/**
  * Image Loader for the Moving Map Navigator 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 static imgldr il;
  private bs hf;                 // instance reference to the bs applet
  private msgpanel mp;           // instance reference for message panel
  private MediaTracker tracker;  // to track when the images have been loaded
  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"};
  private boolean 
    loadingImages = true,  // starts loading as soon as constructed
    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


  imgldr(bs hf, msgpanel mp, int ls, String cb) {
    this.hf = hf;  // instance reference to the bs applet
    this.mp = mp;  // 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); 
    bs.IMG1 = getImg("map1.png");  // try to load the image file
    if(bs.IMG1 != null)
      tracker.addImage(bs.IMG1,0);
    bs.IMG2 = getImg("map2.png");  // try to load the image file
    if(bs.IMG2 != null)
      tracker.addImage(bs.IMG1,0);
    bs.IMG3 = getImg("map3.png");  // try to load the image file
    if(bs.IMG3 != null)
      tracker.addImage(bs.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
      mp.showMsg("Loading images...", 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
    through when tracker gives a completion signal. */

    catch (InterruptedException e) {
      return true;  // image loading not yet finished
    }
    return false;   // tracker says that images are loaded
  }


  // 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) {
          mp.showMsg("Error: couldn't load images.", true);
          errorFTT = false;
        }
      }
      /* if tracker has completed its task, set flag to set to
      indicate 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();
      mp.showMsg("Images Loaded.", false);
    }
    return false;
  }


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

  void killTracker() {
    if(tracker != null) {
      tracker.removeImage(bs.IMG1, 0);
      tracker.removeImage(bs.IMG2, 0);
      tracker.removeImage(bs.IMG3, 0);
      tracker = null;
    }
  }

  boolean TrackerError() {return trackerError;}
}