Add new-mail notifications and persisted settings

Increment 6 — notifications and settings.

- Local new-mail notifications (no push service): MailNotifier posts a notification
  when background sync finds newly-arrived unread mail, and tapping it opens the app.
  Adds a POST_NOTIFICATIONS request on launch.
- MailSyncer detects genuinely new messages (diff against cached ids, skipped on an
  account's first sync) and notifies when the setting is enabled.
- SettingsRepository (Preferences DataStore) persists settings; the Settings screen
  gains a Notifications section, and "Use wallpaper colors" now actually drives the
  Material You theme (MainActivity collects it reactively).
- assemble/test/lint green; verified on the Android 17 emulator — delivered a new
  message and the on-device notification appeared in the shade.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -5,6 +5,7 @@
 
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.READ_CONTACTS" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
     <application
         android:name=".LibreMailApplication"

app/src/main/kotlin/org/libremail/MainActivity.kt

@@ -1,23 +1,53 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 package org.libremail
 
+import android.Manifest
+import android.content.pm.PackageManager
 import android.os.Bundle
 import androidx.activity.ComponentActivity
+import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.platform.LocalContext
+import androidx.core.content.ContextCompat
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
+import org.libremail.data.settings.SettingsRepository
 import org.libremail.ui.LibreMailApp
 import org.libremail.ui.theme.LibreMailTheme
 
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
+
+    @Inject
+    lateinit var settingsRepository: SettingsRepository
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContent {
-            LibreMailTheme {
+            val dynamicColor by settingsRepository.dynamicColor.collectAsStateWithLifecycle(initialValue = true)
+            LibreMailTheme(dynamicColor = dynamicColor) {
+                NotificationPermissionEffect()
                 LibreMailApp()
             }
         }
     }
 }
+
+/** Requests POST_NOTIFICATIONS once on first launch (no-op if already granted). */
+@Composable
+private fun NotificationPermissionEffect() {
+    val context = LocalContext.current
+    val launcher = rememberLauncherForActivityResult(ActivityResultContracts.RequestPermission()) {}
+    LaunchedEffect(Unit) {
+        val granted = ContextCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) ==
+            PackageManager.PERMISSION_GRANTED
+        if (!granted) launcher.launch(Manifest.permission.POST_NOTIFICATIONS)
+    }
+}

app/src/main/kotlin/org/libremail/data/local/dao/MessageDao.kt

@@ -16,6 +16,9 @@ interface MessageDao {
     @Query("SELECT * FROM messages WHERE id = :id LIMIT 1")
     suspend fun getById(id: String): MessageEntity?
 
+    @Query("SELECT id FROM messages WHERE accountId = :accountId")
+    suspend fun getIdsForAccount(accountId: String): List<String>
+
     /** Inserts only new messages, leaving existing rows (and their cached bodies) intact. */
     @Insert(onConflict = OnConflictStrategy.IGNORE)
     suspend fun insertNew(messages: List<MessageEntity>)

app/src/main/kotlin/org/libremail/data/settings/SettingsRepository.kt

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.data.settings
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.booleanPreferencesKey
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.preferencesDataStore
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import javax.inject.Singleton
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.map
+
+private val Context.settingsDataStore: DataStore<Preferences> by preferencesDataStore(name = "libremail_settings")
+
+/** User preferences. Only [dynamicColor] and [newMailNotifications] are wired to behaviour so far. */
+data class AppSettings(
+    val dynamicColor: Boolean = true,
+    val newMailNotifications: Boolean = true,
+    val pushIdle: Boolean = true,
+    val allowStartTls: Boolean = false,
+    val loadRemoteImages: Boolean = false,
+)
+
+@Singleton
+class SettingsRepository @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+    val settings: Flow<AppSettings> = context.settingsDataStore.data.map { prefs ->
+        AppSettings(
+            dynamicColor = prefs[DYNAMIC_COLOR] ?: true,
+            newMailNotifications = prefs[NEW_MAIL_NOTIFICATIONS] ?: true,
+            pushIdle = prefs[PUSH_IDLE] ?: true,
+            allowStartTls = prefs[ALLOW_STARTTLS] ?: false,
+            loadRemoteImages = prefs[LOAD_REMOTE_IMAGES] ?: false,
+        )
+    }
+
+    val dynamicColor: Flow<Boolean> = settings.map { it.dynamicColor }
+
+    suspend fun isNewMailNotificationsEnabled(): Boolean = settings.first().newMailNotifications
+
+    suspend fun setDynamicColor(value: Boolean) = put(DYNAMIC_COLOR, value)
+    suspend fun setNewMailNotifications(value: Boolean) = put(NEW_MAIL_NOTIFICATIONS, value)
+    suspend fun setPushIdle(value: Boolean) = put(PUSH_IDLE, value)
+    suspend fun setAllowStartTls(value: Boolean) = put(ALLOW_STARTTLS, value)
+    suspend fun setLoadRemoteImages(value: Boolean) = put(LOAD_REMOTE_IMAGES, value)
+
+    private suspend fun put(key: Preferences.Key<Boolean>, value: Boolean) {
+        context.settingsDataStore.edit { it[key] = value }
+    }
+
+    private companion object {
+        val DYNAMIC_COLOR = booleanPreferencesKey("dynamic_color")
+        val NEW_MAIL_NOTIFICATIONS = booleanPreferencesKey("new_mail_notifications")
+        val PUSH_IDLE = booleanPreferencesKey("push_idle")
+        val ALLOW_STARTTLS = booleanPreferencesKey("allow_starttls")
+        val LOAD_REMOTE_IMAGES = booleanPreferencesKey("load_remote_images")
+    }
+}

