/* 
    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.wiki.workflow;

import java.io.Serializable;
import java.security.Principal;
import java.util.*;

import org.apache.wiki.api.exceptions.WikiException;

/**
 * Abstact superclass that provides a complete implementation of most
 * Step methods; subclasses need only implement {@link #execute()} and
 * {@link #getActor()}.
 *
 * @since 2.5
 */
public abstract class AbstractStep implements Step
{

    private static final long serialVersionUID = 8635678679349653768L;

    /** Timestamp of when the step started. */
    private Date m_start;

    /** Timestamp of when the step ended. */
    private Date m_end;

    private final String m_key;

    private boolean m_completed;

    private final Map<Outcome, Step> m_successors;

    private Workflow m_workflow;

    private Outcome m_outcome;

    private final List<String> m_errors;

    private boolean m_started;

    /**
     * Protected constructor that creates a new Step with a specified message key.
     * After construction, the protected method {@link #setWorkflow(Workflow)} should be
     * called.
     *
     * @param messageKey
     *            the Step's message key, such as
     *            <code>decision.editPageApproval</code>. By convention, the
     *            message prefix should be a lower-case version of the Step's
     *            type, plus a period (<em>e.g.</em>, <code>task.</code>
     *            and <code>decision.</code>).
     */
    protected AbstractStep( String messageKey )
    {
        m_started = false;
        m_start = Workflow.TIME_NOT_SET;
        m_completed = false;
        m_end = Workflow.TIME_NOT_SET;
        m_errors = new ArrayList<String>();
        m_outcome = Outcome.STEP_CONTINUE;
        m_key = messageKey;
        m_successors = new LinkedHashMap<Outcome, Step>();
    }

    /**
     * Constructs a new Step belonging to a specified Workflow and having a
     * specified message key.
     *
     * @param workflow
     *            the workflow the Step belongs to
     * @param messageKey
     *            the Step's message key, such as
     *            <code>decision.editPageApproval</code>. By convention, the
     *            message prefix should be a lower-case version of the Step's
     *            type, plus a period (<em>e.g.</em>, <code>task.</code>
     *            and <code>decision.</code>).
     */
    public AbstractStep( Workflow workflow, String messageKey )
    {
        this( messageKey );
        setWorkflow( workflow );
    }

    /**
     * {@inheritDoc}
     */
    public final void addSuccessor(Outcome outcome, Step step)
    {
        m_successors.put( outcome, step );
    }

    /**
     * {@inheritDoc}
     */
    public final Collection getAvailableOutcomes()
    {
        Set<Outcome> outcomes = m_successors.keySet();
        return Collections.unmodifiableCollection( outcomes );
    }

    /**
     * {@inheritDoc}
     */
    public final List getErrors()
    {
        return Collections.unmodifiableList( m_errors );
    }

    /**
     * {@inheritDoc}
     */
    public abstract Outcome execute() throws WikiException;

    /**
     * {@inheritDoc}
     */
    public abstract Principal getActor();

    /**
     * {@inheritDoc}
     */
    public final Date getEndTime()
    {
        return m_end;
    }

    /**
     * {@inheritDoc}
     */
    public final Serializable[] getMessageArguments()
    {
        if ( m_workflow == null )
        {
            return new Serializable[0];
        }
        return m_workflow.getMessageArguments();
    }

    /**
     * {@inheritDoc}
     */
    public final String getMessageKey()
    {
        return m_key;
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized Outcome getOutcome()
    {
        return m_outcome;
    }

    /**
     * {@inheritDoc}
     */
    public Principal getOwner()
    {
        if ( m_workflow == null )
        {
            return null;
        }
        return m_workflow.getOwner();
    }

    /**
     * {@inheritDoc}
     */
    public final Date getStartTime()
    {
        return m_start;
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized Workflow getWorkflow()
    {
        return m_workflow;
    }

    /**
     * {@inheritDoc}
     */
    public final boolean isCompleted()
    {
        return m_completed;
    }

    /**
     * {@inheritDoc}
     */
    public final boolean isStarted()
    {
        return m_started;
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized void setOutcome(Outcome outcome)
    {
        // Is this an allowed Outcome?
        if ( !m_successors.containsKey( outcome ) )
        {
            if ( !Outcome.STEP_CONTINUE.equals( outcome ) &&
                 !Outcome.STEP_ABORT.equals( outcome ) )
            {
                 throw new IllegalArgumentException( "Outcome " + outcome.getMessageKey() + " is not supported for this Step." );
            }
        }

        // Is this a "completion" outcome?
        if ( outcome.isCompletion() )
        {
            if ( m_completed )
            {
                throw new IllegalStateException( "Step has already been marked complete; cannot set again." );
            }
            m_completed = true;
            m_end = new Date( System.currentTimeMillis() );
        }
        m_outcome = outcome;
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized void start() throws WikiException
    {
        if ( m_started )
        {
            throw new IllegalStateException( "Step already started." );
        }
        m_started = true;
        m_start = new Date( System.currentTimeMillis() );
    }

    /**
     * {@inheritDoc}
     */
    public final Step getSuccessor( Outcome outcome )
    {
        return m_successors.get( outcome );
    }

    // --------------------------Helper methods--------------------------

    /**
     * Protected method that sets the parent Workflow post-construction.
     * @param workflow the parent workflow to set
     */
    protected final synchronized void setWorkflow( Workflow workflow )
    {
        m_workflow = workflow;
    }

    /**
     * Protected helper method that adds a String representing an error message
     * to the Step's cached errors list.
     *
     * @param message
     *            the error message
     */
    protected final synchronized void addError( String message )
    {
        m_errors.add( message );
    }

}