class ProtobufSerializer

final class ProtobufSerializer {
    private function __construct(string $contentType) {
    }
    public static function getDefault() : ProtobufSerializer {
        return new self(ContentTypes::PROTOBUF);
    }
    
    /**
     * @psalm-param TransportInterface<SUPPORTED_CONTENT_TYPES> $transport
     */
    public static function forTransport(TransportInterface $transport) : ProtobufSerializer {
        return match ($contentType = $transport->contentType()) {    ContentTypes::PROTOBUF, ContentTypes::JSON, ContentTypes::NDJSON => new self($contentType),
            default => throw new InvalidArgumentException(sprintf('Not supported content type "%s"', $contentType)),
        
        };
    }
    public function serializeTraceId(string $traceId) : string {
        // @phpstan-ignore-next-line
        return match ($this->contentType) {    ContentTypes::PROTOBUF => $traceId,
            ContentTypes::JSON, ContentTypes::NDJSON => base64_decode(bin2hex($traceId)),
        
        };
    }
    public function serializeSpanId(string $spanId) : string {
        // @phpstan-ignore-next-line
        return match ($this->contentType) {    ContentTypes::PROTOBUF => $spanId,
            ContentTypes::JSON, ContentTypes::NDJSON => base64_decode(bin2hex($spanId)),
        
        };
    }
    public function serialize(Message $message) : string {
        // @phpstan-ignore-next-line
        return match ($this->contentType) {    ContentTypes::PROTOBUF => $message->serializeToString(),
            ContentTypes::JSON => self::postProcessJsonEnumValues($message, $message->serializeToJsonString()),
            ContentTypes::NDJSON => self::postProcessJsonEnumValues($message, $message->serializeToJsonString()) . "\n",
        
        };
    }
    
    /**
     * @phan-suppress PhanParamTooManyInternal (@see https://github.com/phan/phan/pull/4840)
     * @throws Exception
     */
    public function hydrate(Message $message, string $payload) : void {
        // @phpstan-ignore-next-line
        match ($this->contentType) {    ContentTypes::PROTOBUF => $message->mergeFromString($payload),
            ContentTypes::JSON, ContentTypes::NDJSON => $message->mergeFromJsonString($payload, true),
        
        };
    }
    
    /**
     * Workaround until protobuf exposes `FormatEnumsAsIntegers` option.
     *
     * [JSON Protobuf Encoding](https://opentelemetry.io/docs/specs/otlp/#json-protobuf-encoding):
     * > Values of enum fields MUST be encoded as integer values.
     *
     * @see https://github.com/open-telemetry/opentelemetry-php/issues/978
     * @see https://github.com/protocolbuffers/protobuf/pull/12707
     */
    private static function postProcessJsonEnumValues(Message $message, string $payload) : string {
        $pool = DescriptorPool::getGeneratedPool();
        $desc = $pool->getDescriptorByClassName($message::class);
        if (!$desc instanceof Descriptor) {
            return $payload;
        }
        $data = json_decode($payload);
        unset($payload);
        self::traverseDescriptor($data, $desc);
        return json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
    }
    private static function traverseDescriptor(object $data, Descriptor $desc) : void {
        for ($i = 0, $n = $desc->getFieldCount(); $i < $n; $i++) {
            // @phan-suppress-next-line PhanParamTooManyInternal
            $field = $desc->getField($i);
            $name = lcfirst(strtr(ucwords((string) $field->getName(), '_'), [
                '_' => '',
            ]));
            if (!property_exists($data, $name)) {
                continue;
            }
            if ($field->getLabel() === GPBLabel::REPEATED) {
                foreach ($data->{$name} as $key => $value) {
                    $data->{$name}[$key] = self::traverseFieldDescriptor($value, $field);
                }
            }
            else {
                $data->{$name} = self::traverseFieldDescriptor($data->{$name}, $field);
            }
        }
    }
    private static function traverseFieldDescriptor($data, FieldDescriptor $field) {
        switch ($field->getType()) {
            case GPBType::MESSAGE:
                self::traverseDescriptor($data, $field->getMessageType());
                break;
            case GPBType::ENUM:
                $enum = $field->getEnumType();
                for ($i = 0, $n = $enum->getValueCount(); $i < $n; $i++) {
                    if ($data === $enum->getValue($i)
                        ->getName()) {
                        return $enum->getValue($i)
                            ->getNumber();
                    }
                }
                break;
        }
        return $data;
    }

}