package org.greenstone.gsdl3;

import org.greenstone.gsdl3.core.*;
import org.greenstone.gsdl3.util.*;
import org.greenstone.gsdl3.action.PageAction; // used to get the default action
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Enumeration;
import java.util.HashMap;
import java.io.File;

/** a servlet to serve the greenstone library - we are using servlets instead
 * of cgi
 * the init method is called only once - the first time the servlet classes
 * are loaded. Each time a request comes in to the servlet, the session()
 * method is called in a new thread (calls doGet/doPut etc)
 * takes the a=p&p=home type args and builds a simple request to send to 
 * its receptionist, which returns a result in html, cos output=html
 * is set in the request
 * @see Receptionist
 */
public class LibraryServlet extends HttpServlet {
    
    /** the receptionist to send messages to */
    protected Receptionist recept=null;
    /** the default language - is specified by setting a servlet param,
     * otherwise DEFAULT_LANG is used*/
    protected String default_lang= null;
    /** The default default - used if a default lang is not specified 
     * in the servlet params */
    protected final String DEFAULT_LANG = "en";
    /** container Document to create XML Nodes */
    protected Document doc=null;    
    /** a converter class to parse XML and create Docs */
    protected XMLConverter converter=null;
    /** the cgi stuff - the Receptionist can add new args to this
     * its used by the servlet to determine what args to save */
    //protected GSCGI cgi = null;
    protected GSParams params = null;

    /** user id - new one per session. This doesn't work if session state is saved between restarts - this requires this value to be saved too. */
    protected int next_user_id = 0;

    
    /** initialise the servlet
     */
    public void init(ServletConfig config) throws ServletException {
	// always call super.init;
	super.init(config);
	// disable preferences - does this work anyway??
	//System.setProperty("java.util.prefs.PreferencesFactory", "org.greenstone.gsdl3.util.DisabledPreferencesFactory");

	String library_name = config.getInitParameter(GSConstants.LIBRARY_NAME);
	String gsdl3_home = config.getInitParameter(GSConstants.GSDL3_HOME);
	String site_name = config.getInitParameter(GSConstants.SITE_NAME);
	String interface_name = config.getInitParameter(GSConstants.INTERFACE_NAME);
	this.default_lang = config.getInitParameter(GSConstants.DEFAULT_LANG);
	if (library_name == null || gsdl3_home == null || site_name ==null ||  interface_name ==null) {
	    // must have this
	    System.err.println("initialisation parameters not all set!");
	    System.err.println(" you must have libraryname, gsdl3home, sitename,  interfacename");
	    System.exit(1);
	}

	if (this.default_lang == null) {
	    // choose english
	    this.default_lang = DEFAULT_LANG;
	}
	
	HashMap config_params = new HashMap();
	
	config_params.put(GSConstants.LIBRARY_NAME, library_name);
	config_params.put(GSConstants.GSDL3_HOME, gsdl3_home);
	config_params.put(GSConstants.SITE_NAME, site_name);
	config_params.put(GSConstants.INTERFACE_NAME, interface_name);
	
	this.converter = new XMLConverter();
	this.doc = this.converter.newDOM();
	
	// now try and create MR and recpt
	// new message router - create it and pass reference to recept.
	// the servlet wont use this directly
	String mr_name = (String)config.getInitParameter("messagerouter_class");
	MessageRouter message_router = null;
	if (mr_name == null) { // just use the normal MR
	    message_router = new MessageRouter();
	} else { // try the specified one
	    try {
		message_router = (MessageRouter)Class.forName("org.greenstone.gsdl3.core."+mr_name).newInstance();
	    } catch (Exception e) { // cant use this new one, so use normal one
		System.err.println("LibraryServlet configure exception when trying to use a new MessageRouter "+mr_name+": "+e.getMessage());
		e.printStackTrace();
		message_router = new MessageRouter();
	    }   
	}
	
	message_router.setSiteHome(GSFile.siteHome(gsdl3_home, 
						   site_name));
	message_router.configure();
	
	// the receptionist -the servlet will talk to this
	String recept_name = (String)config.getInitParameter("receptionist_class");
	if (recept_name == null) {
	    this.recept = new DefaultReceptionist();
	} else {
	    try {
		this.recept = (Receptionist)Class.forName("org.greenstone.gsdl3.core."+recept_name).newInstance();
	    } catch (Exception e) { // cant use this new one, so use normal one
		System.err.println("LibraryServlet configure exception when trying to use a new Receptionist "+recept_name+": "+e.getMessage());
		e.printStackTrace();
		this.recept = new DefaultReceptionist();
	    }
	}
	this.recept.setConfigParams(config_params);
	this.recept.setMessageRouter(message_router);
	// the params arg thingy
	
	String params_name = (String)config.getInitParameter("params_class");
	if (params_name == null) {
	    this.params = new GSParams();
	} else {
	    try {
		this.params = (GSParams)Class.forName("org.greenstone.gsdl3.util."+params_name).newInstance();
	    } catch (Exception e) {
		System.err.println("LibraryServlet configure exception when trying to use a new params thing "+params_name+": "+e.getMessage());
		e.printStackTrace();
		this.params = new GSParams();
	    }
	}
	// pass it to the receptionist
	this.recept.setParams(this.params);
	this.recept.configure();
	
    }
    
    public void doGet(HttpServletRequest request,
		      HttpServletResponse response)
	throws ServletException, IOException {
	
