/*
 * ObjectDiffer.java
 *
 * Created on May 24, 2006, 3:49 PM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package usda.weru.util.diff.differs;

import usda.weru.util.diff.*;

/**
 *
 * @author Joseph Levin
 */
public class ObjectDiffer implements Differ{
    
    public int diff(Object a, Object b) throws IncomparableObjectsException{        
        test(Object.class, a, b);
        if (a == null && b == null) return DIFF_SAME;
        else if (a == null) return DIFF_ADDED;
        else if (b == null) return DIFF_REMOVED;  
        else if (a.toString().equals(b.toString())) return DIFF_SAME;
        else return DIFF_CHANGED;
    }
       
    public String toString(){
        return getClass().getSimpleName();
    }
    
    protected void test(Class objectType, Object a, Object b) throws IncomparableObjectsException{
        boolean test;
        if (a == null && b == null)test = true;                    
        else if (a == null && objectType.isAssignableFrom(b.getClass())) test = true;
        else if (b == null && objectType.isAssignableFrom(a.getClass())) test = true;
        else if (objectType.isAssignableFrom(a.getClass()) && objectType.isAssignableFrom(b.getClass())) test = true;
        else test = false;
        
        if (!test){
            Class gcc = DiffEngine.greatestCommonClass(a, b);
            throw new IncomparableObjectsException("Unable to diff " + gcc.getSimpleName() + ".  Expected " + objectType.getSimpleName() + ".");
        }        
    }
    
}