Skip known-unreasonable network location updates

If we have a GPS location of a given accuracy, and our proposed network
location is more than twice as far away as the GPS accuracy, this is
considered unreasonable. Stop sending that network location.

As part of this, also keep track of lower-accuracy GPS locations.

Change-Id: I1893c63c2d716a5e41011cbf39f069491e6b5da6

Author: Tommy Webb

play-services-location/core/provider/src/main/kotlin/org/microg/gms/location/network/NetworkLocationService.kt

@@ -78,6 +78,9 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
     @GuardedBy("gpsLocationBuffer")
     private val gpsLocationBuffer = LinkedList<Location>()
 
+    @GuardedBy("lowAccuracyGpsLocationBuffer")
+    private val lowAccuracyGpsLocationBuffer = LinkedList<Location>()
+
     private var currentLocalMovingWifi: WifiDetails? = null
     private var lastLocalMovingWifiLocationCandidate: Location? = null
 
@@ -391,7 +394,22 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
                 elapsedRealtimeNanos = (old.elapsedRealtimeNanos.toDouble() * (1.0-pct) + new.elapsedRealtimeNanos.toDouble() * pct).toLong()
             }
         }
+        fun Location.isUnreasonableComparedTo(other: Location): Boolean {
+            val distance = distanceTo(other)
+            if (distance > 2 * other.accuracy) {
+                Log.d(TAG, "Unreasonable location ${this.provider} vs ${other.provider} (accuracy ${other.accuracy}): distance $distance")
+                return true
+            }
+            return false
+        }
+        fun Location.reasonableOrNull(): Location? {
+            val gpsLocation = getGpsLocation(elapsedMillis, includeLowAccuracy = true) ?: return this
+            if (isUnreasonableComparedTo(gpsLocation)) return null
+            return this
+        }
         val location = synchronized(locationLock) {
+            lastCellLocation = lastCellLocation?.reasonableOrNull()
+            lastWifiLocation = lastWifiLocation?.reasonableOrNull()
             if (lastCellLocation == null && lastWifiLocation == null) return
             when {
                 // Only non-null
@@ -401,7 +419,7 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
                 lastCellLocation!!.elapsedMillis > lastWifiLocation!!.elapsedMillis + LOCATION_TIME_CLIFF_END_MS -> lastCellLocation
                 lastWifiLocation!!.elapsedMillis > lastCellLocation!!.elapsedMillis + LOCATION_TIME_CLIFF_START_MS -> lastWifiLocation
                 // Wifi out of cell range with higher precision
-                lastCellLocation!!.precision > lastWifiLocation!!.precision && lastWifiLocation!!.distanceTo(lastCellLocation!!) > 2 * lastCellLocation!!.accuracy -> lastCellLocation
+                lastCellLocation!!.precision > lastWifiLocation!!.precision && lastWifiLocation!!.isUnreasonableComparedTo(lastCellLocation!!) -> lastCellLocation
                 // Consider cliff start
                 lastCellLocation!!.elapsedMillis > lastWifiLocation!!.elapsedMillis + LOCATION_TIME_CLIFF_START_MS -> cliffLocations(lastWifiLocation, lastCellLocation)
                 else -> lastWifiLocation
@@ -429,7 +447,9 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
     }
 
     private fun onNewGpsLocation(location: Location) {
-        if (location.accuracy > GPS_PASSIVE_MIN_ACCURACY) return
+        if (location.accuracy > GPS_PASSIVE_MIN_ACCURACY_LOW) return
+        // gpsLocationBuffer field is shadowed by the low accuracy buffer if inaccurate enough.
+        val gpsLocationBuffer = if (location.accuracy > GPS_PASSIVE_MIN_ACCURACY) lowAccuracyGpsLocationBuffer else this.gpsLocationBuffer
         synchronized(gpsLocationBuffer) {
             if (gpsLocationBuffer.isNotEmpty() && gpsLocationBuffer.last.elapsedMillis < SystemClock.elapsedRealtime() - GPS_BUFFER_SIZE * GPS_PASSIVE_INTERVAL) {
                 gpsLocationBuffer.clear()
@@ -440,16 +460,20 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
         }
     }
 
-    private fun getGpsLocation(elapsedMillis: Long): Location? {
+    private fun getGpsLocation(elapsedMillis: Long, includeLowAccuracy: Boolean = false): Location? {
         if (elapsedMillis + GPS_BUFFER_SIZE * GPS_PASSIVE_INTERVAL < SystemClock.elapsedRealtime()) return null
-        synchronized(gpsLocationBuffer) {
-            if (gpsLocationBuffer.isEmpty()) return null
-            for (location in gpsLocationBuffer.descendingIterator()) {
-                if (location.elapsedMillis in (elapsedMillis - GPS_PASSIVE_INTERVAL)..(elapsedMillis + GPS_PASSIVE_INTERVAL)) return location
-                if (location.elapsedMillis < elapsedMillis) return null
+        fun getGpsLocationFromBuffer(gpsLocationBuffer: LinkedList<Location>): Location? {
+            // gpsLocationBuffer field is shadowed by the argument provided.
+            synchronized(gpsLocationBuffer) {
+                if (gpsLocationBuffer.isEmpty()) return null
+                for (location in gpsLocationBuffer.descendingIterator()) {
+                    if (location.elapsedMillis in (elapsedMillis - GPS_PASSIVE_INTERVAL)..(elapsedMillis + GPS_PASSIVE_INTERVAL)) return location
+                    if (location.elapsedMillis < elapsedMillis) return null
+                }
             }
+            return null
         }
-        return null
+        return getGpsLocationFromBuffer(gpsLocationBuffer) ?: if (includeLowAccuracy) getGpsLocationFromBuffer(lowAccuracyGpsLocationBuffer) else null
     }
 
     override fun dump(fd: FileDescriptor?, writer: PrintWriter, args: Array<out String>?) {
@@ -463,6 +487,7 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
         writer.println("Ichnaea settings: endpoint=${settings.ichneaeEndpoint} contribute=${settings.ichnaeaContribute}")
         writer.println("Wifi scan cache size=${wifiScanCache.size()} hits=${wifiScanCache.hitCount()} miss=${wifiScanCache.missCount()} puts=${wifiScanCache.putCount()} evicts=${wifiScanCache.evictionCount()}")
         writer.println("GPS location buffer size=${gpsLocationBuffer.size} first=${gpsLocationBuffer.firstOrNull()?.elapsedMillis?.formatRealtime()} last=${gpsLocationBuffer.lastOrNull()?.elapsedMillis?.formatRealtime()}")
+        writer.println("Low-accuracy GPS location buffer size=${lowAccuracyGpsLocationBuffer.size} first=${lowAccuracyGpsLocationBuffer.firstOrNull()?.elapsedMillis?.formatRealtime()} last=${lowAccuracyGpsLocationBuffer.lastOrNull()?.elapsedMillis?.formatRealtime()}")
         cache.dump(writer)
         synchronized(activeRequests) {
             if (activeRequests.isNotEmpty()) {
@@ -478,6 +503,7 @@ class NetworkLocationService : LifecycleService(), WifiDetailsCallback, CellDeta
         const val GPS_BUFFER_SIZE = 60
         const val GPS_PASSIVE_INTERVAL = 1000L
         const val GPS_PASSIVE_MIN_ACCURACY = 25f
+        const val GPS_PASSIVE_MIN_ACCURACY_LOW = 10000f // 10 kilometers
         const val LOCATION_TIME_CLIFF_START_MS = 30000L
         const val LOCATION_TIME_CLIFF_END_MS = 60000L
         const val DEBOUNCE_DELAY_MS = 5000L