WIP: refactor LiveData to Flows

app/src/main/java/net/vonforst/evmap/storage/CacheLiveData.kt

@@ -3,6 +3,11 @@ package net.vonforst.evmap.storage
 import android.util.Log
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MediatorLiveData
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.emitAll
+import kotlinx.coroutines.flow.firstOrNull
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.map
 import net.vonforst.evmap.model.ChargeLocation
 import net.vonforst.evmap.viewmodel.Resource
 import net.vonforst.evmap.viewmodel.Status
@@ -141,4 +146,44 @@ class PreferCacheLiveData(
             }
         }
     }
+}
+
+/**
+ * Flow-based implementation that allows loading data both from a cache and an API.
+ *
+ * It first tries loading from cache, and if the result is newer than `cacheSoftLimit` it does not
+ * reload from the API.
+ */
+fun preferCacheFlow(
+    cache: Flow<ChargeLocation?>,
+    api: Flow<Resource<ChargeLocation>>,
+    cacheSoftLimit: Duration
+): Flow<Resource<ChargeLocation>> = flow {
+    emit(Resource.loading(null)) // initial state
+
+    val cacheRes = cache.firstOrNull() // read cache once
+    if (cacheRes != null) {
+        if (cacheRes.isDetailed && cacheRes.timeRetrieved > Instant.now() - cacheSoftLimit) {
+            emit(Resource.success(cacheRes))
+            return@flow
+        } else {
+            emit(Resource.loading(cacheRes))
+            emitAll(api.map { apiRes ->
+                when (apiRes.status) {
+                    Status.SUCCESS -> apiRes
+                    Status.ERROR -> Resource.error(apiRes.message, cacheRes)
+                    Status.LOADING -> Resource.loading(cacheRes)
+                }
+            })
+        }
+    } else {
+        // No cache → straight to API
+        emitAll(api.map { apiRes ->
+            when (apiRes.status) {
+                Status.SUCCESS -> apiRes
+                Status.ERROR -> Resource.error(apiRes.message, null)
+                Status.LOADING -> Resource.loading(null)
+            }
+        })
+    }
 }

app/src/main/java/net/vonforst/evmap/storage/ChargeLocationsDao.kt

@@ -14,7 +14,14 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.cancelAndJoin
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.shareIn
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import net.vonforst.evmap.api.ChargepointApi
@@ -34,9 +41,9 @@ import net.vonforst.evmap.utils.splitAtAntimeridian
 import net.vonforst.evmap.viewmodel.Resource
 import net.vonforst.evmap.viewmodel.Status
 import net.vonforst.evmap.viewmodel.await
-import net.vonforst.evmap.viewmodel.singleSwitchMap
 import java.time.Duration
 import java.time.Instant
+import kotlin.time.TimeSource
 
 const val CLUSTER_MAX_ZOOM_LEVEL = 11f
 
@@ -170,10 +177,9 @@ private const val TAG = "ChargeLocationsDao"
  * and clustering functionality.
  */
 class ChargeLocationsRepository(
-    api: ChargepointApi<ReferenceData>, private val scope: CoroutineScope,
+    private val api: ChargepointApi<ReferenceData>, private val scope: CoroutineScope,
     private val db: AppDatabase, private val prefs: PreferenceDataSource
 ) {
-    val api = MutableLiveData<ChargepointApi<ReferenceData>>().apply { value = api }
 
     // if zoom level is below this value, server-side clustering will be used (if the API provides it)
     private val serverSideClusteringThreshold = 9f
@@ -182,35 +188,33 @@ class ChargeLocationsRepository(
     // if cached data is available and more recent than this duration, API will not be queried
     private val cacheSoftLimit = Duration.ofDays(1)
 
