/*
    * Copyright 2006-2007 The Kuali Foundation
    * 
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    * 
   * 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.kuali.rice.kns.rules;
  
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  import javax.servlet.http.HttpServletRequest;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.struts.action.ActionForm;
  import org.kuali.rice.core.util.RiceConstants;
  import org.kuali.rice.kns.document.Document;
  import org.kuali.rice.kns.question.ConfirmationQuestion;
  import org.kuali.rice.kns.rule.PromptBeforeValidation;
  import org.kuali.rice.kns.rule.event.PromptBeforeValidationEvent;
  import org.kuali.rice.kns.util.KNSConstants;
  import org.kuali.rice.kns.web.struts.form.KualiForm;
  
  /**
   * 
   * This class simplifies requesting clarifying user input prior to applying business rules. It mostly shields the classes that
   * extend it from being aware of the web layer, even though the input is collected via a series of one or more request/response
   * cycles.
   * 
   * Beware: method calls with side-effects will have unusual results. While it looks like the doRules method is executed
   * sequentially, in fact, it is more of a geometric series: if n questions are asked, then the code up to and including the first
   * question is executed n times, the second n-1 times, ..., the last question only one time.
   * 
   * 
   */
  public abstract class PromptBeforeValidationBase implements PromptBeforeValidation {
  
      protected static org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(PromptBeforeValidationBase.class);
  
      protected String question;
      protected String buttonClicked;
      protected PromptBeforeValidationEvent event;
      protected KualiForm form;
  
      private class IsAskingException extends RuntimeException {
      }
  
      /**
       * 
       * This class acts similarly to HTTP session, but working inside a REQUEST parameter
       * 
       * 
       */
      /**
       * This is a description of what this class does - wliang don't forget to fill this in. 
       * 
       * @author Kuali Rice Team (rice.collab@kuali.org)
       *
       */
      public class ContextSession {
          private final static String DELIMITER = ".";
          PromptBeforeValidationEvent event;
  
          public ContextSession(String context, PromptBeforeValidationEvent event) {
              this.event = event;
  
              this.event.setQuestionContext(context);
              if (this.event.getQuestionContext() == null) {
                  this.event.setQuestionContext("");
              }
  
          }
  
          /**
           * Whether a question with a given ID has already been asked
           * 
           * @param id the ID of the question, an arbitrary value, but must be consistent
           * @return
           */
          public boolean hasAsked(String id) {
              return StringUtils.contains(event.getQuestionContext(), id);
          }
  
          /**
           * Invoked to indicate that the user should be prompted a question
           * 
           * @param id the ID of the question, an arbitrary value, but must be consistent
           * @param text the question text, to be displayed to the user
           */
         public void askQuestion(String id, String text) {
             event.setQuestionId(id);
             event.setQuestionType(KNSConstants.CONFIRMATION_QUESTION);
             event.setQuestionText(text);
             event.setPerformQuestion(true);
         }
 
         public void setAttribute(String name, String value) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("setAttribute(" + name + "," + value + ")");
             }
             event.setQuestionContext(event.getQuestionContext() + DELIMITER + name + DELIMITER + value);
 
         }
 
         public String getAttribute(String name) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("getAttribute(" + name + ")");
             }
             String result = null;
 
             Iterator values = Arrays.asList(event.getQuestionContext().split("\\" + DELIMITER)).iterator();
 
             while (values.hasNext()) {
                 if (values.next().equals(name)) {
                     try {
                         result = (String) values.next();
                     }
                     catch (NoSuchElementException e) {
                         result = null;
                     }
                 }
             }
             if (LOG.isDebugEnabled()) {
                 LOG.debug("returning " + result);
             }
             return result;
         }
 
     }
 
     /**
      * Implementations will override this method to do perform the actual prompting and/or logic
      * 
      * They are able to utilize the following methods:
      * <li> {@link PromptBeforeValidationBase#abortRulesCheck()}
      * <li> {@link PromptBeforeValidationBase#askOrAnalyzeYesNoQuestion(String, String)}
      * <li> {@link #hasAsked(String)}
      * 
      * @param document
      * @return
      */
     public abstract boolean doPrompts(Document document);
 
     private boolean isAborting;
 
     ContextSession session;
 
     public PromptBeforeValidationBase() {
     }
 
 
     public boolean processPrompts(ActionForm form, HttpServletRequest request, PromptBeforeValidationEvent event) {
         question = request.getParameter(KNSConstants.QUESTION_INST_ATTRIBUTE_NAME);
         buttonClicked = request.getParameter(KNSConstants.QUESTION_CLICKED_BUTTON);
         this.event = event;
         this.form = (KualiForm) form;
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("Question is: " + question);
             LOG.debug("ButtonClicked: " + buttonClicked);
             LOG.debug("QuestionContext() is: " + event.getQuestionContext());
         }
 
         session = new ContextSession(request.getParameter(KNSConstants.QUESTION_CONTEXT), event);
 
         boolean result = false;
 
         try {
             result = doPrompts(event.getDocument());
         }
         catch (IsAskingException e) {
             return false;
         }
 
         if (isAborting) {
             return false;
         }
 
         return result;
     }
 
     /**
      * This bounces the user back to the document as if they had never tried to routed it. (Business rules are not invoked
      * and the action is not executed.)
      * 
      */
     public void abortRulesCheck() {
         event.setActionForwardName(RiceConstants.MAPPING_BASIC);
         isAborting = true;
     }
 
     /**
      * This method poses a Y/N question to the user.  If the user has already answered the question, then it returns whether
      * the answer to the question was yes or no
      * 
      * Code that invokes this method will behave a bit strangely, so you should try to keep it as simple as possible.
      * 
      * @param id an ID for the question
      * @param text the text of the question, to be displayed on the screen
      * @return true if the user answered Yes, false if the user answers no
      * @throws IsAskingException if the user needs to be prompted the question
      */
     public boolean askOrAnalyzeYesNoQuestion(String id, String text) throws IsAskingException {
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("Entering askOrAnalyzeYesNoQuestion(" + id + "," + text + ")");
         }
 
         String cached = (String) session.getAttribute(id);
         if (cached != null) {
             LOG.debug("returning cached value: " + id + "=" + cached);
             return new Boolean(cached).booleanValue();
         }
 
         if (id.equals(question)) {
             session.setAttribute(id, Boolean.toString(!ConfirmationQuestion.NO.equals(buttonClicked)));
             return !ConfirmationQuestion.NO.equals(buttonClicked);
         }
         else if (!session.hasAsked(id)) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Forcing question to be asked: " + id);
             }
             session.askQuestion(id, text);
         }
 
         LOG.debug("Throwing Exception to force return to Action");
         throw new IsAskingException();
     }
 
 }