	HttpSession session = request.getSession(true);
	String uid = (String)session.getAttribute(GSXML.USER_ID_ATT);
	if (uid ==null) {
	    uid = ""+getNextUserId();
	    session.setAttribute(GSXML.USER_ID_ATT, uid);
	}
	request.setCharacterEncoding("UTF-8");
	response.setContentType("text/html;charset=UTF-8");
	PrintWriter out = response.getWriter();

	String lang = request.getParameter(GSParams.LANGUAGE);
	if (lang==null || lang.equals("")) {
	    // try the session cached lang
	    lang = (String)session.getAttribute(GSParams.LANGUAGE);
	    if (lang==null || lang.equals("")) {
		// still not set, use the default
		lang = this.default_lang;
	    }
	}
	
	// set the lang in the session
	session.setAttribute(GSParams.LANGUAGE, lang);

	String output = request.getParameter(GSParams.OUTPUT);
	if (output==null || output.equals("")) {
	    output = "html"; // uses html by default
	}

	// the request to the receptionist	
	Element xml_message = this.doc.createElement(GSXML.MESSAGE_ELEM);
	Element xml_request = GSXML.createBasicRequest(this.doc, GSXML.REQUEST_TYPE_PAGE, "", lang, uid);
	xml_request.setAttribute(GSXML.OUTPUT_ATT, output);
	xml_message.appendChild(xml_request);
	
	
	String action = request.getParameter(GSParams.ACTION);
	String subaction = request.getParameter(GSParams.SUBACTION);
	if (action==null || action.equals("")) {
	    // should we do all the following stuff if using default page?
	    // display the home page  - the default page
	    action = "p";
	    subaction = PageAction.HOME_PAGE;
	    xml_request.setAttribute(GSXML.ACTION_ATT, action);
	    xml_request.setAttribute(GSXML.SUBACTION_ATT, subaction);
	    
	} else {
	
	    xml_request.setAttribute(GSXML.ACTION_ATT, action);
	    if (subaction != null) {
		xml_request.setAttribute(GSXML.SUBACTION_ATT, subaction);
	    }

	    //  create the param list for the greenstone request - includes
	    // the params from the current request and any others from the saved session
	    Element xml_param_list = this.doc.createElement(GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
	    xml_request.appendChild(xml_param_list);
	    
	    Enumeration params = request.getParameterNames();
	    while(params.hasMoreElements()) {
		String name = (String)params.nextElement();
		if (!name.equals(GSParams.ACTION) && !name.equals(GSParams.SUBACTION) && !name.equals(GSParams.LANGUAGE) && !name.equals(GSParams.OUTPUT)) {// we have already dealt with these 
		    String value="";
		    String [] values = request.getParameterValues(name);
		    value = values[0];
		    if (values.length > 1) {
			for (int i=1; i< values.length; i++) {
			    value += ","+values[i];
			}
		    }
		    // either add it to the param list straight away, or save it to the session and add it later
		    if (this.params.shouldSave(name)) {			
			session.setAttribute(name, value);
		    } else { 
			Element param = this.doc.createElement(GSXML.PARAM_ELEM);
			param.setAttribute(GSXML.NAME_ATT, name);
			param.setAttribute(GSXML.VALUE_ATT, GSXML.xmlSafe(value));
			xml_param_list.appendChild(param);
		    }
		}
	    }
	    
	    // put in all the params from the session cache
	    params = session.getAttributeNames();
	    while(params.hasMoreElements()) {
		String name = (String)params.nextElement();
		
		if ( !name.equals(GSParams.LANGUAGE) && !name.equals(GSXML.USER_ID_ATT)) { // lang and uid are stored but we dont want it in the param list cos its already in the request
		    
		    Element param = this.doc.createElement(GSXML.PARAM_ELEM);
		    param.setAttribute(GSXML.NAME_ATT, name);
		    param.setAttribute(GSXML.VALUE_ATT, GSXML.xmlSafe((String)session.getAttribute(name)));
		    xml_param_list.appendChild(param);
		}
	    }

	
	}
	
	if (!output.equals("html")) {
	    response.setContentType("text/xml"); // for now use text
	}
	
	Element xml_result = this.recept.process(xml_message);
	encodeURLs(xml_result, response);
	out.println(this.converter.getPrettyString(xml_result));
    }

    /** this goes through each URL and adds in a session id if needed--
     * its needed if the browser doesn't accept cookies
     */
    protected void encodeURLs(Element data, HttpServletResponse response) {
	
	if (data == null) {
	    return;
	}
	// get all the <a> elements
	NodeList hrefs = data.getElementsByTagName("a");
	for (int i=0; i<hrefs.getLength(); i++) {
	    Element a = (Element)hrefs.item(i);
	    a.setAttribute("href", response.encodeURL(a.getAttribute("href")));
	}
	
	// now find any submit bits - get all the <form> elements
	NodeList forms = data.getElementsByTagName("form");
	for (int i=0; i<forms.getLength(); i++) {
	    Element form = (Element)forms.item(i);
	    form.setAttribute("action", response.encodeURL(form.getAttribute("action")));
	}
	// are these the only cases where URLs occur??
	// we should only do this for greenstone urls?
	
    }

    synchronized protected int getNextUserId() {
	next_user_id++;
	return next_user_id;
    }

}