Copyright 2012 Netflix, Inc.
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 2012 Netflix, Inc.
 * 
 * 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.netflix.hystrix.strategy.concurrency;

import java.util.concurrent.Callable;

import rx.functions.Action0;
import rx.functions.Func2;

import com.netflix.hystrix.strategy.HystrixPlugins;

Wrapper around Func2 that manages the HystrixRequestContext initialization and cleanup for the execution of the Func2 
Type parameters:
<T> –  Return type of Func2
@ExcludeFromJavadoc
/**
 * Wrapper around {@link Func2} that manages the {@link HystrixRequestContext} initialization and cleanup for the execution of the {@link Func2}
 * 
 * @param <T>
 *            Return type of {@link Func2}
 * 
 * @ExcludeFromJavadoc
 */
public class HystrixContexSchedulerAction implements Action0 {

    private final Action0 actual;
    private final HystrixRequestContext parentThreadState;
    private final Callable<Void> c;

    public HystrixContexSchedulerAction(Action0 action) {
        this(HystrixPlugins.getInstance().getConcurrencyStrategy(), action);
    }

    public HystrixContexSchedulerAction(final HystrixConcurrencyStrategy concurrencyStrategy, Action0 action) {
        this.actual = action;
        this.parentThreadState = HystrixRequestContext.getContextForCurrentThread();

        this.c = concurrencyStrategy.wrapCallable(new Callable<Void>() {

            @Override
            public Void call() throws Exception {
                HystrixRequestContext existingState = HystrixRequestContext.getContextForCurrentThread();
                try {
                    // set the state of this thread to that of its parent
                    HystrixRequestContext.setContextOnCurrentThread(parentThreadState);
                    // execute actual Action0 with the state of the parent
                    actual.call();
                    return null;
                } finally {
                    // restore this thread back to its original state
                    HystrixRequestContext.setContextOnCurrentThread(existingState);
                }
            }
        });
    }

    @Override
    public void call() {
        try {
            c.call();
        } catch (Exception e) {
            throw new RuntimeException("Failed executing wrapped Action0", e);
        }
    }

}