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The Amazon Web Services SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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.amazonaws.services.simpleworkflow.flow;

import com.amazonaws.services.simpleworkflow.flow.core.Promise;
import com.amazonaws.services.simpleworkflow.model.DecisionTask;

/**
 * Clock that must be used inside workflow definition code to ensure replay
 * determinism.
 */
public interface WorkflowClock {

    /**
     * @return time of the {@link DecisionTask} start event of the decision
     *         being processed or replayed.
     */
    public long currentTimeMillis();

    /**
     * true indicates if workflow is replaying already processed
     * events to reconstruct it state. false indicates that code is
     * making forward process for the first time. For example can be used to
     * avoid duplicating log records due to replay. 
     */
    public boolean isReplaying();

    /**
     * Create a Value that becomes ready after the specified delay.
     * 
     * @param delay
     *            time-interval after which the Value becomes ready in seconds.
     * @return Promise that becomes ready after the specified delay.
     */
    public abstract Promise createTimer(long delaySeconds);

    /**
     * Create a Value that becomes ready after the specified delay.
     * 
     * @param context
     *            context object that is returned inside the value when it
     *            becomes ready.
     * @return Promise that becomes ready after the specified delay. When ready
     *         it contains value passed as context parameter.
     */
    public abstract  Promise createTimer(long delaySeconds, final T context);

}