VPN Hotspot 2.0: Client+ (#39)

Fix #13, #38. I don't have a lot of confidence that this would work very well for every device.

Also here's an SQL command that hopefully somebody could make into the app for me: `SELECT TrafficRecord.mac, SUM(TrafficRecord.sentPackets), SUM(TrafficRecord.sentBytes), SUM(TrafficRecord.receivedPackets), SUM(TrafficRecord.receivedBytes) FROM TrafficRecord LEFT JOIN TrafficRecord AS Next ON TrafficRecord.id = Next.previousId WHERE Next.id IS NULL GROUP BY TrafficRecord.mac;`

mobile/src/main/java/be/mygod/vpnhotspot/util/Utils.kt

@@ -1,20 +1,33 @@
 package be.mygod.vpnhotspot.util
 
 import android.content.*
+import android.os.Build
 import android.util.Log
 import android.view.View
 import android.widget.ImageView
 import androidx.annotation.DrawableRes
 import androidx.core.view.isVisible
 import androidx.databinding.BindingAdapter
-import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.BuildConfig
 import be.mygod.vpnhotspot.R
 import be.mygod.vpnhotspot.widget.SmartSnackbar
 import com.crashlytics.android.Crashlytics
+import java.net.InetAddress
 import java.net.NetworkInterface
 import java.net.SocketException
 
+/**
+ * This is a hack: we wrap longs around in 1 billion and such. Hopefully every language counts in base 10 and this works
+ * marvelously for everybody.
+ */
+fun Long.toPluralInt(): Int {
+    check(this >= 0)    // please don't mess with me
+    if (this <= Int.MAX_VALUE) return toInt()
+    return (this % 1000000000).toInt() + 1000000000
+}
+
+fun CharSequence?.onEmpty(otherwise: CharSequence): CharSequence = if (isNullOrEmpty()) otherwise else this!!
+
 fun debugLog(tag: String?, message: String?) {
     if (BuildConfig.DEBUG) Log.d(tag, message)
     Crashlytics.log("$tag: $message")
@@ -51,6 +64,19 @@ fun NetworkInterface.formatAddresses() =
                 }))
                 .joinToString("\n")
 
+private val parseNumericAddress by lazy {
+    // parseNumericAddressNoThrow is in dark grey list unfortunately
+    InetAddress::class.java.getDeclaredMethod("parseNumericAddress", String::class.java).apply {
+        isAccessible = true
+    }
+}
+fun parseNumericAddress(address: String) = parseNumericAddress.invoke(null, address) as InetAddress
+fun parseNumericAddressNoThrow(address: String): InetAddress? = try {
+    parseNumericAddress(address)
+} catch (_: IllegalArgumentException) {
+    null
+}
+
 /**
  * Wrapper for kotlin.concurrent.thread that silences uncaught exceptions.
  */
@@ -69,3 +95,6 @@ fun Context.stopAndUnbind(connection: ServiceConnection) {
     connection.onServiceDisconnected(null)
     unbindService(connection)
 }
+
+fun <K, V> HashMap<K, V>.computeIfAbsentCompat(key: K, value: () -> V) = if (Build.VERSION.SDK_INT >= 26)
+    computeIfAbsent(key) { value() } else this[key] ?: value().also { put(key, it) }