/*

  * Copyright 2011 The Kuali Foundation Licensed under the Educational Community

  * License, Version 1.0 (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/ecl1.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.uif.service.impl;

 import java.beans.PropertyDescriptor;

 import java.util.List;

 import java.util.Map;

 import java.util.Map.Entry;

 import org.apache.commons.lang.StringUtils;

 import org.kuali.rice.kns.uif.UifConstants;

 import org.kuali.rice.kns.uif.core.Component;

 import org.kuali.rice.kns.uif.core.PropertyReplacer;

 import org.kuali.rice.kns.uif.layout.LayoutManager;

 import org.kuali.rice.kns.uif.service.ExpressionEvaluatorService;

 import org.kuali.rice.kns.uif.util.ExpressionFunctions;

 import org.kuali.rice.kns.uif.util.ObjectPropertyUtils;

 import org.springframework.expression.EvaluationException;

 import org.springframework.expression.Expression;

 import org.springframework.expression.ExpressionParser;

 import org.springframework.expression.common.TemplateParserContext;

 import org.springframework.expression.spel.standard.SpelExpressionParser;

 import org.springframework.expression.spel.support.StandardEvaluationContext;

 /**

  * Evaluates expression language statements using the Spring EL engine TODO:

  * Look into using Rice KRMS for evaluation

  * 

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

  */

 public class ExpressionEvaluatorServiceImpl implements ExpressionEvaluatorService {

     private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger

             .getLogger(ExpressionEvaluatorServiceImpl.class);

     /**

      * @see org.kuali.rice.kns.uif.service.ExpressionEvaluatorService#evaluateObjectProperties(java.lang.Object,

      *      java.lang.Object, java.util.Map)

      */

     public void evaluateObjectProperties(Object object, Object contextObject, Map<String, Object> evaluationParameters) {

         if (object instanceof Component) {

             evaluatePropertyReplacers(object, contextObject, evaluationParameters);

         }

         visitPropertiesAndEvaluateExpressions(object, contextObject, evaluationParameters);

     }

     /**

      * @see org.kuali.rice.kns.uif.service.ExpressionEvaluatorService#evaluateExpressionTemplate(java.lang.Object,

      *      java.util.Map, java.lang.String)

      */

     public String evaluateExpressionTemplate(Object contextObject, Map<String, Object> evaluationParameters,

             String expressionTemplate) {

         StandardEvaluationContext context = new StandardEvaluationContext(contextObject);

         context.setVariables(evaluationParameters);

         addCustomFunctions(context);

         ExpressionParser parser = new SpelExpressionParser();

         String result = null;

         try {

             Expression expression = null;

             if (StringUtils.contains(expressionTemplate, UifConstants.EL_PLACEHOLDER_PREFIX)) {

                 expression = parser.parseExpression(expressionTemplate, new TemplateParserContext(

                         UifConstants.EL_PLACEHOLDER_PREFIX, UifConstants.EL_PLACEHOLDER_SUFFIX));

             } else {

                 expression = parser.parseExpression(expressionTemplate);

             }

             result = expression.getValue(context, String.class);

         } catch (Exception e) {

             LOG.error("Exception evaluating expression: " + expressionTemplate);

             throw new RuntimeException("Exception evaluating expression: " + expressionTemplate, e);

         }

         return result;

     }

     /**

      * @see org.kuali.rice.kns.uif.service.ExpressionEvaluatorService#evaluateExpression(java.lang.Object,

      *      java.util.Map, java.lang.String)

      */

     public Object evaluateExpression(Object contextObject, Map<String, Object> evaluationParameters,

             String expressionStr) {

         StandardEvaluationContext context = new StandardEvaluationContext(contextObject);

         context.setVariables(evaluationParameters);

         addCustomFunctions(context);

         ExpressionParser parser = new SpelExpressionParser();

         Expression expression = parser.parseExpression(expressionStr);

         Object result = null;

         try {

             result = expression.getValue(context);

         }

         catch (EvaluationException e) {

             LOG.error("Exception evaluating expression: " + expressionStr);

             throw new RuntimeException("Exception evaluating expression: " + expressionStr, e);

         }

         return result;

     }

     /**

      * Registers custom functions for el expressions with the given context

      *

      * @param context - context instance to register functions to

      */

     protected void addCustomFunctions(StandardEvaluationContext context) {

         try {

             context.registerFunction("isAssignableFrom", ExpressionFunctions.class

                     .getDeclaredMethod("isAssignableFrom", new Class[]{Class.class, Class.class}));

         } catch (NoSuchMethodException e) {

             LOG.error("Custom function for el expressions not found: " + e.getMessage());

             throw new RuntimeException("Custom function for el expressions not found: " + e.getMessage(), e);

         }

     }

     /**

      * Iterates through any configured <code>PropertyReplacer</code> instances for the component and

      * evaluates the given condition. If the condition is met, the replacement value is set on the

