class Rfc2231Encoder

final class Rfc2231Encoder implements EncoderInterface {
    
    /**
     * Takes an unencoded string and produces a string encoded according to RFC 2231 from it.
     */
    public function encodeString(string $string, ?string $charset = 'utf-8', int $firstLineOffset = 0, int $maxLineLength = 0) : string {
        $lines = [];
        $lineCount = 0;
        $lines[] = '';
        $currentLine =& $lines[$lineCount++];
        if (0 >= $maxLineLength) {
            $maxLineLength = 75;
        }
        $charStream = new CharacterStream($string, $charset);
        $thisLineLength = $maxLineLength - $firstLineOffset;
        while (null !== ($char = $charStream->read(4))) {
            $encodedChar = rawurlencode($char);
            if ('' !== $currentLine && \strlen($currentLine . $encodedChar) > $thisLineLength) {
                $lines[] = '';
                $currentLine =& $lines[$lineCount++];
                $thisLineLength = $maxLineLength;
            }
            $currentLine .= $encodedChar;
        }
        return implode("\r\n", $lines);
    }

}