// There are two objects defined in this file:
// "slide" - contains all the information for a single slide
// "slideshow" - consists of multiple slide objects and runs the slideshow

//==================================================
// slide object
//==================================================
function slide(src,text) {
  // This is the constructor function for the slide object.
  // It is called automatically when you create a new slide object.
  // For example:
  // s = new slide();

  // 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 slideshow( slideshowname ) {
  // This is the constructor function for the slideshow object.
  // It is called automatically when you create a new object.
  // For example:
  // ss = new slideshow("ss");

  
  // When we reach the last slide, should we loop around to start the
  // slideshow again?
  this.repeat = true;

  // Number of images to pre-fetch.
  // -1 = preload all images.
  this.prefetch = -1;

  // IMAGE element on your HTML page.
  // For example, document.images.SLIDES1IMG
  this.image;

  // ID of a DIV element on your HTML page that will contain the text.
  // For example, "slides2text"
  // Note: after you set this variable, you should call
  // the update() method to update the slideshow display.
  this.textid;
  this.countid;

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

  //--------------------------------------------------
  // Public methods
  //--------------------------------------------------
 this.add_slide = function(slide) {
    // Add a slide to the slideshow.
    // For example:
    // SLIDES1.add_slide(new slide("s1.jpg", "link.html"))
  
    var i = this.slides.length;
  
    // Prefetch the slide image if necessary
    if (this.prefetch == -1) {
      slide.load();
    }

    this.slides[i] = slide;
  }

  //--------------------------------------------------
  this.update = function() {
    // This method updates the slideshow image on the page

    // Make sure the slideshow has been initialized correctly
    if (! this.valid_image()) { return; }
  
    // Convenience variable for the current slide
    var slide = this.slides[ this.current ];

    // Load the slide image if necessary
    slide.load();
  
    // Update the image.
    this.image.src = slide.image.src;

    // Update the text
    this.display_text();
	
	// Update the image count
	this.display_count();

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

  //--------------------------------------------------
  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.display_text = function(text) {
    // Display the text for the current slide
  
    // If the "text" arg was not supplied (usually it isn't),
    // 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;
    }
  }
  
  //--------------------------------------------------
  this.display_count = function() {
	// Get the text to display
	count = "Slide " + (this.current + 1) + " of " + this.slides.length;
	
	// If a count id has been specified,
    // then change the contents of the HTML element
    if (this.countid) {

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

      // Update the text
      r.innerHTML = count;
    }
  }
  
  //==================================================
  // Private methods
  //==================================================

  //--------------------------------------------------
  this.loop = function() {
    // This method is for internal use only.
    // This method gets called automatically by a JavaScript timeout.
    // It advances to the next slide, then sets the next timeout.
    // If the next slide image has not completed loading yet,
    // then do not advance to the next slide yet.

    // 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;
    }
  }
}