package turn

import (
	"fmt"
	"net"

	pionturn "github.com/pion/turn/v4"
)

type Server struct {
	udpConn     net.PacketConn
	tcpListener net.Listener
	srv         *pionturn.Server
}

type Config struct {
	ListenAddr string // "0.0.0.0:3478"
	PublicIP   string
	Realm      string
	Username   string
	Password   string

	MinRelayPort uint16
	MaxRelayPort uint16
}

func relayGen(ip net.IP, minPort, maxPort uint16) pionturn.RelayAddressGenerator {
	if minPort != 0 && maxPort != 0 && minPort <= maxPort {
		return &pionturn.RelayAddressGeneratorPortRange{
			RelayAddress: ip,
			Address:      "0.0.0.0",
			MinPort:      minPort,
			MaxPort:      maxPort,
		}
	}

	return &pionturn.RelayAddressGeneratorStatic{
		RelayAddress: ip,
		Address:      "0.0.0.0",
	}
}

func Start(cfg Config) (*Server, error) {
	ip := net.ParseIP(cfg.PublicIP)
	if ip == nil {
		return nil, fmt.Errorf("turn: invalid PublicIP: %s", cfg.PublicIP)
	}

	udpConn, err := net.ListenPacket("udp4", cfg.ListenAddr)
	if err != nil {
		return nil, err
	}

	tcpListener, err := net.Listen("tcp4", cfg.ListenAddr)
	if err != nil {
		_ = udpConn.Close()
		return nil, err
	}

	rg := relayGen(ip, cfg.MinRelayPort, cfg.MaxRelayPort)

	srv, err := pionturn.NewServer(pionturn.ServerConfig{
		Realm: cfg.Realm,
		AuthHandler: func(username, realm string, srcAddr net.Addr) ([]byte, bool) {
			if username != cfg.Username {
				return nil, false
			}
			return pionturn.GenerateAuthKey(username, realm, cfg.Password), true
		},
		PacketConnConfigs: []pionturn.PacketConnConfig{
			{
				PacketConn:            udpConn,
				RelayAddressGenerator: rg,
			},
		},
		ListenerConfigs: []pionturn.ListenerConfig{
			{
				Listener:              tcpListener,
				RelayAddressGenerator: rg,
			},
		},
	})

	if err != nil {
		_ = tcpListener.Close()
		_ = udpConn.Close()
		return nil, err
	}

	return &Server{
		udpConn:     udpConn,
		tcpListener: tcpListener,
		srv:         srv,
	}, nil
}

func (s *Server) Close() error {
	if s == nil {
		return nil
	}
	if s.srv != nil {
		_ = s.srv.Close()
	}
	if s.tcpListener != nil {
		_ = s.tcpListener.Close()
	}
	if s.udpConn != nil {
		_ = s.udpConn.Close()
	}
	return nil
}