-    val referenceData = this.api.switchMap { api ->
-        when (api) {
-            is GoingElectricApiWrapper -> {
-                GEReferenceDataRepository(
-                    api,
-                    scope,
-                    db.geReferenceDataDao(),
-                    prefs
-                ).getReferenceData()
-            }
-
-            is OpenChargeMapApiWrapper -> {
-                OCMReferenceDataRepository(
-                    api,
-                    scope,
-                    db.ocmReferenceDataDao(),
-                    prefs
-                ).getReferenceData()
-            }
-
-            is OpenStreetMapApiWrapper -> {
-                OSMReferenceDataRepository(db.osmReferenceDataDao()).getReferenceData()
-            }
-
-            else -> {
-                throw RuntimeException("no reference data implemented")
-            }
+    val referenceData = when (api) {
+        is GoingElectricApiWrapper -> {
+            GEReferenceDataRepository(
+                api,
+                scope,
+                db.geReferenceDataDao(),
+                prefs
+            ).getReferenceData()
         }
-    }
+
+        is OpenChargeMapApiWrapper -> {
+            OCMReferenceDataRepository(
+                api,
+                scope,
+                db.ocmReferenceDataDao(),
+                prefs
+            ).getReferenceData()
+        }
+
+        is OpenStreetMapApiWrapper -> {
+            OSMReferenceDataRepository(db.osmReferenceDataDao()).getReferenceData()
+        }
+
+        else -> {
+            throw RuntimeException("no reference data implemented")
+        }
+    }.shareIn(scope, SharingStarted.Lazily, 1)
 
     private val chargeLocationsDao = db.chargeLocationsDao()
     private val savedRegionDao = db.savedRegionDao()
@@ -221,41 +225,36 @@ class ChargeLocationsRepository(
         bounds: LatLngBounds,
         zoom: Float,
         filters: FilterValues?,
-        overrideCache: Boolean = false
-    ): LiveData<Resource<List<ChargepointListItem>>> {
+        overrideCache: Boolean = false,
+    ): Flow<List<ChargepointListItem>> {
         if (bounds.crossesAntimeridian()) {
             val (a, b) = bounds.splitAtAntimeridian()
-            val liveDataA = getChargepoints(a, zoom, filters, overrideCache)
-            val liveDataB = getChargepoints(b, zoom, filters, overrideCache)
-            return combineLiveData(liveDataA, liveDataB)
+            val flowA = getChargepoints(a, zoom, filters, overrideCache)
+            val flowB = getChargepoints(b, zoom, filters, overrideCache)
+            return flowA.combine(flowB) { a, b -> a + b }
         }
 
-        val api = api.value!!
-        val t1 = System.currentTimeMillis()
-        val dbResult = if (filters.isNullOrEmpty()) {
-            liveData {
-                emit(
-                    Resource.success(
-                    chargeLocationsDao.getChargeLocationsClustered(
-                        bounds.southwest.latitude,
-                        bounds.northeast.latitude,
-                        bounds.southwest.longitude,
-                        bounds.northeast.longitude,
-                        api.id,
-                        cacheLimitDate(api),
-                        zoom
-                    )
-                    )
+        val dbResult = flow {
+            val t1 = TimeSource.Monotonic.markNow()
+            val result = if (filters.isNullOrEmpty()) {
+                chargeLocationsDao.getChargeLocationsClustered(
+                    bounds.southwest.latitude,
+                    bounds.northeast.latitude,
+                    bounds.southwest.longitude,
+                    bounds.northeast.longitude,
+                    api.id,
+                    cacheLimitDate(api),
+                    zoom
                 )
+            } else {
+                queryWithFiltersClustered(api, filters, bounds, zoom)
             }
-        } else {
-            queryWithFiltersClustered(api, filters, bounds, zoom)
-        }.map {
-            val t2 = System.currentTimeMillis()
+            val t2 = TimeSource.Monotonic.markNow()
             Log.d(TAG, "DB loading time: ${t2 - t1}")
-            Log.d(TAG, "number of chargers: ${it.data?.size}")
-            it
+            Log.d(TAG, "number of chargers: ${result.size}")
+            emit(result)
         }
+
         val filtersSerialized =
             filters?.filter { it.value != it.filter.defaultValue() }?.takeIf { it.isNotEmpty() }
                 ?.serialize()
@@ -272,8 +271,8 @@ class ChargeLocationsRepository(
         )
         val useClustering = shouldUseServerSideClustering(zoom)
         if (api.supportsOnlineQueries) {
-            val apiResult = liveData {
-                val refData = referenceData.await()
+            val apiResult = flow {
+                val refData = referenceData.first()
                 val time = Instant.now()
                 val result = api.getChargepoints(refData, bounds, zoom, useClustering, filters)
                 emit(applyLocalClustering(result, zoom))
@@ -328,39 +327,11 @@ class ChargeLocationsRepository(
         }
     }
 
