package org.greenstone.gsdl3;

import org.greenstone.gsdl3.comms.*;
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.Node;
import org.w3c.dom.NodeList;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Enumeration;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.io.File;
import java.lang.reflect.Type;
import java.util.Hashtable;
import org.apache.log4j.*;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

// Apache Commons
import org.apache.commons.lang3.*;

/** 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
* 
* 18/Jul/07 xiao
* modify to make the cached parameters collection-specific.
* Most of the work is done in doGet(), except adding an inner class UserSessionCache.
* 
* @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;

	/** Whether or not client-side XSLT support should be exposed */
	protected boolean supports_client_xslt = false;

	/** 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 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;

	/** a hash that contains all the active session IDs mapped to the cached items
*  It is updated whenever the whole site or a particular collection is reconfigured
*  using the command a=s&sa=c or a=s&sa=c&c=xxx
*  It is in the form: sid -> (UserSessionCache object)
*/
	protected Hashtable session_ids_table = new Hashtable();

	/** the maximum interval that the cached info remains in session_ids_table (in seconds) 
*  This is set in web.xml
*/
	protected int session_expiration = 1800;

	static Logger logger = Logger.getLogger(org.greenstone.gsdl3.LibraryServlet.class.getName());

	/** 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 interface_name = config.getInitParameter(GSConstants.INTERFACE_NAME);
		
		String allowXslt = (String)config.getInitParameter(GSConstants.ALLOW_CLIENT_SIDE_XSLT);
		supports_client_xslt = allowXslt != null && allowXslt.equals("true");
		
		this.default_lang = config.getInitParameter(GSConstants.DEFAULT_LANG);
		String sess_expire = config.getInitParameter(GSXML.SESSION_EXPIRATION);
		
		if (sess_expire != null && !sess_expire.equals("")) {
			this.session_expiration = Integer.parseInt(sess_expire);
		}
		
		if (library_name == null || interface_name ==null) {
			// must have this
			System.err.println("initialisation parameters not all set!");
			System.err.println(" you must have libraryname and interfacename");
			System.exit(1);
		}
		
		String site_name = config.getInitParameter(GSConstants.SITE_NAME);
		String remote_site_name = null;
		String remote_site_type = null;
		String remote_site_address = null;
		
		if (site_name == null) {
			// no site, try for communicator
			remote_site_name = config.getInitParameter("remote_site_name");
			remote_site_type = config.getInitParameter("remote_site_type");
			remote_site_address = config.getInitParameter("remote_site_address");
			if (remote_site_name == null || remote_site_type == null || remote_site_address == null) {
				System.err.println("initialisation paramters not all set!");
				System.err.println("if site_name is not set, then you must have remote_site_name, remote_site_type and remote_site_address set");
				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.INTERFACE_NAME, interface_name);	
		config_params.put(GSConstants.ALLOW_CLIENT_SIDE_XSLT, supports_client_xslt);
		
		if (site_name != null) {
			config_params.put(GSConstants.SITE_NAME, site_name);
		}
		this.converter = new XMLConverter();
		this.doc = this.converter.newDOM();
		
		// 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);
		
		// the receptionist uses a MessageRouter or Communicator to send its requests to. We either create a MessageRouter here for the designated site (if site_name set), or we create a Communicator for a remote site. The is given to teh Receptionist, and the servlet never talks to it again.directly.
		if (site_name != null) {
			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.setSiteName(site_name);
			message_router.setLibraryName(library_name);
			message_router.configure();
			this.recept.setMessageRouter(message_router);
		} else {
			// talking to a remote site, create a communicator
			Communicator communicator = null;
			// we need to create the XML to configure the communicator
			Element site_elem = this.doc.createElement(GSXML.SITE_ELEM);
			site_elem.setAttribute(GSXML.TYPE_ATT, remote_site_type);
			site_elem.setAttribute(GSXML.NAME_ATT, remote_site_name);
			site_elem.setAttribute(GSXML.ADDRESS_ATT, remote_site_address);
			
			if (remote_site_type.equals(GSXML.COMM_TYPE_SOAP_JAVA)) {
				communicator = new SOAPCommunicator();
			} else {
				System.err.println("LibraryServlet.init Error: invalid Communicator type: "+remote_site_type);
				System.exit(1);
			}
			
			if (!communicator.configure(site_elem)) {
				System.err.println("LibraryServlet.init Error: Couldn't configure communicator");
				System.exit(1);
			}
			this.recept.setMessageRouter(communicator);
		}
		
