Simplify API required to call methods by reflection. (#45)

* Implement a cleaner way to call methods by reflection.
* Port all callers to the new reflection API.

4 files changed, 115 insertions, 99 deletions

diff --git a/src/main/java/com/google/android/mobly/snippet/bundled/AudioSnippet.java b/src/main/java/com/google/android/mobly/snippet/bundled/AudioSnippet.java
index 1ca96d0..4f6b0ae 100644
--- a/src/main/java/com/google/android/mobly/snippet/bundled/AudioSnippet.java
+++ b/src/main/java/com/google/android/mobly/snippet/bundled/AudioSnippet.java
@@ -78,7 +78,7 @@ public class AudioSnippet implements Snippet {
          * calling muteAll will throw. */
         Class<?> audioSystem = Class.forName("android.media.AudioSystem");
         Method getNumStreamTypes = audioSystem.getDeclaredMethod("getNumStreamTypes");
-        int numStreams = (int) getNumStreamTypes.invoke(null);
+        int numStreams = (int) getNumStreamTypes.invoke(null /* instance */);
         for (int i = 0; i < numStreams; i++) {
             mAudioManager.setStreamVolume(i /* audio stream */, 0 /* value */, 0 /* flags */);
         }
diff --git a/src/main/java/com/google/android/mobly/snippet/bundled/BluetoothAdapterSnippet.java b/src/main/java/com/google/android/mobly/snippet/bundled/BluetoothAdapterSnippet.java
index 7a0a15e..6946216 100644
--- a/src/main/java/com/google/android/mobly/snippet/bundled/BluetoothAdapterSnippet.java
+++ b/src/main/java/com/google/android/mobly/snippet/bundled/BluetoothAdapterSnippet.java
@@ -29,7 +29,6 @@ import com.google.android.mobly.snippet.bundled.utils.JsonSerializer;
 import com.google.android.mobly.snippet.bundled.utils.Utils;
 import com.google.android.mobly.snippet.rpc.Rpc;
 import com.google.android.mobly.snippet.rpc.RpcMinSdk;
-import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
 import org.json.JSONArray;
 import org.json.JSONException;
@@ -146,42 +145,24 @@ public class BluetoothAdapterSnippet implements Snippet {
             throw new BluetoothAdapterSnippetException(
                     "Bluetooth is not enabled, cannot become discoverable.");
         }
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mBluetoothAdapter
-                                    .getClass()
-                                    .getDeclaredMethod("setScanMode", int.class, int.class)
-                                    .invoke(
-                                            mBluetoothAdapter,
-                                            BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE,
-                                            duration);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean)
+                Utils.invokeByReflection(
+                        mBluetoothAdapter,
+                        "setScanMode",
+                        BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE,
+                        duration)) {
             throw new BluetoothAdapterSnippetException("Failed to become discoverable.");
         }
     }
 
