package chat

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

	"github.com/gorilla/websocket"
)

const (
	writeWait      = 10 * time.Second
	pongWait       = 60 * time.Second
	pingPeriod     = (pongWait * 9) / 10
	maxMessageSize = 512
)

type Message struct {
	Type      string `json:"type"` // "chat", "system", "danmaku"
	Username  string `json:"username"`
	Content   string `json:"content"`
	RoomID    string `json:"room_id"`
	IsHistory bool   `json:"is_history"`
}

type Client struct {
	Hub      *Hub
	Conn     *websocket.Conn
	Send     chan []byte
	RoomID   string
	Username string
}

type Hub struct {
	rooms        map[string]map[*Client]bool
	roomsHistory map[string][]Message
	broadcast    chan Message
	register     chan *Client
	unregister   chan *Client
	mutex        sync.RWMutex
}

func NewHub() *Hub {
	return &Hub{
		broadcast:    make(chan Message),
		register:     make(chan *Client),
		unregister:   make(chan *Client),
		rooms:        make(map[string]map[*Client]bool),
		roomsHistory: make(map[string][]Message),
	}
}

func (h *Hub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mutex.Lock()
			if h.rooms[client.RoomID] == nil {
				h.rooms[client.RoomID] = make(map[*Client]bool)
			}
			h.rooms[client.RoomID][client] = true

			// Send existing history to the newly joined client
			if history, ok := h.roomsHistory[client.RoomID]; ok {
				for _, msg := range history {
					msg.IsHistory = true
					msgBytes, _ := json.Marshal(msg)
					// Use select to avoid blocking if client's send channel is full
					select {
					case client.Send <- msgBytes:
					default:
						// If send fails, we could potentially log or ignore
					}
				}
			}
			h.mutex.Unlock()

		case client := <-h.unregister:
			h.mutex.Lock()
			if rooms, ok := h.rooms[client.RoomID]; ok {
				if _, ok := rooms[client]; ok {
					delete(rooms, client)
					close(client.Send)
					// We no longer delete the room from h.rooms here if we want history to persist
					// even if everyone leaves (as long as it's active in DB).
					// But we should clean up if the room is empty and we want to save memory.
					// However, the history is what matters.
					if len(rooms) == 0 {
						delete(h.rooms, client.RoomID)
					}
				}
			}
			h.mutex.Unlock()

		case message := <-h.broadcast:
			h.mutex.Lock()
			// Only store "chat" and "danmaku" messages in history
			if message.Type == "chat" || message.Type == "danmaku" {
				h.roomsHistory[message.RoomID] = append(h.roomsHistory[message.RoomID], message)
				// Limit history size to avoid memory leak (e.g., last 100 messages)
				if len(h.roomsHistory[message.RoomID]) > 100 {
					h.roomsHistory[message.RoomID] = h.roomsHistory[message.RoomID][1:]
				}
			}

			clients := h.rooms[message.RoomID]
			if clients != nil {
				msgBytes, _ := json.Marshal(message)
				for client := range clients {
					select {
					case client.Send <- msgBytes:
					default:
						close(client.Send)
						delete(clients, client)
					}
				}
			}
			h.mutex.Unlock()
		}
	}
}

// ClearRoomHistory removes history for a room, should be called when stream ends
func (h *Hub) ClearRoomHistory(roomID string) {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	delete(h.roomsHistory, roomID)
}

func (h *Hub) RegisterClient(c *Client) {
	h.register <- c
}

// BroadcastToRoom sends a message to the broadcast channel
func (h *Hub) BroadcastToRoom(msg Message) {
	h.broadcast <- msg
}

func (c *Client) ReadPump() {
	defer func() {
		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 {
			break
		}
		var msg Message
		if err := json.Unmarshal(message, &msg); err == nil {
			msg.RoomID = c.RoomID
			msg.Username = c.Username
			c.Hub.broadcast <- msg
		}
	}
}

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
			}
		}
	}
}

var MainHub *Hub

func InitChat() {
	MainHub = NewHub()
	go MainHub.Run()
}