package websocket

import (
	"encoding/json"
	"log"
	"sync"
	"time"

	"github.com/gorilla/websocket"
)

const (
	writeWait      = 10 * time.Second
	pongWait       = 60 * time.Second
	pingPeriod     = (pongWait * 9) / 10
	maxMessageSize = 4096
	sessionTimeout = 25 * time.Minute // Disconnect after 25 minutes
)

// MessageType represents the type of websocket message.
type MessageType string

const (
	// Client -> Server messages
	MsgTypeHighFive MessageType = "high_five"

	// Server -> Client messages
	MsgTypeIdentityJoined  MessageType = "identity_joined"
	MsgTypeIdentityLeft    MessageType = "identity_left"
	MsgTypePopulateRoom    MessageType = "populate_room"
	MsgTypeHighFiveEvent   MessageType = "high_five_event"
	MsgTypeError           MessageType = "error"
	MsgTypeSessionTimeout  MessageType = "session_timeout"
)

// Message represents a websocket message.
type Message struct {
	Type    MessageType            `json:"type"`
	Payload map[string]interface{} `json:"payload,omitempty"`
}

// ClientInfo contains public information about a connected client.
type ClientInfo struct {
	DID    string `json:"did"`
	Handle string `json:"handle"`
}

// Client represents a connected websocket client.
type Client struct {
	hub          *Hub
	conn         *websocket.Conn
	send         chan []byte
	DID          string
	Handle       string
	SessionID    string
	IsReconnect  bool
	ConnectedAt  time.Time
	sessionTimer *time.Timer
}

// Hub maintains the set of active clients and broadcasts messages.
type Hub struct {
	clients    map[*Client]bool
	didClients map[string]*Client // Map DID to client
	broadcast  chan []byte
	register   chan *Client
	unregister chan *Client
	mu         sync.RWMutex

	// Callbacks for handling messages
	onClientJoin  func(client *Client) error
	onClientLeave func(client *Client) error
	onHighFive    func(giver *Client, subjectDID string) error
}

// NewHub creates a new Hub.
func NewHub() *Hub {
	return &Hub{
		clients:    make(map[*Client]bool),
		didClients: make(map[string]*Client),
		broadcast:  make(chan []byte),
		register:   make(chan *Client),
		unregister: make(chan *Client),
	}
}

// SetCallbacks sets the message handler callbacks.
func (h *Hub) SetCallbacks(
	onClientJoin func(client *Client) error,
	onClientLeave func(client *Client) error,
	onHighFive func(giver *Client, subjectDID string) error,
) {
	h.onClientJoin = onClientJoin
	h.onClientLeave = onClientLeave
	h.onHighFive = onHighFive
}

// Run starts the hub's main loop.
func (h *Hub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = true
			if client.DID != "" {
				h.didClients[client.DID] = client
			}
			h.mu.Unlock()
			log.Printf("Client registered: %s (%s)", client.DID, client.Handle)

			// Call the join callback
			if h.onClientJoin != nil {
				if err := h.onClientJoin(client); err != nil {
					log.Printf("error in client join callback: %v", err)
				}
			}

		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				if client.DID != "" {
					delete(h.didClients, client.DID)
				}
				close(client.send)
			}
			h.mu.Unlock()
			log.Printf("Client unregistered: %s (%s)", client.DID, client.Handle)

			// Call the leave callback
			if h.onClientLeave != nil {
				if err := h.onClientLeave(client); err != nil {
					log.Printf("error in client leave callback: %v", err)
				}
			}

		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					h.mu.RUnlock()
					h.mu.Lock()
					close(client.send)
					delete(h.clients, client)
					if client.DID != "" {
						delete(h.didClients, client.DID)
					}
					h.mu.Unlock()
					h.mu.RLock()
				}
			}
			h.mu.RUnlock()
		}
	}
}

// GetClientByDID returns the client for a given DID.
func (h *Hub) GetClientByDID(did string) *Client {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return h.didClients[did]
}

// IsClientConnected checks if a client with the given DID is connected.
func (h *Hub) IsClientConnected(did string) bool {
	h.mu.RLock()
	defer h.mu.RUnlock()
	_, ok := h.didClients[did]
	return ok
}

// SendToClient sends a message to a specific client by DID.
func (h *Hub) SendToClient(did string, msg *Message) error {
	h.mu.RLock()
	client, ok := h.didClients[did]
	h.mu.RUnlock()

	if !ok {
		return nil // Client not connected, not an error
	}

	data, err := json.Marshal(msg)
	if err != nil {
		return err
	}

	select {
	case client.send <- data:
		return nil
	default:
		return nil // Channel full, skip
	}
}

// Register registers a new client.
func (h *Hub) Register(client *Client) {
	h.register <- client
}

// Unregister unregisters a client.
func (h *Hub) Unregister(client *Client) {
	h.unregister <- client
}

// NewClient creates a new client.
func NewClient(hub *Hub, conn *websocket.Conn, did, handle, sessionID string, isReconnect bool) *Client {
	c := &Client{
		hub:         hub,
		conn:        conn,
		send:        make(chan []byte, 256),
		DID:         did,
		Handle:      handle,
		SessionID:   sessionID,
		IsReconnect: isReconnect,
		ConnectedAt: time.Now(),
	}

	// Start session timeout timer
	c.sessionTimer = time.AfterFunc(sessionTimeout, func() {
		c.handleSessionTimeout()
	})

	return c
}

// handleSessionTimeout sends a timeout message and closes the connection.
func (c *Client) handleSessionTimeout() {
	log.Printf("Session timeout for client: %s (%s)", c.DID, c.Handle)