app/src/main/kotlin/org/libremail/data/sync/MailSyncer.kt

@@ -5,18 +5,23 @@ import javax.inject.Inject
 import javax.inject.Singleton
 import org.libremail.data.local.dao.AccountDao
 import org.libremail.data.local.dao.MessageDao
+import org.libremail.data.local.entity.MessageEntity
 import org.libremail.data.local.toDomain
 import org.libremail.data.local.toEntity
+import org.libremail.data.settings.SettingsRepository
 import org.libremail.domain.model.Account
 import org.libremail.mail.ImapClient
+import org.libremail.notifications.MailNotifier
 
-/** Fetches each account's recent INBOX headers and writes them into Room (the source of truth). */
+/** Fetches each account's recent INBOX headers into Room and notifies about newly-arrived mail. */
 @Singleton
 class MailSyncer @Inject constructor(
     private val accountDao: AccountDao,
     private val messageDao: MessageDao,
     private val imapClient: ImapClient,
     private val connectionFactory: MailConnectionFactory,
+    private val settingsRepository: SettingsRepository,
+    private val notifier: MailNotifier,
 ) {
     /** Syncs every account. Succeeds if at least one account synced (or there are none). */
     suspend fun syncAll(): Result<Int> {
@@ -26,24 +31,40 @@ class MailSyncer @Inject constructor(
         var total = 0
         var firstError: Throwable? = null
         var anySuccess = false
+        val newMessages = mutableListOf<MessageEntity>()
         for (entity in accounts) {
             syncAccount(entity.toDomain()).fold(
-                onSuccess = { total += it; anySuccess = true },
+                onSuccess = { result ->
+                    total += result.fetched
+                    newMessages += result.newMessages
+                    anySuccess = true
+                },
                 onFailure = { error -> if (firstError == null) firstError = error },
             )
         }
+
+        if (newMessages.isNotEmpty() && settingsRepository.isNewMailNotificationsEnabled()) {
+            notifier.notifyNewMail(newMessages.sortedByDescending { it.timestampMillis })
+        }
         return if (anySuccess || firstError == null) Result.success(total) else Result.failure(firstError!!)
     }
 
-    private suspend fun syncAccount(account: Account): Result<Int> = runCatching {
+    private suspend fun syncAccount(account: Account): Result<AccountSyncResult> = runCatching {
         val params = connectionFactory.imapParamsFor(account)
         val fetched = imapClient.fetchRecentInbox(params, INBOX_LIMIT)
         val entities = fetched.map { it.toEntity(account.id) }
+
+        val existingIds = messageDao.getIdsForAccount(account.id).toHashSet()
+        // Don't notify on the very first sync of an account (would announce the whole inbox).
+        val newMessages = if (existingIds.isEmpty()) {
+            emptyList()
+        } else {
+            entities.filter { it.id !in existingIds && !it.isRead }
+        }
+
         if (entities.isEmpty()) {
             messageDao.deleteByAccount(account.id)
         } else {
-            // Insert new headers (keeps any already-cached body), refresh header/flag columns,
-            // then drop messages that no longer exist on the server.
             messageDao.insertNew(entities)
             entities.forEach {
                 messageDao.updateHeader(
@@ -58,9 +79,11 @@ class MailSyncer @Inject constructor(
             }
             messageDao.deleteNotIn(account.id, entities.map { it.id })
         }
-        fetched.size
+        AccountSyncResult(fetched = fetched.size, newMessages = newMessages)
     }
 
