protected function consumeHeadline($lines, $current)
	{
		if ($lines[$current][0] === '#') {
			// ATX headline
			$level = 1;
			while (isset($lines[$current][$level]) && $lines[$current][$level] === '#' && $level < 6) {
				$level++;
			}
			$block = [
				'headline',
				'content' => $this->parseInline(trim($lines[$current], "# \t")),
				'level' => $level,
			];
			return [$block, $current];
		} else {
			// underlined headline
			$block = [
				'headline',
				'content' => $this->parseInline($lines[$current]),
				'level' => $lines[$current + 1][0] === '=' ? 1 : 2,
			];
			return [$block, $current + 1];
		}
	}