package main

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

	"golang.org/x/net/http2"
	"golang.org/x/net/http2/hpack"

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

var supportedVersions = map[protocol.VersionNumber]bool{
	30: true,
	32: true,
}

func main() {
	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 := handshake.NewServerConfig(crypto.NewCurve25519KEX(), keyData)

	// TODO: When should a session be created?
	sessions := map[protocol.ConnectionID]*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("Got packet # %d\n", publicHeader.PacketNumber)

		// Send Version Negotiation Packet if the client is speaking a different protocol version
		if publicHeader.VersionFlag && !supportedVersions[publicHeader.VersionNumber] {
			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)
			}
			// TODO: Send all versions
			utils.WriteUint32(fullReply, protocol.VersionNumberToTag(protocol.VersionNumber(32)))
			_, err = conn.WriteToUDP(fullReply.Bytes(), remoteAddr)
			if err != nil {
				panic(err)
			}
			continue
		}

		session, ok := sessions[publicHeader.ConnectionID]
		if !ok {
			session = quic.NewSession(conn, publicHeader.VersionNumber, publicHeader.ConnectionID, serverConfig, handleStream)
			sessions[publicHeader.ConnectionID] = session
		}
		err = session.HandlePacket(remoteAddr, data[0:n-r.Len()], publicHeader, r)
		if err != nil {
			fmt.Printf("Error handling packet: %s\n", err.Error())
		}
	}
}

func handleStream(frame *quic.StreamFrame) []quic.Frame {
	h2r := bytes.NewReader(frame.Data)
	var reply bytes.Buffer
	h2framer := http2.NewFramer(&reply, h2r)
	h2framer.ReadMetaHeaders = hpack.NewDecoder(1024, nil)
	h2frame, err := h2framer.ReadFrame()
	if err != nil {
		return nil
	}
	h2headersFrame := h2frame.(*http2.MetaHeadersFrame)
	fmt.Printf("%#v\n", h2headersFrame)

	var replyHeaders bytes.Buffer
	enc := hpack.NewEncoder(&replyHeaders)
	enc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
	enc.WriteField(hpack.HeaderField{Name: "content-type", Value: "text/plain"})
	enc.WriteField(hpack.HeaderField{Name: "content-length", Value: "12"})
	h2framer.WriteHeaders(http2.HeadersFrameParam{
		StreamID:      h2frame.Header().StreamID,
		EndHeaders:    true,
		BlockFragment: replyHeaders.Bytes(),
	})
	headerStreamFrame := &quic.StreamFrame{
		StreamID: frame.StreamID,
		Data:     reply.Bytes(),
		FinBit:   true,
	}

	dataStreamFrame := &quic.StreamFrame{
		StreamID: h2frame.Header().StreamID,
		Data:     []byte("Hello World!"),
		FinBit:   true,
	}
	fmt.Printf("%#v\n", dataStreamFrame)

	return []quic.Frame{headerStreamFrame, dataStreamFrame}
}