Correctly handle callSuper for Proxy

mobile/src/main/java/be/mygod/vpnhotspot/net/TetheringManager.kt

@@ -18,6 +18,7 @@ import androidx.core.os.BuildCompat
 import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.R
 import be.mygod.vpnhotspot.util.broadcastReceiver
+import be.mygod.vpnhotspot.util.callSuper
 import be.mygod.vpnhotspot.util.ensureReceiverUnregistered
 import com.android.dx.stock.ProxyBuilder
 import timber.log.Timber
@@ -259,25 +260,22 @@ object TetheringManager {
                 build.invoke(builder)
             }
             val proxy = Proxy.newProxyInstance(interfaceStartTetheringCallback.classLoader,
-                    arrayOf(interfaceStartTetheringCallback)) { proxy, method, args ->
+                    arrayOf(interfaceStartTetheringCallback), object : InvocationHandler {
+                override fun invoke(proxy: Any, method: Method, args: Array<out Any?>?): Any? {
                     @Suppress("NAME_SHADOWING") val callback = reference.get()
-                when (val name = method.name) {
+                    return when (val name = method.name) {
                         "onTetheringStarted" -> {
                             if (!args.isNullOrEmpty()) Timber.w("Unexpected args for $name: $args")
                             callback?.onTetheringStarted()
-                        null
                         }
                         "onTetheringFailed" -> {
                             if (args?.size != 1) Timber.w("Unexpected args for $name: $args")
                             callback?.onTetheringFailed(args?.getOrNull(0) as? Int?)
-                        null
-                    }
-                    else -> {
-                        Timber.w("Unexpected method, calling super: $method")
-                        ProxyBuilder.callSuper(proxy, method, args)
                         }
+                        else -> callSuper(interfaceStartTetheringCallback, proxy, method, args)
                     }
                 }
+            })
             startTethering.invoke(instance, request, handler.makeExecutor(), proxy)
             return
         } catch (e: InvocationTargetException) {
@@ -297,10 +295,7 @@ object TetheringManager {
                         callback?.onTetheringFailed()
                         null
                     }
-                    else -> {
+                    else -> ProxyBuilder.callSuper(proxy, method, args)
-                        Timber.w("Unexpected method, calling super: $method")
-                        ProxyBuilder.callSuper(proxy, method, args)
-                    }
                 }
             }
         }.build()
@@ -460,7 +455,7 @@ object TetheringManager {
                     override fun invoke(proxy: Any, method: Method, args: Array<out Any?>?): Any? {
                         @Suppress("NAME_SHADOWING") val callback = reference.get()
                         val noArgs = args?.size ?: 0
-                        when (val name = method.name) {
+                        return when (val name = method.name) {
                             "onTetheringSupported" -> {
                                 if (noArgs != 1) Timber.w("Unexpected args for $name: $args")
                                 callback?.onTetheringSupported(args!![0] as Boolean)
@@ -495,13 +490,9 @@ object TetheringManager {
                                 if (noArgs != 1) Timber.w("Unexpected args for $name: $args")
                                 callback?.onOffloadStatusChanged(args!![0] as Int)
                             }
-                            else -> {
+                            else -> callSuper(interfaceTetheringEventCallback, proxy, method, args)
-                                Timber.w("Unexpected method, calling super: $method")
-                                return ProxyBuilder.callSuper(proxy, method, args)
                         }
                     }
-                        return null
-                    }
                 })
             }
         }

mobile/src/main/java/be/mygod/vpnhotspot/net/wifi/WifiP2pManagerHelper.kt

@@ -5,8 +5,10 @@ import android.net.wifi.WpsInfo
 import android.net.wifi.p2p.WifiP2pGroup
 import android.net.wifi.p2p.WifiP2pManager
 import be.mygod.vpnhotspot.App.Companion.app
-import com.android.dx.stock.ProxyBuilder
+import be.mygod.vpnhotspot.util.callSuper
 import timber.log.Timber
+import java.lang.reflect.InvocationHandler
+import java.lang.reflect.Method
 import java.lang.reflect.Proxy
 
