/*
 * jQuery Backstretch 1.0
 * http://srobbin.com/jquery-plugins/jquery-backstretch/
 *
 * Add a dynamically-resized background image to the page
 *
 * Copyright (c) 2009 Scott Robbin (srobbin.com)
 * Dual licensed under the MIT and GPL licenses.
*/

(function($) {

  $.backstretch = function(src, options, callback) {
    
    //inner functions
    function _autoSlide(first) {
        if (!first || first !== true) {
            _nextSlide();
        }
        slideHandle = setTimeout(_autoSlide, settings.slideDelay);
    }
    
    function _nextSlide() {
        index = (index + 1) % settings.images.length;
        $.backstretchNumber(index, true);
    }
    
    function _updateImg(src) {
        var cur = $('#backstretch-wrap');
        var nxt = cur.clone();
        cur.attr('id', 'backstretch-wrap-old');
        cur.find('div').attr('id', 'backstretch-old');
        nxt.find('img').attr('src', src);
        $('body').prepend(nxt);
        cur.find('img').fadeOut(1000, function() {cur.remove();});
    }
    
    function _init() {
      // Prepend image, wrapped in a DIV, with some positioning and zIndex voodoo
      if(src) {
        var commonCSS = {left: 0, top: 0},
            wrap = $("<div />").attr("id", "backstretch-wrap")
                               .css( $.extend(commonCSS, {position: "absolute", zIndex: -1}) ),
            container = $("<div />").attr("id", "backstretch")
                                    .css( $.extend(commonCSS, {position: "fixed", overflow: "hidden", zIndex: -1}) )
                                    .appendTo(wrap),
            img = $("<img />").attr("src", src)
                              .bind("load", function() {
                                    var self = $(this);
                                    imgRatio = self.width() / self.height();
                                    _adjustBG(function() {
                                      if( settings.hideUntilReady ) {
                                        self.fadeIn(settings.speed, function(){
                                          // Callback, if necessary
                                          if(typeof callback == "function") {
                                            callback();
                                          }
                                        });
                                      }
                                    });
                                  });
        
        if(settings.hideUntilReady) {
            img.hide();
        }
        img.appendTo(container);
          
        $("body").prepend(wrap);

        // Adjust the background size when the window is resized
        $(window).resize(_adjustBG);
      }
      
    }
    
    function _adjustBG(callback) {
      var bgWidth = $(window).width(),
          bgHeight = bgWidth / imgRatio;

      if(bgHeight < $(window).height()) {
        bgHeight = $(window).height();
        bgWidth = bgHeight * imgRatio;
      }

      $("#backstretch img").width( bgWidth ).height( bgHeight );
      
      if (typeof callback == "function") {
        callback();
      }
    }
    
    var settings = {
          hideUntilReady: true, // Hide the image until it's finished loading
          speed: 0, // fadeIn speed for background after image loads (e.g. "fast" or 500)
          slideDelay: 3000,
          callback: function() {}
        },
        imgRatio;
    
    // Extend the settings with those the user has provided
    if(options && typeof options == "object") {
        $.extend(settings, options);
    }
    
    // Initialize
    $(document).ready(_init);
    
    if (typeof src == 'object') {
        settings.images = src;
        src = src[0];
    } else {
        settings.images = [src];
    }
    
    $.backstretchNumber = function(num, keepAutoslide) {
        if (!keepAutoslide) {
            clearTimeout(slideHandle);
        }
        index = num;
        settings.callback(index);
        var nxtimg = settings.images[num];
       _updateImg(nxtimg);
    };
    
    var index = 0;
    var slideHandle;
    if (settings.images.length > 1) {
        _autoSlide(true);
    }
    
    // For chaining
    return this;
    
  };
  
})(jQuery);