/*
Language: Visual Basic .NET
Description: Visual Basic .NET (VB.NET) is a multi-paradigm, object-oriented programming language, implemented on the .NET Framework.
Authors: Poren Chiang <ren.chiang@gmail.com>, Jan Pilzer
Website: https://docs.microsoft.com/dotnet/visual-basic/getting-started
Category: common
*/

/** @type LanguageFn */
export default function(hljs) {
  const regex = hljs.regex;
  /**
   * Character Literal
   * Either a single character ("a"C) or an escaped double quote (""""C).
   */
  const CHARACTER = {
    className: 'string',
    begin: /"(""|[^/n])"C\b/
  };

  const STRING = {
    className: 'string',
    begin: /"/,
    end: /"/,
    illegal: /\n/,
    contains: [
      {
        // double quote escape
        begin: /""/ }
    ]
  };

  /** Date Literals consist of a date, a time, or both separated by whitespace, surrounded by # */
  const MM_DD_YYYY = /\d{1,2}\/\d{1,2}\/\d{4}/;
  const YYYY_MM_DD = /\d{4}-\d{1,2}-\d{1,2}/;
  const TIME_12H = /(\d|1[012])(:\d+){0,2} *(AM|PM)/;
  const TIME_24H = /\d{1,2}(:\d{1,2}){1,2}/;
  const DATE = {
    className: 'literal',
    variants: [
      {
        // #YYYY-MM-DD# (ISO-Date) or #M/D/YYYY# (US-Date)
        begin: regex.concat(/# */, regex.either(YYYY_MM_DD, MM_DD_YYYY), / *#/) },
      {
        // #H:mm[:ss]# (24h Time)
        begin: regex.concat(/# */, TIME_24H, / *#/) },
      {
        // #h[:mm[:ss]] A# (12h Time)
        begin: regex.concat(/# */, TIME_12H, / *#/) },
      {
        // date plus time
        begin: regex.concat(
          /# */,
          regex.either(YYYY_MM_DD, MM_DD_YYYY),
          / +/,
          regex.either(TIME_12H, TIME_24H),
          / *#/
        ) }
    ]
  };

  const NUMBER = {
    className: 'number',
    relevance: 0,
    variants: [
      {
        // Float
        begin: /\b\d[\d_]*((\.[\d_]+(E[+-]?[\d_]+)?)|(E[+-]?[\d_]+))[RFD@!#]?/ },
      {
        // Integer (base 10)
        begin: /\b\d[\d_]*((U?[SIL])|[%&])?/ },
      {
        // Integer (base 16)
        begin: /&H[\dA-F_]+((U?[SIL])|[%&])?/ },
      {
        // Integer (base 8)
        begin: /&O[0-7_]+((U?[SIL])|[%&])?/ },
      {
        // Integer (base 2)
        begin: /&B[01_]+((U?[SIL])|[%&])?/ }
    ]
  };

  const LABEL = {
    className: 'label',
    begin: /^\w+:/
  };

  const DOC_COMMENT = hljs.COMMENT(/'''/, /$/, { contains: [
    {
      className: 'doctag',
      begin: /<\/?/,
      end: />/
    }
  ] });

  const COMMENT = hljs.COMMENT(null, /$/, { variants: [
    { begin: /'/ },
    {
      // TODO: Use multi-class for leading spaces
      begin: /([\t ]|^)REM(?=\s)/ }
  ] });

  const DIRECTIVES = {
    className: 'meta',
    // TODO: Use multi-class for indentation once available
    begin: /[\t ]*#(const|disable|else|elseif|enable|end|externalsource|if|region)\b/,
    end: /$/,
    keywords: { keyword:
        'const disable else elseif enable end externalsource if region then' },
    contains: [ COMMENT ]
  };

  return {
    name: 'Visual Basic .NET',
    aliases: [ 'vb' ],
    case_insensitive: true,
    classNameAliases: { label: 'symbol' },
    keywords: {
      keyword:
        'addhandler alias aggregate ansi as async assembly auto binary by byref byval ' /* a-b */
        + 'call case catch class compare const continue custom declare default delegate dim distinct do ' /* c-d */
        + 'each equals else elseif end enum erase error event exit explicit finally for friend from function ' /* e-f */
        + 'get global goto group handles if implements imports in inherits interface into iterator ' /* g-i */
        + 'join key let lib loop me mid module mustinherit mustoverride mybase myclass ' /* j-m */
        + 'namespace narrowing new next notinheritable notoverridable ' /* n */
        + 'of off on operator option optional order overloads overridable overrides ' /* o */
        + 'paramarray partial preserve private property protected public ' /* p */
        + 'raiseevent readonly redim removehandler resume return ' /* r */
        + 'select set shadows shared skip static step stop structure strict sub synclock ' /* s */
        + 'take text then throw to try unicode until using when where while widening with withevents writeonly yield' /* t-y */,
      built_in:
        // Operators https://docs.microsoft.com/dotnet/visual-basic/language-reference/operators
        'addressof and andalso await directcast gettype getxmlnamespace is isfalse isnot istrue like mod nameof new not or orelse trycast typeof xor '
        // Type Conversion Functions https://docs.microsoft.com/dotnet/visual-basic/language-reference/functions/type-conversion-functions
        + 'cbool cbyte cchar cdate cdbl cdec cint clng cobj csbyte cshort csng cstr cuint culng cushort',
      type:
        // Data types https://docs.microsoft.com/dotnet/visual-basic/language-reference/data-types
        'boolean byte char date decimal double integer long object sbyte short single string uinteger ulong ushort',
      literal: 'true false nothing'
    },
    illegal:
      '//|\\{|\\}|endif|gosub|variant|wend|^\\$ ' /* reserved deprecated keywords */,
    contains: [
      CHARACTER,
      STRING,
      DATE,
      NUMBER,
      LABEL,
      DOC_COMMENT,
      COMMENT,
      DIRECTIVES
    ]
  };
}