/*
 * Copyright (C) 2015 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.tv.util;

import android.os.Handler;
import android.os.Looper;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * An executor service that executes its tasks on the main thread.
 *
 * <p>Shutting down this executor is not supported.
 */
public class MainThreadExecutor extends AbstractExecutorService {

    private static final MainThreadExecutor INSTANCE = new MainThreadExecutor();

    public static MainThreadExecutor getInstance() {
        return INSTANCE;
    }

    private final Handler mHandler = new Handler(Looper.getMainLooper());

    @Override
    public void execute(Runnable runnable) {
        if (Looper.getMainLooper() == Looper.myLooper()) {
            runnable.run();
        } else {
            mHandler.post(runnable);
        }
    }

    /** Not supported and throws an exception when used. */
    @Override
    @Deprecated
    public void shutdown() {
        throw new UnsupportedOperationException();
    }

    /** Not supported and throws an exception when used. */
    @Override
    @Deprecated
    public List<Runnable> shutdownNow() {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean isShutdown() {
        return false;
    }

    @Override
    public boolean isTerminated() {
        return false;
    }

    /** Not supported and throws an exception when used. */
    @Override
    @Deprecated
    public boolean awaitTermination(long l, TimeUnit timeUnit) throws InterruptedException {
        throw new UnsupportedOperationException();
    }
}