/**************************************************************************************
 * Copyright (c) Jonas Bonér, Alexandre Vasseur. All rights reserved.                 *
 * http://aspectwerkz.codehaus.org                                                    *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the LGPL license      *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package org.codehaus.aspectwerkz.connectivity;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.InetAddress;
import java.net.Socket;
import java.util.Map;
import java.util.WeakHashMap;

import org.codehaus.aspectwerkz.exception.WrappedRuntimeException;
import org.codehaus.aspectwerkz.util.UuidGenerator;

/**
 * This class provides a general remote proxy. It uses the Dynamic Proxy mechanism that was introduced with JDK 1.3.
 * <p/>
 * The client proxy sends all requests to a server via a socket connection. The server returns results in the same way.
 * Every object that is transferred (i.e. result of method invocation) has to support the Serializable interface.
 *
 * @author <a href="mailto:jboner@codehaus.org">Jonas Bonér</a>
 */
public class RemoteProxy implements InvocationHandler, Serializable {

    /**
     * The serial version uid for the class.
     *
     * @TODO: recalculate
     */
    private static final long serialVersionUID = 1L;

    /**
     * All the instances that have been wrapped by a proxy. Maps each instance to its handle.
     */
    private transient static Map s_instances = new WeakHashMap();

    /**
     * The server host address.
     */
    private final String m_address;

    /**
     * The server port.
     */
    private final int m_port;

    /**
     * The handle to the instance wrapped by this proxy.
     */
    private String m_handle = null;

    /**
     * The interface class for the wrapped instance.
     */
    private Class[] m_targetInterfaces = null;

    /**
     * The names of all the interfaces for the wrapped instance.
     */
    private String[] m_targetInterfaceNames = null;

    /**
     * The class name for the wrapped instance.
     */
    private String m_targetImplName = null;

    /**
     * The socket.
     */
    private transient Socket m_socket;

    /**
     * The input stream.
     */
    private transient ObjectInputStream m_in;

    /**
     * The output stream.
     */
    private transient ObjectOutputStream m_out;

    /**
     * The class loader to use.
     */
    private transient ClassLoader m_loader;

    /**
     * The client context.
     */
    private transient Object m_context = null;

    /**
     * The dynamic proxy instance to the wrapped instance.
     */
    private transient Object m_proxy = null;

    /**
     * Creates a new proxy to a class. To be used on the client side to create a new proxy to an object.
     *
     * @param interfaces the class name of the interface for the object to create the proxy for
     * @param impl       the class name of the the object to create the proxy for
     * @param address    the address to connect to.
     * @param port       the port to connect to.
     * @return the new remote proxy instance
     */
    public static RemoteProxy createClientProxy(
            final String[] interfaces,
            final String impl,
            final String address,
            final int port) {
        return RemoteProxy.createClientProxy(
                interfaces, impl, address, port,
                Thread.currentThread().getContextClassLoader()
        );
    }

    /**
     * Creates a new proxy to a class. To be used on the client side to create a new proxy to an object.
     *
     * @param interfaces the class name of the interface for the object to create the proxy for
     * @param impl       the class name of the the object to create the proxy for
     * @param address    the address to connect to.
     * @param port       the port to connect to.
     * @param ctx        the context carrying the users principal and credentials
     * @return the new remote proxy instance
     */
    public static RemoteProxy createClientProxy(
            final String[] interfaces,
            final String impl,
            final String address,
            final int port,
            final Object context) {
        return RemoteProxy.createClientProxy(
                interfaces, impl, address, port, context,
                Thread.currentThread().getContextClassLoader()
        );
    }

    /**
     * Creates a new proxy to a class. To be used on the client side to create a new proxy to an object.
     *
     * @param interfaces the class name of the interface for the object to create the proxy for
     * @param impl       the class name of the the object to create the proxy for
     * @param address    the address to connect to.
     * @param port       the port to connect to.
     * @param loader     the class loader to use
     * @return the new remote proxy instance
     */
    public static RemoteProxy createClientProxy(
            final String[] interfaces,
            final String impl,
            final String address,
            final int port,
            final ClassLoader loader) {
        return RemoteProxy.createClientProxy(interfaces, impl, address, port, null, loader);
    }

    /**
     * Creates a new proxy to a class. To be used on the client side to create a new proxy to an object.
     *
     * @param interfaces the class name of the interface for the object to create the proxy for
     * @param impl       the class name of the the object to create the proxy for
     * @param address    the address to connect to.
     * @param port       the port to connect to.
     * @param ctx        the context carrying the users principal and credentials
     * @param loader     the class loader to use
     * @return the new remote proxy instance
     */
    public static RemoteProxy createClientProxy(
            final String[] interfaces,
            final String impl,
            final String address,
            final int port,
            final Object context,
            final ClassLoader loader) {
        return new RemoteProxy(interfaces, impl, address, port, context, loader);
    }

    /**
     * Creates a proxy to a specific <b>instance</b> in the on the server side. This proxy could then be passed to the
     * client which can invoke method on this specific <b>instance</b>.
     *
     * @param the     target instance to create the proxy for
     * @param address the address to connect to.
     * @param port    the port to connect to.
     * @return the new remote proxy instance
     */
    public static RemoteProxy createServerProxy(
            final Object targetlInstance,
            final String address,
            final int port) {
        return new RemoteProxy(targetlInstance, address, port);
    }

    /**
     * Look up and retrives a proxy to an object from the server.
     *
     * @param loader the classloader to use
     * @return the proxy instance
     */
    public Object getInstance(final ClassLoader loader) {
        m_loader = loader;
        return getInstance();
    }