-    private fun combineLiveData(
-        liveDataA: LiveData<Resource<List<ChargepointListItem>>>,
-        liveDataB: LiveData<Resource<List<ChargepointListItem>>>
-    ) = MediatorLiveData<Resource<List<ChargepointListItem>>>().apply {
-        listOf(liveDataA, liveDataB).forEach {
-            addSource(it) {
-                val valA = liveDataA.value
-                val valB = liveDataB.value
-                val combinedList = if (valA?.data != null && valB?.data != null) {
-                    valA.data + valB.data
-                } else if (valA?.data != null) {
-                    valA.data
-                } else if (valB?.data != null) {
-                    valB.data
-                } else null
-                if (valA?.status == Status.SUCCESS && valB?.status == Status.SUCCESS) {
-                    Resource.success(combinedList)
-                } else if (valA?.status == Status.ERROR || valB?.status == Status.ERROR) {
-                    Resource.error(valA?.message ?: valB?.message, combinedList)
-                } else {
-                    Resource.loading(combinedList)
-                }
-            }
-        }
-    }
-
     fun getChargepointsRadius(
         location: LatLng,
         radius: Int,
         filters: FilterValues?
     ): LiveData<Resource<List<ChargeLocation>>> {
-        val api = api.value!!
-
         val radiusMeters = radius.toDouble() * 1000
         val dbResult = if (filters.isNullOrEmpty()) {
             liveData {
@@ -394,7 +365,7 @@ class ChargeLocationsRepository(
         )
         if (api.supportsOnlineQueries) {
             val apiResult = liveData {
-                val refData = referenceData.await()
+                val refData = referenceData.first()
                 val time = Instant.now()
                 val result =
                     api.getChargepointsRadius(
@@ -455,7 +426,7 @@ class ChargeLocationsRepository(
         }
     }
 
-    private fun applyLocalClustering(
+    private suspend fun applyLocalClustering(
         result: Resource<ChargepointList>,
         zoom: Float
     ): Resource<List<ChargepointListItem>> {
@@ -472,7 +443,7 @@ class ChargeLocationsRepository(
         return Resource(result.status, clustered, result.message)
     }
 
-    private fun applyLocalClustering(
+    private suspend fun applyLocalClustering(
         chargers: List<ChargeLocation>,
         zoom: Float
     ): List<ChargepointListItem> {
@@ -482,7 +453,7 @@ class ChargeLocationsRepository(
         val useClustering = chargers.size > 500 || zoom <= CLUSTER_MAX_ZOOM_LEVEL
 
         val chargersClustered = if (useClustering) {
-            Dispatchers.Default.run {
+            withContext(Dispatchers.Default) {
                 cluster(chargers, zoom)
             }
         } else chargers
@@ -492,9 +463,8 @@ class ChargeLocationsRepository(
     fun getChargepointDetail(
         id: Long,
         overrideCache: Boolean = false
-    ): LiveData<Resource<ChargeLocation>> {
-        val api = api.value!!
-        val dbResult = liveData {
+    ): Flow<Resource<ChargeLocation>> {
+        val dbResult = flow {
             emit(
                 chargeLocationsDao.getChargeLocationById(
                     id,
@@ -504,9 +474,8 @@ class ChargeLocationsRepository(
             )
         }
         if (api.supportsOnlineQueries) {
-            val apiResult = liveData {
-                emit(Resource.loading(null))
-                val refData = referenceData.await()
+            val apiResult = flow {
+                val refData = referenceData.first()
                 val result = api.getChargepointDetail(refData, id)
                 emit(result)
                 if (result.status == Status.SUCCESS) {
@@ -516,22 +485,15 @@ class ChargeLocationsRepository(
             return if (overrideCache) {
                 apiResult
             } else {
-                PreferCacheLiveData(dbResult, apiResult, cacheSoftLimit)
+                preferCacheFlow(dbResult, apiResult, cacheSoftLimit)
             }
         } else {
             return dbResult.map { Resource.success(it) }
         }
     }
 
-    fun getFilters(sp: StringProvider) = MediatorLiveData<List<Filter<FilterValue>>>().apply {
-        addSource(referenceData) { refData: ReferenceData? ->
-            refData?.let { value = api.value!!.getFilters(refData, sp) }
-        }
-    }
-
-    suspend fun getFiltersAsync(sp: StringProvider): List<Filter<FilterValue>> {
-        val refData = referenceData.await()
-        return api.value!!.getFilters(refData, sp)
+    fun getFilters(sp: StringProvider) = referenceData.map {
+        api.getFilters(it, sp)
     }
 
     val chargeCardMap by lazy {
@@ -546,29 +508,29 @@ class ChargeLocationsRepository(
         }
     }
 
