/**
 * @param {string} value
 * @returns {RegExp}
 * */

/**
 * @param {RegExp | string } re
 * @returns {string}
 */
function source(re) {
  if (!re) return null;
  if (typeof re === "string") return re;

  return re.source;
}

/**
 * @param {RegExp | string } re
 * @returns {string}
 */
function lookahead(re) {
  return concat('(?=', re, ')');
}

/**
 * @param {...(RegExp | string) } args
 * @returns {string}
 */
function concat(...args) {
  const joined = args.map((x) => source(x)).join("");
  return joined;
}

/*
Language: Ruby
Description: Ruby is a dynamic, open source programming language with a focus on simplicity and productivity.
Website: https://www.ruby-lang.org/
Author: Anton Kovalyov <anton@kovalyov.net>
Contributors: Peter Leonov <gojpeg@yandex.ru>, Vasily Polovnyov <vast@whiteants.net>, Loren Segal <lsegal@soen.ca>, Pascal Hurni <phi@ruby-reactive.org>, Cedric Sohrauer <sohrauer@googlemail.com>
Category: common
*/

function ruby(hljs) {
  var RUBY_METHOD_RE = '([a-zA-Z_]\\w*[!?=]?|[-+~]@|<<|>>|=~|===?|<=>|[<>]=?|\\*\\*|[-/+%^&*~`|]|\\[\\]=?)';
  var RUBY_KEYWORDS = {
    keyword:
      'and then defined module in return redo if BEGIN retry end for self when ' +
      'next until do begin unless END rescue else break undef not super class case ' +
      'require yield alias while ensure elsif or include attr_reader attr_writer attr_accessor ' +
      '__FILE__',
    built_in: 'proc lambda',
    literal:
      'true false nil'
  };
  var YARDOCTAG = {
    className: 'doctag',
    begin: '@[A-Za-z]+'
  };
  var IRB_OBJECT = {
    begin: '#<', end: '>'
  };
  var COMMENT_MODES = [
    hljs.COMMENT(
      '#',
      '$',
      {
        contains: [YARDOCTAG]
      }
    ),
    hljs.COMMENT(
      '^=begin',
      '^=end',
      {
        contains: [YARDOCTAG],
        relevance: 10
      }
    ),
    hljs.COMMENT('^__END__', '\\n$')
  ];
  var SUBST = {
    className: 'subst',
    begin: /#\{/, end: /\}/,
    keywords: RUBY_KEYWORDS
  };
  var STRING = {
    className: 'string',
    contains: [hljs.BACKSLASH_ESCAPE, SUBST],
    variants: [
      {begin: /'/, end: /'/},
      {begin: /"/, end: /"/},
      {begin: /`/, end: /`/},
      {begin: /%[qQwWx]?\(/, end: /\)/},
      {begin: /%[qQwWx]?\[/, end: /\]/},
      {begin: /%[qQwWx]?\{/, end: /\}/},
      {begin: /%[qQwWx]?</, end: />/},
      {begin: /%[qQwWx]?\//, end: /\//},
      {begin: /%[qQwWx]?%/, end: /%/},
      {begin: /%[qQwWx]?-/, end: /-/},
      {begin: /%[qQwWx]?\|/, end: /\|/},
      {
        // \B in the beginning suppresses recognition of ?-sequences where ?
        // is the last character of a preceding identifier, as in: `func?4`
        begin: /\B\?(\\\d{1,3}|\\x[A-Fa-f0-9]{1,2}|\\u[A-Fa-f0-9]{4}|\\?\S)\b/
      },
      { // heredocs
        begin: /<<[-~]?'?(\w+)(?:.|\n)*?\n\s*\1\b/,
        returnBegin: true,
        contains: [
          { begin: /<<[-~]?'?/ },
          hljs.END_SAME_AS_BEGIN({
            begin: /(\w+)/, end: /(\w+)/,
            contains: [hljs.BACKSLASH_ESCAPE, SUBST],
          })
        ]
      }
    ]
  };

  // Ruby syntax is underdocumented, but this grammar seems to be accurate
  // as of version 2.7.2 (confirmed with (irb and `Ripper.sexp(...)`)
  // https://docs.ruby-lang.org/en/2.7.0/doc/syntax/literals_rdoc.html#label-Numbers
  var decimal = '[1-9](_?[0-9])*|0';
  var digits = '[0-9](_?[0-9])*';
  var NUMBER = {
    className: 'number', relevance: 0,
    variants: [
      // decimal integer/float, optionally exponential or rational, optionally imaginary
      { begin: `\\b(${decimal})(\\.(${digits}))?([eE][+-]?(${digits})|r)?i?\\b` },