 object WifiP2pManagerHelper {
@@ -90,17 +92,15 @@ object WifiP2pManagerHelper {
     fun WifiP2pManager.requestPersistentGroupInfo(c: WifiP2pManager.Channel,
                                                   listener: (Collection<WifiP2pGroup>) -> Unit) {
         val proxy = Proxy.newProxyInstance(interfacePersistentGroupInfoListener.classLoader,
-                arrayOf(interfacePersistentGroupInfoListener)) { proxy, method, args ->
+                arrayOf(interfacePersistentGroupInfoListener), object : InvocationHandler {
-                    if (method.name == "onPersistentGroupInfoAvailable") {
+            override fun invoke(proxy: Any, method: Method, args: Array<out Any?>?): Any? = when (method.name) {
+                "onPersistentGroupInfoAvailable" -> {
                     if (args?.size != 1) Timber.w(IllegalArgumentException("Unexpected args: $args"))
-                        @Suppress("UNCHECKED_CAST")
+                    @Suppress("UNCHECKED_CAST") listener(getGroupList.invoke(args!![0]) as Collection<WifiP2pGroup>)
-                        listener(getGroupList.invoke(args[0]) as Collection<WifiP2pGroup>)
-                        null
-                    } else {
-                        Timber.w(IllegalArgumentException("Unexpected method, calling super: $method"))
-                        ProxyBuilder.callSuper(proxy, method, args)
                 }
+                else -> callSuper(interfacePersistentGroupInfoListener, proxy, method, args)
             }
+        })
         requestPersistentGroupInfo.invoke(this, c, proxy)
     }
 }

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

@@ -1,6 +1,7 @@
 package be.mygod.vpnhotspot.util
 
 import android.annotation.SuppressLint
+import android.annotation.TargetApi
 import android.content.*
 import android.net.InetAddresses
 import android.os.Build
@@ -13,6 +14,7 @@ import android.view.MenuItem
 import android.view.View
 import android.widget.ImageView
 import androidx.annotation.DrawableRes
+import androidx.annotation.RequiresApi
 import androidx.core.net.toUri
 import androidx.core.view.isVisible
 import androidx.databinding.BindingAdapter
@@ -21,6 +23,9 @@ import androidx.fragment.app.FragmentManager
 import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.net.MacAddressCompat
 import be.mygod.vpnhotspot.widget.SmartSnackbar
+import java.lang.invoke.MethodHandles
+import java.lang.reflect.InvocationHandler
+import java.lang.reflect.Method
 import java.net.InetAddress
 import java.net.NetworkInterface
 import java.net.SocketException
@@ -129,3 +134,25 @@ var MenuItem.isNotGone: Boolean
         isVisible = value
         isEnabled = value
     }
+
+@get:RequiresApi(26)
+private val newLookup by lazy @TargetApi(26) {
+    MethodHandles.Lookup::class.java.getDeclaredConstructor(Class::class.java, Int::class.java).apply {
+        isAccessible = true
+    }
+}
+
+/**
+ * Call interface super method.
+ *
+ * See also: https://stackoverflow.com/a/49532463/2245107
+ */
+fun InvocationHandler.callSuper(interfaceClass: Class<*>, proxy: Any, method: Method, args: Array<out Any?>?) = when {
+    Build.VERSION.SDK_INT >= 26 -> newLookup.newInstance(interfaceClass, 0xf)     // ALL_MODES
+            .`in`(interfaceClass).unreflectSpecial(method, interfaceClass).bindTo(proxy).run {
+                if (args == null) invokeWithArguments() else invokeWithArguments(*args)
+            }
+    // only Java 8+ has default interface methods; otherwise, we just redispatch it to InvocationHandler
+    args == null -> method(this)
+    else -> method(this, *args)
+}