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

var keywords = parseWords("#end #else #break #stop #[[ #]] " +
                          "#{end} #{else} #{break} #{stop}");
var functions = parseWords("#if #elseif #foreach #set #include #parse #macro #define #evaluate " +
                           "#{if} #{elseif} #{foreach} #{set} #{include} #{parse} #{macro} #{define} #{evaluate}");
var specials = parseWords("$foreach.count $foreach.hasNext $foreach.first $foreach.last $foreach.topmost $foreach.parent.count $foreach.parent.hasNext $foreach.parent.first $foreach.parent.last $foreach.parent $velocityCount $!bodyContent $bodyContent");
var isOperatorChar = /[+\-*&%=<>!?:\/|]/;

function chain(stream, state, f) {
  state.tokenize = f;
  return f(stream, state);
}
function tokenBase(stream, state) {
  var beforeParams = state.beforeParams;
  state.beforeParams = false;
  var ch = stream.next();
  // start of unparsed string?
  if ((ch == "'") && !state.inString && state.inParams) {
    state.lastTokenWasBuiltin = false;
    return chain(stream, state, tokenString(ch));
  }
  // start of parsed string?
  else if ((ch == '"')) {
    state.lastTokenWasBuiltin = false;
    if (state.inString) {
      state.inString = false;
      return "string";
    }
    else if (state.inParams)
      return chain(stream, state, tokenString(ch));
  }
  // is it one of the special signs []{}().,;? Separator?
  else if (/[\[\]{}\(\),;\.]/.test(ch)) {
    if (ch == "(" && beforeParams)
      state.inParams = true;
    else if (ch == ")") {
      state.inParams = false;
      state.lastTokenWasBuiltin = true;
    }
    return null;
  }
  // start of a number value?
  else if (/\d/.test(ch)) {
    state.lastTokenWasBuiltin = false;
    stream.eatWhile(/[\w\.]/);
    return "number";
  }
  // multi line comment?
  else if (ch == "#" && stream.eat("*")) {
    state.lastTokenWasBuiltin = false;
    return chain(stream, state, tokenComment);
  }
  // unparsed content?
  else if (ch == "#" && stream.match(/ *\[ *\[/)) {
    state.lastTokenWasBuiltin = false;
    return chain(stream, state, tokenUnparsed);
  }
  // single line comment?
  else if (ch == "#" && stream.eat("#")) {
    state.lastTokenWasBuiltin = false;
    stream.skipToEnd();
    return "comment";
  }
  // variable?
  else if (ch == "$") {
    stream.eatWhile(/[\w\d\$_\.{}-]/);
    // is it one of the specials?
    if (specials && specials.propertyIsEnumerable(stream.current())) {
      return "keyword";
    }
    else {
      state.lastTokenWasBuiltin = true;
      state.beforeParams = true;
      return "builtin";
    }
  }
  // is it a operator?
  else if (isOperatorChar.test(ch)) {
    state.lastTokenWasBuiltin = false;
    stream.eatWhile(isOperatorChar);
    return "operator";
  }
  else {
    // get the whole word
    stream.eatWhile(/[\w\$_{}@]/);
    var word = stream.current();
    // is it one of the listed keywords?
    if (keywords && keywords.propertyIsEnumerable(word))
      return "keyword";
    // is it one of the listed functions?
    if (functions && functions.propertyIsEnumerable(word) ||
        (stream.current().match(/^#@?[a-z0-9_]+ *$/i) && stream.peek()=="(") &&
        !(functions && functions.propertyIsEnumerable(word.toLowerCase()))) {
      state.beforeParams = true;
      state.lastTokenWasBuiltin = false;
      return "keyword";
    }
    if (state.inString) {
      state.lastTokenWasBuiltin = false;
      return "string";
    }
    if (stream.pos > word.length && stream.string.charAt(stream.pos-word.length-1)=="." && state.lastTokenWasBuiltin)
      return "builtin";
    // default: just a "word"
    state.lastTokenWasBuiltin = false;
    return null;
  }
}

function tokenString(quote) {
  return function(stream, state) {
    var escaped = false, next, end = false;
    while ((next = stream.next()) != null) {
      if ((next == quote) && !escaped) {
        end = true;
        break;
      }
      if (quote=='"' && stream.peek() == '$' && !escaped) {
        state.inString = true;
        end = true;
        break;
      }
      escaped = !escaped && next == "\\";
    }
    if (end) state.tokenize = tokenBase;
    return "string";
  };
}

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

function tokenUnparsed(stream, state) {
  var maybeEnd = 0, ch;
  while (ch = stream.next()) {
    if (ch == "#" && maybeEnd == 2) {
      state.tokenize = tokenBase;
      break;
    }
    if (ch == "]")
      maybeEnd++;
    else if (ch != " ")
      maybeEnd = 0;
  }
  return "meta";
}
// Interface

const velocity = {
  startState: function() {
    return {
      tokenize: tokenBase,
      beforeParams: false,
      inParams: false,
      inString: false,
      lastTokenWasBuiltin: false
    };
  },

  token: function(stream, state) {
    if (stream.eatSpace()) return null;
    return state.tokenize(stream, state);
  },
  languageData: {
    commentTokens: {line: "##", block: {open: "#*", close: "*#"}}
  }
};

export { velocity };
