/*

  * Copyright 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.kew.rule;

 import org.apache.commons.lang.StringUtils;

 import org.kuali.rice.core.api.util.ClassLoaderUtils;

 import org.kuali.rice.kew.engine.RouteContext;

 import org.kuali.rice.kew.exception.WorkflowException;

 /**

  * {@link Rule} implementation 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 class RuleImpl implements Rule {

     /**

      * The default type of rule expression implementation to use if none is explicitly

      * specified for the node.

      */

     public static final String DEFAULT_RULE_EXPRESSION = "WorkflowAttribute";

     /**

      * Package in which rule expression implementations live

      */

     private static final String RULE_EXPRESSION_PACKAGE = "org.kuali.rice.kew.rule";

     /**

      * The class name suffix all rule expressions should have; e.g. FooRuleExpression

      */

     private static final String RULE_EXPRESSION_SUFFIX= "RuleExpression";

     /**

      * The BO of the rule definition in the system

      */

     private final RuleBaseValues ruleDefinition;

     RuleImpl(RuleBaseValues ruleDefinition) {

         this.ruleDefinition = ruleDefinition;

     }

     public RuleBaseValues getDefinition() {

         return ruleDefinition;

     }

     // loads a RuleExpression implementation

     protected RuleExpression loadRuleExpression(String type) throws WorkflowException {

         if (type == null) {

             type = DEFAULT_RULE_EXPRESSION;

         }

         // type is of the format 'category:qualifier'

         // we just want the category

         int colon = type.indexOf(':');

         if (colon == -1) colon = type.length();

         type = type.substring(0, colon);

         type = StringUtils.capitalize(type);

         // load up the rule expression implementation

         String className = RULE_EXPRESSION_PACKAGE + "." + type + RULE_EXPRESSION_SUFFIX;

         Class<?> ruleExpressionClass;

         try {

             ruleExpressionClass = ClassLoaderUtils.getDefaultClassLoader().loadClass(className);

         } catch (ClassNotFoundException cnfe) {

             throw new WorkflowException("Rule expression implementation '" + className + "' not found", cnfe);

         }

         if (!RuleExpression.class.isAssignableFrom(ruleExpressionClass)) {

             throw new WorkflowException("Specified class '" + ruleExpressionClass + "' does not implement RuleExpression interface");

         }

         RuleExpression ruleExpression;

         try {

             ruleExpression = ((Class<RuleExpression>) ruleExpressionClass).newInstance();

         } catch (Exception e) {

                 if (e instanceof RuntimeException) {

                         throw (RuntimeException)e;

                 }

             throw new WorkflowException("Error instantiating rule expression implementation '" + ruleExpressionClass + "'", e);

         }

         return ruleExpression;

     }

     public RuleExpressionResult evaluate(Rule rule, RouteContext context) throws WorkflowException {

         RuleBaseValues ruleDefinition = rule.getDefinition();

         RuleExpressionDef ruleExprDef = ruleDefinition.getRuleExpressionDef();

         String type = DEFAULT_RULE_EXPRESSION;

         if (ruleExprDef != null) {

             type = ruleExprDef.getType();

         }

         RuleExpression ruleExpression = loadRuleExpression(type);        

         return ruleExpression.evaluate(rule, context);

     }

 }