package rtspserver

import (
	"context"
	"crypto/rand"
	"crypto/tls"
	"encoding/binary"
	"strconv"
	"sync"
	"time"

	"github.com/aler9/gortsplib"
	"github.com/aler9/gortsplib/pkg/base"

	"github.com/aler9/rtsp-simple-server/internal/conf"
	"github.com/aler9/rtsp-simple-server/internal/logger"
	"github.com/aler9/rtsp-simple-server/internal/pathman"
	"github.com/aler9/rtsp-simple-server/internal/rtspconn"
	"github.com/aler9/rtsp-simple-server/internal/rtspsession"
	"github.com/aler9/rtsp-simple-server/internal/stats"
)

func newSessionVisualID(sessions map[*gortsplib.ServerSession]*rtspsession.Session) (string, error) {
	for {
		b := make([]byte, 4)
		_, err := rand.Read(b)
		if err != nil {
			return "", err
		}

		id := strconv.FormatUint(uint64(binary.LittleEndian.Uint32(b)), 10)

		alreadyPresent := func() bool {
			for _, s := range sessions {
				if s.VisualID() == id {
					return true
				}
			}
			return false
		}()
		if !alreadyPresent {
			return id, nil
		}
	}
}

// Parent is implemented by program.
type Parent interface {
	Log(logger.Level, string, ...interface{})
}

// Server is a RTSP server.
type Server struct {
	readTimeout         time.Duration
	isTLS               bool
	rtspAddress         string
	protocols           map[conf.Protocol]struct{}
	runOnConnect        string
	runOnConnectRestart bool
	stats               *stats.Stats
	pathMan             *pathman.PathManager
	parent              Parent

	ctx       context.Context
	ctxCancel func()
	wg        sync.WaitGroup
	srv       *gortsplib.Server
	mutex     sync.RWMutex
	conns     map[*gortsplib.ServerConn]*rtspconn.Conn
	sessions  map[*gortsplib.ServerSession]*rtspsession.Session
}

// New allocates a Server.
func New(
	ctxParent context.Context,
	address string,
	readTimeout time.Duration,
	writeTimeout time.Duration,
	readBufferCount int,
	readBufferSize int,
	useUDP bool,
	useMulticast bool,
	rtpAddress string,
	rtcpAddress string,
	multicastIPRange string,
	multicastRTPPort int,
	multicastRTCPPort int,
	isTLS bool,
	serverCert string,
	serverKey string,
	rtspAddress string,
	protocols map[conf.Protocol]struct{},
	runOnConnect string,
	runOnConnectRestart bool,
	stats *stats.Stats,
	pathMan *pathman.PathManager,
	parent Parent) (*Server, error) {
	ctx, ctxCancel := context.WithCancel(ctxParent)

	s := &Server{
		readTimeout: readTimeout,
		isTLS:       isTLS,
		rtspAddress: rtspAddress,
		protocols:   protocols,
		stats:       stats,
		pathMan:     pathMan,
		parent:      parent,
		ctx:         ctx,
		ctxCancel:   ctxCancel,
		conns:       make(map[*gortsplib.ServerConn]*rtspconn.Conn),
		sessions:    make(map[*gortsplib.ServerSession]*rtspsession.Session),
	}

	s.srv = &gortsplib.Server{
		Handler:         s,
		ReadTimeout:     readTimeout,
		WriteTimeout:    writeTimeout,
		ReadBufferCount: readBufferCount,
		ReadBufferSize:  readBufferSize,
	}

	if useUDP {
		s.srv.UDPRTPAddress = rtpAddress
		s.srv.UDPRTCPAddress = rtcpAddress
	}

	if useMulticast {
		s.srv.MulticastIPRange = multicastIPRange
		s.srv.MulticastRTPPort = multicastRTPPort
		s.srv.MulticastRTCPPort = multicastRTCPPort
	}

	if isTLS {
		cert, err := tls.LoadX509KeyPair(serverCert, serverKey)
		if err != nil {
			return nil, err
		}

		s.srv.TLSConfig = &tls.Config{Certificates: []tls.Certificate{cert}}
	}

	err := s.srv.Start(address)
	if err != nil {
		return nil, err
	}

	if s.srv.UDPRTPAddress != "" {
		s.Log(logger.Info, "UDP/RTP listener opened on %s", s.srv.UDPRTPAddress)
	}

	if s.srv.UDPRTCPAddress != "" {
		s.Log(logger.Info, "UDP/RTCP listener opened on %s", s.srv.UDPRTCPAddress)
	}

	s.Log(logger.Info, "TCP listener opened on %s", address)

	s.wg.Add(1)
	go s.run()

	return s, nil
}

// Log is the main logging function.
func (s *Server) Log(level logger.Level, format string, args ...interface{}) {
	label := func() string {
		if s.isTLS {
			return "RTSPS"
		}
		return "RTSP"
	}()
	s.parent.Log(level, "[%s] "+format, append([]interface{}{label}, args...)...)
}

