var keys = require('./keys.js');

// Internal helper to generate functions for escaping and unescaping strings
// to/from HTML interpolation.
function createEscaper(map) {
  var escaper = function(match) {
    return map[match];
  };
  // Regexes for identifying a key that needs to be escaped.
  var source = '(?:' + keys(map).join('|') + ')';
  var testRegexp = RegExp(source);
  var replaceRegexp = RegExp(source, 'g');
  return function(string) {
    string = string == null ? '' : '' + string;
    return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
  };
}

module.exports = createEscaper;