shady-css-parser/src/shady-css/token.ts

A fast, small and flexible CSS parser.

/**
 * @license
 * Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at
 * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
 * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
 * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
 * Google as part of the polymer project is also subject to an additional IP
 * rights grant found at http://polymer.github.io/PATENTS.txt
 */

/**
 * An enumeration of Token types.
 */
export enum TokenType {
  none = 0,
  whitespace = (2 ** 0),
  string = (2 ** 1),
  comment = (2 ** 2),
  word = (2 ** 3),
  boundary = (2 ** 4),
  propertyBoundary = (2 ** 5),
  // Special cases for boundary:
  openParenthesis = (2 ** 6) | TokenType.boundary,
  closeParenthesis = (2 ** 7) | TokenType.boundary,
  at = (2 ** 8) | TokenType.boundary,
  openBrace = (2 ** 9) | TokenType.boundary,
  // [};] are property boundaries:
  closeBrace = (2 ** 10) | TokenType.propertyBoundary | TokenType.boundary,
  semicolon = (2 ** 11) | TokenType.propertyBoundary | TokenType.boundary,
  // : is a chimaeric abomination:
  // foo:bar{}
  // foo:bar;
  colon = (2 ** 12) | TokenType.boundary | TokenType.word,

  // TODO: are these two boundaries? I mean, sometimes they are I guess? Or
  //       maybe they shouldn't exist in the boundaryTokenTypes map.
  hyphen = (2 ** 13),
  underscore = (2 ** 14)
}


/**
 * Class that describes individual tokens as produced by the Tokenizer.
 */
class Token {
  static type = TokenType;

  readonly type: TokenType;
  readonly start: number;
  readonly end: number;
  previous: Token|null;
  next: Token|null;

  /**
   * Create a Token instance.
   * @param type The lexical type of the Token.
   * @param start The start index of the text corresponding to the
   * Token in the CSS text.
   * @param end The end index of the text corresponding to the Token
   * in the CSS text.
   */
  constructor(type: TokenType, start: number, end: number) {
    this.type = type;
    this.start = start;
    this.end = end;
    this.previous = null;
    this.next = null;
  }

  /**
   * Test if the Token matches a given numeric type. Types match if the bitwise
   * AND of the Token's type and the argument type are equivalent to the
   * argument type.
   * @param type The numeric type to test for equivalency with the
   * Token.
   */
  is(type: TokenType) {
    return (this.type & type) === type;
  }
}

/**
 * A mapping of boundary token text to their corresponding types.
 */
const boundaryTokenTypes: {[boundaryText: string]: TokenType | undefined} = {
  '(': Token.type.openParenthesis,
  ')': Token.type.closeParenthesis,
  ':': Token.type.colon,
  '@': Token.type.at,
  '{': Token.type.openBrace,
  '}': Token.type.closeBrace,
  ';': Token.type.semicolon,
  '-': Token.type.hyphen,
  '_': Token.type.underscore
};

export {Token, boundaryTokenTypes};