	// Send session timeout message
	c.SendMessage(&Message{
		Type: MsgTypeSessionTimeout,
		Payload: map[string]interface{}{
			"message": "Your session has expired after 25 minutes. Start a new session to continue giving and receiving high-fives!",
		},
	})

	// Give client time to receive the message before closing
	time.Sleep(100 * time.Millisecond)

	// Close the connection
	c.conn.Close()
}

// StopSessionTimer stops the session timeout timer.
func (c *Client) StopSessionTimer() {
	if c.sessionTimer != nil {
		c.sessionTimer.Stop()
	}
}

// ReadPump pumps messages from the websocket connection to the hub.
func (c *Client) ReadPump() {
	defer func() {
		c.StopSessionTimer()
		c.hub.Unregister(c)
		c.conn.Close()
	}()

	c.conn.SetReadLimit(maxMessageSize)
	c.conn.SetReadDeadline(time.Now().Add(pongWait))
	c.conn.SetPongHandler(func(string) error {
		c.conn.SetReadDeadline(time.Now().Add(pongWait))
		return nil
	})

	for {
		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("websocket error: %v", err)
			}
			break
		}

		var msg Message
		if err := json.Unmarshal(message, &msg); err != nil {
			log.Printf("failed to unmarshal message: %v", err)
			continue
		}

		c.handleMessage(&msg)
	}
}

// handleMessage processes incoming messages.
func (c *Client) handleMessage(msg *Message) {
	var err error

	switch msg.Type {
	case MsgTypeHighFive:
		subjectDID, _ := msg.Payload["subject"].(string)
		if c.hub.onHighFive != nil {
			err = c.hub.onHighFive(c, subjectDID)
		}

	default:
		log.Printf("unknown message type: %s", msg.Type)
	}

	if err != nil {
		log.Printf("error handling message %s: %v", msg.Type, err)
		c.SendError(err.Error())
	}
}

// WritePump pumps messages from the hub to the websocket connection.
func (c *Client) WritePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()

	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			w, err := c.conn.NextWriter(websocket.TextMessage)
			if err != nil {
				return
			}
			w.Write(message)

			if err := w.Close(); err != nil {
				return
			}

		case <-ticker.C:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

// SendMessage sends a message to this client.
func (c *Client) SendMessage(msg *Message) error {
	data, err := json.Marshal(msg)
	if err != nil {
		return err
	}

	select {
	case c.send <- data:
		return nil
	default:
		return nil
	}
}

// SendError sends an error message to this client.
func (c *Client) SendError(errMsg string) {
	c.SendMessage(&Message{
		Type: MsgTypeError,
		Payload: map[string]interface{}{
			"error": errMsg,
		},
	})
}

// BroadcastToAll sends a message to all connected clients.
func (h *Hub) BroadcastToAll(msg *Message) {
	data, err := json.Marshal(msg)
	if err != nil {
		log.Printf("failed to marshal broadcast message: %v", err)
		return
	}

	h.mu.RLock()
	defer h.mu.RUnlock()

	for client := range h.clients {
		select {
		case client.send <- data:
		default:
			// Channel full, skip this client
		}
	}
}

// BroadcastToOthers sends a message to all clients except the one with the given DID.
func (h *Hub) BroadcastToOthers(excludeDID string, msg *Message) {
	data, err := json.Marshal(msg)
	if err != nil {
		log.Printf("failed to marshal broadcast message: %v", err)
		return
	}

	h.mu.RLock()
	defer h.mu.RUnlock()

	for client := range h.clients {
		if client.DID == excludeDID {
			continue
		}
		select {
		case client.send <- data:
		default:
			// Channel full, skip this client
		}
	}
}

// GetAllClients returns information about all connected clients.
func (h *Hub) GetAllClients() []ClientInfo {
	h.mu.RLock()
	defer h.mu.RUnlock()

	clients := make([]ClientInfo, 0, len(h.clients))
	for client := range h.clients {
		clients = append(clients, ClientInfo{
			DID:    client.DID,
			Handle: client.Handle,
		})
	}
	return clients
}

// GetOtherClients returns information about all connected clients except the given DID.
func (h *Hub) GetOtherClients(excludeDID string) []ClientInfo {
	h.mu.RLock()
	defer h.mu.RUnlock()

	clients := make([]ClientInfo, 0, len(h.clients))
	for client := range h.clients {
		if client.DID == excludeDID {
			continue
		}
		clients = append(clients, ClientInfo{
			DID:    client.DID,
			Handle: client.Handle,
		})
	}
	return clients
}

// GetClientCount returns the number of connected clients.
func (h *Hub) GetClientCount() int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return len(h.clients)
}

// StartRoomPopulation sends populate_room messages to a new client in batches.
func (h *Hub) StartRoomPopulation(newClient *Client) {
	go func() {
		// Get all other clients
		clients := h.GetOtherClients(newClient.DID)

		// Shuffle for random order
		for i := len(clients) - 1; i > 0; i-- {
			j := int(time.Now().UnixNano()) % (i + 1)
			clients[i], clients[j] = clients[j], clients[i]
		}

		// Send in batches of 5 every 3 seconds
		batchSize := 5
		for i := 0; i < len(clients); i += batchSize {
			end := i + batchSize
			if end > len(clients) {
				end = len(clients)
			}
			batch := clients[i:end]

			// Convert to interface slice for payload
			identities := make([]map[string]string, len(batch))
			for j, c := range batch {
				identities[j] = map[string]string{
					"did":    c.DID,
					"handle": c.Handle,
				}
			}

			newClient.SendMessage(&Message{
				Type: MsgTypePopulateRoom,
				Payload: map[string]interface{}{
					"identities": identities,
				},
			})

			if end < len(clients) {
				time.Sleep(3 * time.Second)
			}
		}
	}()
}