/**
    * 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.krms.framework.engine.expression;
  
  import org.apache.commons.lang.ObjectUtils;
  import org.kuali.rice.krms.api.engine.IncompatibleTypeException;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  import java.math.BigDecimal;
  import java.math.BigInteger;
  
  /**
   * The default {@link ComparisonOperator}.  If no other {@link EngineComparatorExtension} have been configured to handle
   * a type, the DefaultComparisonOperator will be used.  At the moment the DefaultComparisonOperator is also the default
   * {@link StringCoercionExtension} for coercing types.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  
  public class DefaultComparisonOperator implements EngineComparatorExtension, StringCoercionExtension {
  
      @Override
      public int compare(Object lhs, Object rhs) {
  
          if (lhs == null && rhs == null) {
              return 0;
          } else if (lhs == null) {
              return -1;
          } else if (rhs == null) {
              return 1;
          }
  
          rhs = coerceRhs(lhs, rhs);
          if (ObjectUtils.equals(lhs, rhs)) {
              return 0;
          }
  
          if (lhs instanceof Comparable && rhs instanceof Comparable) {
              int result = ((Comparable)lhs).compareTo(rhs);
              return result;
          }
          else {
              throw new IncompatibleTypeException("DefaultComparisonOperator could not compare values", lhs, rhs.getClass());
          }
      }
  
      @Override
      public boolean canCompare(Object lhs, Object rhs) {
          try {
              compare(lhs, rhs);
              return true;
          } catch (Exception e) {
              return false;
          }
      }
  
      /**
       * 
       * @param lhs
       * @param rhs
       * @return Object
       * @throws IncompatibleTypeException
       */
      private Object coerceRhs(Object lhs, Object rhs) {
          if (lhs != null && rhs != null) {
              if  (!lhs.getClass().equals(rhs.getClass()) && rhs instanceof String) {
                  rhs = coerceRhsHelper(lhs, rhs.toString(), Double.class, Float.class, Long.class, Integer.class);
  
                  if (rhs instanceof String) { // was coercion successful?
                      if (lhs instanceof BigDecimal) {
                          try {
                              rhs = BigDecimal.valueOf(Double.valueOf(rhs.toString()));
                          } catch (NumberFormatException e) {
                              throw new IncompatibleTypeException("Could not coerce String to BigDecimal" + this, rhs, lhs.getClass());
                          }
                      } else if (lhs instanceof BigInteger) {
                          try {
                              rhs = BigInteger.valueOf(Long.valueOf(rhs.toString()));
                          } catch (NumberFormatException e) {
                              throw new IncompatibleTypeException("Could not coerce String to BigInteger" + this, rhs, lhs.getClass());
                          }
                      } else {
                          throw new IncompatibleTypeException("Could not compare values for operator " + this, lhs, rhs.getClass());
                      }
                  }
             }
         }
         return rhs;
     }
 
     /**
      *
      * @param lhs
      * @param rhs
      * @param clazzes
      * @return The object of one of the given types, whose value is rhs
      */
     private Object coerceRhsHelper(Object lhs, String rhs, Class<?> ... clazzes) {
         for (Class clazz : clazzes) {
             if (clazz.isInstance(lhs)) {
                 try {
                     return clazz.getMethod("valueOf", String.class).invoke(null, rhs);
                 } catch (NumberFormatException e) {
                     throw new IncompatibleTypeException("Could not coerce String to " +
                             clazz.getSimpleName() + " " + this, rhs, lhs.getClass());
                 } catch (NoSuchMethodException e) {
                     throw new IncompatibleTypeException("Could not coerce String to " +
                             clazz.getSimpleName() + " " + this, rhs, lhs.getClass());
                 } catch (InvocationTargetException e) {
                     throw new IncompatibleTypeException("Could not coerce String to " +
                             clazz.getSimpleName() + " " + this, rhs, lhs.getClass());
                 } catch (IllegalAccessException e) {
                     throw new IncompatibleTypeException("Could not coerce String to " +
                             clazz.getSimpleName() + " " + this, rhs, lhs.getClass());
                 }
             }
         }
         return rhs;
     }
 
     @Override
     public Object coerce(String type, String value) {
         try {
             Class clazz = Class.forName(type);
             // Constructor that takes string  a bit more generic than the coerceRhs
             Constructor constructor = clazz.getConstructor(new Class[]{String.class});
             Object propObject = constructor.newInstance(value);
             return propObject;
         } catch (Exception e) {
             return null; // TODO EGHM dev log?
         }
     }
 
     @Override
     public boolean canCoerce(String type, String value) {
         return coerce(type, value) != null;
     }
 }