-    private fun queryWithFilters(
+    private suspend fun queryWithFilters(
         api: ChargepointApi<ReferenceData>,
         filters: FilterValues,
         bounds: LatLngBounds
-    ): LiveData<Resource<List<ChargeLocation>>> {
+    ): List<ChargeLocation> {
         return queryWithFilters(api, filters, boundsSpatialIndexQuery(bounds))
     }
 
-    private fun queryWithFiltersClustered(
+    private suspend fun queryWithFiltersClustered(
         api: ChargepointApi<ReferenceData>,
         filters: FilterValues,
         bounds: LatLngBounds,
         zoom: Float
-    ): LiveData<Resource<List<ChargepointListItem>>> {
+    ): List<ChargepointListItem> {
         return queryWithFiltersClustered(api, filters, boundsSpatialIndexQuery(bounds), zoom)
     }
 
-    private fun queryWithFilters(
+    private suspend fun queryWithFilters(
         api: ChargepointApi<ReferenceData>,
         filters: FilterValues,
         location: LatLng,
         radius: Double
-    ): LiveData<Resource<List<ChargeLocation>>> {
+    ): List<ChargeLocation> {
         val region =
             radiusSpatialIndexQuery(location, radius)
         val order =
@@ -582,76 +544,50 @@ class ChargeLocationsRepository(
     private fun radiusSpatialIndexQuery(location: LatLng, radius: Double) =
         "PtDistWithin(coordinates, MakePoint(${location.longitude}, ${location.latitude}, 4326), ${radius}) AND ChargeLocation.ROWID IN (SELECT ROWID FROM SpatialIndex WHERE f_table_name = 'ChargeLocation' AND search_frame = BuildCircleMbr(${location.longitude}, ${location.latitude}, $radius))"
 
-    private fun queryWithFilters(
+    private suspend fun queryWithFilters(
         api: ChargepointApi<ReferenceData>,
         filters: FilterValues,
         regionSql: String,
         orderSql: String? = null
-    ): LiveData<Resource<List<ChargeLocation>>> = referenceData.singleSwitchMap { refData ->
-        try {
-            val query = api.convertFiltersToSQL(filters, refData)
-            val after = cacheLimitDate(api)
-            val sql = buildFilteredQuery(query, regionSql, after, orderSql)
+    ): List<ChargeLocation> {
+        val query = api.convertFiltersToSQL(filters, referenceData.first())
+        val after = cacheLimitDate(api)
+        val sql = buildFilteredQuery(query, regionSql, after, orderSql)
 
-            liveData {
-                emit(
-                    Resource.success(
-                    chargeLocationsDao.getChargeLocationsCustom(
-                        SimpleSQLiteQuery(
-                            sql,
-                            null
-                        )
-                    )
-                    )
-                )
-            }
-        } catch (e: NotImplementedError) {
-            MutableLiveData()  // in this case we cannot get a DB result
-        }
+        return chargeLocationsDao.getChargeLocationsCustom(
+            SimpleSQLiteQuery(
+                sql,
+                null
+            )
+        )
     }
 
-    private fun queryWithFiltersClustered(
+    private suspend fun queryWithFiltersClustered(
         api: ChargepointApi<ReferenceData>,
         filters: FilterValues,
         regionSql: String,
         zoom: Float,
         orderSql: String? = null
-    ): LiveData<Resource<List<ChargepointListItem>>> = referenceData.singleSwitchMap { refData ->
-        try {
-            if (zoom > CLUSTER_MAX_ZOOM_LEVEL) {
-                queryWithFilters(api, filters, regionSql, orderSql).map { it }
-            } else {
-                val query = api.convertFiltersToSQL(filters, refData)
-                val after = cacheLimitDate(api)
-                val clusterPrecision = getClusterPrecision(zoom)
-                val sql = buildFilteredQuery(query, regionSql, after, orderSql, clusterPrecision)
+    ): List<ChargepointListItem> = if (zoom > CLUSTER_MAX_ZOOM_LEVEL) {
+        queryWithFilters(api, filters, regionSql, orderSql).map { it }
+    } else {
+        val query = api.convertFiltersToSQL(filters, referenceData.first())
+        val after = cacheLimitDate(api)
+        val clusterPrecision = getClusterPrecision(zoom)
+        val sql = buildFilteredQuery(query, regionSql, after, orderSql, clusterPrecision)
 
