'use client';
function switchState(source, setState, f) {
  setState(f);
  return f(source, setState);
}

// These should all be Unicode extended, as per the Haskell 2010 report
var smallRE = /[a-z_]/;
var largeRE = /[A-Z]/;
var digitRE = /\d/;
var hexitRE = /[0-9A-Fa-f]/;
var octitRE = /[0-7]/;
var idRE = /[a-z_A-Z0-9'\xa1-\uffff]/;
var symbolRE = /[-!#$%&*+.\/<=>?@\\^|~:]/;
var specialRE = /[(),;[\]`{}]/;
var whiteCharRE = /[ \t\v\f]/; // newlines are handled in tokenizer

function normal(source, setState) {
  if (source.eatWhile(whiteCharRE)) {
    return null;
  }

  var ch = source.next();
  if (specialRE.test(ch)) {
    if (ch == '{' && source.eat('-')) {
      var t = "comment";
      if (source.eat('#')) {
        t = "meta";
      }
      return switchState(source, setState, ncomment(t, 1));
    }
    return null;
  }

  if (ch == '\'') {
    if (source.eat('\\')) {
      source.next();  // should handle other escapes here
    }
    else {
      source.next();
    }
    if (source.eat('\'')) {
      return "string";
    }
    return "error";
  }

  if (ch == '"') {
    return switchState(source, setState, stringLiteral);
  }

  if (largeRE.test(ch)) {
    source.eatWhile(idRE);
    if (source.eat('.')) {
      return "qualifier";
    }
    return "type";
  }

  if (smallRE.test(ch)) {
    source.eatWhile(idRE);
    return "variable";
  }

  if (digitRE.test(ch)) {
    if (ch == '0') {
      if (source.eat(/[xX]/)) {
        source.eatWhile(hexitRE); // should require at least 1
        return "integer";
      }
      if (source.eat(/[oO]/)) {
        source.eatWhile(octitRE); // should require at least 1
        return "number";
      }
    }
    source.eatWhile(digitRE);
    var t = "number";
    if (source.match(/^\.\d+/)) {
      t = "number";
    }
    if (source.eat(/[eE]/)) {
      t = "number";
      source.eat(/[-+]/);
      source.eatWhile(digitRE); // should require at least 1
    }
    return t;
  }

  if (ch == "." && source.eat("."))
    return "keyword";

  if (symbolRE.test(ch)) {
    if (ch == '-' && source.eat(/-/)) {
      source.eatWhile(/-/);
      if (!source.eat(symbolRE)) {
        source.skipToEnd();
        return "comment";
      }
    }
    source.eatWhile(symbolRE);
    return "variable"
  }

  return "error";
}

function ncomment(type, nest) {
  if (nest == 0) {
    return normal;
  }
  return function(source, setState) {
    var currNest = nest;
    while (!source.eol()) {
      var ch = source.next();
      if (ch == '{' && source.eat('-')) {
        ++currNest;
      }
      else if (ch == '-' && source.eat('}')) {
        --currNest;
        if (currNest == 0) {
          setState(normal);
          return type;
        }
      }
    }
    setState(ncomment(type, currNest));
    return type;
  };
}

function stringLiteral(source, setState) {
  while (!source.eol()) {
    var ch = source.next();
    if (ch == '"') {
      setState(normal);
      return "string";
    }
    if (ch == '\\') {
      if (source.eol() || source.eat(whiteCharRE)) {
        setState(stringGap);
        return "string";
      }
      if (source.eat('&')) ;
      else {
        source.next(); // should handle other escapes here
      }
    }
  }
  setState(normal);
  return "error";
}

function stringGap(source, setState) {
  if (source.eat('\\')) {
    return switchState(source, setState, stringLiteral);
  }
  source.next();
  setState(normal);
  return "error";
}


var wellKnownWords = (function() {
  var wkw = {};
  function setType(t) {
    return function () {
      for (var i = 0; i < arguments.length; i++)
        wkw[arguments[i]] = t;
    };
  }