		// 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();
		
	}


	private void logUsageInfo(HttpServletRequest request){
		String usageInfo = "";
		
		//session-info: get params stored in the session
		HttpSession session = request.getSession(true);
		Enumeration attributeNames = session.getAttributeNames();
		while(attributeNames.hasMoreElements()) {
			String name = (String)attributeNames.nextElement();
			usageInfo +=name+"="+session.getAttribute(name)+" ";
		}
		
		//logged info = general-info + session-info
		usageInfo =
		request.getServletPath()+" "+ //serlvet
		"["+request.getQueryString()+"]" +" "+ //the query string
		"["+usageInfo.trim()+"]" +" "+ // params stored in a session
		request.getRemoteAddr()+" "+   //remote address
		request.getRequestedSessionId()+" "+ //session id
		request.getHeader("user-agent")+" "; //the remote brower info
		
		logger.info(usageInfo);
		
	}

	public class UserSessionCache implements HttpSessionBindingListener {

		String session_id = "";
		
		/** a hash that maps the session ID to a hashtable that maps the coll_name to its parameters 
	*  coll_name -> Hashtable (param_name -> param_value)
	*/
		protected Hashtable coll_name_params_table = null;
		
		public UserSessionCache(String id, Hashtable table) {
			session_id = id;      
			coll_name_params_table = (table == null)? new Hashtable() : table;      
		}

		protected void cleanupCache(String coll_name) {
			if (coll_name_params_table.containsKey(coll_name)) {
				coll_name_params_table.remove(coll_name);
			}
		}

		protected Hashtable getParamsTable() {
			return coll_name_params_table;
		}

		public void valueBound(HttpSessionBindingEvent event) {
			// Do nothing
		}

		public void valueUnbound(HttpSessionBindingEvent event) {
			if(session_ids_table.containsKey(session_id)) {
				session_ids_table.remove(session_id);
			}
		}

		public int tableSize() {
			return (coll_name_params_table == null)? 0 : coll_name_params_table.size();
		}

	}

	public void doGet (HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
		logUsageInfo (request);

		String query_string = request.getQueryString();
		if (query_string!=null){
			String[] query_arr = StringUtils.split(query_string, "&");
			boolean redirect = false;
			String href = null;
			String rl = null;
			String[] nameval = new String[2]; // Reuse it for memory efficiency purposes	

			for (int i=0;i<query_arr.length;i++){

				if (query_arr[i].startsWith("el=")){
					if (query_arr[i].substring(query_arr[i].indexOf("=")+1,query_arr[i].length()).equals("direct")){
						redirect = true;
					}
				}else if(query_arr[i].startsWith("href=")){
					href = query_arr[i].substring(query_arr[i].indexOf("=")+1,query_arr[i].length());
					href = StringUtils.replace(href, "%2f", "/");
					href = StringUtils.replace(href, "%7e", "~");
					href = StringUtils.replace(href, "%3f", "?");
					href = StringUtils.replace(href, "%3A", "\\:");
				}else if(query_arr[i].startsWith("rl=")){
					rl = query_arr[i].substring(query_arr[i].indexOf("=")+1,query_arr[i].length());
				}
			}

			//if query_string contains "el=", the web page will be redirected to the external URl, otherwise a greenstone page with an external URL will be displayed
			//"rl=0" this is an external link
			//"rl=1" this is an internal link
			if ((redirect) && (href != null) && (rl.equals("0"))){// This is an external link, the web page is re-directed to the external URL (&el=&rl=0&href="http://...")
				response.setContentType("text/xml");
				response.sendRedirect(href);
			}
		}
		
		// Nested Diagnostic Configurator to identify the client for
		HttpSession session = request.getSession (true);
		session.setMaxInactiveInterval(session_expiration);
		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
		}
		
		// If server output, force a switch to traditional interface
		//output = (output.equals("server")) ? "html" : output;
		
		// Force change the output mode if client-side XSLT is supported - server vs. client
		// BUT only if the library allows client-side transforms	
		if(supports_client_xslt) {
			// MUST be done before the xml_message is built
			Cookie[] cookies = request.getCookies();
			Cookie xsltCookie = null;
			
