Copyright (c) 2016-present, RxJava Contributors.
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.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 * 
 * 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 io.reactivex.internal.schedulers;

import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.disposables.Disposable;
import io.reactivex.internal.functions.Functions;
import io.reactivex.schedulers.SchedulerRunnableIntrospection;

Base functionality for direct tasks that manage a runnable and cancellation/completion.
Since:
2.0.8/**
 * Base functionality for direct tasks that manage a runnable and cancellation/completion.
 * @since 2.0.8
 */
abstract class AbstractDirectTask
extends AtomicReference<Future<?>>
implements Disposable, SchedulerRunnableIntrospection {

    private static final long serialVersionUID = 1811839108042568751L;

    protected final Runnable runnable;

    protected Thread runner;

    protected static final FutureTask<Void> FINISHED = new FutureTask<Void>(Functions.EMPTY_RUNNABLE, null);

    protected static final FutureTask<Void> DISPOSED = new FutureTask<Void>(Functions.EMPTY_RUNNABLE, null);

    AbstractDirectTask(Runnable runnable) {
        this.runnable = runnable;
    }

    @Override
    public final void dispose() {
        Future<?> f = get();
        if (f != FINISHED && f != DISPOSED) {
            if (compareAndSet(f, DISPOSED)) {
                if (f != null) {
                    f.cancel(runner != Thread.currentThread());
                }
            }
        }
    }

    @Override
    public final boolean isDisposed() {
        Future<?> f = get();
        return f == FINISHED || f == DISPOSED;
    }

    public final void setFuture(Future<?> future) {
        for (;;) {
            Future<?> f = get();
            if (f == FINISHED) {
                break;
            }
            if (f == DISPOSED) {
                future.cancel(runner != Thread.currentThread());
                break;
            }
            if (compareAndSet(f, future)) {
                break;
            }
        }
    }

    @Override
    public Runnable getWrappedRunnable() {
        return runnable;
    }
}