package collaboration

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

type Hub struct {
	rooms map[string]*Room
	mu    sync.RWMutex
}

type Room struct {
	documentRKey string
	clients      map[*Client]bool
	broadcast    chan *broadcastMsg
	register     chan *Client
	unregister   chan *Client
	mu           sync.RWMutex
}

// broadcastMsg carries a message and an optional sender to exclude.
type broadcastMsg struct {
	data   []byte
	except *Client // nil = send to all
}

func NewHub() *Hub {
	return &Hub{
		rooms: make(map[string]*Room),
	}
}

func (h *Hub) GetOrCreateRoom(rkey string) *Room {
	h.mu.Lock()
	defer h.mu.Unlock()
	if room, exists := h.rooms[rkey]; exists {
		return room
	}
	room := &Room{
		documentRKey: rkey,
		clients:      make(map[*Client]bool),
		broadcast:    make(chan *broadcastMsg, 256),
		register:     make(chan *Client),
		unregister:   make(chan *Client),
	}
	h.rooms[rkey] = room
	go room.run()
	return room
}

func (h *Hub) GetRoom(rkey string) *Room {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return h.rooms[rkey]
}

func (r *Room) run() {
	for {
		select {
		case client := <-r.register:
			r.mu.Lock()
			r.clients[client] = true
			r.mu.Unlock()
			r.broadcastPresence()
		case client := <-r.unregister:
			r.mu.Lock()
			if _, ok := r.clients[client]; ok {
				delete(r.clients, client)
				close(client.send)
			}
			r.mu.Unlock()
			r.broadcastPresence()
		case msg := <-r.broadcast:
			r.mu.RLock()
			for client := range r.clients {
				if client == msg.except {
					continue
				}
				select {
				case client.send <- msg.data:
				default:
					close(client.send)
					delete(r.clients, client)
				}
			}
			r.mu.RUnlock()
		}
	}
}

// Broadcast sends to all clients in the room.
func (r *Room) Broadcast(data []byte) {
	r.broadcast <- &broadcastMsg{data: data}
}

// BroadcastExcept sends to all clients except the given sender.
func (r *Room) BroadcastExcept(data []byte, except *Client) {
	r.broadcast <- &broadcastMsg{data: data, except: except}
}

func (r *Room) RegisterClient(client *Client) {
	r.register <- client
}

func (r *Room) UnregisterClient(client *Client) {
	r.unregister <- client
}

func (r *Room) GetPresence() []PresenceUser {
	r.mu.RLock()
	defer r.mu.RUnlock()
	users := make([]PresenceUser, 0, len(r.clients))
	for client := range r.clients {
		users = append(users, PresenceUser{
			DID:    client.DID,
			Name:   client.Name,
			Handle: client.Handle,
			Color:  client.Color,
			Avatar: client.Avatar,
		})
	}
	return users
}

func (r *Room) broadcastPresence() {
	presence := PresenceMessage{
		Type:  "presence",
		Users: r.GetPresence(),
	}
	data, err := json.Marshal(presence)
	if err != nil {
		log.Printf("broadcastPresence: marshal failed: %v", err)
		return
	}
	r.Broadcast(data)
}