/*==================================================*
 $Id: slideshow.js,v 1.7 2003/05/25 16:00:09 pat Exp pat $
 Copyright 2000-2003 Patrick Fitzgerald
 http://slideshow.barelyfitz.com/

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *==================================================*/

// 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,link,text,target,attr) {
// 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;

  // Link URL
  this.link = link;

  // Text to display
  this.text = text;

  // Name of the target window ("_blank")
  this.target = target;

  // Attributes for the target window:
  // width=n,height=n,resizable=yes or no,scrollbars=yes or no,
  // toolbar=yes or no,location=yes or no,directories=yes or no,
  // status=yes or no,menubar=yes or no,copyhistory=yes or no
  // Example: "width=200,height=300"
  this.attr = attr;

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

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

    if (!document.images) { return; }

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

  //--------------------------------------------------
  this.hotlink = function() {
  // This function jumps to the slide's link.
  // If a window was specified for the slide, then it opens a new window.

    if (this.target) {

      // If window attributes are specified, use them to open the new window
      if (this.attr) {
        window.open(this.link, this.target, this.attr);
  
      } else {
        // If window attributes are not specified, do not use them
        // (this will copy the attributes from the originating window)
        window.open(this.link, this.target);
      }

    } else {
      // Open the hotlink in the current window
      location.href = this.link;
    }
  }
}

//==================================================
// 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");

  // Name of this object
  // (required if you want your slideshow to auto-play)
  // For example, "SLIDES1"
  this.name = slideshowname;

  // 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.
  //  0 = load each image is it is used.
  //  n = pre-fetch n images ahead of the current image.
  // I recommend preloading all images unless you have large
  // images, or a large amount of 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;

  // TEXTAREA element on your HTML page.
  // For example, document.SLIDES1FORM.SLIDES1TEXT
  // This is a depracated method for displaying the text.
  this.textarea;

   // Milliseconds to pause between slides
  this.timeout = 3000;

  // 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"))
  
    // If this version of JavaScript does not allow us to
    // change images, then we can't do the slideshow.
    if (!document.images) { return; }
  
    var i = this.slides.length;
  
    // Prefetch the slide image if necessary
    if (this.prefetch == -1) {
      slide.load();
    }

    this.slides[i] = slide;
  }

  //--------------------------------------------------
  this.play = function(timeout) {
  // This function implements the automatically running slideshow.
  
    // Make sure we're not already playing
    this.pause();
  
    // If a new timeout was specified (optional)
    // set it here
    if (timeout) {
      this.timeout = timeout;
    }
  
    // After the timeout, call this.loop()
    this.timeoutid = setTimeout( this.name + ".loop()", this.timeout);
  }

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

  //--------------------------------------------------
  this.update = function() {
  // This function updates the slideshow image on the page
  
    // Make sure the slideshow has been initialized correctly
    if (! this.valid_image()) { return; }
  
    // Load the slide image if necessary
    this.slides[ this.current ].load();
  
    // Update the image.
    this.image.src = this.slides[ this.current ].image.src;
  
    // Update the text
    this.display_text();

    // Pre-fetch the next slide image(s) if necessary
    if (this.prefetch > 0) {
      for (i = this.current + 1;
           i <= (this.current + this.prefetch) && i < this.slides.length;
           i++) {
        this.slides[i].load();
      }
    }
  }

  //--------------------------------------------------
  this.goto_slide = function(n) {
  // This function jumpts to the slide number you specify.
  // If you use slide number -1, then it jumps to the last slide.
  // You can use this to make links that go to a specific slide,
  // or to go to the beginning or end of the slideshow.
  // Examples:
  // onClick="myslides.goto_slide(0)"
  // onClick="myslides.goto_slide(-1)"
  // onClick="myslides.goto_slide(5)"
  
    if (n == -1) {
      n = this.slides.length - 1;
    }
  
    if (n < this.slides.length && n >= 0) {
      this.current = n;
    }
  
    this.update();
  }

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

  //--------------------------------------------------
  this.get_all_text = function(before_slide, after_slide) {
  // Return the text for all of the slides.
  // For the text of each slide, add "before_slide" in front of the
  // text, and "after_slide" after the text.
  // For example:
  // document.write("<ul>");
  // document.write(s.get_all_text("<li>","\n"));
  // document.write("<\/ul>");
  
    all_text = "";
  
