var BUILTIN = "builtin", COMMENT = "comment", STRING = "string",
    ATOM = "atom", NUMBER = "number", BRACKET = "bracket";
var INDENT_WORD_SKIP = 2;

function makeKeywords(str) {
  var obj = {}, words = str.split(" ");
  for (var i = 0; i < words.length; ++i) obj[words[i]] = true;
  return obj;
}

var keywords = makeKeywords("λ case-lambda call/cc class cond-expand define-class define-values exit-handler field import inherit init-field interface let*-values let-values let/ec mixin opt-lambda override protect provide public rename require require-for-syntax syntax syntax-case syntax-error unit/sig unless when with-syntax and begin call-with-current-continuation call-with-input-file call-with-output-file case cond define define-syntax define-macro defmacro delay do dynamic-wind else for-each if lambda let let* let-syntax letrec letrec-syntax map or syntax-rules abs acos angle append apply asin assoc assq assv atan boolean? caar cadr call-with-input-file call-with-output-file call-with-values car cdddar cddddr cdr ceiling char->integer char-alphabetic? char-ci<=? char-ci<? char-ci=? char-ci>=? char-ci>? char-downcase char-lower-case? char-numeric? char-ready? char-upcase char-upper-case? char-whitespace? char<=? char<? char=? char>=? char>? char? close-input-port close-output-port complex? cons cos current-input-port current-output-port denominator display eof-object? eq? equal? eqv? eval even? exact->inexact exact? exp expt #f floor force gcd imag-part inexact->exact inexact? input-port? integer->char integer? interaction-environment lcm length list list->string list->vector list-ref list-tail list? load log magnitude make-polar make-rectangular make-string make-vector max member memq memv min modulo negative? newline not null-environment null? number->string number? numerator odd? open-input-file open-output-file output-port? pair? peek-char port? positive? procedure? quasiquote quote quotient rational? rationalize read read-char real-part real? remainder reverse round scheme-report-environment set! set-car! set-cdr! sin sqrt string string->list string->number string->symbol string-append string-ci<=? string-ci<? string-ci=? string-ci>=? string-ci>? string-copy string-fill! string-length string-ref string-set! string<=? string<? string=? string>=? string>? string? substring symbol->string symbol? #t tan transcript-off transcript-on truncate values vector vector->list vector-fill! vector-length vector-ref vector-set! with-input-from-file with-output-to-file write write-char zero?");
var indentKeys = makeKeywords("define let letrec let* lambda define-macro defmacro let-syntax letrec-syntax let-values let*-values define-syntax syntax-rules define-values when unless");

function stateStack(indent, type, prev) { // represents a state stack object
  this.indent = indent;
  this.type = type;
  this.prev = prev;
}

function pushStack(state, indent, type) {
  state.indentStack = new stateStack(indent, type, state.indentStack);
}

function popStack(state) {
  state.indentStack = state.indentStack.prev;
}

var binaryMatcher = new RegExp(/^(?:[-+]i|[-+][01]+#*(?:\/[01]+#*)?i|[-+]?[01]+#*(?:\/[01]+#*)?@[-+]?[01]+#*(?:\/[01]+#*)?|[-+]?[01]+#*(?:\/[01]+#*)?[-+](?:[01]+#*(?:\/[01]+#*)?)?i|[-+]?[01]+#*(?:\/[01]+#*)?)(?=[()\s;"]|$)/i);
var octalMatcher = new RegExp(/^(?:[-+]i|[-+][0-7]+#*(?:\/[0-7]+#*)?i|[-+]?[0-7]+#*(?:\/[0-7]+#*)?@[-+]?[0-7]+#*(?:\/[0-7]+#*)?|[-+]?[0-7]+#*(?:\/[0-7]+#*)?[-+](?:[0-7]+#*(?:\/[0-7]+#*)?)?i|[-+]?[0-7]+#*(?:\/[0-7]+#*)?)(?=[()\s;"]|$)/i);
var hexMatcher = new RegExp(/^(?:[-+]i|[-+][\da-f]+#*(?:\/[\da-f]+#*)?i|[-+]?[\da-f]+#*(?:\/[\da-f]+#*)?@[-+]?[\da-f]+#*(?:\/[\da-f]+#*)?|[-+]?[\da-f]+#*(?:\/[\da-f]+#*)?[-+](?:[\da-f]+#*(?:\/[\da-f]+#*)?)?i|[-+]?[\da-f]+#*(?:\/[\da-f]+#*)?)(?=[()\s;"]|$)/i);
var decimalMatcher = new RegExp(/^(?:[-+]i|[-+](?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*)i|[-+]?(?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*)@[-+]?(?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*)|[-+]?(?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*)[-+](?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*)?i|(?:(?:(?:\d+#+\.?#*|\d+\.\d*#*|\.\d+#*|\d+)(?:[esfdl][-+]?\d+)?)|\d+#*\/\d+#*))(?=[()\s;"]|$)/i);

function isBinaryNumber (stream) {
  return stream.match(binaryMatcher);
}

function isOctalNumber (stream) {
  return stream.match(octalMatcher);
}

function isDecimalNumber (stream, backup) {
  if (backup === true) {
    stream.backUp(1);
  }
  return stream.match(decimalMatcher);
}

function isHexNumber (stream) {
  return stream.match(hexMatcher);
}

const scheme = {
  startState: function () {
    return {
      indentStack: null,
      indentation: 0,
      mode: false,
      sExprComment: false,
      sExprQuote: false
    };
  },

  token: function (stream, state) {
    if (state.indentStack == null && stream.sol()) {
      // update indentation, but only if indentStack is empty
      state.indentation = stream.indentation();
    }