// Close closes a Server.
func (s *Server) Close() {
	s.ctxCancel()
	s.wg.Wait()
}

func (s *Server) run() {
	defer s.wg.Done()

	s.wg.Add(1)
	serverErr := make(chan error)
	go func() {
		defer s.wg.Done()

		err := s.srv.Wait()

		select {
		case serverErr <- err:
		case <-s.ctx.Done():
		}
	}()

outer:
	select {
	case err := <-serverErr:
		s.Log(logger.Warn, "ERR: %s", err)
		break outer

	case <-s.ctx.Done():
		break outer
	}

	s.ctxCancel()

	s.srv.Close()
}

// OnConnOpen implements gortsplib.ServerHandlerOnConnOpen.
func (s *Server) OnConnOpen(ctx *gortsplib.ServerHandlerOnConnOpenCtx) {
	c := rtspconn.New(
		s.rtspAddress,
		s.readTimeout,
		s.runOnConnect,
		s.runOnConnectRestart,
		s.pathMan,
		s.stats,
		ctx.Conn,
		s)

	s.mutex.Lock()
	s.conns[ctx.Conn] = c
	s.mutex.Unlock()
}

// OnConnClose implements gortsplib.ServerHandlerOnConnClose.
func (s *Server) OnConnClose(ctx *gortsplib.ServerHandlerOnConnCloseCtx) {
	s.mutex.Lock()
	c := s.conns[ctx.Conn]
	delete(s.conns, ctx.Conn)
	s.mutex.Unlock()

	c.ParentClose(ctx.Error)
}

// OnRequest implements gortsplib.ServerHandlerOnRequest.
func (s *Server) OnRequest(sc *gortsplib.ServerConn, req *base.Request) {
	s.mutex.Lock()
	c := s.conns[sc]
	s.mutex.Unlock()

	c.OnRequest(req)
}

// OnResponse implements gortsplib.ServerHandlerOnResponse.
func (s *Server) OnResponse(sc *gortsplib.ServerConn, res *base.Response) {
	s.mutex.Lock()
	c := s.conns[sc]
	s.mutex.Unlock()

	c.OnResponse(res)
}

// OnSessionOpen implements gortsplib.ServerHandlerOnSessionOpen.
func (s *Server) OnSessionOpen(ctx *gortsplib.ServerHandlerOnSessionOpenCtx) {
	s.mutex.Lock()

	// do not use ss.ID() in logs, since it allows to take ownership of a session
	// use a new random ID
	visualID, _ := newSessionVisualID(s.sessions)

	se := rtspsession.New(
		s.rtspAddress,
		s.protocols,
		visualID,
		ctx.Session,
		ctx.Conn,
		s.pathMan,
		s)

	s.sessions[ctx.Session] = se
	s.mutex.Unlock()
}

// OnSessionClose implements gortsplib.ServerHandlerOnSessionClose.
func (s *Server) OnSessionClose(ctx *gortsplib.ServerHandlerOnSessionCloseCtx) {
	s.mutex.Lock()
	se := s.sessions[ctx.Session]
	delete(s.sessions, ctx.Session)
	s.mutex.Unlock()

	se.ParentClose()
}

// OnDescribe implements gortsplib.ServerHandlerOnDescribe.
func (s *Server) OnDescribe(ctx *gortsplib.ServerHandlerOnDescribeCtx) (*base.Response, *gortsplib.ServerStream, error) {
	s.mutex.RLock()
	c := s.conns[ctx.Conn]
	s.mutex.RUnlock()
	return c.OnDescribe(ctx)
}

// OnAnnounce implements gortsplib.ServerHandlerOnAnnounce.
func (s *Server) OnAnnounce(ctx *gortsplib.ServerHandlerOnAnnounceCtx) (*base.Response, error) {
	s.mutex.RLock()
	c := s.conns[ctx.Conn]
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	return se.OnAnnounce(c, ctx)
}

// OnSetup implements gortsplib.ServerHandlerOnSetup.
func (s *Server) OnSetup(ctx *gortsplib.ServerHandlerOnSetupCtx) (*base.Response, *gortsplib.ServerStream, error) {
	s.mutex.RLock()
	c := s.conns[ctx.Conn]
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	return se.OnSetup(c, ctx)
}

// OnPlay implements gortsplib.ServerHandlerOnPlay.
func (s *Server) OnPlay(ctx *gortsplib.ServerHandlerOnPlayCtx) (*base.Response, error) {
	s.mutex.RLock()
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	return se.OnPlay(ctx)
}

// OnRecord implements gortsplib.ServerHandlerOnRecord.
func (s *Server) OnRecord(ctx *gortsplib.ServerHandlerOnRecordCtx) (*base.Response, error) {
	s.mutex.RLock()
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	return se.OnRecord(ctx)
}

// OnPause implements gortsplib.ServerHandlerOnPause.
func (s *Server) OnPause(ctx *gortsplib.ServerHandlerOnPauseCtx) (*base.Response, error) {
	s.mutex.RLock()
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	return se.OnPause(ctx)
}

// OnFrame implements gortsplib.ServerHandlerOnFrame.
func (s *Server) OnFrame(ctx *gortsplib.ServerHandlerOnFrameCtx) {
	s.mutex.RLock()
	se := s.sessions[ctx.Session]
	s.mutex.RUnlock()
	se.OnIncomingFrame(ctx)
}