/**
 * Helpers
 */

function escape(html, encode) {
  return html
    .replace(!encode ? /&(?!#?\w+;)/g : /&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#39;');
}

function unescape(html) {
  return html.replace(/&([#\w]+);/g, function(_, n) {
    n = n.toLowerCase();
    if (n === 'colon') return ':';
    if (n.charAt(0) === '#') {
      return n.charAt(1) === 'x'
        ? String.fromCharCode(parseInt(n.substring(2), 16))
        : String.fromCharCode(+n.substring(1));
    }
    return '';
  });
}

function replace(regex, opt) {
  regex = regex.source;
  opt = opt || '';
  return function self(name, val) {
    if (!name) return new RegExp(regex, opt);
    val = val.source || val;
    val = val.replace(/(^|[^\[])\^/g, '$1');
    regex = regex.replace(name, val);
    return self;
  };
}

function noop() {}
noop.exec = noop;

function merge(obj) {
  var i = 1
    , target
    , key;

  for (; i < arguments.length; i++) {
    target = arguments[i];
    for (key in target) {
      if (Object.prototype.hasOwnProperty.call(target, key)) {
        obj[key] = target[key];
      }
    }
  }

  return obj;
}

module.exports = {
  escape: escape,
  unescape: unescape,
  replace: replace,
  noop: noop,
  merge: merge,
};