      * corresponding property

      *

      * @param object - object instance with property replacers list, should be either a component or layout manager

      * @param contextObject - context for el evaluation

      * @param evaluationParameters - parameters for el evaluation

      */

     protected void evaluatePropertyReplacers(Object object, Object contextObject,

                                              Map<String, Object> evaluationParameters) {

         List<PropertyReplacer> replacers = null;

         if (Component.class.isAssignableFrom(object.getClass())) {

             replacers = ((Component) object).getPropertyReplacers();

         } else if (LayoutManager.class.isAssignableFrom(object.getClass())) {

             replacers = ((LayoutManager) object).getPropertyReplacers();

         }

         for (PropertyReplacer propertyReplacer : replacers) {

             String conditionEvaluation =

                     evaluateExpressionTemplate(contextObject, evaluationParameters, propertyReplacer.getCondition());

             boolean conditionSuccess = Boolean.parseBoolean(conditionEvaluation);

             if (conditionSuccess) {

                 ObjectPropertyUtils.setPropertyValue(object, propertyReplacer.getPropertyName(),

                         propertyReplacer.getReplacement());

             }

         }

     }

     /**

      * Iterates through the properties of the given object and checks for property values that contain

      * an el expression. If an expression is found it will be evaluated and the result of that evaluation

      * set back into the property value

      *

      * <p>

      *  If the property contains an el template (part static text and part expression), only the expression

      *  part will be replaced with the result. More than one expressions may be contained within the template

      * </p>

      *

      * <p>

      *  A special check is done for Map property types. When found the Map is iterated over and expressions

      *  contained in the map value are evaluated

      * </p>

      *

      * @param object - object to evaluate properties for

      * @param contextObject - context for el evaluation

      * @param evaluationParameters - parameters for el evaluation

      */

     protected void visitPropertiesAndEvaluateExpressions(Object object, Object contextObject,

             Map<String, Object> evaluationParameters) {

         // iterate through object properties and check for expressions

         PropertyDescriptor[] propertyDescriptors = ObjectPropertyUtils.getPropertyDescriptors(object);

         for (int i = 0; i < propertyDescriptors.length; i++) {

             PropertyDescriptor descriptor = propertyDescriptors[i];

             if (descriptor.getWriteMethod() == null) {

                 continue;

             }

             String propertyName = descriptor.getName();

             if (String.class.isAssignableFrom(descriptor.getPropertyType())) {

                 String propertyValue = ObjectPropertyUtils.getPropertyValue(object, propertyName);

                 if (StringUtils.isNotBlank(propertyValue)

                         && (containsElPlaceholder(propertyValue) || StringUtils.startsWith(propertyName,

                                 UifConstants.EL_CONDITIONAL_PROPERTY_PREFIX))) {

                     // evaluate any expressions and reset property value

                     propertyValue = evaluateExpressionTemplate(contextObject, evaluationParameters, propertyValue);

                     String propertyNameToSet = propertyName;

                     if (StringUtils.startsWith(propertyName, UifConstants.EL_CONDITIONAL_PROPERTY_PREFIX)) {

                         // get the target property by convention

                         propertyNameToSet = StringUtils.removeStart(propertyName,

                                 UifConstants.EL_CONDITIONAL_PROPERTY_PREFIX);

                         propertyNameToSet = StringUtils.substring(propertyNameToSet, 0, 1).toLowerCase()

                                 + StringUtils.substring(propertyNameToSet, 1, propertyNameToSet.length());

                     }

                     ObjectPropertyUtils.setPropertyValue(object, propertyNameToSet, propertyValue);

                 }

             }

             else if (Map.class.isAssignableFrom(descriptor.getPropertyType())) {

                 Map<Object, Object> propertyValue = ObjectPropertyUtils.getPropertyValue(object, propertyName);

                 if (propertyValue != null) {

                     for (Entry<Object, Object> entry : propertyValue.entrySet()) {

                         if ((entry.getValue() != null) && String.class.isAssignableFrom(entry.getValue().getClass())

                                 && containsElPlaceholder((String) entry.getValue())) {

                             String entryValue = evaluateExpressionTemplate(contextObject, evaluationParameters,

                                     (String) entry.getValue());

                             propertyValue.put(entry.getKey(), entryValue);

                         }

                     }

                 }

             }

         }

     }

     /**

      * @see org.kuali.rice.kns.uif.service.ExpressionEvaluatorService#containsElPlaceholder(java.lang.String)

      */

     public boolean containsElPlaceholder(String value) {

         boolean containsElPlaceholder = false;

         String elPlaceholder = StringUtils.substringBetween(value, UifConstants.EL_PLACEHOLDER_PREFIX,

                 UifConstants.EL_PLACEHOLDER_SUFFIX);

         if (elPlaceholder != null) {

             containsElPlaceholder = true;

         }

         return containsElPlaceholder;

     }

 }