package main

import (
	"encoding/base64"
	"fmt"
	"log"
	"math/rand"
	"time"

	"badat.dev/maeqtt/v2/mqtt/packets"
)

func init() {
	rand.Seed(time.Now().UnixNano())
}

func Auth(username string, password []byte) bool {
	return true
}

type Session struct {
	ClientID *string

	// Nullable
	Connection          *Connection
	SubscriptionChannel chan packets.PublishPacket

	ExpiryInterval time.Duration
	expireTimer    time.Timer // TODO
}

func NewSession(conn *Connection, p packets.ConnectPacket) Session {
	sess := Session{}
	sess.SubscriptionChannel = make(chan packets.PublishPacket)

	sess.Connect(conn, p)
	return sess
}

func (s *Session) Connect(conn *Connection, p packets.ConnectPacket) {
	if s.Connection != nil {
		//TODO
		panic("Disconnect if already have a connection, unimplemented")
	}
	connAck := packets.ConnackPacket{}

	s.updateExpireTimer(p.Properties.SessionExpiryInterval.Value)

	if p.ClientId != nil {
		if s.ClientID == nil {
			s.ClientID = genClientID()
		}
		connAck.Properties.AssignedClientIdentifier.Value = s.ClientID
	}

	true := byte(1)
	false := byte(0)
	connAck.Properties.WildcardSubscriptionAvailable.Value = &true

	connAck.Properties.RetainAvailable.Value = &false
	connAck.Properties.SharedSubscriptionAvailable.Value = &false


	s.Connection = conn
	err := s.Connection.sendPacket(connAck)
	if err != nil {
		panic(err)
	}
}

// Starts a loop the recieves and responds to packets
func (s *Session) HandlerLoop() {
	for s.Connection != nil {
		select {
		case packet := <-s.Connection.PacketChannel:
			packet.Visit(s)
		case _ = <-s.Connection.ClientDisconnectedChan:
			s.OnDisconnect()
		case subMessage := <-s.SubscriptionChannel:
			//TODO, log for now
			log.Printf("Recieved subscription message, handling UNIMPLEMENTED, message: %v", subMessage)
		}
	}
}

func (s *Session) Disconnect() error {
	panic("Disconnection unimplemented")
	err := s.Connection.close()
	if err != nil {
		return err
	}
	s.OnDisconnect()
	return nil
}

func (s *Session) OnDisconnect() {
	s.Connection = nil
	s.resetExpireTimer()
	log.Printf("Client disconnected, id: %s", *s.ClientID)
}

// newTime is nullable
func (s *Session) updateExpireTimer(newTime *uint32) {
	var expiry = uint32(0)
	if newTime != nil {
		expiry = *newTime
	} else {
		expiry = uint32(0)
	}
	s.ExpiryInterval = time.Duration(expiry) * time.Second

	if s.Connection == nil {
		s.resetExpireTimer()
	}
}
func (s *Session) resetExpireTimer() {
	//s.expireTimer.Reset(s.ExpiryInterval)
}

func genClientID() *string {
	buf := make([]byte, 32)
	_, err := rand.Read(buf)
	if err != nil {
		// I don't think this can actually happen but just in case panic
		panic(fmt.Errorf("Failed to generate a client id, %e", err))
	}
	id := "Client_rand_" + base64.URLEncoding.WithPadding(base64.NoPadding).EncodeToString(buf)
	return &id
}

func (s *Session) VisitConnect(_ packets.ConnectPacket) {
	// ERROR CANNOT RECIEVE CONNECT ON AN ALREADY OPEN CONNECTION
	s.Disconnect()
}

func (s *Session) VisitPublish(p packets.PublishPacket) {
	println("UNIMPLEMENTED, Publishing packet, message:", string(p.Payload))
	subs, lock := Subscriptions.GetSubscriptions(p.TopicName) 
	defer lock.Unlock()

	for _, sub := range subs {
		go func(sub Subscription) {sub <- p}(sub)
	}
}

func (s *Session) VisitDisconnect(p packets.DisconnectPacket) {
	//TODO FINISH
	// HANDLE CLIENT DISCONNECTING
	s.OnDisconnect()
}

func (s *Session) VisitSubscribe(p packets.SubscribePacket) {
	//TODO FINISH
	for _, filter := range p.TopicFilters {
		Subscriptions.Subscribe(filter.Topic, s.SubscriptionChannel)		
	}
}

func (s *Session) VisitUnsubscribe(_ packets.UnsubscribePacket) {
	panic("not implemented") // TODO: Implement
}

func (s *Session) VisitPing(p packets.PingreqPacket) {
	s.Connection.sendPacket(packets.PingrespPacket{})
}

func (s *Session) VisitPubackPacket(_ packets.PubackPacket) {
	panic("not implemented") // TODO: Implement
}

func (s *Session) VisitPubrecPacket(_ packets.PubrecPacket) {
	panic("not implemented") // TODO: Implement
}

func (s *Session) VisitPubrelPacket(_ packets.PubrelPacket) {
	panic("not implemented") // TODO: Implement
}

func (s *Session) VisitPubcompPacket(_ packets.PubcompPacket) {
	panic("not implemented") // TODO: Implement
}