/* micro-style-loader runtime */

function createStyleTag () {
  var head = document.head || document.getElementsByTagName('head')[0];
  var style = document.createElement('style');
  style.type = 'text/css';
  head.appendChild(style);
  return style;
}

function removeTag (tag) {
  if (tag.parentNode) {
    tag.parentNode.removeChild(tag);
  }
}

// multi-tag mode
function insertMultiple (source, map) {
  var style = createStyleTag();

  var css = source;
  if (map) {
    var base64 = btoa(unescape(encodeURIComponent(JSON.stringify(map))));
    css += '\n/*# sourceMappingURL=data:application/json;charset=utf-8;base64,' + base64 + ' */';
  }

  if (style.styleSheet) {
    style.styleSheet.cssText = css;
  } else {
    style.appendChild(document.createTextNode(css));
  }

  return function () { removeTag(style) };
}

var singleTag = null;
var uniqueIndex = 0;
var textList = {};

function insertSingle (css) { // single tag mode does not support source maps
  // initialize the single tag if needed
  if (!singleTag) { singleTag = createStyleTag(); }

  function recomputeText () {
    var sortedKeys = Object.keys(textList)
      .sort(function(a,b) { return a - b; })
      .map(function (key) { return textList[key] })
      .join('\n')
  }

  if (singleTag.styleSheet) {
    // update textlist
    var currentIndex = uniqueIndex;
    uniqueIndex += 1;
    textList[currentIndex] = css;

    // update css text
    singleTag.styleSheet.cssText = recomputeText();

    return function () {
      delete textList[currentIndex];
      singleTag.styleSheet.cssText = recomputeText();
    }
  } else {
    // append a text node to the style tag
    var textNode = document.createTextNode(css);
    singleTag.appendChild(textNode);

    return function () { remove(textNode); }
  }
}

var useSingleTag = false;
var insert = useSingleTag ? insertSingle : insertMultiple;
var modules = {};
function use (moduleId, source, map) {
  if (modules[moduleId]) { // module is already inserted
    if (modules[moduleId].source !== source) {
      modules[moduleId].remove(); // source changed: remove the module (and reinsert after)
    } else {
      return; // same source, nothing to do
    }
  }

  var removeStyle = insert(source, map);

  // ensure removeStyle is only called once a & when style is presented
  function remove () {
    if (modules[moduleId]) {
      removeStyle();
      modules[moduleId] = null;
    }
  }

  var newModule = { source: source, map: map, remove: remove };
  modules[moduleId] = newModule;

  return remove;
}

module.exports = {
  modules: modules,
  use: use
};