.DefaultLanguageIdentifierFactory
+import app.pachli.languageidentification.LanguageIdentifier
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import kotlinx.coroutines.CoroutineScope
+
+@InstallIn(SingletonComponent::class)
+@Module
+object LanguageIdentifierFactoryModule {
+    @Provides
+    @Singleton
+    fun providesLanguageIdentifierFactory(
+        @ApplicationScope externalScope: CoroutineScope,
+        @ApplicationContext context: Context,
+    ): LanguageIdentifier.Factory = DefaultLanguageIdentifierFactory(externalScope, context)
+}

app/src/google/kotlin/app/pachli/di/LanguageIdentifierFactoryModule.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 Pachli Association
+ *
+ * This file is a part of Pachli.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Pachli is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Pachli; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package app.pachli.di
+
+import android.content.Context
+import app.pachli.core.common.di.ApplicationScope
+import app.pachli.languageidentification.LanguageIdentifier
+import app.pachli.languageidentification.MlKitLanguageIdentifier
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import kotlinx.coroutines.CoroutineScope
+
+@InstallIn(SingletonComponent::class)
+@Module
+object LanguageIdentifierFactoryModule {
+    @Provides
+    @Singleton
+    fun providesLanguageIdentifierFactory(
+        @ApplicationScope externalScope: CoroutineScope,
+        @ApplicationContext context: Context,
+    ): LanguageIdentifier.Factory = MlKitLanguageIdentifier.Factory(externalScope, context)
+}

app/src/google/kotlin/app/pachli/languageidentification/MlKitLanguageIdentifier.kt

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2024 Pachli Association
+ *
+ * This file is a part of Pachli.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Pachli is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Pachli; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package app.pachli.languageidentification
+
+import android.content.Context
+import com.github.michaelbull.result.Err
+import com.github.michaelbull.result.Result
+import com.github.michaelbull.result.coroutines.runSuspendCatching
+import com.github.michaelbull.result.mapError
+import com.google.android.gms.common.moduleinstall.ModuleInstall
+import com.google.android.gms.common.moduleinstall.ModuleInstallRequest
+import com.google.mlkit.nl.languageid.LanguageIdentification
+import com.google.mlkit.nl.languageid.LanguageIdentifier as GoogleLanguageIdentifier
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.tasks.await
+import timber.log.Timber
+
+/**
+ * [LanguageIdentifier] that uses Google's ML Kit to perform the language
+ * identification.
+ */
+class MlKitLanguageIdentifier private constructor() : LanguageIdentifier {
+    private var client: GoogleLanguageIdentifier? = null
+
+    init {
+        client = LanguageIdentification.getClient()
+    }
+
+    override suspend fun identifyPossibleLanguages(text: String): Result<List<IdentifiedLanguage>, LanguageIdentifierError> {
+        return client?.let { client ->
+            // May throw an MlKitException, so catch and map error
+            runSuspendCatching {
+                client.identifyPossibleLanguages(text).await().map {
+                    IdentifiedLanguage(
+                        confidence = it.confidence,
+                        languageTag = it.languageTag,
+                    )
+                }
+            }.mapError { LanguageIdentifierError.Unknown(it) }
+        } ?: Err(LanguageIdentifierError.UseAfterClose)
+    }
+
+    override fun close() {
+        client?.close()
+        client = null
+    }
+
+    /**
+     * Factory for LanguageIdentifer based on Google's ML Kit.
+     *
+     * When the factory is constructed a [com.google.android.gms.tasks.Task]
+     * to check and install the language module is launched, increasing the
+     * chances the module will be installed before it is first used.
+     */
+    class Factory(
+        private val externalScope: CoroutineScope,
+        private val context: Context,
+    ) : LanguageIdentifier.Factory() {
+        private val moduleInstallClient = ModuleInstall.getClient(context)
+
+        init {
+            LanguageIdentification.getClient().use { langIdClient ->
+                val moduleInstallRequest = ModuleInstallRequest.newBuilder()
+                    .addApi(langIdClient)
+                    .build()
+
+                moduleInstallClient.installModules(moduleInstallRequest)
+            }
+        }
+
+        /**
+         * Returns a [MlKitLanguageIdentifier] if the relevant modules are
+         * installed, defers to [DefaultLanguageIdentifierFactory] if not.
+         */
+        override suspend fun newInstance(): LanguageIdentifier {
+            LanguageIdentification.getClient().use { langIdClient ->
+                val modulesAreAvailable = moduleInstallClient
+                    .areModulesAvailable(langIdClient)
+                    .await()
+                    .areModulesAvailable()
+
+                return if (modulesAreAvailable) {
+                    Timber.d("mlkit langid module available")
+                    MlKitLanguageIdentifier()
+                } else {
+                    Timber.d("mlkit langid module *not* available")
+                    DefaultLanguageIdentifierFactory(externalScope, context)
+                        .newInstance()
+                }
+            }
+        }
+    }
+}

app/src/main/AndroidManifest.xml

@@ -25,6 +25,10 @@
         android:networkSecurityConfig="@xml/network_security_config"
         android:enableOnBackInvokedCallback="true">
 
+        <meta-data
+            android:name="com.google.mlkit.vision.DEPENDENCIES"
+            android:value="langid" />
+
         <activity
             android:name=".feature.login.LoginActivity"
             android:windowSoftInputMode="adjustResize"

app/src/main/java/app/pachli/adapter/LocaleAdapter.kt

@@ -27,6 +27,15 @@ import app.pachli.util.modernLanguageCode
 import com.google.android.material.color.MaterialColors
 import java.util.Locale
 
+/**
+ * Display a list of [Locale] in a spinner.
+ *
+ * At rest the locale is represented by the uppercase 2-3 character language code without
+ * any subcategories ("EN", "DE", "ZH") etc.
+ *
+ * In the menu the locale is presented as "Local name (name)". E.g,. when the current
+ * locale is English the German locale is displayed as "German (Deutsch)".
+ */
 class LocaleAdapter(context: Context, resource: Int, locales: List<Locale>) : ArrayAdapter<Locale>(context, resource, locales) {
     override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
         return (super.getView(position, convertView, parent) as TextView).apply {