nathansmith / adapt

/*
  Adapt.js licensed under GPL and MIT.

  Read more here: http://adapt.960.gs
*/

// Closure.
(function(w, d, config, undefined) {
  // If no config, exit.
  if (!config) {
    return;
  }

  // Empty vars to use later.
  var url, url_old, timer;

  // Alias config values.
  var callback = typeof config.callback === 'function' ? config.callback : undefined;
  var path = config.path ? config.path : '';
  var range = config.range;
  var range_len = range.length;

  // Create empty link tag:
  // <link rel="stylesheet" />
  var css = d.createElement('link');
  css.rel = 'stylesheet';

  // Called from within adapt().
  function change(i, width) {
    // Set the URL.
    css.href = url;
    url_old = url;

    // Call callback, if defined.
    callback && callback(i, width);
  }

  // Adapt to width.
  function adapt() {
    // This clearTimeout is for IE.
    // Really it belongs in react(),
    // but doesn't do any harm here.
    clearTimeout(timer);

    // Parse browser width.
    var width = w.innerWidth || d.documentElement.clientWidth || d.body.clientWidth || 0;

    // While loop vars.
    var arr, arr_0, val_1, val_2, is_range, file;

    // How many ranges?
    var i = range_len;
    var last = range_len - 1;

    while (i--) {
      // Turn string into array.
      arr = range[i].split('=');

      // Width is to the left of "=".
      arr_0 = arr[0];

      // File name is to the right of "=".
      // Presuppoes a file with no spaces.
      // If no file specified, assign [i].
      file = arr[1] ? arr[1].replace(/\s/g, '') : i;

      // Assume min/max if "to" isn't present.
      is_range = arr_0.match('to');

      // If it's a range, split left/right sides of "to",
      // and then convert each one into numerical values.
      // If it's not a range, turn maximum into a number.
      val_1 = is_range ? parseInt(arr_0.split('to')[0], 10) : parseInt(arr_0, 10);
      val_2 = is_range ? parseInt(arr_0.split('to')[1], 10) : undefined;

      // Check for maxiumum or range.
      if ((!val_2 && i === last && width > val_1) || (width > val_1 && width <= val_2)) {
        // Built full URL to CSS file.
        url = path + file;
        break;
      }
      else {
        // Blank if no conditions met.
        url = '';
      }
    }

    // Was it created yet?
    if (!url_old) {
      // Apply changes.
      change(i, width);

      // Add the CSS, only if path is defined.
      // Use faster document.head if possible.
      path && (d.head || d.getElementsByTagName('head')[0]).appendChild(css);
    }
    else if (url_old !== url) {
      // Apply changes.
      change(i, width);
    }
  }

  // Fire off once.
  adapt();

  // Slight delay.
  function react() {
    // Clear the timer as window resize fires,
    // so that it only calls adapt() when the
    // user has finished resizing the window.
    clearTimeout(timer);
    timer = setTimeout(adapt, 100);
  }

  // Do we want to watch for
  // resize and device tilt?
  if (config.dynamic) {
    // Event listener for window resize,
    // also triggered by phone rotation.
    if (w.addEventListener) {
      // Good browsers.
      w.addEventListener('resize', react, false);
    }
    else if (w.attachEvent) {
      // Legacy IE support.
      w.attachEvent('onresize', react);
    }
    else {
      // Old-school fallback.
      w.onresize = react;
    }
  }

// Pass in window, document, config, undefined.
})(this, this.document, ADAPT_CONFIG);