package org.openslx.thrifthelper;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import org.apache.log4j.Logger;
import org.apache.thrift.TException;
import org.apache.thrift.transport.TTransportException;

public class ThriftHandler<T extends Object> implements InvocationHandler {

	private final static Logger LOGGER = Logger.getLogger(ThriftHandler.class);
	
	public interface ClientCreationCallback<T> {
		public T get();
	}

	private final ThreadLocal<T> clients = new ThreadLocal<T>();
	private final ClientCreationCallback<T> callback;

	public ThriftHandler(final Class<T> clazz, ClientCreationCallback<T> cb) {
		callback = cb;
		thriftMethods = Collections.unmodifiableSet(new HashSet<String>() {
			private static final long serialVersionUID = 8983506538154055231L;
			{
				Method[] methods = clazz.getMethods();
				for (int i = 0; i < methods.length; i++) {
					boolean thrift = false;
					Class<?>[] type = methods[i].getExceptionTypes();
					for (int e = 0; e < type.length; e++) {
						if (TException.class.isAssignableFrom(type[e]))
							thrift = true;

					}
					String name = methods[i].getName();
					if (thrift && !name.startsWith("send_") && !name.startsWith("recv_")) {
						add(name);
					}
				}
			}
		});
	}

	private final Set<String> thriftMethods;

	public Object invoke(Object tproxy, Method method, Object[] args) throws Throwable {

		// first find the thrift methods
		if (!thriftMethods.contains(method.getName())) {
			try {
				return method.invoke(method, args);
			} catch (InvocationTargetException e) {
				// TODO Auto-generated catch block
				Throwable cause = e.getCause();
				if (cause == null) {
					throw new RuntimeException();
				}
				throw cause;
			}
		}
		LOGGER.debug("Proxying '" + method.getName() + "'");

		T client = getClient(false);
		Throwable cause = null;
		for (int i = 0; i < 3; i++) {
			try {
				return method.invoke(client, args);
			} catch (InvocationTargetException e) {
				cause = e.getCause();
				if (cause instanceof TTransportException) {
					LOGGER.debug("Transport error - re-initialising ...");
					// new client
					client = getClient(true);
				}
			}
		}

		if (cause != null)
			throw cause;
		return null;

	}

	private T getClient(boolean forceNew) {
		T client = clients.get();
		if (client != null && !forceNew) {
			return client;
		}
		client = callback.get();
		if (client == null) {
			// TODO own exception
			throw new RuntimeException();
		}
		clients.set(client);
		return client;
	}
}