Create the DiscoveryExecutor Class

This is a no-op refactor. Move the DiscoveryExecutor from
MdnsDiscoveryManager to a standalone class for subsequent
changes.

Bug: 366373064
Test: atest FrameworksNetTests NsdManagerTest
Change-Id: Idbfbbb423ddfe78a37db1b189aef945401b0a1e9
diff --git a/service-t/src/com/android/server/connectivity/mdns/DiscoveryExecutor.java b/service-t/src/com/android/server/connectivity/mdns/DiscoveryExecutor.java
new file mode 100644
index 0000000..21af1a1
--- /dev/null
+++ b/service-t/src/com/android/server/connectivity/mdns/DiscoveryExecutor.java
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.connectivity.mdns;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.Looper;
+import android.util.Log;
+import android.util.Pair;
+
+import androidx.annotation.GuardedBy;
+
+import com.android.net.module.util.HandlerUtils;
+
+import java.util.ArrayList;
+import java.util.concurrent.Executor;
+
+/**
+ * A utility class to generate a handler, optionally with a looper, and to run functions on the
+ * newly created handler.
+ */
+public class DiscoveryExecutor implements Executor {
+    private static final String TAG = DiscoveryExecutor.class.getSimpleName();
+    @Nullable
+    private final HandlerThread mHandlerThread;
+
+    @GuardedBy("mPendingTasks")
+    @Nullable
+    private Handler mHandler;
+    // Store pending tasks and associated delay time. Each Pair represents a pending task
+    // (first) and its delay time (second).
+    @GuardedBy("mPendingTasks")
+    @NonNull
+    private final ArrayList<Pair<Runnable, Long>> mPendingTasks = new ArrayList<>();
+
+    DiscoveryExecutor(@Nullable Looper defaultLooper) {
+        if (defaultLooper != null) {
+            this.mHandlerThread = null;
+            synchronized (mPendingTasks) {
+                this.mHandler = new Handler(defaultLooper);
+            }
+        } else {
+            this.mHandlerThread = new HandlerThread(MdnsDiscoveryManager.class.getSimpleName()) {
+                @Override
+                protected void onLooperPrepared() {
+                    synchronized (mPendingTasks) {
+                        mHandler = new Handler(getLooper());
+                        for (Pair<Runnable, Long> pendingTask : mPendingTasks) {
+                            mHandler.postDelayed(pendingTask.first, pendingTask.second);
+                        }
+                        mPendingTasks.clear();
+                    }
+                }
+            };
+            this.mHandlerThread.start();
+        }
+    }
+
+    /**
+     * Check if the current thread is the expected thread. If it is, run the given function.
+     * Otherwise, execute it using the handler.
+     */
+    public void checkAndRunOnHandlerThread(@NonNull Runnable function) {
+        if (this.mHandlerThread == null) {
+            // Callers are expected to already be running on the handler when a defaultLooper
+            // was provided
+            function.run();
+        } else {
+            execute(function);
+        }
+    }
+
+    /** Execute the given function */
+    @Override
+    public void execute(Runnable function) {
+        executeDelayed(function, 0L /* delayMillis */);
+    }
+
+    /** Execute the given function after the specified amount of time elapses. */
+    public void executeDelayed(Runnable function, long delayMillis) {
+        final Handler handler;
+        synchronized (mPendingTasks) {
+            if (this.mHandler == null) {
+                mPendingTasks.add(Pair.create(function, delayMillis));
+                return;
+            } else {
+                handler = this.mHandler;
+            }
+        }
+        handler.postDelayed(function, delayMillis);
+    }
+
+    /** Shutdown the thread if necessary. */
+    public void shutDown() {
+        if (this.mHandlerThread != null) {
+            this.mHandlerThread.quitSafely();
+        }
+    }
+
+    /**
+     * Ensures that the current running thread is the same as the handler thread.
+     */
+    public void ensureRunningOnHandlerThread() {
+        synchronized (mPendingTasks) {
+            HandlerUtils.ensureRunningOnHandlerThread(mHandler);
+        }
+    }
+
+    /**
+     * Runs the specified task synchronously for dump method.
+     */
+    public void runWithScissorsForDumpIfReady(@NonNull Runnable function) {
+        final Handler handler;
+        synchronized (mPendingTasks) {
+            if (this.mHandler == null) {
+                Log.d(TAG, "The handler is not ready. Ignore the DiscoveryManager dump");
+                return;
+            } else {
+                handler = this.mHandler;
+            }
+        }
+        HandlerUtils.runWithScissorsForDump(handler, function, 10_000);
+    }
+}
diff --git a/service-t/src/com/android/server/connectivity/mdns/MdnsDiscoveryManager.java b/service-t/src/com/android/server/connectivity/mdns/MdnsDiscoveryManager.java
index c833422..33bcb70 100644
--- a/service-t/src/com/android/server/connectivity/mdns/MdnsDiscoveryManager.java
+++ b/service-t/src/com/android/server/connectivity/mdns/MdnsDiscoveryManager.java
@@ -16,24 +16,17 @@
 