      // explicit decimal/binary/octal/hexadecimal integer,
      // optionally rational and/or imaginary
      { begin: "\\b0[dD][0-9](_?[0-9])*r?i?\\b" },
      { begin: "\\b0[bB][0-1](_?[0-1])*r?i?\\b" },
      { begin: "\\b0[oO][0-7](_?[0-7])*r?i?\\b" },
      { begin: "\\b0[xX][0-9a-fA-F](_?[0-9a-fA-F])*r?i?\\b" },

      // 0-prefixed implicit octal integer, optionally rational and/or imaginary
      { begin: "\\b0(_?[0-7])+r?i?\\b" },
    ]
  };

  var PARAMS = {
    className: 'params',
    begin: '\\(', end: '\\)', endsParent: true,
    keywords: RUBY_KEYWORDS
  };

  var RUBY_DEFAULT_CONTAINS = [
    STRING,
    {
      className: 'class',
      beginKeywords: 'class module', end: '$|;',
      illegal: /=/,
      contains: [
        hljs.inherit(hljs.TITLE_MODE, {begin: '[A-Za-z_]\\w*(::\\w+)*(\\?|!)?'}),
        {
          begin: '<\\s*',
          contains: [{
            begin: '(' + hljs.IDENT_RE + '::)?' + hljs.IDENT_RE
          }]
        }
      ].concat(COMMENT_MODES)
    },
    {
      className: 'function',
      // def method_name(
      // def method_name;
      // def method_name (end of line)
      begin: concat(/def\s*/, lookahead(RUBY_METHOD_RE + "\\s*(\\(|;|$)")),
      keywords: "def",
      end: '$|;',
      contains: [
        hljs.inherit(hljs.TITLE_MODE, {begin: RUBY_METHOD_RE}),
        PARAMS
      ].concat(COMMENT_MODES)
    },
    {
      // swallow namespace qualifiers before symbols
      begin: hljs.IDENT_RE + '::'
    },
    {
      className: 'symbol',
      begin: hljs.UNDERSCORE_IDENT_RE + '(!|\\?)?:',
      relevance: 0
    },
    {
      className: 'symbol',
      begin: ':(?!\\s)',
      contains: [STRING, {begin: RUBY_METHOD_RE}],
      relevance: 0
    },
    NUMBER,
    {
      // negative-look forward attemps to prevent false matches like:
      // @ident@ or $ident$ that might indicate this is not ruby at all
      className: "variable",
      begin: '(\\$\\W)|((\\$|@@?)(\\w+))(?=[^@$?])' + `(?![A-Za-z])(?![@$?'])`
    },
    {
      className: 'params',
      begin: /\|/,
      end: /\|/,
      relevance:0, // this could be a lot of things (in other languages) other than params
      keywords: RUBY_KEYWORDS
    },
    { // regexp container
      begin: '(' + hljs.RE_STARTERS_RE + '|unless)\\s*',
      keywords: 'unless',
      contains: [
        {
          className: 'regexp',
          contains: [hljs.BACKSLASH_ESCAPE, SUBST],
          illegal: /\n/,
          variants: [
            {begin: '/', end: '/[a-z]*'},
            {begin: /%r\{/, end: /\}[a-z]*/},
            {begin: '%r\\(', end: '\\)[a-z]*'},
            {begin: '%r!', end: '![a-z]*'},
            {begin: '%r\\[', end: '\\][a-z]*'}
          ]
        }
      ].concat(IRB_OBJECT, COMMENT_MODES),
      relevance: 0
    }
  ].concat(IRB_OBJECT, COMMENT_MODES);

  SUBST.contains = RUBY_DEFAULT_CONTAINS;
  PARAMS.contains = RUBY_DEFAULT_CONTAINS;

  // >>
  // ?>
  var SIMPLE_PROMPT = "[>?]>";
  // irb(main):001:0>
  var DEFAULT_PROMPT = "[\\w#]+\\(\\w+\\):\\d+:\\d+>";
  var RVM_PROMPT = "(\\w+-)?\\d+\\.\\d+\\.\\d(p\\d+)?[^>]+>";

  var IRB_DEFAULT = [
    {
      begin: /^\s*=>/,
      starts: {
        end: '$', contains: RUBY_DEFAULT_CONTAINS
      }
    },
    {
      className: 'meta',
      begin: '^('+SIMPLE_PROMPT+"|"+DEFAULT_PROMPT+'|'+RVM_PROMPT+')(?=[ ])',
      starts: {
        end: '$', contains: RUBY_DEFAULT_CONTAINS
      }
    }
  ];

  COMMENT_MODES.unshift(IRB_OBJECT);

  return {
    name: 'Ruby',
    aliases: ['rb', 'gemspec', 'podspec', 'thor', 'irb'],
    keywords: RUBY_KEYWORDS,
    illegal: /\/\*/,
    contains: [
        hljs.SHEBANG({binary:"ruby"}),
      ]
      .concat(IRB_DEFAULT)
      .concat(COMMENT_MODES)
      .concat(RUBY_DEFAULT_CONTAINS)
  };
}

module.exports = ruby;