feat: add change alerts for schedule updates with notifications

android/app/src/main/kotlin/org/xtimms/psu/schedule/ScheduleApp.kt

@@ -26,6 +26,7 @@ class ScheduleApp : Application() {
         notes = NotesStore(this)
         attendance = AttendanceStore(this)
         Reminders.createChannel(this)
+        org.xtimms.psu.schedule.notify.ChangeAlerts.createChannel(this)
         SyncWorker.schedule(this)
     }
 }

android/app/src/main/kotlin/org/xtimms/psu/schedule/data/Settings.kt

@@ -41,6 +41,8 @@ data class UserSettings(
     val dynamicColor: Boolean = false,
     val reminders: Boolean = false,
     val reminderMinutes: Int = 10,
+    /** A notification when the background sync finds changes in the group's document. */
+    val changeAlerts: Boolean = true,
     val recent: List<SavedGroup> = emptyList(),
     val display: Display = Display(),
     /** Lessons hidden in the open group, as [Lesson.hideKey]s. */
@@ -59,6 +61,7 @@ class Settings(private val context: Context) {
         val dynamic = booleanPreferencesKey("dynamic_color")
         val reminders = booleanPreferencesKey("reminders")
         val minutes = intPreferencesKey("reminder_minutes")
+        val changeAlerts = booleanPreferencesKey("change_alerts")
         val recent = stringPreferencesKey("recent")
         val colors = booleanPreferencesKey("show_colors")
         val teachers = booleanPreferencesKey("show_teachers")
@@ -91,6 +94,7 @@ class Settings(private val context: Context) {
             dynamicColor = this[Keys.dynamic] ?: false,
             reminders = this[Keys.reminders] ?: false,
             reminderMinutes = this[Keys.minutes] ?: 10,
+            changeAlerts = this[Keys.changeAlerts] ?: true,
             recent = this[Keys.recent]?.let {
                 runCatching { json.decodeFromString<List<SavedGroup>>(it) }.getOrNull()
             }.orEmpty(),
@@ -136,6 +140,7 @@ class Settings(private val context: Context) {
     suspend fun setDynamicColor(on: Boolean) = context.store.edit { it[Keys.dynamic] = on }
     suspend fun setReminders(on: Boolean) = context.store.edit { it[Keys.reminders] = on }
     suspend fun setReminderMinutes(minutes: Int) = context.store.edit { it[Keys.minutes] = minutes }
+    suspend fun setChangeAlerts(on: Boolean) = context.store.edit { it[Keys.changeAlerts] = on }
 
     /** Hides or shows again a recurring lesson of the open group. */
     suspend fun setHidden(key: String, hidden: Boolean) = context.store.edit { prefs ->

android/app/src/main/kotlin/org/xtimms/psu/schedule/notify/ChangeAlerts.kt

@@ -0,0 +1,68 @@
+package org.xtimms.psu.schedule.notify
+
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import org.xtimms.psu.schedule.MainActivity
+import org.xtimms.psu.schedule.R
+import org.xtimms.psu.schedule.data.ScheduleChanges
+import org.xtimms.psu.schedule.data.dayName
+import org.xtimms.psu.schedule.data.longLabel
+import org.xtimms.psu.schedule.data.parseDate
+import org.xtimms.psu.schedule.ui.changeDate
+import org.xtimms.psu.schedule.ui.changesLabel
+
+/**
+ * A notification when the background sync finds that the university republished the group's
+ * document and something changed. Local, like the reminders: the sync itself notices it, every
+ * few hours, without a push server. Opening it shows the overview with the changes card.
+ */
+object ChangeAlerts {
+    private const val CHANNEL = "schedule_changes"
+    private const val ID = 900
+
+    fun createChannel(context: Context) {
+        val channel = NotificationChannel(
+            CHANNEL,
+            context.getString(R.string.channel_changes),
+            NotificationManager.IMPORTANCE_DEFAULT,
+        ).apply { description = "Когда университет перезалил документ группы и в расписании что-то поменялось" }
+        context.getSystemService(NotificationManager::class.java).createNotificationChannel(channel)
+    }
+
+    /** "Проектирование общественных зданий: аудитория 374 → 375", up to [max] lines. */
+    fun summary(record: ScheduleChanges, max: Int = 4): List<String> {
+        val lines = record.changed.map { c ->
+            c.after.lesson.subject + ": " + c.fields.joinToString(", ") { "${it.label.lowercase()} ${it.from} → ${it.to}" }
+                .ifEmpty { "изменилась запись Word" }
+        } + record.added.map { "Добавлено: ${it.lesson.subject}, ${it.date?.let { d -> parseDate(d).longLabel() } ?: dayName(it.day).lowercase()} ${it.lesson.start}" } +
+            record.removed.map { "Удалено: ${it.lesson.subject}" }
+        return if (lines.size > max) lines.take(max - 1) + "И ещё ${lines.size - max + 1}" else lines
+    }
+
+    fun show(context: Context, record: ScheduleChanges) {
+        if (!Reminders.canNotify(context)) return
+        val open = PendingIntent.getActivity(
+            context,
+            1,
+            Intent(context, MainActivity::class.java).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),
+            PendingIntent.FLAG_IMMUTABLE,
+        )
+        val text = changesLabel(record.count) + (changeDate(record.to)?.let { " · файл от $it" } ?: "")
+        val notification = NotificationCompat.Builder(context, CHANNEL)
+            .setSmallIcon(R.drawable.ic_notification)
+            .setContentTitle("Расписание ${record.group} изменилось")
+            .setContentText(text)
+            .setStyle(NotificationCompat.BigTextStyle().bigText((listOf(text) + summary(record)).joinToString("\n")))
+            .setCategory(NotificationCompat.CATEGORY_STATUS)
+            .setContentIntent(open)
+            .setAutoCancel(true)
+            .build()
+        @Suppress("MissingPermission")
+        NotificationManagerCompat.from(context).notify(ID, notification)
+    }
+}

