botlang / botlang-js

/**

 * Representation of the input stream with some util functions. The class is used by the botlang

 * lexer which takes an instance of `Input` as a constructor argument and converts it into a

 * token stream.

 */

class Input {

  /**

   * Create an Input.

   * @param {String} input

   */

  /**

   * Determine whether or not there are no more values in the stream.

   * @return {Boolean}

   */

  eof() {

    return '' === this.peek();

  }

  /**

   * Throw a new Error.

   * @param  {String} message

   * @throws {Error}

   * @return {void}

   */

  error(message) {

    throw new Error(`${message} (Line: ${this.line}, Column: ${this.column})`);

  }

  /**

   * Return the next character from the input stream.

   * @return {String}

   */

  next() {

    const character = this.input.charAt(this.position += 1);

    // Keep track of the current column and line number

    if ('\n' === character) {

      this.column = 0;

      this.line += 1;

    } else {

      this.column += 1;

    }

    return character;

  }

  /**

   * Return the character from the current position without "consuming" it.

   * @return {String}

   */

  peek() {

    return this.input.charAt(this.position);

  }

}

export default Input;