    /**
     * Look up and retrives a proxy to an object from the server.
     *
     * @return the proxy instance
     */
    public Object getInstance() {
        if (m_proxy != null) {
            return m_proxy;
        }
        if (m_loader == null) {
            m_loader = Thread.currentThread().getContextClassLoader();
        }

        try {
            m_socket = new Socket(InetAddress.getByName(m_address), m_port);
            m_socket.setTcpNoDelay(true);
            m_out = new ObjectOutputStream(m_socket.getOutputStream());
            m_in = new ObjectInputStream(m_socket.getInputStream());
        }
        catch (Exception e) {
            throw new WrappedRuntimeException(e);
        }

        if (m_handle == null) {
            // is a client side proxy
            if (m_targetInterfaceNames == null) {
                throw new IllegalStateException("interface class name can not be null");
            }
            if (m_targetImplName == null) {
                throw new IllegalStateException("implementation class name can not be null");
            }

            try {
                // create a new instance on the server and get the handle to it in return
                m_out.write(Command.CREATE);
                m_out.writeObject(m_targetImplName);
                m_out.flush();
                m_handle = (String)m_in.readObject();

                m_targetInterfaces = new Class[m_targetInterfaceNames.length];
                for (int i = 0; i < m_targetInterfaceNames.length; i++) {
                    try {
                        m_targetInterfaces[i] = m_loader.loadClass(m_targetInterfaceNames[i]);
                    }
                    catch (ClassNotFoundException e) {
                        throw new WrappedRuntimeException(e);
                    }
                }
            }
            catch (Exception e) {
                throw new WrappedRuntimeException(e);
            }
        }
        m_proxy = Proxy.newProxyInstance(m_loader, m_targetInterfaces, this);
        return m_proxy;
    }

    /**
     * This method is invoked automatically by the proxy. Should not be called directly.
     *
     * @param proxy  the proxy instance that the method was invoked on
     * @param method the Method instance corresponding to the interface method invoked on the proxy instance.
     * @param args   an array of objects containing the values of the arguments passed in the method invocation on the
     *               proxy instance.
     * @return the value to return from the method invocation on the proxy instance.
     */
    public Object invoke(final Object proxy, final Method method, final Object[] args) {
        try {
            m_out.write(Command.INVOKE);
            m_out.writeObject(m_context);
            m_out.writeObject(m_handle);
            m_out.writeObject(method.getName());
            m_out.writeObject(method.getParameterTypes());
            m_out.writeObject(args);
            m_out.flush();

            final Object response = m_in.readObject();
            if (response instanceof Exception) {
                throw (Exception)response;
            }
            return response;
        }
        catch (Exception e) {
            throw new WrappedRuntimeException(e);
        }
    }

    /**
     * Closes the proxy and the connection to the server.
     */
    public void close() {
        try {
            m_out.write(Command.CLOSE);
            m_out.flush();
            m_out.close();
            m_in.close();
            m_socket.close();
        }
        catch (IOException e) {
            throw new WrappedRuntimeException(e);
        }
    }

    /**
     * Returns a proxy wrapped instance by its handle.
     *
     * @param handle the handle
     * @return the instance
     */
    public static Object getWrappedInstance(final String handle) {
        return s_instances.get(handle);
    }

    /**
     * Wraps a new instance and maps it to a handle.
     *
     * @param instance the instance to wrap
     * @return the handle for the instance
     */
    public static String wrapInstance(final Object instance) {
        final String handle = UuidGenerator.generate(instance);
        s_instances.put(handle, instance);
        return handle;
    }

    /**
     * Creates a new proxy based on the interface and class names passes to it. For client-side use. This method is
     * never called directly.
     *
     * @param interfaces the class name of the interface for the object to create the proxy for
     * @param impl       the class name of the the object to create the proxy for
     * @param address    the address to connect to.
     * @param port       the port to connect to.
     * @param ctx        the context carrying the users principal and credentials
     * @param loader     the class loader to use
     */
    private RemoteProxy(
            final String[] interfaces,
            final String impl,
            final String address,
            final int port,
            final Object context,
            final ClassLoader loader) {
        if (interfaces == null || interfaces.length == 0) {
            throw new IllegalArgumentException("at least one interface must be specified");
        }
        if (impl == null) {
            throw new IllegalArgumentException("implementation class name can not be null");
        }
        if (address == null) {
            throw new IllegalArgumentException("address can not be null");
        }
        if (port < 0) {
            throw new IllegalArgumentException("port not valid");
        }

        m_targetInterfaceNames = interfaces;
        m_targetImplName = impl;
        m_address = address;
        m_port = port;
        m_context = context;
        m_loader = loader;
    }

    /**
     * Creates a new proxy based on the instance passed to it. For server-side use. This method is never called
     * directly.
     *
     * @param the     target instance to create the proxy for
     * @param address the address to connect to.
     * @param port    the port to connect to.
     */
    private RemoteProxy(
            final Object targetInstance,
            final String address,
            final int port) {
        if (targetInstance == null) {
            throw new IllegalArgumentException("target instance can not be null");
        }
        if (address == null) {
            throw new IllegalArgumentException("address can not be null");
        }
        if (port < 0) {
            throw new IllegalArgumentException("port not valid");
        }

        m_targetInterfaces = targetInstance.getClass().getInterfaces();
        m_address = address;
        m_port = port;
        m_handle = wrapInstance(targetInstance);
    }
}
