package protocol

import (
	"fmt"
)

// A PacketNumber in QUIC
type PacketNumber uint64

// PacketNumberLen is the length of the packet number in bytes
type PacketNumberLen uint8

const (
	// PacketNumberLenInvalid is the default value and not a valid length for a packet number
	PacketNumberLenInvalid PacketNumberLen = 0
	// PacketNumberLen1 is a packet number length of 1 byte
	PacketNumberLen1 PacketNumberLen = 1
	// PacketNumberLen2 is a packet number length of 2 bytes
	PacketNumberLen2 PacketNumberLen = 2
	// PacketNumberLen4 is a packet number length of 4 bytes
	PacketNumberLen4 PacketNumberLen = 4
	// PacketNumberLen6 is a packet number length of 6 bytes
	PacketNumberLen6 PacketNumberLen = 6
)

// The PacketType is the Long Header Type (only used for the IETF draft header format)
type PacketType uint8

const (
	// PacketTypeInitial is the packet type of an Initial packet
	PacketTypeInitial PacketType = 0x7f
	// PacketTypeRetry is the packet type of a Retry packet
	PacketTypeRetry PacketType = 0x7e
	// PacketTypeHandshake is the packet type of a Handshake packet
	PacketTypeHandshake PacketType = 0x7d
	// PacketType0RTT is the packet type of a 0-RTT packet
	PacketType0RTT PacketType = 0x7c
)

func (t PacketType) String() string {
	switch t {
	case PacketTypeInitial:
		return "Initial"
	case PacketTypeRetry:
		return "Retry"
	case PacketTypeHandshake:
		return "Handshake"
	case PacketType0RTT:
		return "0-RTT Protected"
	default:
		return fmt.Sprintf("unknown packet type: %d", t)
	}
}

// A ByteCount in QUIC
type ByteCount uint64

// MaxByteCount is the maximum value of a ByteCount
const MaxByteCount = ByteCount(1<<62 - 1)

// An ApplicationErrorCode is an application-defined error code.
type ApplicationErrorCode uint16

// MaxReceivePacketSize maximum packet size of any QUIC packet, based on
// ethernet's max size, minus the IP and UDP headers. IPv6 has a 40 byte header,
// UDP adds an additional 8 bytes.  This is a total overhead of 48 bytes.
// Ethernet's max packet size is 1500 bytes,  1500 - 48 = 1452.
const MaxReceivePacketSize ByteCount = 1452

// DefaultTCPMSS is the default maximum packet size used in the Linux TCP implementation.
// Used in QUIC for congestion window computations in bytes.
const DefaultTCPMSS ByteCount = 1460

// MinClientHelloSize is the minimum size the server expects an inchoate CHLO to have (in gQUIC)
const MinClientHelloSize = 1024

// MinInitialPacketSize is the minimum size an Initial packet (in IETF QUIC) is required to have.
const MinInitialPacketSize = 1200

// MaxClientHellos is the maximum number of times we'll send a client hello
// The value 3 accounts for:
// * one failure due to an incorrect or missing source-address token
// * one failure due the server's certificate chain being unavailable and the server being unwilling to send it without a valid source-address token
const MaxClientHellos = 3

// ConnectionIDLenGQUIC is the length of the source Connection ID used on gQUIC QUIC packets.
const ConnectionIDLenGQUIC = 8

// MinConnectionIDLenInitial is the minimum length of the destination connection ID on an Initial packet.
const MinConnectionIDLenInitial = 8