curator-master/curator-framework/src/main/java/org/apache/curator/framework/imps/Backgrounding.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.curator.framework.imps;

import com.google.common.base.Throwables;
import java.util.concurrent.Executor;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.framework.api.UnhandledErrorListener;
import org.apache.curator.utils.ThreadUtils;
import org.apache.zookeeper.KeeperException;

public class Backgrounding {
    private final boolean inBackground;
    private final Object context;
    private final BackgroundCallback callback;
    private final UnhandledErrorListener errorListener;

    Backgrounding(Object context) {
        this.inBackground = true;
        this.context = context;
        this.callback = null;
        errorListener = null;
    }

    Backgrounding(BackgroundCallback callback) {
        this.inBackground = true;
        this.context = null;
        this.callback = callback;
        errorListener = null;
    }

    Backgrounding(boolean inBackground) {
        this.inBackground = inBackground;
        this.context = null;
        this.callback = null;
        errorListener = null;
    }

    Backgrounding(BackgroundCallback callback, Object context) {
        this.inBackground = true;
        this.context = context;
        this.callback = callback;
        errorListener = null;
    }

    Backgrounding(CuratorFrameworkImpl client, BackgroundCallback callback, Object context, Executor executor) {
        this(wrapCallback(client, callback, executor), context);
    }

    Backgrounding(CuratorFrameworkImpl client, BackgroundCallback callback, Executor executor) {
        this(wrapCallback(client, callback, executor));
    }

    Backgrounding(Backgrounding rhs, UnhandledErrorListener errorListener) {
        if (rhs == null) {
            rhs = new Backgrounding();
        }
        this.inBackground = rhs.inBackground;
        this.context = rhs.context;
        this.callback = rhs.callback;
        this.errorListener = errorListener;
    }

    public Backgrounding(BackgroundCallback callback, UnhandledErrorListener errorListener) {
        this.callback = callback;
        this.errorListener = errorListener;
        inBackground = true;
        context = null;
    }

    Backgrounding() {
        inBackground = false;
        context = null;
        this.callback = null;
        errorListener = null;
    }

    boolean inBackground() {
        return inBackground;
    }

    Object getContext() {
        return context;
    }

    BackgroundCallback getCallback() {
        return callback;
    }

    void checkError(Throwable e, Watching watching) throws Exception {
        if (e != null) {
            if (errorListener != null) {
                errorListener.unhandledError("n/a", e);
            } else if (e instanceof Exception) {
                throw (Exception) e;
            } else {
                Throwables.propagate(e);
            }
        }
    }

    private static BackgroundCallback wrapCallback(
            final CuratorFrameworkImpl client, final BackgroundCallback callback, final Executor executor) {
        return new BackgroundCallback() {
            @Override
            public void processResult(CuratorFramework dummy, final CuratorEvent event) throws Exception {
                executor.execute(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            callback.processResult(client, event);
                        } catch (Exception e) {
                            ThreadUtils.checkInterrupted(e);
                            if (e instanceof KeeperException) {
                                client.validateConnection(client.codeToState(((KeeperException) e).code()));
                            }
                            client.logError("Background operation result handling threw exception", e);
                        }
                    }
                });
            }
        };
    }
}
