package twitchpubsub

import (
	"time"

	"encoding/json"
	"errors"
	"github.com/google/uuid"
	"github.com/gorilla/websocket"
	"log"
	"strings"
	"sync"
)

const (
	Ping = "PING"
	Pong = "PONG"
	Message = "MESSAGE"
	Response = "RESPONSE"

	TwitchUrl = "wss://pubsub-edge.twitch.tv"
)

type twitchMessage struct {
	Type string `json:"type"`
	Nonce string `json:"nonce,omitempty"`
	Error string `json:"error,omitempty"`
	Data struct {
		Topic string
		Message string
	     } `json:"data"`
}

type twitchListen struct {
	Type string `json:"type"`
	Nonce string `json:"nonce"`
	Data *twitchListenData `json:"data"`
}

type twitchListenData struct {
	Topics []string `json:"topics"`
	AuthToken string `json:"auth_token,omitempty"`
}

type TwitchPubSub struct {
	sync.RWMutex

	wsConn       *websocket.Conn
	wsMutex sync.RWMutex

	debug bool

	// Event handlers
	handlersMu   sync.RWMutex
	handlers     map[string][]*eventHandlerInstance
	onceHandlers map[string][]*eventHandlerInstance

	// Responses
	listening chan interface{}
	responseCh chan *twitchMessage

	SubscribedTopics []string
	LastPing time.Time
}

func NewTwitchPubSub() *TwitchPubSub {
	t := &TwitchPubSub{
		responseCh: make(chan *twitchMessage),
		SubscribedTopics: make([]string, 0),
	}

	return t
}

func (t *TwitchPubSub) EnableDebug() {
	t.debug = true
}

func (t *TwitchPubSub) Open() error {
	t.Lock()
	defer t.Unlock()

	if t.debug {
		log.Println("Opening connection to", TwitchUrl)
	}

	c, _, err := websocket.DefaultDialer.Dial(TwitchUrl, nil)

	if err != nil {
		if t.debug {
			log.Println("error opening connection:", err)
		}
		return err
	}

	t.wsConn = c

	t.listening = make(chan interface{})

	go t.reader(t.wsConn, t.listening)
	go t.pinger(t.wsConn, t.listening)

	if len(t.SubscribedTopics) > 0 {
		return t.listen(t.SubscribedTopics)
	} else {
		t.wsMutex.Lock()
		defer t.wsMutex.Unlock()
		t.LastPing = time.Now()
		return t.wsConn.WriteJSON(&twitchMessage{Type: Ping})
	}

	return nil
}

func (t *TwitchPubSub) Close() error {
	if t.listening != nil {
		close(t.listening)
		t.listening = nil
	}

	t.Lock()

	if t.wsConn != nil {
		// To cleanly close a connection, a client should send a close
		// frame and wait for the server to close the connection.
		t.wsConn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))

		time.Sleep(1 * time.Second)

		t.wsConn.Close()

		t.wsConn = nil
	}

	t.Unlock()

	return nil
}

func (t *TwitchPubSub) reconnect() error {
	wait := time.Duration(1)

	for {
		if t.debug {
			log.Println("Reconnecting")
		}

		err := t.Open()

		if err == nil {
			return err
		}

		if t.debug {
			log.Println("Unable to reconnect")
		}

		<-time.After(wait * time.Second)
		wait *= 2

		if wait > 600 {
			wait = 600
		}
	}
}

func (t *TwitchPubSub) Listen(topics []string) error {
	err := t.listen(topics)

	if err == nil {
		// Update topic list
		t.SubscribedTopics = append(t.SubscribedTopics, topics...)
	}

	return err
}

func (t *TwitchPubSub) listen(topics []string) error {
	if t.debug {
		log.Println("Attempting to listen to topics", topics)
	}

	nonce := strings.Replace(uuid.New().String(), "-", "", -1)

	t.wsMutex.Lock()
	t.wsConn.WriteJSON(&twitchListen{
		Type: "LISTEN",
		Nonce: nonce,
		Data: &twitchListenData{Topics: topics},
	})
	t.wsMutex.Unlock()

	msg := <- t.responseCh

	if msg.Nonce != nonce {
		// Something is wrong, concurrent access?
		return errors.New("unexpected nonce")
	}

	if len(msg.Error) > 0 {
		return errors.New(msg.Error)
	}

	return nil
}

func (t *TwitchPubSub) Unlisten(topics []string) error {
	nonce := strings.Replace(uuid.New().String(), "-", "", -1)

	for i := 0; i < len(topics); i++ {
		for x := 0; x < len(t.SubscribedTopics); x++ {
			if t.SubscribedTopics[x] == topics[i] {
				t.SubscribedTopics = append(t.SubscribedTopics[:x], t.SubscribedTopics[x+1:]...)
				break
			}
		}
	}

	t.wsMutex.Lock()
	t.wsConn.WriteJSON(&twitchListen{
		Type: "UNLISTEN",
		Nonce: nonce,
		Data: &twitchListenData{Topics: topics},
	})
	t.wsMutex.Unlock()

	msg := <- t.responseCh

	if msg.Nonce != nonce {
		// Something is wrong, concurrent access?
		return errors.New("unexpected nonce")
	}

	if len(msg.Error) > 0 {
		return errors.New(msg.Error)
	}

	return nil
}

func (t *TwitchPubSub) reader(wsConn *websocket.Conn, listening <-chan interface{}) {
	for {
		t.wsConn.SetReadDeadline(t.LastPing.Add(45 * time.Second))

		var message twitchMessage
		err := t.wsConn.ReadJSON(&message)

		if err != nil {
			t.RLock()
			sameConnection := t.wsConn == wsConn
			t.RUnlock()

			if t.debug {
				log.Println("Unexpected error", err, "- attempting to reconnect")
			}

			if sameConnection {
				t.Close()
				t.reconnect()
			}
			return
		}

		select {
		case <-listening:
			return
		default:
			if message.Type == Pong {
				// PONG!
			} else if message.Type == Message {
				var data interface{}

				if err := json.Unmarshal([]byte(message.Data.Message), &data); err != nil {
					continue
				}

				if strings.Index(message.Data.Topic, "video-playback") == 0 {
					m := data.(map[string]interface{})
					ch := message.Data.Topic[strings.Index(message.Data.Topic, ".") + 1:]
					ty := m["type"].(string)
					server_time := time.Unix(int64(m["server_time"].(float64)), 0)

					if ty == "viewcount" {
						go t.handle(ty, &ViewerCount{Channel: ch, Viewers: int(m["viewers"].(float64)), ServerTime: server_time})
					} else if ty == "stream-up" {
						go t.handle(ty, &StreamUp{Channel: ch, ServerTime: server_time})
					} else if ty == "stream-down" {
						go t.handle(ty, &StreamDown{Channel: ch, ServerTime: server_time})
					}
				}
			} else if message.Type == Response {
				t.responseCh <- &message
			} else if message.Type == reconnectEventType {
				go t.handle(message.Type, &Reconnect{})
				t.Close()
				t.reconnect()
			}
		}
	}
}

func (t *TwitchPubSub) pinger(wsConn *websocket.Conn, listening <-chan interface{}) {
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		if t.debug {
			log.Println("Sending ping")
		}
		t.LastPing = time.Now()
		t.wsMutex.Lock()
		err := wsConn.WriteJSON(&twitchMessage{Type: Ping})
		t.wsMutex.Unlock()

		if err != nil {
			return
		}

		select {
		case <-ticker.C:
		// continue loop and send heartbeat
		case <-listening:
			return
		}
	}
}