text: 'use strict';
  
  /**
   * modified from https://github.com/mdx-js/mdx/blob/master/packages/mdx
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2017-2018 Compositor and Zeit, Inc.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  const IMPORT_REGEX = /^import\s/;
  const EXPORT_REGEX = /^export\s/;
  const BLOCKS_REGEX = '[a-z][a-z0-9]*(\\.[a-z][a-z0-9]*)*|';
  const COMMENT_REGEX = /<!---->|<!---?[^>-](?:-?[^-])*-->/;
  const EMPTY_NEWLINE = '\n\n';
  
  const isImport = (text)=>IMPORT_REGEX.test(text);
  const isExport = (text)=>EXPORT_REGEX.test(text);
  
  const tokenizeEsSyntax = (eat, value)=>{
  	const index = value.indexOf(EMPTY_NEWLINE);
  	const subvalue = value.slice(0, index);
  
  	if(isExport(subvalue) || isImport(subvalue)){
  		return eat(subvalue)({
  			type: isExport(subvalue) ? 'export' : 'import',
  			value: subvalue,
  		});
  	}
  };
  
  /* istanbul ignore next */
  tokenizeEsSyntax.locator = (value /*, fromIndex*/)=>(isExport(value) || isImport(value) ? -1 : 1);
  
  function esSyntax() {
  	const {Parser} = this;
  	const tokenizers = Parser.prototype.blockTokenizers;
  	const methods = Parser.prototype.blockMethods;
  
  	tokenizers.esSyntax = tokenizeEsSyntax;
  
  	methods.splice(methods.indexOf('paragraph'), 0, 'esSyntax');
  }
  
  module.exports = {
  	esSyntax,
  	BLOCKS_REGEX,
  	COMMENT_REGEX,
  };
  