/**
    * 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.kuali.rice.core.api.exception.RiceIllegalStateException;
  import org.kuali.rice.core.api.util.ClassLoaderUtils;
  import org.kuali.rice.kew.engine.RouteContext;
  
  /**
   * {@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 org.kuali.rice.kew.api.rule.Rule ruleDefinition;
  
      RuleImpl(org.kuali.rice.kew.api.rule.Rule ruleDefinition) {
          this.ruleDefinition = ruleDefinition;
      }
  
      public org.kuali.rice.kew.api.rule.Rule getDefinition() {
          return ruleDefinition;
      }
  
      // loads a RuleExpression implementation
      protected RuleExpression loadRuleExpression(String type) {
          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 RiceIllegalStateException("Rule expression implementation '" + className + "' not found", cnfe);
          }
          if (!RuleExpression.class.isAssignableFrom(ruleExpressionClass)) {
              throw new RiceIllegalStateException("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 RiceIllegalStateException("Error instantiating rule expression implementation '" + ruleExpressionClass + "'", e);
          }
  
          return ruleExpression;
      }
  
      public RuleExpressionResult evaluate(Rule rule, RouteContext context) {
          org.kuali.rice.kew.api.rule.RuleExpression ruleExprDef = ruleDefinition.getRuleExpressionDef();
          String type = DEFAULT_RULE_EXPRESSION;
          if (ruleExprDef != null) {
              type = ruleExprDef.getType();
          }
          RuleExpression ruleExpression = loadRuleExpression(type);        
          return ruleExpression.evaluate(rule, context);
      }
 }