var ERRORCLASS = 'error';

function wordRegexp(words) {
  return new RegExp("^((" + words.join(")|(") + "))\\b", "i");
}

var singleOperators = new RegExp("^[\\+\\-\\*/%&\\\\|\\^~<>!]");
var singleDelimiters = new RegExp('^[\\(\\)\\[\\]\\{\\}@,:`=;\\.]');
var doubleOperators = new RegExp("^((==)|(<>)|(<=)|(>=)|(<>)|(<<)|(>>)|(//)|(\\*\\*))");
var doubleDelimiters = new RegExp("^((\\+=)|(\\-=)|(\\*=)|(%=)|(/=)|(&=)|(\\|=)|(\\^=))");
var tripleDelimiters = new RegExp("^((//=)|(>>=)|(<<=)|(\\*\\*=))");
var identifiers = new RegExp("^[_A-Za-z][_A-Za-z0-9]*");

var openingKeywords = ['class','module', 'sub','enum','select','while','if','function', 'get','set','property', 'try', 'structure', 'synclock', 'using', 'with'];
var middleKeywords = ['else','elseif','case', 'catch', 'finally'];
var endKeywords = ['next','loop'];

var operatorKeywords = ['and', "andalso", 'or', 'orelse', 'xor', 'in', 'not', 'is', 'isnot', 'like'];
var wordOperators = wordRegexp(operatorKeywords);

var commonKeywords = ["#const", "#else", "#elseif", "#end", "#if", "#region", "addhandler", "addressof", "alias", "as", "byref", "byval", "cbool", "cbyte", "cchar", "cdate", "cdbl", "cdec", "cint", "clng", "cobj", "compare", "const", "continue", "csbyte", "cshort", "csng", "cstr", "cuint", "culng", "cushort", "declare", "default", "delegate", "dim", "directcast", "each", "erase", "error", "event", "exit", "explicit", "false", "for", "friend", "gettype", "goto", "handles", "implements", "imports", "infer", "inherits", "interface", "isfalse", "istrue", "lib", "me", "mod", "mustinherit", "mustoverride", "my", "mybase", "myclass", "namespace", "narrowing", "new", "nothing", "notinheritable", "notoverridable", "of", "off", "on", "operator", "option", "optional", "out", "overloads", "overridable", "overrides", "paramarray", "partial", "private", "protected", "public", "raiseevent", "readonly", "redim", "removehandler", "resume", "return", "shadows", "shared", "static", "step", "stop", "strict", "then", "throw", "to", "true", "trycast", "typeof", "until", "until", "when", "widening", "withevents", "writeonly"];

var commontypes = ['object', 'boolean', 'char', 'string', 'byte', 'sbyte', 'short', 'ushort', 'int16', 'uint16', 'integer', 'uinteger', 'int32', 'uint32', 'long', 'ulong', 'int64', 'uint64', 'decimal', 'single', 'double', 'float', 'date', 'datetime', 'intptr', 'uintptr'];

var keywords = wordRegexp(commonKeywords);
var types = wordRegexp(commontypes);
var stringPrefixes = '"';

var opening = wordRegexp(openingKeywords);
var middle = wordRegexp(middleKeywords);
var closing = wordRegexp(endKeywords);
var doubleClosing = wordRegexp(['end']);
var doOpening = wordRegexp(['do']);

function indent(_stream, state) {
  state.currentIndent++;
}

function dedent(_stream, state) {
  state.currentIndent--;
}
// tokenizers
function tokenBase(stream, state) {
  if (stream.eatSpace()) {
    return null;
  }

  var ch = stream.peek();

  // Handle Comments
  if (ch === "'") {
    stream.skipToEnd();
    return 'comment';
  }


  // Handle Number Literals
  if (stream.match(/^((&H)|(&O))?[0-9\.a-f]/i, false)) {
    var floatLiteral = false;
    // Floats
    if (stream.match(/^\d*\.\d+F?/i)) { floatLiteral = true; }
    else if (stream.match(/^\d+\.\d*F?/)) { floatLiteral = true; }
    else if (stream.match(/^\.\d+F?/)) { floatLiteral = true; }

    if (floatLiteral) {
      // Float literals may be "imaginary"
      stream.eat(/J/i);
      return 'number';
    }
    // Integers
    var intLiteral = false;
    // Hex
    if (stream.match(/^&H[0-9a-f]+/i)) { intLiteral = true; }
    // Octal
    else if (stream.match(/^&O[0-7]+/i)) { intLiteral = true; }
    // Decimal
    else if (stream.match(/^[1-9]\d*F?/)) {
      // Decimal literals may be "imaginary"
      stream.eat(/J/i);
      // TODO - Can you have imaginary longs?
      intLiteral = true;
    }
    // Zero by itself with no other piece of number.
    else if (stream.match(/^0(?![\dx])/i)) { intLiteral = true; }
    if (intLiteral) {
      // Integer literals may be "long"
      stream.eat(/L/i);
      return 'number';
    }
  }

