define(function() {
//>>excludeStart('excludeRequireCss', pragmas.excludeRequireCss)
  if (typeof window == 'undefined')
    return { load: function(n, r, load){ load() } };

  var head = document.getElementsByTagName('head')[0];

  var engine = window.navigator.userAgent.match(/Trident\/([^ ;]*)|AppleWebKit\/([^ ;]*)|Opera\/([^ ;]*)|rv\:([^ ;]*)(.*?)Gecko\/([^ ;]*)|MSIE\s([^ ;]*)|AndroidWebKit\/([^ ;]*)/) || 0;

  // use <style> @import load method (IE < 9, Firefox < 18)
  var useImportLoad = false;
  
  // set to false for explicit <link> load checking when onload doesn't work perfectly (webkit)
  var useOnload = true;

  // trident / msie
  if (engine[1] || engine[7])
    useImportLoad = parseInt(engine[1]) < 6 || parseInt(engine[7]) <= 9;
  // webkit
  else if (engine[2] || engine[8])
    useOnload = false;
  // gecko
  else if (engine[4])
    useImportLoad = parseInt(engine[4]) < 18;

//>>excludeEnd('excludeRequireCss')
  //main api object
  var cssAPI = {};

//>>excludeStart('excludeRequireCss', pragmas.excludeRequireCss)
  cssAPI.pluginBuilder = './css-builder';

  // <style> @import load method
  var curStyle, curSheet;
  var createStyle = function () {
    curStyle = document.createElement('style');
    head.appendChild(curStyle);
    curSheet = curStyle.styleSheet || curStyle.sheet;
  }
  var ieCnt = 0;
  var ieLoads = [];
  var ieCurCallback;
  
  var createIeLoad = function(url) {
    curSheet.addImport(url);
    curStyle.onload = function(){ processIeLoad() };
    
    ieCnt++;
    if (ieCnt == 31) {
      createStyle();
      ieCnt = 0;
    }
  }
  var processIeLoad = function() {
    ieCurCallback();
 
    var nextLoad = ieLoads.shift();
 
    if (!nextLoad) {
      ieCurCallback = null;
      return;
    }
 
    ieCurCallback = nextLoad[1];
    createIeLoad(nextLoad[0]);
  }
  var importLoad = function(url, callback) {
    if (!curSheet || !curSheet.addImport)
      createStyle();

    if (curSheet && curSheet.addImport) {
      // old IE
      if (ieCurCallback) {
        ieLoads.push([url, callback]);
      }
      else {
        createIeLoad(url);
        ieCurCallback = callback;
      }
    }
    else {
      // old Firefox
      curStyle.textContent = '@import "' + url + '";';

      var loadInterval = setInterval(function() {
        try {
          curStyle.sheet.cssRules;
          clearInterval(loadInterval);
          callback();
        } catch(e) {}
      }, 10);
    }
  }

  // <link> load method
  var linkLoad = function(url, callback) {
    var link = document.createElement('link');
    link.type = 'text/css';
    link.rel = 'stylesheet';
    if (useOnload)
      link.onload = function() {
        link.onload = function() {};
        // for style dimensions queries, a short delay can still be necessary
        setTimeout(callback, 7);
      }
    else
      var loadInterval = setInterval(function() {
        for (var i = 0; i < document.styleSheets.length; i++) {
          var sheet = document.styleSheets[i];
          if (sheet.href == link.href) {
            clearInterval(loadInterval);
            return callback();
          }
        }
      }, 10);
    link.href = url;
    head.appendChild(link);
  }

//>>excludeEnd('excludeRequireCss')
  cssAPI.normalize = function(name, normalize) {
    if (name.substr(name.length - 4, 4) == '.css')
      name = name.substr(0, name.length - 4);

    return normalize(name);
  }

//>>excludeStart('excludeRequireCss', pragmas.excludeRequireCss)
  cssAPI.load = function(cssId, req, load, config) {

    (useImportLoad ? importLoad : linkLoad)(req.toUrl(cssId + '.css'), load);

  }

//>>excludeEnd('excludeRequireCss')
  return cssAPI;
});