class SMime

abstract class SMime {
    protected function normalizeFilePath(string $path) : string {
        if (!file_exists($path)) {
            throw new RuntimeException(\sprintf('File does not exist: "%s".', $path));
        }
        return 'file://' . str_replace('\\', '/', realpath($path));
    }
    protected function iteratorToFile(iterable $iterator, $stream) : void {
        foreach ($iterator as $chunk) {
            fwrite($stream, $chunk);
        }
    }
    protected function convertMessageToSMimePart($stream, string $type, string $subtype) : SMimePart {
        rewind($stream);
        $headers = '';
        while (!feof($stream)) {
            $buffer = fread($stream, 78);
            $headers .= $buffer;
            // Detect ending of header list
            if (preg_match('/(\\r\\n\\r\\n|\\n\\n)/', $headers, $match)) {
                $headersPosEnd = strpos($headers, $headerBodySeparator = $match[0]);
                break;
            }
        }
        $headers = $this->getMessageHeaders(trim(substr($headers, 0, $headersPosEnd)));
        fseek($stream, $headersPosEnd + \strlen($headerBodySeparator));
        return new SMimePart($this->getStreamIterator($stream), $type, $subtype, $this->getParametersFromHeader($headers['content-type']));
    }
    protected function getStreamIterator($stream) : iterable {
        while (!feof($stream)) {
            (yield str_replace("\n", "\r\n", str_replace("\r\n", "\n", fread($stream, 16372))));
        }
    }
    private function getMessageHeaders(string $headerData) : array {
        $headers = [];
        $headerLines = explode("\r\n", str_replace("\n", "\r\n", str_replace("\r\n", "\n", $headerData)));
        $currentHeaderName = '';
        // Transform header lines into an associative array
        foreach ($headerLines as $headerLine) {
            // Empty lines between headers indicate a new mime-entity
            if ('' === $headerLine) {
                break;
            }
            // Handle headers that span multiple lines
            if (!str_contains($headerLine, ':')) {
                $headers[$currentHeaderName] .= ' ' . trim($headerLine);
                continue;
            }
            $header = explode(':', $headerLine, 2);
            $currentHeaderName = strtolower($header[0]);
            $headers[$currentHeaderName] = trim($header[1]);
        }
        return $headers;
    }
    private function getParametersFromHeader(string $header) : array {
        $params = [];
        preg_match_all('/(?P<name>[a-z-0-9]+)=(?P<value>"[^"]+"|(?:[^\\s;]+|$))(?:\\s+;)?/i', $header, $matches);
        foreach ($matches['value'] as $pos => $paramValue) {
            $params[$matches['name'][$pos]] = trim($paramValue, '"');
        }
        return $params;
    }

}