  setType("keyword")(
    "case", "class", "data", "default", "deriving", "do", "else", "foreign",
    "if", "import", "in", "infix", "infixl", "infixr", "instance", "let",
    "module", "newtype", "of", "then", "type", "where", "_");

  setType("keyword")(
    "\.\.", ":", "::", "=", "\\", "<-", "->", "@", "~", "=>");

  setType("builtin")(
    "!!", "$!", "$", "&&", "+", "++", "-", ".", "/", "/=", "<", "<*", "<=",
    "<$>", "<*>", "=<<", "==", ">", ">=", ">>", ">>=", "^", "^^", "||", "*",
    "*>", "**");

  setType("builtin")(
    "Applicative", "Bool", "Bounded", "Char", "Double", "EQ", "Either", "Enum",
    "Eq", "False", "FilePath", "Float", "Floating", "Fractional", "Functor",
    "GT", "IO", "IOError", "Int", "Integer", "Integral", "Just", "LT", "Left",
    "Maybe", "Monad", "Nothing", "Num", "Ord", "Ordering", "Rational", "Read",
    "ReadS", "Real", "RealFloat", "RealFrac", "Right", "Show", "ShowS",
    "String", "True");

  setType("builtin")(
    "abs", "acos", "acosh", "all", "and", "any", "appendFile", "asTypeOf",
    "asin", "asinh", "atan", "atan2", "atanh", "break", "catch", "ceiling",
    "compare", "concat", "concatMap", "const", "cos", "cosh", "curry",
    "cycle", "decodeFloat", "div", "divMod", "drop", "dropWhile", "either",
    "elem", "encodeFloat", "enumFrom", "enumFromThen", "enumFromThenTo",
    "enumFromTo", "error", "even", "exp", "exponent", "fail", "filter",
    "flip", "floatDigits", "floatRadix", "floatRange", "floor", "fmap",
    "foldl", "foldl1", "foldr", "foldr1", "fromEnum", "fromInteger",
    "fromIntegral", "fromRational", "fst", "gcd", "getChar", "getContents",
    "getLine", "head", "id", "init", "interact", "ioError", "isDenormalized",
    "isIEEE", "isInfinite", "isNaN", "isNegativeZero", "iterate", "last",
    "lcm", "length", "lex", "lines", "log", "logBase", "lookup", "map",
    "mapM", "mapM_", "max", "maxBound", "maximum", "maybe", "min", "minBound",
    "minimum", "mod", "negate", "not", "notElem", "null", "odd", "or",
    "otherwise", "pi", "pred", "print", "product", "properFraction", "pure",
    "putChar", "putStr", "putStrLn", "quot", "quotRem", "read", "readFile",
    "readIO", "readList", "readLn", "readParen", "reads", "readsPrec",
    "realToFrac", "recip", "rem", "repeat", "replicate", "return", "reverse",
    "round", "scaleFloat", "scanl", "scanl1", "scanr", "scanr1", "seq",
    "sequence", "sequence_", "show", "showChar", "showList", "showParen",
    "showString", "shows", "showsPrec", "significand", "signum", "sin",
    "sinh", "snd", "span", "splitAt", "sqrt", "subtract", "succ", "sum",
    "tail", "take", "takeWhile", "tan", "tanh", "toEnum", "toInteger",
    "toRational", "truncate", "uncurry", "undefined", "unlines", "until",
    "unwords", "unzip", "unzip3", "userError", "words", "writeFile", "zip",
    "zip3", "zipWith", "zipWith3");

  return wkw;
})();

const haskell = {
  name: "haskell",
  startState: function ()  { return { f: normal }; },
  copyState:  function (s) { return { f: s.f }; },

  token: function(stream, state) {
    var t = state.f(stream, function(s) { state.f = s; });
    var w = stream.current();
    return wellKnownWords.hasOwnProperty(w) ? wellKnownWords[w] : t;
  },

  languageData: {
    commentTokens: {line: "--", block: {open: "{-", close: "-}"}}
  }
};

export { haskell };