     @Rpc(description = "Stop being discoverable in Bluetooth.")
     public void btStopBeingDiscoverable() throws Throwable {
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mBluetoothAdapter
-                                    .getClass()
-                                    .getDeclaredMethod("setScanMode", int.class, int.class)
-                                    .invoke(
-                                            mBluetoothAdapter,
-                                            BluetoothAdapter.SCAN_MODE_NONE,
-                                            0 /* duration is not used for this */);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean)
+                Utils.invokeByReflection(
+                        mBluetoothAdapter,
+                        "setScanMode",
+                        BluetoothAdapter.SCAN_MODE_NONE,
+                        0 /* duration is not used for this */)) {
             throw new BluetoothAdapterSnippetException("Failed to stop being discoverable.");
         }
     }
@@ -206,18 +187,7 @@ public class BluetoothAdapterSnippet implements Snippet {
     @RpcMinSdk(Build.VERSION_CODES.KITKAT)
     @Rpc(description = "Enable Bluetooth HCI snoop log for debugging.")
     public void btEnableHciSnoopLog() throws Throwable {
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mBluetoothAdapter
-                                    .getClass()
-                                    .getDeclaredMethod("configHciSnoopLog", boolean.class)
-                                    .invoke(mBluetoothAdapter, true);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean) Utils.invokeByReflection(mBluetoothAdapter, "configHciSnoopLog", true)) {
             throw new BluetoothAdapterSnippetException("Failed to enable HCI snoop log.");
         }
     }
@@ -225,18 +195,7 @@ public class BluetoothAdapterSnippet implements Snippet {
     @RpcMinSdk(Build.VERSION_CODES.KITKAT)
     @Rpc(description = "Disable Bluetooth HCI snoop log.")
     public void btDisableHciSnoopLog() throws Throwable {
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mBluetoothAdapter
-                                    .getClass()
-                                    .getDeclaredMethod("configHciSnoopLog", boolean.class)
-                                    .invoke(mBluetoothAdapter, false);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean) Utils.invokeByReflection(mBluetoothAdapter, "configHciSnoopLog", false)) {
             throw new BluetoothAdapterSnippetException("Failed to disable HCI snoop log.");
         }
     }
diff --git a/src/main/java/com/google/android/mobly/snippet/bundled/WifiManagerSnippet.java b/src/main/java/com/google/android/mobly/snippet/bundled/WifiManagerSnippet.java
index bc57ab0..f2ac9eb 100644
--- a/src/main/java/com/google/android/mobly/snippet/bundled/WifiManagerSnippet.java
+++ b/src/main/java/com/google/android/mobly/snippet/bundled/WifiManagerSnippet.java
@@ -31,7 +31,6 @@ import com.google.android.mobly.snippet.bundled.utils.JsonSerializer;
 import com.google.android.mobly.snippet.bundled.utils.Utils;
 import com.google.android.mobly.snippet.rpc.Rpc;
 import com.google.android.mobly.snippet.util.Log;
-import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
 import org.json.JSONArray;
 import org.json.JSONException;
@@ -243,15 +242,7 @@ public class WifiManagerSnippet implements Snippet {
 
     @Rpc(description = "Check whether Wi-Fi Soft AP (hotspot) is enabled.")
     public boolean wifiIsApEnabled() throws Throwable {
-        try {
-            return (boolean)
-                    mWifiManager
-                            .getClass()
-                            .getDeclaredMethod("isWifiApEnabled")
-                            .invoke(mWifiManager);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
+        return (boolean) Utils.invokeByReflection(mWifiManager, "isWifiApEnabled");
     }
 
     /**
@@ -270,21 +261,9 @@ public class WifiManagerSnippet implements Snippet {
             // WifiConfiguration.SSID literally, unlike the WifiManager connection logic.
             wifiConfiguration.SSID = JsonSerializer.trimQuotationMarks(wifiConfiguration.SSID);
         }
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mWifiManager
-                                    .getClass()
-                                    .getDeclaredMethod(
-                                            "setWifiApEnabled",
-                                            WifiConfiguration.class,
-                                            boolean.class)
-                                    .invoke(mWifiManager, wifiConfiguration, true);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean)
+                Utils.invokeByReflection(
+                        mWifiManager, "setWifiApEnabled", wifiConfiguration, true)) {
             throw new WifiManagerSnippetException("Failed to initiate turning on Wi-Fi Soft AP.");
         }
         if (!Utils.waitUntil(() -> wifiIsApEnabled() == true, 60)) {
@@ -297,24 +276,12 @@ public class WifiManagerSnippet implements Snippet {
     /** Disables Wi-Fi Soft AP (hotspot). */
     @Rpc(description = "Disable Wi-Fi Soft AP (hotspot).")
     public void wifiDisableSoftAp() throws Throwable {
-        boolean success;
-        try {
-            success =
-                    (boolean)
-                            mWifiManager
-                                    .getClass()
-                                    .getDeclaredMethod(
-                                            "setWifiApEnabled",
-                                            WifiConfiguration.class,
-                                            boolean.class)
-                                    .invoke(
-                                            mWifiManager,
-                                            null, /* No configuration needed for disabling */
-                                            false);
-        } catch (InvocationTargetException e) {
-            throw e.getCause();
-        }
-        if (!success) {
+        if (!(boolean)
+                Utils.invokeByReflection(
+                        mWifiManager,
+                        "setWifiApEnabled",
+                        null /* No configuration needed for disabling */,
+                        false)) {
             throw new WifiManagerSnippetException("Failed to initiate turning off Wi-Fi Soft AP.");
         }
         if (!Utils.waitUntil(() -> wifiIsApEnabled() == false, 60)) {
diff --git a/src/main/java/com/google/android/mobly/snippet/bundled/utils/Utils.java b/src/main/java/com/google/android/mobly/snippet/bundled/utils/Utils.java
index 0ea5313..8736d85 100644
--- a/src/main/java/com/google/android/mobly/snippet/bundled/utils/Utils.java
+++ b/src/main/java/com/google/android/mobly/snippet/bundled/utils/Utils.java
@@ -16,6 +16,11 @@
 
 package com.google.android.mobly.snippet.bundled.utils;
 