			// The client has cookies enabled and a value set - use it!
			if(cookies != null) {
				for(Cookie c : cookies) {
					if(c.getName().equals("supportsXSLT")) {
						xsltCookie = c;
						break;
					}
				}
				output = (xsltCookie != null && xsltCookie.getValue().equals("true") && output.equals("html")) ? "xsltclient" : output;
			}
		}
		
		// 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);
		String collection = request.getParameter(GSParams.COLLECTION);
		String service = request.getParameter(GSParams.SERVICE);

		// We clean up the cache session_ids_table if system
		// commands are issued (and also don't need to do caching for this request)
		boolean should_cache = true;
		if(action != null && action.equals(GSParams.SYSTEM)) {
			should_cache = false;

			// we may want to remove all collection cache info, or just a specific collection
			boolean clean_all = true; 
			String clean_collection = null;
			// system commands are to activate/deactivate stuff
			// collection param is in the sc parameter.
			// don't like the fact that it is hard coded here
			String coll = request.getParameter(GSParams.SYSTEM_CLUSTER);
			if (coll != null && !coll.equals("")) {
				clean_all = false;
				clean_collection = coll;
			} else {
				// check other system types
				if (subaction.equals("a") || subaction.equals("d")) {
					String module_name = request.getParameter("sn");
					if (module_name != null && !module_name.equals("")) {
						clean_all = false;
						clean_collection = module_name;
					}
				}
			}
			if (clean_all) {
				session_ids_table = new Hashtable(); 
				session.removeAttribute(GSXML.USER_SESSION_CACHE_ATT);
			} else {
				// just clean up info for clean_collection
				ArrayList cache_list = new ArrayList(session_ids_table.values());
				for (int i=0; i<cache_list.size(); i++) {
					UserSessionCache cache = (UserSessionCache)cache_list.get(i);
					cache.cleanupCache(clean_collection);
				}
				
			}

		}
		
		// cache_key is the collection name, or service name
		String cache_key = collection;
		if (cache_key == null || cache_key.equals("")) {
			cache_key = service;
		}
		
		// logger.info("should_cache= " + should_cache);

		//clear the collection-specific cache in the session, since we have no way to know whether this session is 
		//about the same collection as the last session or not.
		Enumeration attributeNames = session.getAttributeNames();
		while(attributeNames.hasMoreElements()) {
			String name = (String)attributeNames.nextElement();
			if (!name.equals (GSXML.USER_SESSION_CACHE_ATT)
					&& !name.equals (GSParams.LANGUAGE) 
					&& !name.equals (GSXML.USER_ID_ATT)) {

				session.removeAttribute(name);
			}
		}
		
		UserSessionCache session_cache = null;
		Hashtable param_table = null;    
		Hashtable table = null;
		String sid = session.getId();
		if (should_cache == true && cache_key != null && !cache_key.equals("")) {
			if (session_ids_table.containsKey(sid)) {
				session_cache = (UserSessionCache)session_ids_table.get(sid);
				param_table = session_cache.getParamsTable();
				logger.info("collections in table: " + tableToString(param_table));
				if (param_table.containsKey(cache_key)) {
					//logger.info("existing table: " + collection);
					table = (Hashtable)param_table.get(cache_key);
				} else {
					table = new Hashtable();
					param_table.put(cache_key, table);
					//logger.info("new table: " + collection);
				}
			} else {
				param_table = new Hashtable();
				table = new Hashtable();
				param_table.put(cache_key, table);
				session_cache = new UserSessionCache(sid, param_table);
				session_ids_table.put(sid, session_cache);
				session.setAttribute(GSXML.USER_SESSION_CACHE_ATT, session_cache);
				//logger.info("new session id");
			}
		}

		if (action==null || action.equals ("")) {
			// should we do all the following stuff if using default page?
			// display the home page  - the default page
			xml_request.setAttribute (GSXML.ACTION_ATT, "p");
			xml_request.setAttribute (GSXML.SUBACTION_ATT, PageAction.HOME_PAGE);
		}
		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) && table != null) {
						table.put(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 everything in the table into the session
			// do we need to do this? why not just put from table into param list
			if (table != null) {
				Enumeration keys = table.keys ();
				while(keys.hasMoreElements ()) {
					String name = (String)keys.nextElement();
					session.setAttribute(name, (String)table.get(name));
				}
			}
			
