WIP - work with background location being optional

app/src/main/java/com/geeksville/mesh/android/ContextServices.kt

@@ -1,9 +1,13 @@
 package com.geeksville.mesh.android
 
+import android.Manifest
 import android.app.NotificationManager
 import android.bluetooth.BluetoothManager
 import android.content.Context
+import android.content.pm.PackageManager
 import android.hardware.usb.UsbManager
+import android.os.Build
+import androidx.core.content.ContextCompat
 
 /**
  * @return null on platforms without a BlueTooth driver (i.e. the emulator)
@@ -13,3 +17,28 @@ val Context.bluetoothManager: BluetoothManager? get() = getSystemService(Context
 val Context.usbManager: UsbManager get() = requireNotNull(getSystemService(Context.USB_SERVICE) as? UsbManager?) { "USB_SERVICE is not available"}
 
 val Context.notificationManager: NotificationManager get() = requireNotNull(getSystemService(Context.NOTIFICATION_SERVICE) as? NotificationManager?)
+
+/**
+ * return a list of the permissions we don't have
+ */
+fun Context.getMissingPermissions(perms: List<String>) = perms.filter {
+    ContextCompat.checkSelfPermission(
+        this,
+        it
+    ) != PackageManager.PERMISSION_GRANTED
+}
+
+/**
+ * A list of missing background location permissions (or empty if we already have what we need)
+ */
+fun Context.getBackgroundPermissions(): List<String> {
+    val perms = mutableListOf<String>()
+
+    if (Build.VERSION.SDK_INT >= 29) // only added later
+        perms.add(Manifest.permission.ACCESS_BACKGROUND_LOCATION)
+
+    return getMissingPermissions(perms)
+}
+
+/** @return true if the user already has background location permission */
+fun Context.hasBackgroundPermission() = getBackgroundPermissions().isEmpty()