[Rx -> Coroutine] Convert Flowable to Flow in MapController (#1837)

* Convert flowable to flow in MapController for streaming camera update requests

* Update unit tests [currently all of them with non-empty stream are failing]

* Change method param for panAndZoomCamera to coordinates

* Simplify code using withIndex()

* Rename to _cameraPosition

* Move to BaseMapViewModel

* Simplify the camera update flow by directly emitting positions from the coroutines

* Remove MapController.kt and tests

* Move logic for getting last saved position to a method

ground/src/main/java/com/google/android/ground/ui/common/AbstractMapContainerFragment.kt

@@ -62,8 +62,8 @@ abstract class AbstractMapContainerFragment : AbstractFragment() {
       getMapViewModel().locationLock.collect { onLocationLockStateChange(it, map) }
     }
     getMapViewModel().mapType.observe(viewLifecycleOwner) { map.mapType = it }
-    getMapViewModel().cameraUpdateRequests.observe(viewLifecycleOwner) { update ->
-      update.ifUnhandled { data -> onCameraUpdateRequest(data, map) }
+    lifecycleScope.launch {
+      getMapViewModel().getCameraUpdates().collect { onCameraUpdateRequest(it, map) }
     }
 
     // Enable map controls

ground/src/main/java/com/google/android/ground/ui/common/BaseMapViewModel.kt

@@ -21,12 +21,16 @@ import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.asLiveData
 import androidx.lifecycle.toLiveData
 import androidx.lifecycle.viewModelScope
+import com.google.android.ground.Config.DEFAULT_LOI_ZOOM_LEVEL
 import com.google.android.ground.R
+import com.google.android.ground.coroutines.IoDispatcher
+import com.google.android.ground.model.Survey
+import com.google.android.ground.model.geometry.Coordinates
 import com.google.android.ground.model.imagery.TileSource
+import com.google.android.ground.repository.LocationOfInterestRepository
 import com.google.android.ground.repository.MapStateRepository
 import com.google.android.ground.repository.OfflineAreaRepository
 import com.google.android.ground.repository.SurveyRepository
-import com.google.android.ground.rx.Event
 import com.google.android.ground.rx.annotations.Hot
 import com.google.android.ground.system.FINE_LOCATION_UPDATES_REQUEST
 import com.google.android.ground.system.LocationManager
@@ -35,21 +39,26 @@ import com.google.android.ground.system.PermissionsManager
 import com.google.android.ground.system.SettingsManager
 import com.google.android.ground.ui.map.Bounds
 import com.google.android.ground.ui.map.CameraPosition
-import com.google.android.ground.ui.map.MapController
 import com.google.android.ground.ui.map.MapType
+import com.google.android.ground.ui.map.gms.GmsExt.toBounds
+import com.google.android.ground.ui.map.gms.toCoordinates
 import io.reactivex.BackpressureStrategy
 import io.reactivex.Flowable
 import io.reactivex.subjects.PublishSubject
 import io.reactivex.subjects.Subject
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.mapNotNull
 import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.flow.transform
+import kotlinx.coroutines.flow.withIndex
 import kotlinx.coroutines.launch
 import timber.log.Timber
 
@@ -61,10 +70,12 @@ constructor(
   private val settingsManager: SettingsManager,
   private val offlineAreaRepository: OfflineAreaRepository,
   private val permissionsManager: PermissionsManager,
-  mapController: MapController,
-  surveyRepository: SurveyRepository,
+  private val surveyRepository: SurveyRepository,
+  private val locationOfInterestRepository: LocationOfInterestRepository,
+  @IoDispatcher private val ioDispatcher: CoroutineDispatcher,
 ) : AbstractViewModel() {
 
+  private val _cameraPosition = MutableStateFlow<CameraPosition?>(null)
   private val cameraZoomSubject: @Hot Subject<Float> = PublishSubject.create()
   val cameraZoomUpdates: Flowable<Float> = cameraZoomSubject.toFlowable(BackpressureStrategy.LATEST)
 