 package com.android.server.connectivity.mdns;
 
-import static com.android.internal.annotations.VisibleForTesting.Visibility;
-
 import android.Manifest.permission;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
-import android.os.Handler;
-import android.os.HandlerThread;
 import android.os.Looper;
 import android.util.ArrayMap;
 import android.util.Log;
 import android.util.Pair;
 
-import androidx.annotation.GuardedBy;
-
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.net.module.util.DnsUtils;
-import com.android.net.module.util.HandlerUtils;
 import com.android.net.module.util.SharedLog;
 
 import java.io.IOException;
@@ -41,7 +34,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
-import java.util.concurrent.Executor;
 
 /**
  * This class keeps tracking the set of registered {@link MdnsServiceBrowserListener} instances, and
@@ -137,98 +129,6 @@
     }
 
     /**
-     * A utility class to generate a handler, optionally with a looper, and to run functions on the
-     * newly created handler.
-     */
-    @VisibleForTesting(visibility = Visibility.PRIVATE)
-    static class DiscoveryExecutor implements Executor {
-        private final HandlerThread handlerThread;
-
-        @GuardedBy("pendingTasks")
-        @Nullable private Handler handler;
-        // Store pending tasks and associated delay time. Each Pair represents a pending task
-        // (first) and its delay time (second).
-        @GuardedBy("pendingTasks")
-        @NonNull private final ArrayList<Pair<Runnable, Long>> pendingTasks = new ArrayList<>();
-
-        DiscoveryExecutor(@Nullable Looper defaultLooper) {
-            if (defaultLooper != null) {
-                this.handlerThread = null;
-                synchronized (pendingTasks) {
-                    this.handler = new Handler(defaultLooper);
-                }
-            } else {
-                this.handlerThread = new HandlerThread(MdnsDiscoveryManager.class.getSimpleName()) {
-                    @Override
-                    protected void onLooperPrepared() {
-                        synchronized (pendingTasks) {
-                            handler = new Handler(getLooper());
-                            for (Pair<Runnable, Long> pendingTask : pendingTasks) {
-                                handler.postDelayed(pendingTask.first, pendingTask.second);
-                            }
-                            pendingTasks.clear();
-                        }
-                    }
-                };
-                this.handlerThread.start();
-            }
-        }
-
-        public void checkAndRunOnHandlerThread(@NonNull Runnable function) {
-            if (this.handlerThread == null) {
-                // Callers are expected to already be running on the handler when a defaultLooper
-                // was provided
-                function.run();
-            } else {
-                execute(function);
-            }
-        }
-
-        @Override
-        public void execute(Runnable function) {
-            executeDelayed(function, 0L /* delayMillis */);
-        }
-
-        public void executeDelayed(Runnable function, long delayMillis) {
-            final Handler handler;
-            synchronized (pendingTasks) {
-                if (this.handler == null) {
-                    pendingTasks.add(Pair.create(function, delayMillis));
-                    return;
-                } else {
-                    handler = this.handler;
-                }
-            }
-            handler.postDelayed(function, delayMillis);
-        }
-
-        void shutDown() {
-            if (this.handlerThread != null) {
-                this.handlerThread.quitSafely();
-            }
-        }
-
-        void ensureRunningOnHandlerThread() {
-            synchronized (pendingTasks) {
-                HandlerUtils.ensureRunningOnHandlerThread(handler);
-            }
-        }
-
-        public void runWithScissorsForDumpIfReady(@NonNull Runnable function) {
-            final Handler handler;
-            synchronized (pendingTasks) {
-                if (this.handler == null) {
-                    Log.d(TAG, "The handler is not ready. Ignore the DiscoveryManager dump");
-                    return;
-                } else {
-                    handler = this.handler;
-                }
-            }
-            HandlerUtils.runWithScissorsForDump(handler, function, 10_000);
-        }
-    }
-
-    /**
      * Do the cleanup of the MdnsDiscoveryManager
      */
     public void shutDown() {
