/*
 * Created on Mar 20, 2004
 */
package jspflow;

import java.io.IOException;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.mozilla.javascript.Scriptable;

import flow.Argument;
import flow.JSWebapp;
import flow.JavaScriptInterpreter;

/**
 * Controls flow of JSP application using Cocoon's Control Flow engine.
 * @author David M Johnson
 */
public class FlowServlet extends HttpServlet {

   /**
    * Initialize JavaScript interpreter with system and user scripts, store 
    * interpreter ServletContext.
    */
   public void init() throws ServletException {     
      try {
         JavaScriptInterpreter interp = new JavaScriptInterpreter();      
         interp.initialize();     
         interp.register("C:\\allfiles\\scratch\\JspFlow\\src\\flow\\system.js");
         interp.register("C:\\allfiles\\scratch\\JspFlow\\web\\WEB-INF\\numberguess.js");
         getServletContext().setAttribute("controlFlow", interp);
      }
      catch (Exception e) {
         throw new ServletException("ERROR initializing Control Flow", e);
      }
   }
   
   public JavaScriptInterpreter getControlFlow() {
      return (JavaScriptInterpreter)getServletContext().getAttribute("controlFlow");
   }

   /**
    * Handle by either starting a new Control Flow or continuing an existing 
    * one. The logic is:<br />
    * - If request contains contid, then continue existing flow.<br />
    * - Else start a new flow.<br />
    * 
    * @param request the request send by the client to the server
    * @param response the response send by the server to the client
    * @throws ServletException if an error occurred
    * @throws IOException if an error occurred
    */
   public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

      if (request.getParameter("contid") == null) {
         
         // --- start a new flow        
         
         // flow will return values in tray
         List args = new LinkedList();
         List tray = new LinkedList(); 
         args.add(new Argument("tray", tray));
         
         try {
            // call control script function
            getControlFlow().callFunction("main", args, request, response);              
            
            // retrieve page, continuation ID, and attributes from tray
            String page = (String)tray.get(0);
            String contid = (String)tray.get(1);
            Map atts = JSWebapp.jsobjectToMap((Scriptable)tray.get(2));
            
            dispatchToPage(request, response, page, contid, atts);
         }
         catch (Exception e) {
            throw new ServletException(
               "ERROR starting execution of Control Flow: "+e.getMessage(), e);
         }
      }
      else {
         
         // --- continue an existing flow
         
         // flow will return values in tray
         try {
            // kick off continuation
            List tray = getControlFlow().handleContinuation(
               request.getParameter("contid"), new LinkedList(), request, response);            
            
            // retrieve page, continuation ID, and attributes from tray
            String page = (String)tray.get(0);
            String contid = (String)tray.get(1);
            Map atts = JSWebapp.jsobjectToMap((Scriptable)tray.get(2));
            
            dispatchToPage(request, response, page, contid, atts);
         }
         catch (Exception e) {
            e.printStackTrace();
            throw new ServletException("ERROR starting execution of Control Flow", e);
         }
      }
   }

   /**
    * Add continuation ID and attributes to request scope, dispatch to page.
    * @param request
    * @param response
    * @param page     JSP page name to which to dispath.
    * @param contid   Continuation ID to be set in request.
    * @param atts     Attributes to be set in request.
    * @throws ServletException
    * @throws IOException
    */
   private void dispatchToPage(
         HttpServletRequest request, HttpServletResponse response, 
         String page, String contid, Map atts) 
      throws ServletException, IOException {
            
      request.setAttribute("contid", contid);
      
      Iterator attkeys = atts.keySet().iterator();
      while (attkeys.hasNext()) 
      {
         String attkey = (String)attkeys.next();
         request.setAttribute(attkey, JSWebapp.jsobjectToObject(atts.get(attkey)));
      }
      
      RequestDispatcher dispatcher = request.getRequestDispatcher(page);
      dispatcher.forward(request, response);
   }

   /**
    * Calls doGet().
    * @param request the request send by the client to the server
    * @param response the response send by the server to the client
    * @throws ServletException if an error occurred
    * @throws IOException if an error occurred
    */
   public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
      doGet(request, response);
   }

}