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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 java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflow;
import com.amazonaws.services.simpleworkflow.flow.common.WorkflowExecutionUtils;
import com.amazonaws.services.simpleworkflow.flow.core.AsyncTaskInfo;
import com.amazonaws.services.simpleworkflow.flow.generic.WorkflowDefinition;
import com.amazonaws.services.simpleworkflow.flow.generic.WorkflowDefinitionFactoryFactory;
import com.amazonaws.services.simpleworkflow.flow.pojo.POJOWorkflowDefinition;
import com.amazonaws.services.simpleworkflow.flow.pojo.POJOWorkflowDefinitionFactoryFactory;
import com.amazonaws.services.simpleworkflow.flow.pojo.POJOWorkflowImplementationFactory;
import com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecisionTaskHandler;
import com.amazonaws.services.simpleworkflow.model.DecisionTask;
import com.amazonaws.services.simpleworkflow.model.EventType;
import com.amazonaws.services.simpleworkflow.model.History;
import com.amazonaws.services.simpleworkflow.model.HistoryEvent;
import com.amazonaws.services.simpleworkflow.model.RespondDecisionTaskCompletedRequest;
import com.amazonaws.services.simpleworkflow.model.WorkflowExecution;
import com.amazonaws.services.simpleworkflow.model.WorkflowExecutionInfo;
import com.amazonaws.services.simpleworkflow.model.WorkflowExecutionStartedEventAttributes;
import com.amazonaws.services.simpleworkflow.model.WorkflowType;

public class WorkflowReplayer {

    private final class WorkflowReplayerPOJOFactoryFactory extends POJOWorkflowDefinitionFactoryFactory {

        private final T workflowImplementation;

        private WorkflowReplayerPOJOFactoryFactory(T workflowImplementation) throws InstantiationException, IllegalAccessException {
            this.workflowImplementation = workflowImplementation;
            super.addWorkflowImplementationType(workflowImplementation.getClass());
        }

        @Override
        protected POJOWorkflowImplementationFactory getImplementationFactory(Class workflowImplementationType,
                Class workflowInteface, WorkflowType workflowType) {
            return new POJOWorkflowImplementationFactory() {

                @Override
                public Object newInstance(DecisionContext decisionContext) throws Exception {
                    return workflowImplementation;
                }

                @Override
                public void deleteInstance(Object instance) {
                }
            };
        }
    }

    private abstract class DecisionTaskIterator implements Iterator {

        private DecisionTask next;
        
        private boolean initialized;

        protected void initNext() {
            initialized = true;
            next = getNextHistoryTask(null);
        }

        @Override
        public boolean hasNext() {
            if (!initialized) {
                initNext();
            }
            
            if (next == null) {
                return false;
            }
            List events = next.getEvents();
            if (events.size() == 0) {
                return false;
            }
            if (replayUpToEventId == 0) {
                return true;
            }
            HistoryEvent firstEvent = next.getEvents().get(0);
            return firstEvent.getEventId() <= replayUpToEventId;
        }

        @Override
        public DecisionTask next() {
            if (!hasNext()) {
                throw new IllegalStateException("hasNext() == false");
            }
            DecisionTask result = next;
            if (next.getNextPageToken() == null) {
                next = null;
            }
            else {
                next = getNextHistoryTask(next.getNextPageToken());
            }
            return result;
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }

        protected List truncateHistory(List events) {
            if (events.size() == 0) {
                return null;
            }
            if (replayUpToEventId == 0) {
                return events;
            }
            HistoryEvent lastEvent = events.get(events.size() - 1);
            if (lastEvent.getEventId() <= replayUpToEventId) {
                return events;
            }
            List truncated = new ArrayList();
            for (HistoryEvent event : events) {
                if (event.getEventId() > replayUpToEventId) {
                    break;
                }
                truncated.add(event);
            }
            if (truncated.size() == 0) {
                return null;
            }
            return truncated;
        }

        protected abstract DecisionTask getNextHistoryTask(String nextPageToken);

