/**
 * cssfilter
 *
 * @author 老雷<leizongmin@gmail.com>
 */

var DEFAULT = require('./default');
var parseStyle = require('./parser');
var _ = require('./util');


/**
 * 返回值是否为空
 *
 * @param {Object} obj
 * @return {Boolean}
 */
function isNull (obj) {
  return (obj === undefined || obj === null);
}

/**
 * 浅拷贝对象
 *
 * @param {Object} obj
 * @return {Object}
 */
function shallowCopyObject (obj) {
  var ret = {};
  for (var i in obj) {
    ret[i] = obj[i];
  }
  return ret;
}

/**
 * 创建CSS过滤器
 *
 * @param {Object} options
 *   - {Object} whiteList
 *   - {Function} onAttr
 *   - {Function} onIgnoreAttr
 *   - {Function} safeAttrValue
 */
function FilterCSS (options) {
  options = shallowCopyObject(options || {});
  options.whiteList = options.whiteList || DEFAULT.whiteList;
  options.onAttr = options.onAttr || DEFAULT.onAttr;
  options.onIgnoreAttr = options.onIgnoreAttr || DEFAULT.onIgnoreAttr;
  options.safeAttrValue = options.safeAttrValue || DEFAULT.safeAttrValue;
  this.options = options;
}

FilterCSS.prototype.process = function (css) {
  // 兼容各种奇葩输入
  css = css || '';
  css = css.toString();
  if (!css) return '';

  var me = this;
  var options = me.options;
  var whiteList = options.whiteList;
  var onAttr = options.onAttr;
  var onIgnoreAttr = options.onIgnoreAttr;
  var safeAttrValue = options.safeAttrValue;

  var retCSS = parseStyle(css, function (sourcePosition, position, name, value, source) {

    var check = whiteList[name];
    var isWhite = false;
    if (check === true) isWhite = check;
    else if (typeof check === 'function') isWhite = check(value);
    else if (check instanceof RegExp) isWhite = check.test(value);
    if (isWhite !== true) isWhite = false;

    // 如果过滤后 value 为空则直接忽略
    value = safeAttrValue(name, value);
    if (!value) return;

    var opts = {
      position: position,
      sourcePosition: sourcePosition,
      source: source,
      isWhite: isWhite
    };

    if (isWhite) {

      var ret = onAttr(name, value, opts);
      if (isNull(ret)) {
        return name + ':' + value;
      } else {
        return ret;
      }

    } else {

      var ret = onIgnoreAttr(name, value, opts);
      if (!isNull(ret)) {
        return ret;
      }

    }
  });

  return retCSS;
};


module.exports = FilterCSS;