var keywords = {
  "term": true,
  "method": true, "accu": true,
  "rule": true, "then": true, "is": true, "and": true, "or": true,
  "if": true, "default": true
};

var start_blocks = {
  "var_input": true,
  "var_output": true,
  "fuzzify": true,
  "defuzzify": true,
  "function_block": true,
  "ruleblock": true
};

var end_blocks = {
  "end_ruleblock": true,
  "end_defuzzify": true,
  "end_function_block": true,
  "end_fuzzify": true,
  "end_var": true
};

var atoms = {
  "true": true, "false": true, "nan": true,
  "real": true, "min": true, "max": true, "cog": true, "cogs": true
};

var isOperatorChar = /[+\-*&^%:=<>!|\/]/;

function tokenBase(stream, state) {
  var ch = stream.next();

  if (/[\d\.]/.test(ch)) {
    if (ch == ".") {
      stream.match(/^[0-9]+([eE][\-+]?[0-9]+)?/);
    } else if (ch == "0") {
      stream.match(/^[xX][0-9a-fA-F]+/) || stream.match(/^0[0-7]+/);
    } else {
      stream.match(/^[0-9]*\.?[0-9]*([eE][\-+]?[0-9]+)?/);
    }
    return "number";
  }

  if (ch == "/" || ch == "(") {
    if (stream.eat("*")) {
      state.tokenize = tokenComment;
      return tokenComment(stream, state);
    }
    if (stream.eat("/")) {
      stream.skipToEnd();
      return "comment";
    }
  }
  if (isOperatorChar.test(ch)) {
    stream.eatWhile(isOperatorChar);
    return "operator";
  }
  stream.eatWhile(/[\w\$_\xa1-\uffff]/);

  var cur = stream.current().toLowerCase();
  if (keywords.propertyIsEnumerable(cur) ||
      start_blocks.propertyIsEnumerable(cur) ||
      end_blocks.propertyIsEnumerable(cur)) {
    return "keyword";
  }
  if (atoms.propertyIsEnumerable(cur)) return "atom";
  return "variable";
}


function tokenComment(stream, state) {
  var maybeEnd = false, ch;
  while (ch = stream.next()) {
    if ((ch == "/" || ch == ")") && maybeEnd) {
      state.tokenize = tokenBase;
      break;
    }
    maybeEnd = (ch == "*");
  }
  return "comment";
}

function Context(indented, column, type, align, prev) {
  this.indented = indented;
  this.column = column;
  this.type = type;
  this.align = align;
  this.prev = prev;
}

function pushContext(state, col, type) {
  return state.context = new Context(state.indented, col, type, null, state.context);
}

function popContext(state) {
  if (!state.context.prev) return;
  var t = state.context.type;
  if (t == "end_block")
    state.indented = state.context.indented;
  return state.context = state.context.prev;
}

// Interface

const fcl = {
  startState: function(indentUnit) {
    return {
      tokenize: null,
      context: new Context(-indentUnit, 0, "top", false),
      indented: 0,
      startOfLine: true
    };
  },

  token: function(stream, state) {
    var ctx = state.context;
    if (stream.sol()) {
      if (ctx.align == null) ctx.align = false;
      state.indented = stream.indentation();
      state.startOfLine = true;
    }
    if (stream.eatSpace()) return null;

    var style = (state.tokenize || tokenBase)(stream, state);
    if (style == "comment") return style;
    if (ctx.align == null) ctx.align = true;

    var cur = stream.current().toLowerCase();

    if (start_blocks.propertyIsEnumerable(cur)) pushContext(state, stream.column(), "end_block");
    else if (end_blocks.propertyIsEnumerable(cur))  popContext(state);

    state.startOfLine = false;
    return style;
  },

  indent: function(state, textAfter, cx) {
    if (state.tokenize != tokenBase && state.tokenize != null) return 0;
    var ctx = state.context;

    var closing = end_blocks.propertyIsEnumerable(textAfter);
    if (ctx.align) return ctx.column + (closing ? 0 : 1);
    else return ctx.indented + (closing ? 0 : cx.unit);
  },

  languageData: {
    commentTokens: {line: "//", block: {open: "(*", close: "*)"}}
  }
};

export { fcl };
