data: add CalendarRepository + Impl with SharedFlow re-emit on data-source ticks

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepository.kt

@@ -0,0 +1,16 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.EventDetail
+import de.jeanlucmakiola.calendula.domain.EventInstance
+import kotlinx.coroutines.flow.Flow
+import kotlin.time.Instant
+
+interface CalendarRepository {
+    fun calendars(): Flow<List<CalendarSource>>
+    fun instances(range: ClosedRange<Instant>): Flow<List<EventInstance>>
+    suspend fun eventDetail(eventId: Long): EventDetail
+}
+
+class NoSuchEventException(eventId: Long) :
+    NoSuchElementException("No event with id=$eventId")

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt

@@ -0,0 +1,62 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import de.jeanlucmakiola.calendula.data.di.IoDispatcher
+import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.EventDetail
+import de.jeanlucmakiola.calendula.domain.EventInstance
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOn
+import kotlinx.coroutines.flow.onStart
+import kotlinx.coroutines.withContext
+import kotlin.time.Instant
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * One ContentResolver-backed observer for the lifetime of the App process.
+ * Each public flow re-queries on subscribe and after every tick from the
+ * data source.
+ */
+@Singleton
+class CalendarRepositoryImpl @Inject constructor(
+    private val dataSource: CalendarDataSource,
+    @IoDispatcher private val io: CoroutineDispatcher,
+) : CalendarRepository {
+
+    private val ticks = MutableSharedFlow<Unit>(
+        replay = 0,
+        extraBufferCapacity = 1,
+    )
+
+    init {
+        dataSource.registerChangeListener { ticks.tryEmit(Unit) }
+    }
+
+    override fun calendars(): Flow<List<CalendarSource>> =
+        ticks
+            .onStart { emit(Unit) }
+            .reQuery { dataSource.calendars() }
+            .flowOn(io)
+
+    override fun instances(range: ClosedRange<Instant>): Flow<List<EventInstance>> =
+        ticks
+            .onStart { emit(Unit) }
+            .reQuery {
+                dataSource.instances(
+                    beginMillis = range.start.toEpochMillis(),
+                    endMillis = range.endInclusive.toEpochMillis(),
+                )
+            }
+            .flowOn(io)
+
+    override suspend fun eventDetail(eventId: Long): EventDetail = withContext(io) {
+        dataSource.eventDetail(eventId) ?: throw NoSuchEventException(eventId)
+    }
+}
+
+private fun <T> Flow<Unit>.reQuery(block: suspend () -> T): Flow<T> = flow {
+    collect { emit(block()) }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/di/Qualifiers.kt

@@ -0,0 +1,7 @@
+package de.jeanlucmakiola.calendula.data.di
+
+import javax.inject.Qualifier
+
+@Qualifier
+@Retention(AnnotationRetention.BINARY)
+annotation class IoDispatcher