package main

import (
	"bytes"
	"fmt"
	"net"
	"os"

	"github.com/lucas-clemente/quic-go"
	"github.com/lucas-clemente/quic-go/crypto"
	"github.com/lucas-clemente/quic-go/utils"
)

const (
	// QuicVersionNumber32 is the QUIC protocol version
	QuicVersionNumber32 = 32
)

func main() {
	QuicVersion32, _ := utils.ReadUint32BigEndian(bytes.NewReader([]byte{'Q', '0', 48 + (QuicVersionNumber32/10)%10, 48 + QuicVersionNumber32%10}))

	path := os.Getenv("GOPATH") + "/src/github.com/lucas-clemente/quic-go/example/"
	keyData, err := crypto.LoadKeyData(path+"cert.der", path+"key.der")
	if err != nil {
		panic(err)
	}

	serverConfig := quic.NewServerConfig(crypto.NewCurve25519KEX(), keyData)

	// TODO: When should a session be created?
	sessions := map[uint64]*quic.Session{}

	addr, err := net.ResolveUDPAddr("udp", "localhost:6121")
	if err != nil {
		panic(err)
	}

	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		panic(err)
	}

	for {
		data := make([]byte, 0x10000)
		n, remoteAddr, err := conn.ReadFromUDP(data)
		if err != nil {
			panic(err)
		}
		data = data[:n]
		r := bytes.NewReader(data)

		fmt.Printf("Received %d bytes from %v\n", n, remoteAddr)

		publicHeader, err := quic.ParsePublicHeader(r)
		if err != nil {
			panic(err)
		}
		fmt.Printf("%#v\n", publicHeader)

		// Send Version Negotiation Packet if the client is speaking a different protocol version
		if publicHeader.VersionFlag && publicHeader.QuicVersion != QuicVersion32 {
			fmt.Println("Sending VersionNegotiationPacket")
			fullReply := &bytes.Buffer{}
			responsePublicHeader := quic.PublicHeader{ConnectionID: publicHeader.ConnectionID, PacketNumber: 1, VersionFlag: true}
			err = responsePublicHeader.WritePublicHeader(fullReply)
			if err != nil {
				panic(err)
			}
			utils.WriteUint32BigEndian(fullReply, QuicVersion32)
			_, err := conn.WriteToUDP(fullReply.Bytes(), remoteAddr)
			if err != nil {
				panic(err)
			}
			continue
		}

		session, ok := sessions[publicHeader.ConnectionID]
		if !ok {
			session = quic.NewSession(conn, publicHeader.ConnectionID, serverConfig)
			sessions[publicHeader.ConnectionID] = session
		}
		session.HandlePacket(remoteAddr, data[0:n-r.Len()], publicHeader, r)
	}
}