package com.orientechnologies.orient.core.command;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class OCloneHelper {
	public static void main(String[] args) {
	}
	
	/*
	 * Tries to clone any Java object by using 3 techniques:
	 * 	- instanceof (most verbose but faster performance)
	 * 	- reflection (medium performance)
	 * 	- serialization (applies for any object type but has a performance overhead)
	 */
	public static Object cloneObject (Object objectToClone, Object previousClone) {

		// ***************************************************************************************************************************************
		// 1. Class by class cloning (only clones known types)
		// ***************************************************************************************************************************************
		// Clone any Map (shallow clone should be enough at this level)
		if (objectToClone instanceof Map) {
			Map recycledMap = (Map) previousClone;
			if (recycledMap == null)
				recycledMap = new HashMap();
			else recycledMap.clear();
			recycledMap.putAll((Map)objectToClone);
			return recycledMap;
			
		// Clone any collection (shallow clone should be enough at this level)
		} else if (objectToClone instanceof Collection) {
			Collection recycledCollection = (Collection) previousClone;
			if (recycledCollection == null)
				recycledCollection = new ArrayList();
			else recycledCollection.clear();
			recycledCollection.addAll((Collection)objectToClone);
			return recycledCollection;
			
		// Clone String
		} else if (objectToClone instanceof String) {
			return objectToClone;
			
		// Clone Date
		} else if (objectToClone instanceof Date) {
			Date clonedDate = (Date) ((Date)objectToClone).clone();
			return clonedDate;
			
		} else {
			// ***************************************************************************************************************************************
			// 2. Polymorphic clone (by reflection, looks for a clone() method in hierarchy and invoke it)
			// ***************************************************************************************************************************************
			try {
				  Object newClone = null;
				  for (Class obj = objectToClone.getClass(); !obj.equals(Object.class); obj = obj.getSuperclass()) {
					  Method m[] = obj.getDeclaredMethods();
					  for (int i = 0; i < m.length; i++) {
						  if (m[i].getName().equals("clone")) {
							  m[i].setAccessible(true);
							  newClone = m[i].invoke(objectToClone);
							  System.out.println(objectToClone.getClass() + " cloned by Reflection. Performance can be improved by adding the class to the list of known types");
							  return newClone;
						  }
					  }
				  }
				  throw new Exception("Method clone not found");
				  
			// ***************************************************************************************************************************************
			// 3. Polymorphic clone (Deep cloning by Serialization)
			// ***************************************************************************************************************************************
			} catch (Throwable  e1) {
				try {
					ByteArrayOutputStream bytes = new ByteArrayOutputStream() {
						public synchronized byte[] toByteArray() {
							return buf;
						}
					};
					ObjectOutputStream out = new ObjectOutputStream(bytes);
					out.writeObject(objectToClone);
					out.close();
					ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(bytes.toByteArray()));
					System.out.println(objectToClone.getClass() + " cloned by Serialization. Performance can be improved by adding the class to the list of known types");
					return in.readObject();
					
				// ***************************************************************************************************************************************
				// 4. Impossible to clone
				// ***************************************************************************************************************************************					
				} catch (Throwable  e2) {
					e2.printStackTrace();
					return null;
				}
			}
		}
	}
}