-                liveData {
-                    val clusters = chargeLocationsDao.getChargeLocationClustersCustom(
-                        SimpleSQLiteQuery(
-                            sql,
-                            null
-                        )
-                    )
-                    val singleChargers =
-                        chargeLocationsDao.getChargeLocationsById(clusters.filter { it.clusterCount == 1 }
-                            .map { it.ids }
-                            .flatten(), prefs.dataSource, after)
-                    emit(
-                        Resource.success(
-                        clusters.filter { it.clusterCount > 1 }
-                            .map { it.convert() } + singleChargers
-                    ))
-                }
-            }
-        } catch (e: NotImplementedError) {
-            MutableLiveData(
-                Resource.error(
-                    e.message,
-                    null
-                )
-            )  // in this case we cannot get a DB result
-        }
+        val clusters = chargeLocationsDao.getChargeLocationClustersCustom(
+            SimpleSQLiteQuery(
+                sql,
+                null
+            )
+        )
+        val singleChargers =
+            chargeLocationsDao.getChargeLocationsById(clusters.filter { it.clusterCount == 1 }
+                .map { it.ids }
+                .flatten(), prefs.dataSource, after)
+        clusters.filter { it.clusterCount > 1 }
+                .map { it.convert() } + singleChargers
     }
 
     private fun buildFilteredQuery(
@@ -691,7 +627,6 @@ class ChargeLocationsRepository(
     }.toString()
 
     private suspend fun fullDownload() {
-        val api = api.value!!
         if (!api.supportsFullDownload) return
 
         val time = Instant.now()

app/src/main/java/net/vonforst/evmap/storage/GEReferenceDataDao.kt

@@ -1,9 +1,15 @@
 package net.vonforst.evmap.storage
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.MediatorLiveData
-import androidx.room.*
+import androidx.room.Dao
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import androidx.room.Transaction
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.launch
 import net.vonforst.evmap.api.goingelectric.GEChargeCard
 import net.vonforst.evmap.api.goingelectric.GEReferenceData
@@ -36,7 +42,7 @@ abstract class GEReferenceDataDao {
     }
 
     @Query("SELECT * FROM genetwork")
-    abstract fun getAllNetworks(): LiveData<List<GENetwork>>
+    abstract fun getAllNetworks(): Flow<List<GENetwork>>
 
     // PLUGS
     @Insert(onConflict = OnConflictStrategy.REPLACE)
@@ -54,7 +60,7 @@ abstract class GEReferenceDataDao {
     }
 
     @Query("SELECT * FROM geplug")
-    abstract fun getAllPlugs(): LiveData<List<GEPlug>>
+    abstract fun getAllPlugs(): Flow<List<GEPlug>>
 
     // CHARGE CARDS
     @Insert(onConflict = OnConflictStrategy.REPLACE)
@@ -72,31 +78,21 @@ abstract class GEReferenceDataDao {
     }
 
     @Query("SELECT * FROM gechargecard")
-    abstract fun getAllChargeCards(): LiveData<List<GEChargeCard>>
+    abstract fun getAllChargeCards(): Flow<List<GEChargeCard>>
 }
 
 class GEReferenceDataRepository(
     private val api: GoingElectricApiWrapper, private val scope: CoroutineScope,
     private val dao: GEReferenceDataDao, private val prefs: PreferenceDataSource
 ) {
-    fun getReferenceData(): LiveData<GEReferenceData> {
+    fun getReferenceData(): Flow<GEReferenceData> {
         scope.launch {
             updateData()
         }
         val plugs = dao.getAllPlugs()
         val networks = dao.getAllNetworks()
         val chargeCards = dao.getAllChargeCards()
-        return MediatorLiveData<GEReferenceData>().apply {
-            value = null
-            listOf(chargeCards, networks, plugs).map { source ->
-                addSource(source) { _ ->
-                    val p = plugs.value ?: return@addSource
-                    val n = networks.value ?: return@addSource
-                    val cc = chargeCards.value ?: return@addSource
-                    value = GEReferenceData(p.map { it.name }, n.map { it.name }, cc)
-                }
-            }
-        }
+        return combine(plugs, networks, chargeCards) { p, n, c -> GEReferenceData(p.map { it.name }, n.map { it.name }, c) }
     }
 