@@ -91,7 +102,6 @@ constructor(
         else LOCATION_LOCK_ICON_DISABLED
       }
       .stateIn(viewModelScope, SharingStarted.Lazily, LOCATION_LOCK_ICON_DISABLED)
-  val cameraUpdateRequests: LiveData<Event<CameraPosition>>
 
   val locationAccuracy: StateFlow<Float?> =
     locationLock
@@ -108,12 +118,14 @@ constructor(
   val offlineImageryEnabled: Flow<Boolean> = mapStateRepository.offlineImageryFlow
 
   init {
-    cameraUpdateRequests = mapController.getCameraUpdates().map { Event.create(it) }.toLiveData()
     mapType = mapStateRepository.mapTypeFlowable.toLiveData()
     tileOverlays =
       surveyRepository.activeSurveyFlow
         .mapNotNull { it?.tileSources?.mapNotNull(this::toLocalTileSource) ?: listOf() }
         .asLiveData()
+
+    viewModelScope.launch(ioDispatcher) { updateCameraPositionOnLocationChange() }
+    viewModelScope.launch(ioDispatcher) { updateCameraPositionOnSurveyChange() }
   }
 
   // TODO(#1790): Maybe create a new data class object which is not of type TileSource.
@@ -175,6 +187,60 @@ constructor(
     }
   }
 
+  /** Emits a stream of camera update requests. */
+  fun getCameraUpdates(): Flow<CameraPosition> = _cameraPosition.filterNotNull()
+
+  /**
+   * Updates map camera when location changes. The first update pans and zooms the camera to the
+   * appropriate zoom level and subsequent ones only pan the map.
+   */
+  private suspend fun updateCameraPositionOnLocationChange() {
+    locationManager.locationUpdates
+      .map { it.toCoordinates() }
+      .withIndex()
+      .collect { (index, coordinates) ->
+        if (index == 0) {
+          panAndZoomCamera(coordinates)
+        } else {
+          panCamera(coordinates)
+        }
+      }
+  }
+
+  /** Updates map camera when active survey changes. */
+  private suspend fun updateCameraPositionOnSurveyChange() {
+    surveyRepository.activeSurveyFlow
+      .filterNotNull()
+      .transform { getLastSavedPositionOrDefaultBounds(it)?.apply { emit(this) } }
+      .collect { updatePosition(it) }
+  }
+
+  private suspend fun getLastSavedPositionOrDefaultBounds(survey: Survey): CameraPosition? {
+    // Attempt to fetch last saved position from local storage.
+    val savedPosition = mapStateRepository.getCameraPosition(survey.id)
+    if (savedPosition != null) {
+      return savedPosition.copy(isAllowZoomOut = true)
+    }
+
+    // Compute the default viewport which includes all LOIs in the given survey.
+    val geometries = locationOfInterestRepository.getAllGeometries(survey)
+    return geometries.toBounds()?.let { CameraPosition(bounds = it) }
+  }
+
+  /** Requests moving the map camera to [coordinates]. */
+  private fun panCamera(coordinates: Coordinates) {
+    updatePosition(CameraPosition(coordinates))
+  }
+
+  /** Requests moving the map camera to [coordinates] with zoom level [DEFAULT_LOI_ZOOM_LEVEL]. */
+  fun panAndZoomCamera(coordinates: Coordinates) {
+    updatePosition(CameraPosition(coordinates, DEFAULT_LOI_ZOOM_LEVEL))
+  }
+
+  private fun updatePosition(cameraPosition: CameraPosition) {
+    _cameraPosition.value = cameraPosition
+  }
+
   /** Called when the map camera is moved. */
   open fun onMapCameraMoved(newCameraPosition: CameraPosition) {
     newCameraPosition.zoomLevel?.let { cameraZoomSubject.onNext(it) }

ground/src/main/java/com/google/android/ground/ui/home/mapcontainer/HomeScreenMapContainerFragment.kt

@@ -204,7 +204,7 @@ class HomeScreenMapContainerFragment : Hilt_HomeScreenMapContainerFragment() {
         state.locationOfInterest
           ?.geometry
           ?.takeIf { it is Point }
-          ?.let { mapContainerViewModel.panAndZoomCamera(Point(it.center())) }
+          ?.let { mapContainerViewModel.panAndZoomCamera(it.center()) }
       }
       BottomSheetState.Visibility.HIDDEN -> {
         map.enableGestures()

ground/src/main/java/com/google/android/ground/ui/home/mapcontainer/HomeScreenMapContainerViewModel.kt

