/**
    * Copyright 2005-2012 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.kew.rule;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.log4j.Logger;
  import org.kuali.rice.core.api.exception.RiceIllegalStateException;
  import org.kuali.rice.kew.api.rule.RuleExpressionContract;
  import org.kuali.rice.kew.engine.RouteContext;
  import org.kuali.rice.kew.api.exception.WorkflowException;
  
  import java.text.ParseException;
  import java.util.ArrayList;
  import java.util.List;
  
  
  /**
   * Expression implementation for "meta rules".  A "meta rule" consists of a sequence of
   * subordinate rule evaluations each processed according to an associated modifier:
   * <dl>
   *   <dt>next<dt>
   *   <dd>proceed with rule evaluation</dd>
   *   <dt>true</dt>
   *   <dd>if this rule evaluates to true, then return the responsibilities associated with the rule</dd>
   *   <dt>false</dt>
   *   <dd>if this rule evaluates to false, then return the responsibilities associated with the rule</dd>
   * </dl>
   * E.g.
   * <div><tt>bizRule1: next; bizRule2: true; bizRule3: false</tt></div>
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class MetaRuleExpression extends AccumulatingBSFRuleExpression {
      private static final Logger LOG = Logger.getLogger(MetaRuleExpression.class);
  
      @Override
      public RuleExpressionResult evaluate(Rule rule, RouteContext context) {
          org.kuali.rice.kew.api.rule.RuleContract ruleDefinition = rule.getDefinition();
          RuleExpressionContract exprDef = ruleDefinition.getRuleExpressionDef();
          if (exprDef == null) {
              throw new RiceIllegalStateException("No expression defined in rule definition: " + ruleDefinition);
          }
          String expression = exprDef.getExpression();
          if (StringUtils.isEmpty(expression)) {
              throw new RiceIllegalStateException("Empty expression in rule definition: " + ruleDefinition);
          }
  
          String lang = parseLang(ruleDefinition.getRuleExpressionDef().getType(), null);
          if (lang == null) {
              // if no language qualifier is specified, parse it as a built-in meta rule expression
              return evaluateBuiltinExpression(expression, rule, context);
          } else {
              return super.evaluate(rule, context);
          }
      }
  
      /**
       * Evaluates the builtin "meta" rule expression
       * @param expression the builtin meta rule expression
       * @param rule the rule
       * @param context the route context
       * @return RuleExpressionResult the result
       * @throws WorkflowException
       */
      private RuleExpressionResult evaluateBuiltinExpression(String expression, Rule rule, RouteContext context) {
          try {
              KRAMetaRuleEngine engine = new KRAMetaRuleEngine(expression);
  
              int responsibilityPriority = 0; // responsibility priority, lower value means higher priority (due to sort)...increment as we go
              RuleExpressionResult result = null;
              boolean success = false;
              List<org.kuali.rice.kew.api.rule.RuleResponsibility> responsibilities = new ArrayList<org.kuali.rice.kew.api.rule.RuleResponsibility>();
              while (!engine.isDone()) {
                  result = engine.processSingleStatement(context);
                  if (result.isSuccess() && result.getResponsibilities() != null) {
                      // accumulate responsibilities if the evaluation was successful
                      // make sure to reduce priority for each subsequent rule in order for sequential activation to work as desired
                      for (org.kuali.rice.kew.api.rule.RuleResponsibility responsibility: result.getResponsibilities()) {
                          org.kuali.rice.kew.api.rule.RuleResponsibility.Builder builder =
                                  org.kuali.rice.kew.api.rule.RuleResponsibility.Builder.create(responsibility);
                          builder.setPriority(Integer.valueOf(responsibilityPriority));
                          responsibilities.add(builder.build());
                      }
                      // decrement responsibilityPriority for next rule expression result responsibilities
                      responsibilityPriority++;
                      success = true;
                  }
             }
             result = new RuleExpressionResult(rule, success, responsibilities);
             LOG.debug("MetaRuleExpression returning result: " + result);
             return result;
         } catch (ParseException pe) {
             throw new RiceIllegalStateException("Error parsing expression", pe);
         }
     }
 }