//==================================================
// slide object
//==================================================
function tslide(src,text) {

  // Image URL
  this.src = src;
  
  // Text to display
  this.text = text;

  // Create an image object for the slide
  if (document.images) {
    this.image = new Image();
  }

  // Flag to tell when load() has already been called
  this.loaded = false;

  //--------------------------------------------------
  this.load = function() {
    // This method loads the image for the slide

    if (!document.images) { return; }

    if (!this.loaded) {
      this.image.src = this.src;
      this.loaded = true;
    }
  }
}

//==================================================
// slideshow object
//==================================================
function tslideshow( slideshowname ) {

  // Name of this object
  this.name = slideshowname;

  this.repeat = true;

  this.prefetch = -1;

  this.image;

  this.textid;

  this.timeout = 3000;

  // These are private variables
  this.slides = new Array();
  this.current = 0;
  this.timeoutid = 0;

  //--------------------------------------------------
  // Public methods
  //--------------------------------------------------
  this.add_slide = function(tslide) {
  
    var i = this.slides.length;
  
    // Prefetch the slide image if necessary
    if (this.prefetch == -1) {
      tslide.load();
    }

    this.slides[i] = tslide;
  }

  //--------------------------------------------------
  this.play = function(timeout) {
  
    // Make sure we're not already playing
    this.pause();
  
    // If the timeout argument was specified (optional)
    // then make it the new default
    if (timeout) {
      this.timeout = timeout;
    }
  
    // If the current slide has a custom timeout, use it;
    // otherwise use the default timeout
    if (typeof this.slides[ this.current ].timeout != 'undefined') {
      timeout = this.slides[ this.current ].timeout;
    } else {
      timeout = this.timeout;
    }

    // After the timeout, call this.loop()
    this.timeoutid = setTimeout( this.name + ".loop()", timeout);
  }

  //--------------------------------------------------
  this.pause = function() {
    // This method stops the slideshow if it is automatically running.
  
    if (this.timeoutid != 0) {

      clearTimeout(this.timeoutid);
      this.timeoutid = 0;

    }
  }

  //--------------------------------------------------
  this.update = function() {

    // Make sure the slideshow has been initialized correctly
    if (! this.valid_image()) { return; }
  
    // Call the pre-update hook function if one was specified
    if (typeof this.pre_update_hook == 'function') {
      this.pre_update_hook();
    }

    // Convenience variable for the current slide
    var tslide = this.slides[ this.current ];

    // Determine if the browser supports filters
    var dofilter = false;
    if (this.image &&
        typeof this.image.filters != 'undefined' &&
        typeof this.image.filters[0] != 'undefined') {

      dofilter = true;

    }

    // Load the slide image if necessary
    tslide.load();
  
    // Apply the filters for the image transition
    if (dofilter) {

      // If the user has specified a custom filter for this slide,
      // then set it now
      if (tslide.filter &&
          this.image.style &&
          this.image.style.filter) {

        this.image.style.filter = tslide.filter;

      }
      this.image.filters[0].Apply();
    }

    // Update the image.
    this.image.src = tslide.image.src;

    // Play the image transition filters
    if (dofilter) {
      this.image.filters[0].Play();
    }

    // Update the text
    this.display_text();

    // Call the post-update hook function if one was specified
    if (typeof this.post_update_hook == 'function') {
      this.post_update_hook();
    }

    // Do we need to pre-fetch images?
    if (this.prefetch > 0) {

      var next, prev, count;

      // Pre-fetch the next slide image(s)
      next = this.current;
      prev = this.current;
      count = 0;
      do {

        // Get the next and previous slide number
        // Loop past the ends of the slideshow if necessary
        if (++next >= this.slides.length) next = 0;
        if (--prev < 0) prev = this.slides.length - 1;

        // Preload the slide image
        this.slides[next].load();
        this.slides[prev].load();

        // Keep going until we have fetched
        // the designated number of slides

      } while (++count < this.prefetch);
    }
  }


  //--------------------------------------------------
  this.next = function() {
    // This method advances to the next slide.

    // Increment the image number
    if (this.current < this.slides.length - 1) {
      this.current++;
    } else if (this.repeat) {
      this.current = 0;
    }

    this.update();
  }


  //--------------------------------------------------
  this.previous = function() {
    // This method goes to the previous slide.
  
    // Decrement the image number
    if (this.current > 0) {
      this.current--;
    } else if (this.repeat) {
      this.current = this.slides.length - 1;
    }
  
    this.update();
  }


  //--------------------------------------------------
  this.get_text = function() {
    // This method returns the text of the current slide
  
    return(this.slides[ this.current ].text);
  }


  //--------------------------------------------------
  this.get_all_text = function(before_slide, after_slide) {
  
    all_text = "";
  
    // Loop through all the slides in the slideshow
    for (i=0; i < this.slides.length; i++) {
  
      tslide = this.slides[i];
    
      if (tslide.text) {
        all_text += before_slide + tslide.text + after_slide;
      }
  
    }
  
    return(all_text);
  }


  //--------------------------------------------------
  this.display_text = function(text) {
  
    // get the text from the slideshow
    if (!text) {
      text = this.slides[ this.current ].text;
    }

    // If a text id has been specified,
    // then change the contents of the HTML element
    if (this.textid) {

      r = this.getElementById(this.textid);
      if (!r) { return false; }
      if (typeof r.innerHTML == 'undefined') { return false; }

      // Update the text
      r.innerHTML = text;
    }
  }

  //==================================================
  // Private methods
  //==================================================

  //--------------------------------------------------
  this.loop = function() {

    // Make sure the next slide image has finished loading
    if (this.current < this.slides.length - 1) {
      next_slide = this.slides[this.current + 1];
      if (next_slide.image.complete == null || next_slide.image.complete) {
        this.next();
      }
    } else { // we're at the last slide
      this.next();
    }
    
    // Keep playing the slideshow
    this.play( );
  }


  //--------------------------------------------------
  this.valid_image = function() {
    // Returns 1 if a valid image has been set for the slideshow
  
    if (!this.image)
    {
      return false;
    }
    else {
      return true;
    }
  }

  //--------------------------------------------------
  this.getElementById = function(element_id) {
    // This method returns the element corresponding to the id

    if (document.getElementById) {
      return document.getElementById(element_id);
    }
    else if (document.all) {
      return document.all[element_id];
    }
    else if (document.layers) {
      return document.layers[element_id];
    } else {
      return undefined;
    }
  }
  
}