/*
 * Copyright 2010 salaboy.
 *
 * Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 * under the License.
 */
package org.drools.persistence.jpa.marshaller;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Id;
import org.drools.marshalling.ObjectMarshallingStrategy;
import org.drools.runtime.Environment;
import org.drools.runtime.EnvironmentName;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 * @author salaboy
 */
public class JPAPlaceholderResolverStrategy implements ObjectMarshallingStrategy {
    private static Logger log = LoggerFactory.getLogger(JPAPlaceholderResolverStrategy.class);
    private Environment env;
    
    public JPAPlaceholderResolverStrategy(Environment env) {
        this.env = env;
    }
    
    public boolean accept(Object object) {
        return isEntity(object);
    }

    public void write(ObjectOutputStream os, Object object) throws IOException {
        
        
            os.writeUTF(object.getClass().getCanonicalName());
            os.writeObject(getClassIdValue(object));
       
    }

    public Object read(ObjectInputStream is) throws IOException, ClassNotFoundException {
        String canonicalName = is.readUTF();
        Object id = is.readObject();
        EntityManagerFactory emf = (EntityManagerFactory) env.get(EnvironmentName.ENTITY_MANAGER_FACTORY);
        EntityManager em = emf.createEntityManager();
        return em.find(Class.forName(canonicalName), id);
    }

    public static Serializable getClassIdValue(Object o)  {
        Class<? extends Object> varClass = o.getClass();
        Serializable idValue = null;
        try{
            do {
                Field[] fields = varClass.getDeclaredFields();
                for (int i = 0; i < fields.length && idValue == null; i++) {
                    Field field = fields[i];
                    Id id = field.getAnnotation(Id.class);
                    if (id != null) {
                        try {
                            idValue = callIdMethod(o, "get"
                                    + Character.toUpperCase(field.getName().charAt(0))
                                    + field.getName().substring(1));
                        } catch (NoSuchMethodException e) {
                            idValue = (Serializable) field.get(o);
                        }
                    }
                }
            } while ((varClass = varClass.getSuperclass()) != null && idValue == null);
            if (idValue == null) {
                varClass = o.getClass();
                do {
                    Method[] methods = varClass.getMethods();
                    for (int i = 0; i < methods.length && idValue == null; i++) {
                        Method method = methods[i];
                        Id id = method.getAnnotation(Id.class);
                        if (id != null) {
                            idValue = (Serializable) method.invoke(o);
                        }
                    }
                } while ((varClass = varClass.getSuperclass()) != null && idValue == null);
            }
        }
        catch(Exception ex){
            log.error(ex.getMessage());
        }
        return idValue;
    }

    private static Serializable callIdMethod(Object target, String methodName) throws IllegalArgumentException,
            SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
        return (Serializable) target.getClass().getMethod(methodName, (Class[]) null).invoke(target, new Object[]{});
    }
    
    private static boolean isEntity(Object o){
        Class<? extends Object> varClass = o.getClass();
        do {
                Field[] fields = varClass.getDeclaredFields();
                for (int i = 0; i < fields.length; i++) {
                    Field field = fields[i];
                    Id id = field.getAnnotation(Id.class);
                    if (id != null) {
                       return true;
                    }
                }
        } while ((varClass = varClass.getSuperclass()) != null);
        varClass = o.getClass();
        do {
                    Method[] methods = varClass.getMethods();
                    for (int i = 0; i < methods.length; i++) {
                        Method method = methods[i];
                        Id id = method.getAnnotation(Id.class);
                        if (id != null) {
                            return true;
                        }
                    }
        } while ((varClass = varClass.getSuperclass()) != null );
        
        return false;
    }
}