/**
  * Image Loader for the HF Broadcast Receiver Demonstrator Applet
  * @author Robert J Morton
  * @version 12 Dec 2007 */

import java.awt.Component;     // Java Abstract Windowing Toolkit
import java.awt.MediaTracker;  // for the new-fangled 1.1 event handling
import java.awt.image.BufferedImage;
import javax.imageio.*;
import java.io.*;   // file input/output handling
import java.net.*;  // for downloading data from the remote server

public class imgldr {
  private hfbrx hf;  // instance reference to the hfbrx_swing applet
  private messagespanel sm;  // instance reference for message panel
  private MediaTracker tracker;  // to track when the images have been loaded
  private boolean 
    loadingImages = true,
    trackerError = false,  // true indicates that tracker encountered an error
    loadFTT = true,        // to avoid an erase and repaint of the loading of
    errorFTT = true;       // load-error message once per refresh cycle
  private int ls = 0;      // load switch: 0=local file, 1=jar, 2=server
  private String cb = "";  // URL path to image file
  private String[] S = {"local directory", "jar file", "remote server"};


  imgldr(hfbrx hf, messagespanel sm, int ls, String cb) {
    this.hf = hf;  // instance reference to the movmap applet
    this.sm = sm;  // instance of message panel
    this.ls = ls;  // load switch
    this.cb = cb;  // URL path to image file

    /* Create a media tracker and register images with it. Media tracker
    monitors the progress of loading process for each image files. */

    tracker = new MediaTracker(hf); 
    hfbrx.IMG1 = getImg("map.png");  // try to load the image file
    if(hfbrx.IMG1 != null)
      tracker.addImage(hfbrx.IMG1,0);
  }


  private BufferedImage getImg(String F) {
    BufferedImage I = null;
    try {
      switch(ls) {
        case 0:
          I = ImageIO.read(new File(F));
          break;
        case 1:
          I = ImageIO.read(getClass().getResourceAsStream(F));
          break;
        case 2:
          I = ImageIO.read(new URL(cb + F));
      }
    } catch (IOException e) {
      System.out.println("Couldn't load " + F + " from " + S[ls] + ".");
      System.out.println(e);
    }
    return I;
  }


  boolean awaitingImages() {
    if(tracker == null)
      return false;

    if(loadFTT) {  // if this is the first time through here
      sm.showMsg("Loading image from server...", false);
      loadFTT = false;  // avoid repeating display every cycle      
    }

    try {
      tracker.waitForAll();  // keep checking the tracker for a signal

      /* If the tracker does not say anything, return without
      servicing the app's run() thread, otherwise, will drop
      thru when tracker gives a completion signal. */

    } catch (InterruptedException e) {
      return true;
    }
    return false;
  }


  // Returns true when image loading has terminated.
  boolean imagesLoaded() {

    if(tracker == null)
      return true;

    /* If the image loading process still running,
    get the status of the image loading process. */

    if(loadingImages) {
      int ts = tracker.statusAll(false);

      /* if the loading process has completed with
      an error, set the image loading failure flag */

      if((ts & MediaTracker.ERRORED) != 0) {
        trackerError = true;

        /* If this is the first time through on this image loading
        attempt, show the error message and set the error display
        flag false to avoid re-displaying the message each pass. */

        if(errorFTT) {
          sm.showMsg("Error: couldn't load image.", true);
          errorFTT = false;
        }
      }

      /* if tracker has completed its task, set flag to indi-
      cate that image loading has terminated successfully. */

      if(ts == MediaTracker.COMPLETE)
        loadingImages = false;
    }

    /* else, image the loading process has just finished,
    so dispense with this instance of the Media Tracker
    and refresh message display if not already done. */

    else {
      killTracker();
      sm.showMsg("Image Loaded.", false);
    }
    return false;
  }


  /* If this instance of the Media Tracker still
  exists, remove (de-register) the image from the
  tracker then destroy (garbage) the tracker. */

  void killTracker() {
    if(tracker != null) {
      tracker.removeImage(hfbrx.IMG1,0);
      tracker = null;
    }
  }

   boolean TrackerError() {return trackerError;}
}