/**

  * Copyright 2005-2011 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.validation;

 import org.apache.commons.lang.StringUtils;

 import org.kuali.rice.kew.api.WorkflowRuntimeException;

 import org.kuali.rice.kew.api.validation.RuleValidationContext;

 import org.kuali.rice.kew.api.validation.ValidationResults;

 import org.kuali.rice.kew.framework.KewFrameworkServiceLocator;

 import org.kuali.rice.kew.framework.validation.RuleValidationAttributeExporterService;

 import org.kuali.rice.kew.rule.RuleValidationAttribute;

 import java.lang.reflect.InvocationHandler;

 import java.lang.reflect.Method;

 import java.lang.reflect.Proxy;

 /**

  * RuleValidationAttributeResolver reference impl.  Returns a proxy which delegates to the appropriate

  * RuleValidationExporterService.

  *

  * @see org.kuali.rice.kew.rule.RuleValidationAttribute

  * @see org.kuali.rice.kew.framework.validation.RuleValidationAttributeExporterService

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

  */

 public class RuleValidationAttributeResolverImpl implements RuleValidationAttributeResolver {

     @Override

     public RuleValidationAttribute resolveRuleValidationAttribute(final String attributeName, String applicationId) throws Exception {

         final RuleValidationAttributeExporterService service = findRuleValidationAttributeExporterService(applicationId);

         return (RuleValidationAttribute) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class<?>[] { RuleValidationAttribute.class }, new RuleValidationAttributeInvocationHandler() {

             @Override

             protected ValidationResults invokeValidate(RuleValidationContext context) throws Exception {

                 return service.validate(attributeName, context);

             }

         });

     }

     protected RuleValidationAttributeExporterService findRuleValidationAttributeExporterService(String applicationId) {

         RuleValidationAttributeExporterService service = KewFrameworkServiceLocator.getRuleValidationAttributeExporterService(applicationId);

         if (service == null) {

             throw new WorkflowRuntimeException("Failed to locate RuleValidationAttributeExporterService for applicationId: " + applicationId);

         }

         return service;

     }

     protected static abstract class RuleValidationAttributeInvocationHandler implements InvocationHandler {

         @Override

         public ValidationResults invoke(Object o, Method method, Object[] objects) throws Throwable {

             if (!StringUtils.equals(method.getName(), "validate")) {

                 throw new UnsupportedOperationException("RuleValidationAttribute only supports 'validate'");

             }

             return invokeValidate((RuleValidationContext) objects[0]);

         }

         protected abstract ValidationResults invokeValidate(RuleValidationContext context) throws Exception;

     }

 }