// Move pointer to position of token
// --------------------------------------------------------------------------------
// @param [string] $source: JSON complete source
// @param [number] $pointer: current pointer
// @param [string] $token: token to reach
// --------------------------------------------------------------------------------
// @throw "Expected $token; found {x}."
// @throw "Expected $token but reached end of stream."
// --------------------------------------------------------------------------------
// @return [number|false] new pointer

@function _consume($source, $pointer, $token) {
  $length: str-length($source);

  @while $pointer <= $length {
    $char: str-slice($source, $pointer, $pointer);
    $pointer: $pointer + 1;

    @if $char == $token {
      @return $pointer;
    } @else if $char == " " or $char == "	" {
      // @continue;
    } @else {
      @return _throw(
        "Expected `" + $token + "; ` found `" + $char + "`.",
        $pointer
      );
    }
  }

  @return _throw(
    "Expected `" + $token + "` but reached end of stream.",
    $pointer
  );
}