     private suspend fun updateData() {

app/src/main/java/net/vonforst/evmap/storage/OCMReferenceDataDao.kt

@@ -1,11 +1,19 @@
 package net.vonforst.evmap.storage
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.MediatorLiveData
-import androidx.room.*
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+import androidx.room.Transaction
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.launch
-import net.vonforst.evmap.api.openchargemap.*
+import net.vonforst.evmap.api.openchargemap.OCMConnectionType
+import net.vonforst.evmap.api.openchargemap.OCMCountry
+import net.vonforst.evmap.api.openchargemap.OCMOperator
+import net.vonforst.evmap.api.openchargemap.OCMReferenceData
+import net.vonforst.evmap.api.openchargemap.OpenChargeMapApiWrapper
 import net.vonforst.evmap.viewmodel.Status
 import java.time.Duration
 import java.time.Instant
@@ -28,7 +36,7 @@ abstract class OCMReferenceDataDao {
     }
 
     @Query("SELECT * FROM ocmconnectiontype")
-    abstract fun getAllConnectionTypes(): LiveData<List<OCMConnectionType>>
+    abstract fun getAllConnectionTypes(): Flow<List<OCMConnectionType>>
 
     // COUNTRIES
     @Insert(onConflict = OnConflictStrategy.REPLACE)
@@ -46,7 +54,7 @@ abstract class OCMReferenceDataDao {
     }
 
     @Query("SELECT * FROM ocmcountry")
-    abstract fun getAllCountries(): LiveData<List<OCMCountry>>
+    abstract fun getAllCountries(): Flow<List<OCMCountry>>
 
     // OPERATORS
     @Insert(onConflict = OnConflictStrategy.REPLACE)
@@ -64,32 +72,21 @@ abstract class OCMReferenceDataDao {
     }
 
     @Query("SELECT * FROM ocmoperator")
-    abstract fun getAllOperators(): LiveData<List<OCMOperator>>
+    abstract fun getAllOperators(): Flow<List<OCMOperator>>
 }
 
 class OCMReferenceDataRepository(
     private val api: OpenChargeMapApiWrapper, private val scope: CoroutineScope,
     private val dao: OCMReferenceDataDao, private val prefs: PreferenceDataSource
 ) {
-    fun getReferenceData(): LiveData<OCMReferenceData> {
+    fun getReferenceData(): Flow<OCMReferenceData> {
         scope.launch {
             updateData()
         }
         val connectionTypes = dao.getAllConnectionTypes()
         val countries = dao.getAllCountries()
         val operators = dao.getAllOperators()
-        return MediatorLiveData<OCMReferenceData>().apply {
-            value = null
-            listOf(countries, connectionTypes, operators).map { source ->
-                addSource(source) { _ ->
-                    val ct = connectionTypes.value
-                    val c = countries.value
-                    val o = operators.value
-                    if (ct.isNullOrEmpty() || c.isNullOrEmpty() || o.isNullOrEmpty()) return@addSource
-                    value = OCMReferenceData(ct, c, o)
-                }
-            }
-        }
+        return combine(connectionTypes, countries, operators) { ct, c, o -> OCMReferenceData(ct, c, o) }
     }
 
     private suspend fun updateData() {

app/src/main/java/net/vonforst/evmap/storage/OSMReferenceDataDao.kt

@@ -4,6 +4,8 @@ import androidx.lifecycle.LiveData
 import androidx.lifecycle.MediatorLiveData
 import androidx.room.*
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
 import net.vonforst.evmap.api.openchargemap.*
 import net.vonforst.evmap.api.openstreetmap.OSMReferenceData
@@ -32,19 +34,13 @@ abstract class OSMReferenceDataDao {
     }
 
     @Query("SELECT * FROM osmnetwork")
-    abstract fun getAllNetworks(): LiveData<List<OSMNetwork>>
+    abstract fun getAllNetworks(): Flow<List<OSMNetwork>>
 }
 
 class OSMReferenceDataRepository(private val dao: OSMReferenceDataDao) {
-    fun getReferenceData(): LiveData<OSMReferenceData> {
+    fun getReferenceData(): Flow<OSMReferenceData> {
         val networks = dao.getAllNetworks()
-        return MediatorLiveData<OSMReferenceData>().apply {
-            value = null
-            addSource(networks) { _ ->
-                val n = networks.value ?: return@addSource
-                value = OSMReferenceData(n.map { it.name })
-            }
-        }
+        return networks.map { OSMReferenceData(it.map { it.name }) }
     }
 