    // skip spaces
    if (stream.eatSpace()) {
      return null;
    }
    var returnType = null;

    switch(state.mode){
    case "string": // multi-line string parsing mode
      var next, escaped = false;
      while ((next = stream.next()) != null) {
        if (next == "\"" && !escaped) {

          state.mode = false;
          break;
        }
        escaped = !escaped && next == "\\";
      }
      returnType = STRING; // continue on in scheme-string mode
      break;
    case "comment": // comment parsing mode
      var next, maybeEnd = false;
      while ((next = stream.next()) != null) {
        if (next == "#" && maybeEnd) {

          state.mode = false;
          break;
        }
        maybeEnd = (next == "|");
      }
      returnType = COMMENT;
      break;
    case "s-expr-comment": // s-expr commenting mode
      state.mode = false;
      if(stream.peek() == "(" || stream.peek() == "["){
        // actually start scheme s-expr commenting mode
        state.sExprComment = 0;
      }else {
        // if not we just comment the entire of the next token
        stream.eatWhile(/[^\s\(\)\[\]]/); // eat symbol atom
        returnType = COMMENT;
        break;
      }
    default: // default parsing mode
      var ch = stream.next();

      if (ch == "\"") {
        state.mode = "string";
        returnType = STRING;

      } else if (ch == "'") {
        if (stream.peek() == "(" || stream.peek() == "["){
          if (typeof state.sExprQuote != "number") {
            state.sExprQuote = 0;
          } // else already in a quoted expression
          returnType = ATOM;
        } else {
          stream.eatWhile(/[\w_\-!$%&*+\.\/:<=>?@\^~]/);
          returnType = ATOM;
        }
      } else if (ch == '#') {
        if (stream.eat("|")) {                    // Multi-line comment
          state.mode = "comment"; // toggle to comment mode
          returnType = COMMENT;
        } else if (stream.eat(/[tf]/i)) {            // #t/#f (atom)
          returnType = ATOM;
        } else if (stream.eat(';')) {                // S-Expr comment
          state.mode = "s-expr-comment";
          returnType = COMMENT;
        } else {
          var numTest = null, hasExactness = false, hasRadix = true;
          if (stream.eat(/[ei]/i)) {
            hasExactness = true;
          } else {
            stream.backUp(1);       // must be radix specifier
          }
          if (stream.match(/^#b/i)) {
            numTest = isBinaryNumber;
          } else if (stream.match(/^#o/i)) {
            numTest = isOctalNumber;
          } else if (stream.match(/^#x/i)) {
            numTest = isHexNumber;
          } else if (stream.match(/^#d/i)) {
            numTest = isDecimalNumber;
          } else if (stream.match(/^[-+0-9.]/, false)) {
            hasRadix = false;
            numTest = isDecimalNumber;
            // re-consume the initial # if all matches failed
          } else if (!hasExactness) {
            stream.eat('#');
          }
          if (numTest != null) {
            if (hasRadix && !hasExactness) {
              // consume optional exactness after radix
              stream.match(/^#[ei]/i);
            }
            if (numTest(stream))
              returnType = NUMBER;
          }
        }
      } else if (/^[-+0-9.]/.test(ch) && isDecimalNumber(stream, true)) { // match non-prefixed number, must be decimal
        returnType = NUMBER;
      } else if (ch == ";") { // comment
        stream.skipToEnd(); // rest of the line is a comment
        returnType = COMMENT;
      } else if (ch == "(" || ch == "[") {
        var keyWord = ''; var indentTemp = stream.column(), letter;
        /**
           Either
           (indent-word ..
           (non-indent-word ..
           (;something else, bracket, etc.
        */

        while ((letter = stream.eat(/[^\s\(\[\;\)\]]/)) != null) {
          keyWord += letter;
        }

        if (keyWord.length > 0 && indentKeys.propertyIsEnumerable(keyWord)) { // indent-word

          pushStack(state, indentTemp + INDENT_WORD_SKIP, ch);
        } else { // non-indent word
          // we continue eating the spaces
          stream.eatSpace();
          if (stream.eol() || stream.peek() == ";") {
            // nothing significant after
            // we restart indentation 1 space after
            pushStack(state, indentTemp + 1, ch);
          } else {
            pushStack(state, indentTemp + stream.current().length, ch); // else we match
          }
        }
        stream.backUp(stream.current().length - 1); // undo all the eating

        if(typeof state.sExprComment == "number") state.sExprComment++;
        if(typeof state.sExprQuote == "number") state.sExprQuote++;

        returnType = BRACKET;
      } else if (ch == ")" || ch == "]") {
        returnType = BRACKET;
        if (state.indentStack != null && state.indentStack.type == (ch == ")" ? "(" : "[")) {
          popStack(state);

          if(typeof state.sExprComment == "number"){
            if(--state.sExprComment == 0){
              returnType = COMMENT; // final closing bracket
              state.sExprComment = false; // turn off s-expr commenting mode
            }
          }
          if(typeof state.sExprQuote == "number"){
            if(--state.sExprQuote == 0){
              returnType = ATOM; // final closing bracket
              state.sExprQuote = false; // turn off s-expr quote mode
            }
          }
        }
      } else {
        stream.eatWhile(/[\w_\-!$%&*+\.\/:<=>?@\^~]/);

        if (keywords && keywords.propertyIsEnumerable(stream.current())) {
          returnType = BUILTIN;
        } else returnType = "variable";
      }
    }
    return (typeof state.sExprComment == "number") ? COMMENT : ((typeof state.sExprQuote == "number") ? ATOM : returnType);
  },

  indent: function (state) {
    if (state.indentStack == null) return state.indentation;
    return state.indentStack.indent;
  },

  languageData: {
    closeBrackets: {brackets: ["(", "[", "{", '"']},
    commentTokens: {line: ";;"}
  }
};

export { scheme };
