/*
 *    Copyright 2009-2012 The MyBatis Team
 *
 *    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.
 */
package org.apache.ibatis.executor.loader;

import java.lang.reflect.Method;
import java.util.List;
import java.util.Locale;
import java.util.Set;

import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import org.apache.ibatis.executor.ExecutorException;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.reflection.ExceptionUtil;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.property.PropertyCopier;
import org.apache.ibatis.reflection.property.PropertyNamer;
import org.apache.ibatis.session.Configuration;

public final class ResultObjectProxy {

  private static final Log log = LogFactory.getLog(ResultObjectProxy.class);

  private static final String FINALIZE_METHOD = "finalize";
  private static final String WRITE_REPLACE_METHOD = "writeReplace";

  private ResultObjectProxy() {
    // disable construction
  }

  public static Object createProxy(Object target, ResultLoaderMap lazyLoader, Configuration configuration, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    return EnhancedResultObjectProxyImpl.createProxy(target, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs);
  }

  public static Object createDeserializationProxy(Object target, Set<String> unloadedProperties, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
    return EnhancedDeserializationProxyImpl.createProxy(target, unloadedProperties, objectFactory, constructorArgTypes, constructorArgs);
  }

  private static Object crateProxy(Class<?> type, Callback callback, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {

    Enhancer enhancer = new Enhancer();
    enhancer.setCallback(callback);
    enhancer.setSuperclass(type);

    try {
      type.getDeclaredMethod(WRITE_REPLACE_METHOD);
      // ObjectOutputStream will call writeReplace of objects returned by writeReplace
      log.debug(WRITE_REPLACE_METHOD + " method was found on bean " + type + ", make sure it returns this");
    } catch (NoSuchMethodException e) {
      enhancer.setInterfaces(new Class[] { WriteReplaceInterface.class });
    } catch (SecurityException e) {
      // nothing to do here
    }

    Object enhanced = null;
    if (constructorArgTypes.isEmpty()) {
      enhanced = enhancer.create();
    } else {
      Class<?>[] typesArray = constructorArgTypes.toArray(new Class[constructorArgTypes.size()]);
      Object[] valuesArray = constructorArgs.toArray(new Object[constructorArgs.size()]);
      enhanced = enhancer.create(typesArray, valuesArray);
    }
    return enhanced;
  }

  private static class EnhancedResultObjectProxyImpl implements MethodInterceptor {
    private Class<?> type;
    private ResultLoaderMap lazyLoader;
    private boolean aggressive;
    private Set<String> lazyLoadTriggerMethods;
    private ObjectFactory objectFactory;
    private List<Class<?>> constructorArgTypes;
    private List<Object> constructorArgs;

    private EnhancedResultObjectProxyImpl(Class<?> type, ResultLoaderMap lazyLoader, Configuration configuration, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      this.type = type;
      this.lazyLoader = lazyLoader;
      this.aggressive = configuration.isAggressiveLazyLoading();
      this.lazyLoadTriggerMethods = configuration.getLazyLoadTriggerMethods();
      this.objectFactory = objectFactory;
      this.constructorArgTypes = constructorArgTypes;
      this.constructorArgs = constructorArgs;
    }

    public static Object createProxy(Object target, ResultLoaderMap lazyLoader, Configuration configuration, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      final Class<?> type = target.getClass();
      EnhancedResultObjectProxyImpl callback = new EnhancedResultObjectProxyImpl(type, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs);
      Object enhanced = crateProxy(type, callback, constructorArgTypes, constructorArgs);
      PropertyCopier.copyBeanProperties(type, target, enhanced);
      return enhanced;
    }

    public Object intercept(Object enhanced, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
      final String methodName = method.getName();
      try {
        synchronized (lazyLoader) {
          if (WRITE_REPLACE_METHOD.equals(methodName)) {
            Object original = null;
            if (constructorArgTypes.isEmpty()) {
              original = objectFactory.create(type);
            } else {
              original = objectFactory.create(type, constructorArgTypes, constructorArgs);
            }
            PropertyCopier.copyBeanProperties(type, enhanced, original);
            if (lazyLoader.size() > 0) {
              return new SerialStateHolder(original, lazyLoader.getPropertyNames(), objectFactory, constructorArgTypes, constructorArgs);
            } else {
              return original;
            }
          } else {
            if (lazyLoader.size() > 0 && !FINALIZE_METHOD.equals(methodName)) {
              if (aggressive || lazyLoadTriggerMethods.contains(methodName)) {
                lazyLoader.loadAll();
              } else if (PropertyNamer.isProperty(methodName)) {
                final String property = PropertyNamer.methodToProperty(methodName);
                if (lazyLoader.hasLoader(property)) {
                  lazyLoader.load(property);
                }
              }
            }
          }
        }
        return methodProxy.invokeSuper(enhanced, args);
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
    }
  }

  private static class EnhancedDeserializationProxyImpl implements MethodInterceptor {
    private Class<?> type;
    private Set<String> unloadedProperties;
    private ObjectFactory objectFactory;
    private List<Class<?>> constructorArgTypes;
    private List<Object> constructorArgs;

    private EnhancedDeserializationProxyImpl(Class<?> type, Set<String> unloadedProperties, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      this.type = type;
      this.unloadedProperties = unloadedProperties;
      this.objectFactory = objectFactory;
      this.constructorArgTypes = constructorArgTypes;
      this.constructorArgs = constructorArgs;
    }

    public static Object createProxy(Object target, Set<String> unloadedProperties, ObjectFactory objectFactory, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
      final Class<?> type = target.getClass();
      EnhancedDeserializationProxyImpl callback = new EnhancedDeserializationProxyImpl(type, unloadedProperties, objectFactory, constructorArgTypes, constructorArgs);
      Object enhanced = crateProxy(type, callback, constructorArgTypes, constructorArgs);
      PropertyCopier.copyBeanProperties(type, target, enhanced);
      return enhanced;
    }

    public Object intercept(Object enhanced, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
      final String methodName = method.getName();
      try {
        if (WRITE_REPLACE_METHOD.equals(methodName)) {
          Object original = null;
          if (constructorArgTypes.isEmpty()) {
            original = objectFactory.create(type);
          } else {
            original = objectFactory.create(type, constructorArgTypes, constructorArgs);
          }
          PropertyCopier.copyBeanProperties(type, enhanced, original);
          return new SerialStateHolder(original, unloadedProperties, objectFactory, constructorArgTypes, constructorArgs);
        } else {
          if (!FINALIZE_METHOD.equals(methodName) && PropertyNamer.isProperty(methodName)) {
            final String property = PropertyNamer.methodToProperty(methodName);
            if (unloadedProperties.contains(property.toUpperCase(Locale.ENGLISH))) {
              throw new ExecutorException("An attempt has been made to read a not loaded lazy property '"
                  + property
                  + "' of a disconnected object");
            }
          }
          return methodProxy.invokeSuper(enhanced, args);
        }
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
    }
  }

}