android/app/src/main/kotlin/org/xtimms/psu/schedule/ui/MainViewModel.kt

@@ -154,6 +154,8 @@ class MainViewModel(application: Application) : AndroidViewModel(application) {
         SyncWorker.afterChange(getApplication())
     }
 
+    fun setChangeAlerts(on: Boolean) = viewModelScope.launch { app.settings.setChangeAlerts(on) }
+
     fun setReminderMinutes(minutes: Int) = viewModelScope.launch {
         app.settings.setReminderMinutes(minutes)
         SyncWorker.afterChange(getApplication())

android/app/src/main/kotlin/org/xtimms/psu/schedule/ui/SettingsScreen.kt

@@ -57,6 +57,9 @@ fun SettingsScreen(vm: MainViewModel, onBack: () -> Unit) {
     val permission = rememberLauncherForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
         vm.setReminders(granted)
     }
+    val changesPermission = rememberLauncherForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
+        vm.setChangeAlerts(granted)
+    }
 
     val scroll = TopAppBarDefaults.pinnedScrollBehavior()
     Column(Modifier.fillMaxSize().nestedScroll(scroll.nestedScrollConnection)) {
@@ -146,6 +149,17 @@ fun SettingsScreen(vm: MainViewModel, onBack: () -> Unit) {
                         )
                     }) { Text("Разрешить точное время") }
                 }
+                // On by default; Android 13+ still needs the permission, asked when switched on.
+                val alertsAllowed = s.changeAlerts && Reminders.canNotify(context)
+                SwitchRow(
+                    "Изменения в расписании",
+                    "Уведомление, когда университет перезалил документ и у группы что-то поменялось. Приходит при фоновом обновлении, раз в несколько часов.",
+                    alertsAllowed,
+                ) { on ->
+                    if (on && Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU && !Reminders.canNotify(context))
+                        changesPermission.launch(Manifest.permission.POST_NOTIFICATIONS)
+                    else vm.setChangeAlerts(on)
+                }
                 if (s.reminders) {
                     Text("За сколько минут", style = MaterialTheme.typography.bodyMedium, color = MaterialTheme.colorScheme.onSurfaceVariant)
                     ConnectedChoice(

android/app/src/main/kotlin/org/xtimms/psu/schedule/work/SyncWorker.kt

@@ -12,6 +12,7 @@ import androidx.work.PeriodicWorkRequestBuilder
 import androidx.work.WorkManager
 import androidx.work.WorkerParameters
 import org.xtimms.psu.schedule.app
+import org.xtimms.psu.schedule.notify.ChangeAlerts
 import org.xtimms.psu.schedule.notify.Reminders
 import org.xtimms.psu.schedule.widget.TodayWidget
 import java.util.concurrent.TimeUnit
@@ -23,7 +24,15 @@ import java.util.concurrent.TimeUnit
 class SyncWorker(context: Context, params: WorkerParameters) : CoroutineWorker(context, params) {
     override suspend fun doWork(): Result {
         val app = applicationContext.app
+        val before = app.repository.changes.value.map { it.at }.toSet()
         app.repository.refresh()
+        // A change found by this run, for the open group: tell the student without waiting for
+        // them to open the app. The overview's card shows the same record.
+        val t = app.repository.timetable.value
+        val found = app.repository.changes.value.firstOrNull {
+            it.document == t?.document?.id && it.group == t.group && !it.seen && it.at !in before
+        }
+        if (found != null && app.settings.now().changeAlerts) ChangeAlerts.show(applicationContext, found)
         afterChange(applicationContext)
         return Result.success()
     }

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

@@ -4,6 +4,7 @@
     <string name="widget_name">Сегодня</string>
     <string name="widget_description">Текущая и следующая пара вашей группы</string>
     <string name="channel_reminders">Перед парой</string>
+    <string name="channel_changes">Изменения в расписании</string>
     <string name="next_widget_name">Следующая пара</string>
     <string name="next_widget_description">Когда следующая пара, что это и в какой аудитории</string>
     <string name="tile_name">Пара</string>