			// put in all the params from the session cache
			params = session.getAttributeNames ();
			while(params.hasMoreElements ()) {
				String name = (String)params.nextElement ();
				
				if ( !name.equals (GSXML.USER_SESSION_CACHE_ATT) 
						&& !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);
					String value =  GSXML.xmlSafe ((String)session.getAttribute (name));

					// ugly hack to undo : escaping
					value = StringUtils.replace(value, "%3A", "\\:");
					param.setAttribute (GSXML.VALUE_ATT,value);
					xml_param_list.appendChild (param);
				}
			}
		}
		
		if (!output.equals("html") && !output.equals("server") && !output.equals("xsltclient")) {
			response.setContentType ("text/xml"); // for now use text
		}
		
		//Add custom HTTP headers if requested
		Gson gson = new Gson();
		Type type = new TypeToken<List<Map<String,String>>>() {}.getType();
		List<Map<String,String>> httpHeaders = gson.fromJson(request.getParameter(GSParams.HTTPHEADERFIELDS), type);
		if (httpHeaders != null && httpHeaders.size() > 0) {
			
			for(int j = 0; j < httpHeaders.size(); j++)
			{
				Map nameValueMap = (Map)httpHeaders.get(j);
				String name = (String)nameValueMap.get("name");
				String value = (String)nameValueMap.get("value");
				
				if(name != null && value != null)
				{
					response.setHeader(name, value);
				}
			}
		}
		
		//GSXML.printXMLNode(xml_message);
		Node xml_result = this.recept.process(xml_message);
		encodeURLs (xml_result, response);
		out.println (this.converter.getPrettyString (xml_result));
		
		displaySize(session_ids_table);

	} //end of doGet(HttpServletRequest, HttpServletResponse)

	//a debugging method
	private void displaySize(Hashtable table) {
		if(table == null) {
			logger.info("cached table is null");
			return;
		}
		if (table.size() == 0) {
			logger.info("cached table size is zero");
			return;
		}
		int num_cached_coll = 0;
		ArrayList cache_list = new ArrayList(table.values());
		for (int i=0; i<cache_list.size(); i++) {
			num_cached_coll += ((UserSessionCache)cache_list.get(i)).tableSize();
		}
		logger.info("Number of sessions : total number of cached collection info = " + table.size() + " : " + num_cached_coll);
	}

	/** merely a debugging method! */
	private String tableToString(Hashtable table) {
		String str = "";
		Enumeration keys = table.keys ();
		while(keys.hasMoreElements ()) {
			String name = (String)keys.nextElement();
			str += name + ", ";
		}
		return str;
	}

	/** this goes through each URL and adds in a session id if needed--
* its needed if the browser doesn't accept cookies
* also escapes things if needed
*/
	protected void encodeURLs(Node dataNode, HttpServletResponse response) {
		
		if (dataNode == null) {
			return;
		}

		Element data =null;

		short nodeType = dataNode.getNodeType();
		if (nodeType == Node.DOCUMENT_NODE) {
			Document docNode = (Document)dataNode;
			data = docNode.getDocumentElement() ;
		}
		else {
			data = (Element)dataNode;
		}

		if ( data != null ) {

			// get all the <a> elements
			NodeList hrefs = data.getElementsByTagName("a");
			// Instead of calculating each iteration...
			int hrefscount = hrefs.getLength();

			for (int i=0; hrefs!=null && i < hrefscount; i++) {
				Element a = (Element)hrefs.item(i);
				// ugly hack to get rid of : in the args - interferes with session handling
				String href = a.getAttribute("href");
				if (!href.equals("")) {
					if (href.indexOf("?")!=-1) {
						String[] parts = StringUtils.split(href, "\\?", -1);
						if (parts.length == 1)
						{
							parts[0] = StringUtils.replace(parts[0], ":", "%3A");
							href = "?"+parts[0];
						}
						else
						{
							parts[1] = StringUtils.replace(parts[1], ":", "%3A");
							href = parts[0]+"?"+parts[1];
						}
						
					}
					a.setAttribute("href", response.encodeURL(href));
				}
			}
			
			// now find any submit bits - get all the <form> elements
			NodeList forms = data.getElementsByTagName("form");
			int formscount = forms.getLength();
			for (int i=0; forms!=null && i < formscount; 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;
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {

		doGet(request,response);
		
	}
}