+    private data class AccountSyncResult(val fetched: Int, val newMessages: List<MessageEntity>)
+
     private companion object {
         const val INBOX_LIMIT = 50
     }

app/src/main/kotlin/org/libremail/notifications/MailNotifier.kt

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.notifications
+
+import android.Manifest
+import android.annotation.SuppressLint
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import android.content.pm.PackageManager
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import androidx.core.content.ContextCompat
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import javax.inject.Singleton
+import org.libremail.MainActivity
+import org.libremail.R
+import org.libremail.data.local.entity.MessageEntity
+
+/** Posts on-device new-mail notifications (no push service involved). */
+@Singleton
+class MailNotifier @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+    // Permission is checked via hasPermission() below; lint can't trace the indirect guard.
+    @SuppressLint("MissingPermission")
+    fun notifyNewMail(messages: List<MessageEntity>) {
+        if (messages.isEmpty() || !hasPermission()) return
+        ensureChannel()
+
+        val title = if (messages.size == 1) {
+            messages.first().sender
+        } else {
+            context.getString(R.string.notif_new_mail_count, messages.size)
+        }
+        val text = if (messages.size == 1) {
+            messages.first().subject
+        } else {
+            messages.joinToString(", ") { it.sender }
+        }
+
+        val intent = Intent(context, MainActivity::class.java).apply {
+            flags = Intent.FLAG_ACTIVITY_SINGLE_TOP or Intent.FLAG_ACTIVITY_CLEAR_TOP
+        }
+        val pendingIntent = PendingIntent.getActivity(
+            context,
+            0,
+            intent,
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT,
+        )
+
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_launcher_monochrome)
+            .setContentTitle(title)
+            .setContentText(text)
+            .setStyle(NotificationCompat.BigTextStyle().bigText(text))
+            .setCategory(NotificationCompat.CATEGORY_EMAIL)
+            .setAutoCancel(true)
+            .setContentIntent(pendingIntent)
+            .build()
+
+        NotificationManagerCompat.from(context).notify(NOTIFICATION_ID, notification)
+    }
+
+    private fun hasPermission(): Boolean =
+        ContextCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) ==
+            PackageManager.PERMISSION_GRANTED
+
+    private fun ensureChannel() {
+        val channel = NotificationChannel(
+            CHANNEL_ID,
+            context.getString(R.string.notif_channel_new_mail),
+            NotificationManager.IMPORTANCE_DEFAULT,
+        )
+        NotificationManagerCompat.from(context).createNotificationChannel(channel)
+    }
+
+    private companion object {
+        const val CHANNEL_ID = "new_mail"
+        const val NOTIFICATION_ID = 1001
+    }
+}

app/src/main/kotlin/org/libremail/ui/settings/SettingsScreen.kt

@@ -43,8 +43,10 @@ fun SettingsScreen(
     onSelectTab: (TopDest) -> Unit,
     viewModel: SettingsViewModel = hiltViewModel(),
 ) {
-    val state by viewModel.state.collectAsStateWithLifecycle()
+    val settings by viewModel.settings.collectAsStateWithLifecycle()
     val accounts by viewModel.accounts.collectAsStateWithLifecycle()
+    val advancedExpanded by viewModel.advancedExpanded.collectAsStateWithLifecycle()
+
     Scaffold(
         topBar = { TopAppBar(title = { Text(stringResource(R.string.title_settings)) }) },
         bottomBar = { LibreMailBottomBar(current = TopDest.SETTINGS, onSelect = onSelectTab) },
@@ -71,31 +73,40 @@ fun SettingsScreen(
             ClickRow(title = stringResource(R.string.settings_add_account), onClick = onAddAccount)
             HorizontalDivider()
 
+            SectionHeader(stringResource(R.string.settings_notifications))
+            SwitchRow(
+                title = stringResource(R.string.settings_new_mail),
+                checked = settings.newMailNotifications,
+                onCheckedChange = viewModel::setNewMailNotifications,
+                subtitle = stringResource(R.string.settings_new_mail_summary),
+            )
+            HorizontalDivider()
+
             SectionHeader(stringResource(R.string.settings_appearance))
             SwitchRow(
                 title = stringResource(R.string.settings_dynamic_color),
-                checked = state.dynamicColor,
+                checked = settings.dynamicColor,
                 onCheckedChange = viewModel::setDynamicColor,
                 subtitle = stringResource(R.string.settings_dynamic_color_summary),
             )
             HorizontalDivider()
 