    }

    private class ServiceDecisionTaskIterator extends DecisionTaskIterator {

        private final AmazonSimpleWorkflow service;

        private final String domain;

        private final WorkflowExecution workflowExecution;

        public ServiceDecisionTaskIterator(AmazonSimpleWorkflow service, String domain, WorkflowExecution workflowExecution) {
            this.service = service;
            this.domain = domain;
            this.workflowExecution = workflowExecution;
        }

        protected DecisionTask getNextHistoryTask(String nextPageToken) {
            WorkflowExecutionInfo executionInfo = WorkflowExecutionUtils.describeWorkflowInstance(service, domain,
                    workflowExecution);
            History history = WorkflowExecutionUtils.getHistoryPage(nextPageToken, service, domain, workflowExecution);
            DecisionTask task = new DecisionTask();
            List events = history.getEvents();
            events = truncateHistory(events);
            if (events == null) {
                return null;
            }
            task.setEvents(events);
            task.setWorkflowExecution(workflowExecution);
            task.setWorkflowType(executionInfo.getWorkflowType());
            task.setNextPageToken(history.getNextPageToken());
            return task;
        }

    }

    private class HistoryIterableDecisionTaskIterator extends DecisionTaskIterator {

        private final WorkflowExecution workflowExecution;

        private final Iterable history;

        public HistoryIterableDecisionTaskIterator(WorkflowExecution workflowExecution, Iterable history) {
            this.workflowExecution = workflowExecution;
            this.history = history;
        }

        @Override
        protected DecisionTask getNextHistoryTask(String nextPageToken) {
            DecisionTask result = new DecisionTask();
            Iterator iterator = history.iterator();
            if (!iterator.hasNext()) {
                throw new IllegalStateException("empty history");
            }
            HistoryEvent startEvent = iterator.next();
            WorkflowExecutionStartedEventAttributes startedAttributes = startEvent.getWorkflowExecutionStartedEventAttributes();
            if (startedAttributes == null) {
                throw new IllegalStateException("first event is not WorkflowExecutionStarted: " + startEvent);
            }
            List events = new ArrayList();
            events.add(startEvent);
            EventType eventType = null;
            int lastStartedIndex = 0;
            int index = 1;
            long previousStartedEventId = 0;
            long startedEventId = 0;
            while (iterator.hasNext()) {
                HistoryEvent event = iterator.next();
                eventType = EventType.fromValue(event.getEventType());
                events.add(event);
                if (eventType == EventType.DecisionTaskStarted) {
                    previousStartedEventId = startedEventId;
                    startedEventId = event.getEventId();
                    lastStartedIndex = index;
                }
                index++;
            }
            if (events.size() > lastStartedIndex + 1) {
                events = events.subList(0, lastStartedIndex + 1);
            }
            result.setEvents(events);
            result.setPreviousStartedEventId(previousStartedEventId);
            result.setStartedEventId(startedEventId);
            result.setWorkflowExecution(workflowExecution);
            WorkflowType workflowType = startedAttributes.getWorkflowType();
            result.setWorkflowType(workflowType);
            return result;
        }
    }

    private final Iterator taskIterator;

    private final AsyncDecisionTaskHandler taskHandler;

    private int replayUpToEventId;

    public WorkflowReplayer(AmazonSimpleWorkflow service, String domain, WorkflowExecution workflowExecution,
            Class workflowImplementationType) throws InstantiationException, IllegalAccessException {
        POJOWorkflowDefinitionFactoryFactory ff = new POJOWorkflowDefinitionFactoryFactory();
        ff.addWorkflowImplementationType(workflowImplementationType);
        taskIterator = new ServiceDecisionTaskIterator(service, domain, workflowExecution);
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(AmazonSimpleWorkflow service, String domain, WorkflowExecution workflowExecution,
            final T workflowImplementation) throws InstantiationException, IllegalAccessException {
        WorkflowDefinitionFactoryFactory ff = new WorkflowReplayerPOJOFactoryFactory(workflowImplementation);
        taskIterator = new ServiceDecisionTaskIterator(service, domain, workflowExecution);
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(AmazonSimpleWorkflow service, String domain, WorkflowExecution workflowExecution,
            WorkflowDefinitionFactoryFactory workflowDefinitionFactoryFactory)
            throws InstantiationException, IllegalAccessException {
        taskIterator = new ServiceDecisionTaskIterator(service, domain, workflowExecution);
        taskHandler = new AsyncDecisionTaskHandler(workflowDefinitionFactoryFactory);
    }