diff --git a/tests/unit/java/com/android/server/connectivity/mdns/DiscoveryExecutorTest.kt b/tests/unit/java/com/android/server/connectivity/mdns/DiscoveryExecutorTest.kt
new file mode 100644
index 0000000..51539a0
--- /dev/null
+++ b/tests/unit/java/com/android/server/connectivity/mdns/DiscoveryExecutorTest.kt
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.connectivity.mdns
+
+import android.os.Build
+import android.os.HandlerThread
+import android.testing.TestableLooper
+import com.android.testutils.DevSdkIgnoreRule
+import com.android.testutils.DevSdkIgnoreRunner
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.TimeUnit
+import org.junit.After
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+
+private const val DEFAULT_TIMEOUT = 2000L
+
+@DevSdkIgnoreRunner.MonitorThreadLeak
+@RunWith(DevSdkIgnoreRunner::class)
+@DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.S_V2)
+class DiscoveryExecutorTest {
+    private val thread = HandlerThread(DiscoveryExecutorTest::class.simpleName).apply { start() }
+
+    @After
+    fun tearDown() {
+        thread.quitSafely()
+        thread.join()
+    }
+
+    @Test
+    fun testCheckAndRunOnHandlerThread() {
+        val testableLooper = TestableLooper(thread.looper)
+        val executor = DiscoveryExecutor(testableLooper.looper)
+        try {
+            val future = CompletableFuture<Boolean>()
+            executor.checkAndRunOnHandlerThread { future.complete(true) }
+            testableLooper.processAllMessages()
+            assertTrue(future.get(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS))
+        } finally {
+            testableLooper.destroy()
+        }
+
+        // Create a DiscoveryExecutor with the null defaultLooper and verify the task can execute
+        // normally.
+        val executor2 = DiscoveryExecutor(null /* defaultLooper */)
+        val future2 = CompletableFuture<Boolean>()
+        executor2.checkAndRunOnHandlerThread { future2.complete(true) }
+        assertTrue(future2.get(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS))
+        executor2.shutDown()
+    }
+
+    @Test
+    fun testExecute() {
+        val testableLooper = TestableLooper(thread.looper)
+        val executor = DiscoveryExecutor(testableLooper.looper)
+        try {
+            val future = CompletableFuture<Boolean>()
+            executor.execute { future.complete(true) }
+            assertFalse(future.isDone)
+            testableLooper.processAllMessages()
+            assertTrue(future.get(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS))
+        } finally {
+            testableLooper.destroy()
+        }
+    }
+
+    @Test
+    fun testExecuteDelayed() {
+        val testableLooper = TestableLooper(thread.looper)
+        val executor = DiscoveryExecutor(testableLooper.looper)
+        try {
+            // Verify the executeDelayed method
+            val future = CompletableFuture<Boolean>()
+            // Schedule a task with 999 ms delay
+            executor.executeDelayed({ future.complete(true) }, 999L)
+            testableLooper.processAllMessages()
+            assertFalse(future.isDone)
+
+            // 500 ms have elapsed but do not exceed the target time (999 ms)
+            // The function should not be executed.
+            testableLooper.moveTimeForward(500L)
+            testableLooper.processAllMessages()
+            assertFalse(future.isDone)
+
+            // 500 ms have elapsed again and have exceeded the target time (999 ms).
+            // The function should be executed.
+            testableLooper.moveTimeForward(500L)
+            testableLooper.processAllMessages()
+            assertTrue(future.get(500L, TimeUnit.MILLISECONDS))
+        } finally {
+            testableLooper.destroy()
+        }
+    }
+}
diff --git a/tests/unit/java/com/android/server/connectivity/mdns/MdnsDiscoveryManagerTests.java b/tests/unit/java/com/android/server/connectivity/mdns/MdnsDiscoveryManagerTests.java
index 71a3274..758b822 100644
--- a/tests/unit/java/com/android/server/connectivity/mdns/MdnsDiscoveryManagerTests.java
+++ b/tests/unit/java/com/android/server/connectivity/mdns/MdnsDiscoveryManagerTests.java
@@ -19,8 +19,6 @@
 import static com.android.testutils.DevSdkIgnoreRuleKt.SC_V2;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doReturn;
@@ -35,12 +33,10 @@
 import android.net.Network;
 import android.os.Handler;
 import android.os.HandlerThread;
-import android.testing.TestableLooper;
 import android.text.TextUtils;
 import android.util.Pair;
 