+import com.google.common.primitives.Primitives;
+import com.google.common.reflect.TypeToken;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
 public final class Utils {
     private Utils() {}
 
@@ -56,4 +61,89 @@ public final class Utils {
     public interface Predicate {
         boolean waitCondition() throws Throwable;
     }
+
+    /**
+     * Simplified API to invoke an instance method by reflection.
+     *
+     * <p>Sample usage:
+     *
+     * <pre>
+     *   boolean result = (boolean) Utils.invokeByReflection(
+     *           mWifiManager,
+     *           "setWifiApEnabled", null /* wifiConfiguration * /, true /* enabled * /);
+     * </pre>
+     *
+     * @param instance Instance of object defining the method to call.
+     * @param methodName Name of the method to call. Can be inherited.
+     * @param args Variadic array of arguments to supply to the method. Their types will be used to
+     *     locate a suitable method to call. Subtypes, primitive types, boxed types, and {@code
+     *     null} arguments are properly handled.
+     * @return The return value of the method, or {@code null} if no return value.
+     * @throws NoSuchMethodException If no suitable method could be found.
+     * @throws Throwable The exception raised by the method, if any.
+     */
+    public static Object invokeByReflection(Object instance, String methodName, Object... args)
+            throws Throwable {
+        // Java doesn't know if invokeByReflection(instance, name, null) means that the array is
+        // null or that it's a non-null array containing a single null element. We mean the latter.
+        // Silly Java.
+        if (args == null) {
+            args = new Object[] {null};
+        }
+        // Can't use Class#getMethod(Class<?>...) because it expects that the passed in classes
+        // exactly match the parameters of the method, and doesn't handle superclasses.
+        Method method = null;
+        METHOD_SEARCHER:
+        for (Method candidateMethod : instance.getClass().getMethods()) {
+            // getMethods() returns only public methods, so we don't need to worry about checking
+            // whether the method is accessible.
+            if (!candidateMethod.getName().equals(methodName)) {
+                continue;
+            }
+            Class<?>[] declaredParams = candidateMethod.getParameterTypes();
+            if (declaredParams.length != args.length) {
+                continue;
+            }
+            for (int i = 0; i < declaredParams.length; i++) {
+                if (args[i] == null) {
+                    // Null is assignable to anything except primitives.
+                    if (declaredParams[i].isPrimitive()) {
+                        continue METHOD_SEARCHER;
+                    }
+                } else {
+                    // Allow autoboxing during reflection by wrapping primitives.
+                    Class<?> declaredClass = Primitives.wrap(declaredParams[i]);
+                    Class<?> actualClass = Primitives.wrap(args[i].getClass());
+                    TypeToken<?> declaredParamType = TypeToken.of(declaredClass);
+                    TypeToken<?> actualParamType = TypeToken.of(actualClass);
+                    if (!declaredParamType.isSupertypeOf(actualParamType)) {
+                        continue METHOD_SEARCHER;
+                    }
+                }
+            }
+            method = candidateMethod;
+            break;
+        }
+        if (method == null) {
+            StringBuilder methodString =
+                    new StringBuilder(instance.getClass().getName())
+                            .append('#')
+                            .append(methodName)
+                            .append('(');
+            for (int i = 0; i < args.length - 1; i++) {
+                methodString.append(args[i].getClass().getSimpleName()).append(", ");
+            }
+            if (args.length > 0) {
+                methodString.append(args[args.length - 1].getClass().getSimpleName());
+            }
+            methodString.append(')');
+            throw new NoSuchMethodException(methodString.toString());
+        }
+        try {
+            Object result = method.invoke(instance, args);
+            return result;
+        } catch (InvocationTargetException e) {
+            throw e.getCause();
+        }
+    }
 }