/*
Language: R
Description: R is a free software environment for statistical computing and graphics.
Author: Joe Cheng <joe@rstudio.org>
Website: https://www.r-project.org
Category: scientific
*/

export default function(hljs) {
  var IDENT_RE = '([a-zA-Z]|\\.[a-zA-Z.])[a-zA-Z0-9._]*';

  return {
    name: 'R',
    contains: [
      hljs.HASH_COMMENT_MODE,
      {
        begin: IDENT_RE,
        keywords: {
          $pattern: IDENT_RE,
          keyword:
            'function if in break next repeat else for return switch while try tryCatch ' +
            'stop warning require library attach detach source setMethod setGeneric ' +
            'setGroupGeneric setClass ...',
          literal:
            'NULL NA TRUE FALSE T F Inf NaN NA_integer_|10 NA_real_|10 NA_character_|10 ' +
            'NA_complex_|10'
        },
        relevance: 0
      },
      {
        // hex value
        className: 'number',
        begin: "0[xX][0-9a-fA-F]+[Li]?\\b",
        relevance: 0
      },
      {
        // explicit integer
        className: 'number',
        begin: "\\d+(?:[eE][+\\-]?\\d*)?L\\b",
        relevance: 0
      },
      {
        // number with trailing decimal
        className: 'number',
        begin: "\\d+\\.(?!\\d)(?:i\\b)?",
        relevance: 0
      },
      {
        // number
        className: 'number',
        begin: "\\d+(?:\\.\\d*)?(?:[eE][+\\-]?\\d*)?i?\\b",
        relevance: 0
      },
      {
        // number with leading decimal
        className: 'number',
        begin: "\\.\\d+(?:[eE][+\\-]?\\d*)?i?\\b",
        relevance: 0
      },

      {
        // escaped identifier
        begin: '`',
        end: '`',
        relevance: 0
      },

      {
        className: 'string',
        contains: [hljs.BACKSLASH_ESCAPE],
        variants: [
          {begin: '"', end: '"'},
          {begin: "'", end: "'"}
        ]
      }
    ]
  };
}