  // Handle Strings
  if (stream.match(stringPrefixes)) {
    state.tokenize = tokenStringFactory(stream.current());
    return state.tokenize(stream, state);
  }

  // Handle operators and Delimiters
  if (stream.match(tripleDelimiters) || stream.match(doubleDelimiters)) {
    return null;
  }
  if (stream.match(doubleOperators)
      || stream.match(singleOperators)
      || stream.match(wordOperators)) {
    return 'operator';
  }
  if (stream.match(singleDelimiters)) {
    return null;
  }
  if (stream.match(doOpening)) {
    indent(stream,state);
    state.doInCurrentLine = true;
    return 'keyword';
  }
  if (stream.match(opening)) {
    if (! state.doInCurrentLine)
      indent(stream,state);
    else
      state.doInCurrentLine = false;
    return 'keyword';
  }
  if (stream.match(middle)) {
    return 'keyword';
  }

  if (stream.match(doubleClosing)) {
    dedent(stream,state);
    dedent(stream,state);
    return 'keyword';
  }
  if (stream.match(closing)) {
    dedent(stream,state);
    return 'keyword';
  }

  if (stream.match(types)) {
    return 'keyword';
  }

  if (stream.match(keywords)) {
    return 'keyword';
  }

  if (stream.match(identifiers)) {
    return 'variable';
  }

  // Handle non-detected items
  stream.next();
  return ERRORCLASS;
}

function tokenStringFactory(delimiter) {
  var singleline = delimiter.length == 1;
  var OUTCLASS = 'string';

  return function(stream, state) {
    while (!stream.eol()) {
      stream.eatWhile(/[^'"]/);
      if (stream.match(delimiter)) {
        state.tokenize = tokenBase;
        return OUTCLASS;
      } else {
        stream.eat(/['"]/);
      }
    }
    if (singleline) {
      state.tokenize = tokenBase;
    }
    return OUTCLASS;
  };
}


function tokenLexer(stream, state) {
  var style = state.tokenize(stream, state);
  var current = stream.current();

  // Handle '.' connected identifiers
  if (current === '.') {
    style = state.tokenize(stream, state);
    if (style === 'variable') {
      return 'variable';
    } else {
      return ERRORCLASS;
    }
  }


  var delimiter_index = '[({'.indexOf(current);
  if (delimiter_index !== -1) {
    indent(stream, state );
  }
  delimiter_index = '])}'.indexOf(current);
  if (delimiter_index !== -1) {
    if (dedent(stream, state)) {
      return ERRORCLASS;
    }
  }

  return style;
}

const vb = {
  startState: function() {
    return {
      tokenize: tokenBase,
      lastToken: null,
      currentIndent: 0,
      nextLineIndent: 0,
      doInCurrentLine: false


    };
  },

  token: function(stream, state) {
    if (stream.sol()) {
      state.currentIndent += state.nextLineIndent;
      state.nextLineIndent = 0;
      state.doInCurrentLine = 0;
    }
    var style = tokenLexer(stream, state);

    state.lastToken = {style:style, content: stream.current()};



    return style;
  },

  indent: function(state, textAfter, cx) {
    var trueText = textAfter.replace(/^\s+|\s+$/g, '') ;
    if (trueText.match(closing) || trueText.match(doubleClosing) || trueText.match(middle)) return cx.unit*(state.currentIndent-1);
    if(state.currentIndent < 0) return 0;
    return state.currentIndent * cx.unit;
  },

  languageData: {
    closeBrackets: {brackets: ["(", "[", "{", '"']},
    commentTokens: {line: "'"},
    autocomplete: openingKeywords.concat(middleKeywords).concat(endKeywords)
      .concat(operatorKeywords).concat(commonKeywords).concat(commontypes)
  }
};

export { vb };