-            AdvancedHeader(expanded = state.advancedExpanded, onToggle = viewModel::toggleAdvanced)
-            AnimatedVisibility(visible = state.advancedExpanded) {
+            AdvancedHeader(expanded = advancedExpanded, onToggle = viewModel::toggleAdvanced)
+            AnimatedVisibility(visible = advancedExpanded) {
                 Column {
                     SwitchRow(
                         title = stringResource(R.string.settings_adv_idle),
-                        checked = state.pushIdle,
+                        checked = settings.pushIdle,
                         onCheckedChange = viewModel::setPushIdle,
                     )
                     SwitchRow(
                         title = stringResource(R.string.settings_adv_starttls),
-                        checked = state.allowStartTls,
+                        checked = settings.allowStartTls,
                         onCheckedChange = viewModel::setAllowStartTls,
                     )
                     SwitchRow(
                         title = stringResource(R.string.settings_adv_remote_images),
-                        checked = state.loadRemoteImages,
+                        checked = settings.loadRemoteImages,
                         onCheckedChange = viewModel::setLoadRemoteImages,
                     )
                 }

app/src/main/kotlin/org/libremail/ui/settings/SettingsViewModel.kt

@@ -12,35 +12,37 @@ import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import org.libremail.data.settings.AppSettings
+import org.libremail.data.settings.SettingsRepository
 import org.libremail.domain.model.Account
 import org.libremail.domain.repository.AccountRepository
 
-data class SettingsUiState(
-    val dynamicColor: Boolean = true,
-    val advancedExpanded: Boolean = false,
-    val pushIdle: Boolean = true,
-    val allowStartTls: Boolean = false,
-    val loadRemoteImages: Boolean = false,
-)
-
 @HiltViewModel
 class SettingsViewModel @Inject constructor(
     private val accountRepository: AccountRepository,
+    private val settingsRepository: SettingsRepository,
 ) : ViewModel() {
 
-    private val _state = MutableStateFlow(SettingsUiState())
-    val state: StateFlow<SettingsUiState> = _state.asStateFlow()
-
     val accounts: StateFlow<List<Account>> = accountRepository.observeAccounts()
         .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyList())
 
-    fun removeAccount(id: String) {
-        viewModelScope.launch { accountRepository.deleteAccount(id) }
-    }
+    val settings: StateFlow<AppSettings> = settingsRepository.settings
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), AppSettings())
 
-    fun setDynamicColor(value: Boolean) = _state.update { it.copy(dynamicColor = value) }
-    fun toggleAdvanced() = _state.update { it.copy(advancedExpanded = !it.advancedExpanded) }
-    fun setPushIdle(value: Boolean) = _state.update { it.copy(pushIdle = value) }
-    fun setAllowStartTls(value: Boolean) = _state.update { it.copy(allowStartTls = value) }
-    fun setLoadRemoteImages(value: Boolean) = _state.update { it.copy(loadRemoteImages = value) }
+    private val _advancedExpanded = MutableStateFlow(false)
+    val advancedExpanded: StateFlow<Boolean> = _advancedExpanded.asStateFlow()
+
+    fun toggleAdvanced() = _advancedExpanded.update { !it }
+
+    fun removeAccount(id: String) = viewModelScope.launch { accountRepository.deleteAccount(id) }.let {}
+
+    fun setDynamicColor(value: Boolean) = update { settingsRepository.setDynamicColor(value) }
+    fun setNewMailNotifications(value: Boolean) = update { settingsRepository.setNewMailNotifications(value) }
+    fun setPushIdle(value: Boolean) = update { settingsRepository.setPushIdle(value) }
+    fun setAllowStartTls(value: Boolean) = update { settingsRepository.setAllowStartTls(value) }
+    fun setLoadRemoteImages(value: Boolean) = update { settingsRepository.setLoadRemoteImages(value) }
+
+    private inline fun update(crossinline action: suspend () -> Unit) {
+        viewModelScope.launch { action() }
+    }
 }

app/src/main/res/values/strings.xml

@@ -59,8 +59,15 @@
     <string name="manual_smtp_security">SMTP security</string>
     <string name="manual_test_and_add">Test &amp; add account</string>
 
+    <!-- Notifications -->
+    <string name="notif_channel_new_mail">New mail</string>
+    <string name="notif_new_mail_count">%1$d new messages</string>
+
     <!-- Settings -->
     <string name="settings_accounts">Accounts</string>
+    <string name="settings_notifications">Notifications</string>
+    <string name="settings_new_mail">New-mail notifications</string>
+    <string name="settings_new_mail_summary">Show a notification when new mail arrives</string>
     <string name="settings_no_accounts">No accounts yet</string>
     <string name="account_remove">Remove</string>
     <string name="settings_appearance">Appearance</string>