     suspend fun updateReferenceData(refData: OSMReferenceData) {

app/src/main/java/net/vonforst/evmap/storage/SavedRegionDao.kt

@@ -1,8 +1,12 @@
 package net.vonforst.evmap.storage
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.map
-import androidx.room.*
+import androidx.room.Dao
+import androidx.room.Entity
+import androidx.room.Index
+import androidx.room.Insert
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import androidx.room.SkipQueryVerification
 import co.anbora.labs.spatia.geometry.Geometry
 import co.anbora.labs.spatia.geometry.LineString
 import co.anbora.labs.spatia.geometry.Polygon
@@ -35,31 +39,31 @@ abstract class SavedRegionDao {
 
     @SkipQueryVerification
     @Query("SELECT Covers(GUnion(region), BuildMbr(:lng1, :lat1, :lng2, :lat2, 4326)) FROM savedregion WHERE dataSource == :dataSource AND timeRetrieved > :after AND Intersects(region, BuildMbr(:lng1, :lat1, :lng2, :lat2, 4326)) AND (filters == :filters OR filters IS NULL) AND (isDetailed OR NOT :isDetailed)")
-    protected abstract fun savedRegionCoversInt(
+    protected abstract suspend fun savedRegionCoversInt(
         lat1: Double,
         lat2: Double,
         lng1: Double,
         lng2: Double,
         dataSource: String, after: Long, filters: String? = null, isDetailed: Boolean = false
-    ): LiveData<Int>
+    ): Int
 
     @SkipQueryVerification
     @Query("SELECT Covers(GUnion(region), MakeEllipse(:lng, :lat, :radiusLng, :radiusLat, 4326)) FROM savedregion WHERE dataSource == :dataSource AND timeRetrieved > :after AND Intersects(region, MakeEllipse(:lng, :lat, :radiusLng, :radiusLat, 4326)) AND (filters == :filters OR filters IS NULL) AND (isDetailed OR NOT :isDetailed)")
-    protected abstract fun savedRegionCoversRadiusInt(
+    protected abstract suspend fun savedRegionCoversRadiusInt(
         lat: Double,
         lng: Double,
         radiusLat: Double,
         radiusLng: Double,
         dataSource: String, after: Long, filters: String? = null, isDetailed: Boolean = false
-    ): LiveData<Int>
+    ): Int
 
-    fun savedRegionCovers(
+    suspend fun savedRegionCovers(
         lat1: Double,
         lat2: Double,
         lng1: Double,
         lng2: Double,
         dataSource: String, after: Long, filters: String? = null, isDetailed: Boolean = false
-    ): LiveData<Boolean> {
+    ): Boolean {
         return savedRegionCoversInt(
             lat1,
             lat2,
@@ -69,15 +73,15 @@ abstract class SavedRegionDao {
             after,
             filters,
             isDetailed
-        ).map { it == 1 }
+        ) == 1
     }
 
-    fun savedRegionCoversRadius(
+    suspend fun savedRegionCoversRadius(
         lat: Double,
         lng: Double,
         radius: Double,
         dataSource: String, after: Long, filters: String? = null, isDetailed: Boolean = false
-    ): LiveData<Boolean> {
+    ): Boolean {
         val (radiusLat, radiusLng) = circleAsEllipse(lat, lng, radius)
         return savedRegionCoversRadiusInt(
             lat,
@@ -88,7 +92,7 @@ abstract class SavedRegionDao {
             after,
             filters,
             isDetailed
-        ).map { it == 1 }
+        ) == 1
     }
 
     @Insert

app/src/main/java/net/vonforst/evmap/viewmodel/Utils.kt

@@ -148,20 +148,4 @@ suspend fun <T> LiveData<Resource<T>>.awaitFinished(): Resource<T> {
             removeObserver(observer)
         }
     }
-}
-
-inline fun <X, Y> LiveData<X>.singleSwitchMap(crossinline transform: (X) -> LiveData<Y>?): MediatorLiveData<Y> {
-    val result = MediatorLiveData<Y>()
-    result.addSource(this@singleSwitchMap, object : Observer<X> {
-        override fun onChanged(t: X) {
-            if (t == null) return
-            result.removeSource(this@singleSwitchMap)
-            transform(t)?.let { transformed ->
-                result.addSource(transformed) {
-                    result.value = it
-                }
-            }
-        }
-    })
-    return result
 }