@@ -20,6 +20,7 @@ import androidx.lifecycle.toLiveData
 import androidx.lifecycle.viewModelScope
 import com.google.android.ground.Config.CLUSTERING_ZOOM_THRESHOLD
 import com.google.android.ground.Config.ZOOM_LEVEL_THRESHOLD
+import com.google.android.ground.coroutines.IoDispatcher
 import com.google.android.ground.model.geometry.Point
 import com.google.android.ground.model.job.Job
 import com.google.android.ground.model.locationofinterest.LocationOfInterest
@@ -36,12 +37,12 @@ import com.google.android.ground.ui.common.BaseMapViewModel
 import com.google.android.ground.ui.common.SharedViewModel
 import com.google.android.ground.ui.map.CameraPosition
 import com.google.android.ground.ui.map.Feature
-import com.google.android.ground.ui.map.MapController
 import io.reactivex.Flowable
 import io.reactivex.Observable
 import io.reactivex.subjects.PublishSubject
 import io.reactivex.subjects.Subject
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
@@ -58,22 +59,23 @@ class HomeScreenMapContainerViewModel
 @Inject
 internal constructor(
   private val locationOfInterestRepository: LocationOfInterestRepository,
-  private val mapController: MapController,
   private val mapStateRepository: MapStateRepository,
   locationManager: LocationManager,
   settingsManager: SettingsManager,
   offlineAreaRepository: OfflineAreaRepository,
   permissionsManager: PermissionsManager,
   surveyRepository: SurveyRepository,
+  @IoDispatcher private val ioDispatcher: CoroutineDispatcher
 ) :
   BaseMapViewModel(
     locationManager,
     mapStateRepository,
     settingsManager,
     offlineAreaRepository,
     permissionsManager,
-    mapController,
-    surveyRepository
+    surveyRepository,
+    locationOfInterestRepository,
+    ioDispatcher
   ) {
 
   val mapLocationOfInterestFeatures: StateFlow<Set<Feature>>
@@ -163,13 +165,9 @@ internal constructor(
     val geometry = features[0].geometry
 
     if (geometry is Point) {
-      mapController.panAndZoomCamera(geometry.coordinates)
+      panAndZoomCamera(geometry.coordinates)
     }
   }
 
-  fun panAndZoomCamera(position: Point) {
-    mapController.panAndZoomCamera(position.coordinates)
-  }
-
   fun getZoomThresholdCrossed(): Observable<Nil> = zoomThresholdCrossed
 }

ground/src/main/java/com/google/android/ground/ui/offlinebasemap/selector/OfflineAreaSelectorViewModel.kt

@@ -19,6 +19,7 @@ import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.viewModelScope
 import com.google.android.ground.coroutines.IoDispatcher
 import com.google.android.ground.model.imagery.TileSource
+import com.google.android.ground.repository.LocationOfInterestRepository
 import com.google.android.ground.repository.MapStateRepository
 import com.google.android.ground.repository.OfflineAreaRepository
 import com.google.android.ground.repository.SurveyRepository
@@ -30,7 +31,6 @@ import com.google.android.ground.ui.common.Navigator
 import com.google.android.ground.ui.common.SharedViewModel
 import com.google.android.ground.ui.map.Bounds
 import com.google.android.ground.ui.map.Map
-import com.google.android.ground.ui.map.MapController
 import com.google.android.ground.ui.map.MapType
 import javax.inject.Inject
 import kotlinx.coroutines.CoroutineDispatcher
@@ -49,16 +49,17 @@ internal constructor(
   mapStateRepository: MapStateRepository,
   settingsManager: SettingsManager,
   permissionsManager: PermissionsManager,
-  mapController: MapController,
+  locationOfInterestRepository: LocationOfInterestRepository
 ) :
   BaseMapViewModel(
     locationManager,
     mapStateRepository,
     settingsManager,
     offlineAreaRepository,
     permissionsManager,
-    mapController,
-    surveyRepository
+    surveyRepository,
+    locationOfInterestRepository,
+    ioDispatcher
   ) {
   enum class DownloadMessage {
     STARTED,