 import com.android.net.module.util.SharedLog;
-import com.android.server.connectivity.mdns.MdnsDiscoveryManager.DiscoveryExecutor;
 import com.android.server.connectivity.mdns.MdnsSocketClientBase.SocketCreationCallback;
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRunner;
@@ -60,9 +56,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
 
 /** Tests for {@link MdnsDiscoveryManager}. */
 @DevSdkIgnoreRunner.MonitorThreadLeak
@@ -435,45 +429,6 @@
     }
 
     @Test
-    public void testDiscoveryExecutor() throws Exception {
-        final TestableLooper testableLooper = new TestableLooper(thread.getLooper());
-        final DiscoveryExecutor executor = new DiscoveryExecutor(testableLooper.getLooper());
-        try {
-            // Verify the checkAndRunOnHandlerThread method
-            final CompletableFuture<Boolean> future1 = new CompletableFuture<>();
-            executor.checkAndRunOnHandlerThread(()-> future1.complete(true));
-            assertTrue(future1.get(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS));
-
-            // Verify the execute method
-            final CompletableFuture<Boolean> future2 = new CompletableFuture<>();
-            executor.execute(()-> future2.complete(true));
-            testableLooper.processAllMessages();
-            assertTrue(future2.get(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS));
-
-            // Verify the executeDelayed method
-            final CompletableFuture<Boolean> future3 = new CompletableFuture<>();
-            // Schedule a task with 999 ms delay
-            executor.executeDelayed(()-> future3.complete(true), 999L);
-            testableLooper.processAllMessages();
-            assertFalse(future3.isDone());
-
-            // 500 ms have elapsed but do not exceed the target time (999 ms)
-            // The function should not be executed.
-            testableLooper.moveTimeForward(500L);
-            testableLooper.processAllMessages();
-            assertFalse(future3.isDone());
-
-            // 500 ms have elapsed again and have exceeded the target time (999 ms).
-            // The function should be executed.
-            testableLooper.moveTimeForward(500L);
-            testableLooper.processAllMessages();
-            assertTrue(future3.get(500L, TimeUnit.MILLISECONDS));
-        } finally {
-            testableLooper.destroy();
-        }
-    }
-
-    @Test
     public void testRemoveServicesAfterAllListenersUnregistered() throws IOException {
         final MdnsFeatureFlags mdnsFeatureFlags = MdnsFeatureFlags.newBuilder()
                 .setIsCachedServicesRemovalEnabled(true)