    // Loop through all the slides in the slideshow
    for (i=0; i < this.slides.length; i++) {
  
      slide = this.slides[i];
    
      if (slide.text) {
        all_text += before_slide + slide.text + after_slide;
      }
  
    }
  
    return(all_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 textarea has been specified,
    // then change the text displayed in it
    if (this.textarea) {
      this.textarea.value = text;
    }
  
    // If a text id has been specified,
    // then change the contents of the HTML element
    if (this.textid) {
      // Make sure we don't cause an error
      // for browsers that do not support getElementById
      if (!document.getElementById){ return false; }
  
      r = document.getElementById(this.textid);
      if (!r){ return false; }
      r.innerHTML = text;
    }
  }

  //--------------------------------------------------
  this.hotlink = function() {
  // This function calls the hotlink() method for the current slide.
  
    this.slides[ this.current ].hotlink();
  }

  //--------------------------------------------------
  this.save_position = function(cookiename) {
  // Saves the position of the slideshow in a cookie,
  // so when you return to this page, the position in the slideshow
  // won't be lost.
  
    if (!cookiename) {
      cookiename = this.name + '_slideshow';
    }
  
    document.cookie = cookiename + '=' + this.current;
  }

  //--------------------------------------------------
  this.restore_position = function(cookiename) {
  // If you previously called slideshow_save_position(),
  // returns the slideshow to the previous state.
  
    //Get cookie code by Shelley Powers
  
    if (!cookiename) {
      cookiename = this.name + '_slideshow';
    }
  
    var search = cookiename + "=";
  
    if (document.cookie.length > 0) {
      offset = document.cookie.indexOf(search);
      // if cookie exists
      if (offset != -1) { 
        offset += search.length;
        // set index of beginning of value
        end = document.cookie.indexOf(";", offset);
        // set index of end of cookie value
        if (end == -1) end = document.cookie.length;
        this.current = parseInt(unescape(document.cookie.substring(offset, end)));
        }
     }
  }

  //--------------------------------------------------
  this.noscript = function() {
  // This function is not for use as part of your slideshow,
  // but you can call it to get a plain HTML version of the slideshow
  // images and text.
  // You should copy the HTML and put it within a NOSCRIPT element, to
  // give non-javascript browsers access to your slideshow information.
  // This also ensures that your slideshow text and images are indexed
  // by search engines.
  
    $html = "\n";
  
    // Loop through all the slides in the slideshow
    for (i=0; i < this.slides.length; i++) {
  
      slide = this.slides[i];
  
      $html += '<P>';
  
      if (slide.link) {
        $html += '<a href="' + slide.link + '">';
      }
  
      $html += '<img src="' + slide.src + '" ALT="slideshow image">';
  
      if (slide.link) {
        $html += "<\/a>";
      }
  
      if (slide.text) {
        $html += "<BR>\n" + slide.text;
      }
  
      $html += "<\/P>" + "\n\n";
    }
  
    // Make the HTML browser-safe
    $html = $html.replace(/\&/g, "&amp;" );
    $html = $html.replace(/</g, "&lt;" );
    $html = $html.replace(/>/g, "&gt;" );
  
    return('<pre>' + $html + '</pre>');
  }

  //--------------------------------------------------  
  // Private methods
  //--------------------------------------------------
  this.loop = function() {
  // This function is for internal use only.
  // This function 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)
    {
      // Stop the slideshow
      this.pause;
  
      // Display an error message
      window.status = "Error: slideshow image not initialized for " + this.name;
          
      return 0;
    }
    else {
      return 1;
    }
  }

  //--------------------------------------------------  
  // Deprecated methods
  // I don't recommend the use of the following methods,
  // but they are included for backward compatibility.
  // You can delete them if you don't need them.
  //--------------------------------------------------

  //--------------------------------------------------
  this.set_image = function(imageobject) {
  // This function is deprecated; you should use
  // the following code instead:
  // s.image = document.images.myimagename;
  // s.update();
    if (!document.images)
      return;
    this.image = imageobject;
  }

  //--------------------------------------------------
  this.set_textarea = function(textareaobject) {
  // This function is deprecated; you should use
  // the following code instead:
  // s.textarea = document.form.textareaname;
  // s.update();
    this.textarea = textareaobject;
    this.display_text();
  }

  //--------------------------------------------------
  this.set_textid = function(textidstr) {
  // This function is deprecated; you should use
  // the following code instead:
  // s.textid = "mytextid";
  // s.update();
    this.textid = textidstr;
    this.display_text();
  }
}