sap

type AddressType uint8

type Header struct {
	// The version number field MUST be set to 1
	Version uint8

	// If the A bit is 0, the originating source field contains a 32-bit IPv4 address.
	// If the A bit is 1, the originating source contains a 128-bit IPv6 address.
	AddressType AddressType

	// SAP announcers MUST set this to 0, SAP listeners MUST ignore the contents of this field.
	Reserved uint8

	// If this bit is set to 0 this is a session announcement packet
	// If this bit is set to 1 this is a session deletion packet.
	MessageType MessageType

	// If the encryption bit is set to 1, the payload of the SAP packet is encrypted.
	// If this bit is 0 the packet is not encrypted.
	Encrypted uint8

	// If the compressed bit is set to 1, the payload is
	// compressed using the zlib compression algorithm (https://datatracker.ietf.org/doc/html/rfc2974#ref-3)
	Compressed uint8

	// An 8 bit unsigned quantity giving the number of 32 bit words following the main SAP header that contain aauthentication data.
	// If it is zero, no authentication header is present.
	AuthenticationLength uint8

	// Digital signature of the packet, with length as specified by the authentication length header field.
	AuthenticationData []uint32

	// A 16 bit quantity that, used in combination with the originating source, provides a globally unique identifier
	// indicating the precise version of this announcement.
	//
	// It MUST be unique for each session announced by a particular SAP announcer
	// and it MUST be changed if the session description is modified
	// (and a session deletion message SHOULD be sent for the old version of the session).
	//
	// SAP listeners MAY silently discard messages if the message
	// identifier hash is set to zero.
	MessageIDHash uint16

	// This gives the IP address of the original source
	// of the message.  This is an IPv4 address if the A field is set to
	// zero, else it is an IPv6 address. The address is stored in
	// network byte order.
	OriginatingSource net.IP

	// The payload type field is a MIME content type specifier, describing the format of the payload.
	//
	// This is a variable length ASCII text string, followed by a single zero byte (ASCII NUL).
	// The payload type SHOULD be included in all packets.
	// If the payload type is `application/sdp' both the payload type and its terminating zero byte MAY be omitted
	//
	// Technically, it is part of the Payload, but makes more sense to parse it with the rest of the header
	PayloadType string
}

type MessageType uint8

type Option func(*Header)

type Packet struct {
	Header
	Payload []byte
}