/* Written by Erik Krause, 2006.  http://www.drivenbycuriosity.com/mywp
 *  Free for use in a good home.  
*/

import com.google.gwt.user.client.HTTPRequest;
import com.google.gwt.user.client.ResponseTextHandler;
import java.util.Vector;
import java.util.List;

public class ServerComm implements ResponseTextHandler {
/* handles basic I/O with server
 * @gwt.typeArgs waitingReqs <com.erik.nextcodes.client.ServerData>
 * @gwt.typeArgs workingReqs <com.erik.nextcodes.client.ServerData> 
 */
  private final static ServerComm instance = new ServerComm();
  private final static String url = "http://www.drivenbycuriosity.com/sample_files/ServerComm.php";
  private static List waitingReqs = new Vector();  // objects wanting data from the server
  private static List workingReqs = new Vector();  // objects waiting for server response 
  private static String waitingPost = "";            // data sent from an object to the server
  
  public interface ServerData {
	  public String getTitle();           
	  public void serverDataHandler(String[] s);
  }
  
  private ServerComm() {
    // weak version of a singleton that should be ok in a javascript environment
  }
  
  public static void requestUpdate(ServerData sd) {
    // add requester to waiting list
    waitingReqs.add(sd);

    // start a request if we aren't waiting for a response
    if (!pendingRequest()) {
      doRequest();
    }
  }
  
  public static void requestUpdate(ServerData sd, String data) {
    // add string to waiting post data
    if (waitingPost.length() > 0) {
      waitingPost = waitingPost + "&";
    }
    // note the following does no encoding of data whatsoever.  extra ampersands will cause
    // problems and arbitrary data may have issues.
    waitingPost = waitingPost + "sender[]=" + sd.getTitle() + "&data[]=" + data;
    
    requestUpdate(sd); 
  }
  
  private static boolean pendingRequest() {
    return (workingReqs.size()!=0);  // have a request waiting if 
  }
  
  private static void doRequest() {
    String addlPost = "";
    
    // combine all requesters into a single post as they go from waiting to working 
    for (int i=0; i<waitingReqs.size(); i++) {
      addlPost += "&refresh[]="+((ServerData) waitingReqs.get(i)).getTitle();
    }
    
    if (waitingPost.length() == 0) {
      waitingPost = addlPost.substring(1);
    } else {
      waitingPost += addlPost;
    }
    
    if (HTTPRequest.asyncPost(url, waitingPost, instance)) {
      // move waiting to working, get ready for more data requests
      workingReqs.addAll(waitingReqs);
      waitingReqs.clear();
      waitingPost = "";
    } else {
      // notify of problem
    }
  }

  /*
   * @gwt.typeArgs title <java.util.String>
   * @gwt.typeArgs data <java.util.String>
   */
  public void onCompletion(String rt) {
    String[] response = rt.replaceAll("\r", "").split("\n");
    List title = new Vector(); //[response.length];
    List data = new Vector(); //String[response.length];

    for (int i=0; i<response.length; i++) {
      int firstcomma = (response[i]).indexOf(",");
      if (firstcomma < 0) {
        title.add(response[i]);  // didn't find comma, assume no data returned for some reason
        data.add("");            // data with no requester doesn't make sense... no data for a request is fine
      } else {
        title.add((response[i]).substring(0,firstcomma));  // requesting title
        data.add((response[i]).substring(firstcomma+1));     // corresponding data
      }
    }
    
    for (int i=0; i<workingReqs.size(); i++) {
      ServerData sd = ((ServerData) workingReqs.get(i));
      int index = title.indexOf(sd.getTitle());
      if (index != -1) {
        sd.serverDataHandler( ((String) data.get(index)).split(":&:") );
      } else {
        // hmm... didn't get any returned data for some requester 
      }
    }
    workingReqs.clear();
    title.clear();
    data.clear();
    
    if (waitingReqs.size()>0) {
      /* deferred command might be better, although it doesn't work under win2k 
       * currently because of the timer problem.
       */
//      DeferredCommand.add(new Command() {
//        public void execute() {
          ServerComm.doRequest(); 
//        }
//      });
    }
  }
}