/* 
    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 org.apache.wiki.api.core.Engine;
import org.apache.wiki.api.exceptions.WikiException;

import java.security.Principal;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Factory class that creates common Workflow instances such as a standard approval workflow.
 */
public final class WorkflowBuilder {

    private static final Map< Engine, WorkflowBuilder > BUILDERS = new ConcurrentHashMap<>();
    private final Engine m_engine;

    /**
     * Private constructor that creates a new WorkflowBuilder for the supplied Engine.
     * @param engine the wiki engine
     */
    private WorkflowBuilder( final Engine engine )
    {
        m_engine = engine;
    }

    /**
     * Returns the WorkflowBuilder instance for a Engine. Only one WorkflowBuilder
     * exists for a given engine.
     * @param engine the wiki engine
     * @return the workflow builder
     */
    public static WorkflowBuilder getBuilder( final Engine engine ) {
        WorkflowBuilder builder = BUILDERS.get( engine );
        if ( builder == null ) {
            builder = new WorkflowBuilder( engine );
            BUILDERS.put( engine, builder );
        }
        return builder;
    }

    /**
     * <p>Builds an approval workflow that requests approval from a named
     * user, {@link org.apache.wiki.auth.authorize.Group} or
     * {@link org.apache.wiki.auth.authorize.Role} before running a Task.</p>
     * <p>The Principal who approves the activity is determined by looking up
     * the property <code>jspwiki.approver.<var>workflowApproverKey</var></code>
     * in <code>jspwiki.properties</code>. If that Principal resolves to a known user, Group
     * Role, a Decision will be placed in the respective workflow queue (or multiple queues,
     * if necessary). Only one approver needs to make the Decision, and if the request is
     * approved, the completion task will be executed. If the request is denied, a
     * {@link SimpleNotification} with a message corresponding to the <code>rejectedMessage</code>
     * message key will be placed in the submitter's workflow queue.</p>
     * <p>To help approvers determine how to make the Decision, callers can supply an
     * array of Fact objects to this method, which will be added to the Decision in the order
     * they appear in the array. These items will be displayed in the web UI.
     * In addition, the value of the first Fact will also be added as the third message
     * argument for the workflow (the first two are always the submitter and the approver).
     * For example, the PageManager code that creates the "save page approval" workflow
     * adds the name of the page as its first Fact; this results in the page name being
     * substituted correctly into the resulting message:
     * "Save wiki page &lt;strong&gt;{2}&lt;/strong&gt;".</p>
     * @param submitter the user submitting the request
     * @param workflowApproverKey the key that names the user, Group or Role who must approve
     * the request. The key is looked up in <code>jspwiki.properties</code>, and is derived
     * by prepending <code>jspwiki.approver</code> to the value of <code>workflowApproverKey</code>
     * @param prepTask the initial task that should run before the Decision step is processed.
     * If this parameter is <code>null</code>, the Decision will run as the first Step instead
     * @param decisionKey the message key in <code>default.properties</code> that contains
     * the text that will appear in approvers' workflow queues indicating they need to make
     * a Decision; for example, <code>decision.saveWikiPage</code>. In the i18n message bundle
     * file, this key might return text that reads "Approve page &lt;strong&gt;{2}&lt;/strong&gt;"
     * @param facts an array of {@link Fact} objects that will be shown to the approver
     * to aid decision-making. The facts will be displayed in the order supplied in the array
     * @param completionTask the Task that will run if the Decision is approved
     * @param rejectedMessageKey the message key in <code>default.properties</code> that contains
     * the text that will appear in the submitter's workflow queue if request was
     * not approved; for example, <code>notification.saveWikiPage.reject</code>. In the
     * i18n message bundle file, this key might might return
     * text that reads "Your request to save page &lt;strong&gt;{2}&lt;/strong&gt; was rejected."
     * If this parameter is <code>null</code>, no message will be sent
     * @return the created workflow
     * @throws WikiException if the name of the approving user, Role or Group cannot be determined
     */
    public Workflow buildApprovalWorkflow( final Principal submitter,
                                           final String workflowApproverKey,
                                           final Step prepTask,
                                           final String decisionKey,
                                           final Fact[] facts,
                                           final Step completionTask,
                                           final String rejectedMessageKey ) throws WikiException {
        final WorkflowManager mgr = m_engine.getManager( WorkflowManager.class );
        final Workflow workflow = new Workflow( workflowApproverKey, submitter );

        // Is a Decision required to run the approve task?
        final boolean decisionRequired = mgr.requiresApproval( workflowApproverKey );

        // If Decision required, create a simple approval workflow
        if ( decisionRequired ) {
            // Look up the name of the approver (user or group) listed in jspwiki.properties; approvals go to the approver's decision queue
            final Principal approverPrincipal = mgr.getApprover( workflowApproverKey );
            final Decision decision = new SimpleDecision( workflow.getId(), workflow.getAttributes(), decisionKey, approverPrincipal );

            // Add facts to the Decision, if any were supplied
            if( facts != null ) {
                for( final Fact fact : facts ) {
                    decision.addFact( fact );
                }
                // Add the first one as a message key
                if( facts.length > 0 ) {
                    workflow.addMessageArgument( facts[ 0 ].getValue() );
                }
            }

            // If rejected, sent a notification
            if ( rejectedMessageKey != null ) {
                final SimpleNotification rejectNotification = new SimpleNotification( workflow.getId(), workflow.getAttributes(), rejectedMessageKey, submitter );
                decision.addSuccessor( Outcome.DECISION_DENY, rejectNotification );
            }

            // If approved, run the 'approved' task
            decision.addSuccessor( Outcome.DECISION_APPROVE, completionTask );

            // Set the first step
            if( prepTask == null ) {
                workflow.setFirstStep( decision );
            } else {
                workflow.setFirstStep( prepTask );
                prepTask.addSuccessor( Outcome.STEP_COMPLETE, decision );
            }
        } else { // If Decision not required, just run the prep + approved tasks in succession
            // Set the first step
            if ( prepTask == null ) {
                workflow.setFirstStep( completionTask );
            } else {
                workflow.setFirstStep( prepTask );
                prepTask.addSuccessor( Outcome.STEP_COMPLETE, completionTask );
            }
        }

        // Make sure our tasks have this workflow as the parent, then return
        if( prepTask != null ) {
            prepTask.setWorkflow( workflow.getId(), workflow.getAttributes() );
        }
        completionTask.setWorkflow( workflow.getId(), workflow.getAttributes() );
        return workflow;
    }

}