    public WorkflowReplayer(Iterable history, WorkflowExecution workflowExecution,
            Class workflowImplementationType) throws InstantiationException, IllegalAccessException {
        POJOWorkflowDefinitionFactoryFactory ff = new POJOWorkflowDefinitionFactoryFactory();
        ff.addWorkflowImplementationType(workflowImplementationType);
        taskIterator = new HistoryIterableDecisionTaskIterator(workflowExecution, history);
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(Iterable history, WorkflowExecution workflowExecution, final T workflowImplementation)
            throws InstantiationException, IllegalAccessException {
        WorkflowDefinitionFactoryFactory ff = new WorkflowReplayerPOJOFactoryFactory(workflowImplementation);
        taskIterator = new HistoryIterableDecisionTaskIterator(workflowExecution, history);
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(Iterable history, WorkflowExecution workflowExecution,
            WorkflowDefinitionFactoryFactory workflowDefinitionFactoryFactory)
            throws InstantiationException, IllegalAccessException {
        taskIterator = new HistoryIterableDecisionTaskIterator(workflowExecution, history);
        taskHandler = new AsyncDecisionTaskHandler(workflowDefinitionFactoryFactory);
    }

    public WorkflowReplayer(Iterator decisionTasks, Class workflowImplementationType)
            throws InstantiationException, IllegalAccessException {
        POJOWorkflowDefinitionFactoryFactory ff = new POJOWorkflowDefinitionFactoryFactory();
        ff.addWorkflowImplementationType(workflowImplementationType);
        taskIterator = decisionTasks;
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(Iterator decisionTasks, final T workflowImplementation)
            throws InstantiationException, IllegalAccessException {
        WorkflowDefinitionFactoryFactory ff = new WorkflowReplayerPOJOFactoryFactory(workflowImplementation);
        taskIterator = decisionTasks;
        taskHandler = new AsyncDecisionTaskHandler(ff);
    }

    public WorkflowReplayer(Iterator decisionTasks,
            WorkflowDefinitionFactoryFactory workflowDefinitionFactoryFactory)
            throws InstantiationException, IllegalAccessException {
        taskIterator = decisionTasks;
        taskHandler = new AsyncDecisionTaskHandler(workflowDefinitionFactoryFactory);
    }

    public int getReplayUpToEventId() {
        return replayUpToEventId;
    }

    /**
     * The replay stops at the event with the given eventId. Default is 0.
     * 
     * @param replayUpToEventId
     *            0 means the whole history.
     */
    public void setReplayUpToEventId(int replayUpToEventId) {
        this.replayUpToEventId = replayUpToEventId;
    }

    public RespondDecisionTaskCompletedRequest replay() throws Exception {
        return taskHandler.handleDecisionTask(taskIterator);
    }

    @SuppressWarnings("unchecked")
    public T loadWorkflow() throws Exception {
        WorkflowDefinition definition = taskHandler.loadWorkflowThroughReplay(taskIterator);
        POJOWorkflowDefinition pojoDefinition = (POJOWorkflowDefinition) definition;
        return (T) pojoDefinition.getImplementationInstance();
    }

    public List getAsynchronousThreadDump() throws Exception {
        return taskHandler.getAsynchronousThreadDump(taskIterator);
    }

    public String getAsynchronousThreadDumpAsString() throws Exception {
        return taskHandler.getAsynchronousThreadDumpAsString(taskIterator);
    }
}