package net.sourceforge.fenixedu.presentationTier.servlets.gwt;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;

import com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.server.rpc.RPC;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;

public class FenixGWTServlet extends RemoteServiceServlet {

    public ServletConfig servletConfig = null;

    private Map<String, RemoteServiceServlet> dispatchMap;

    public FenixGWTServlet() {
        super();
        dispatchMap = new HashMap<String, RemoteServiceServlet>();
    }

    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        this.servletConfig = config;
    }

    @Override
    public void destroy() {
        for (Entry<String, RemoteServiceServlet> entry : dispatchMap.entrySet()) {
            entry.getValue().destroy();
        }
    }

    @Override
    public String processCall(String payload) throws SerializationException {
        try {
            FenixRPCRequest rpcRequest = FenixRPC.decodeRequest(payload, this.getClass(), this);

            String remoteServiceName = getServerSideEquivalent(rpcRequest.getRemoteServiceInterfaceName());

            RemoteServiceServlet remoteService = appointServlet(remoteServiceName);

            /**
             * Delegates method invocation to proper servlet. We do not call <code>remoteService.processCall(payload);</code>
             * because while invoking the specific servlet we lose reference to <code>getThreadLocalRequest()</code>, essential
             * to determine the <code>SerializationPolicy</code>. Eventual overrides of
             * <code>onAfterRequestDeserialized(rpcRequest);</code> should be implemented in this class.
             */
            String result =
                    RPC.invokeAndEncodeResponse(remoteService, rpcRequest.getMethod(), rpcRequest.getParameters(),
                            rpcRequest.getSerializationPolicy(), rpcRequest.getFlags());

            return result;

        } catch (IncompatibleRemoteServiceException e) {
            return RPC.encodeResponseForFailure(null, e);
        }
    }

    private RemoteServiceServlet appointServlet(String className) {
        if (dispatchMap.get(className) == null) {
            Class<RemoteServiceServlet> servletClass;

            try {
                servletClass = (Class<RemoteServiceServlet>) Class.forName(className);
            } catch (ClassNotFoundException e) {
                throw new IncompatibleRemoteServiceException(e.getMessage(), e);
            }

            RemoteServiceServlet servlet;

            try {
                servlet = servletClass.newInstance();
            } catch (InstantiationException e) {
                throw new IncompatibleRemoteServiceException(e.getMessage(), e);
            } catch (IllegalAccessException e) {
                throw new IncompatibleRemoteServiceException(e.getMessage(), e);
            }

            try {
                servlet.init(this.servletConfig);
            } catch (ServletException e) {
                throw new IncompatibleRemoteServiceException(e.getMessage(), e);
            }

            dispatchMap.put(className, servlet);
        }
        return dispatchMap.get(className);
    }

    private String getServerSideEquivalent(String remoteServiceInterfaceName) {
        String serverSideEquivalent = remoteServiceInterfaceName.replace(".client.", ".server.");
        serverSideEquivalent += "Impl";
        return serverSideEquivalent;
    }

    @Override
    //Overridden for debug purpose only
    protected void doUnexpectedFailure(Throwable e) {
        System.out.println("\n\n--------------Unwrapped Exception Starts Here------------");
        e.printStackTrace();
        System.out.println("--------------Unwrapped Exception Ends Here------------\n\n");
        super.doUnexpectedFailure(e);
    }

}