// Package ws provides WebSocket connection management for Cyrene.
package ws

import (
	"encoding/json"
	"log"
	"net/http"
	"sync"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin:     func(r *http.Request) bool { return true },
}

// Hub manages all active WebSocket connections.
type Hub struct {
	mu      sync.RWMutex
	clients map[*Client]bool

	register   chan *Client
	unregister chan *Client
	broadcast  chan []byte
}

// Client represents a single WebSocket connection.
type Client struct {
	hub    *Hub
	conn   *websocket.Conn
	send   chan []byte
	UserID string
	closed bool
	mu     sync.Mutex
}

// Message represents a WebSocket message envelope.
type Message struct {
	Type      string `json:"type"`
	Content   string `json:"content,omitempty"`
	SessionID string `json:"session_id,omitempty"`
	Timestamp int64  `json:"timestamp,omitempty"`
	Error     string `json:"error,omitempty"`
}

// NewHub creates and starts a new WebSocket hub.
func NewHub() *Hub {
	h := &Hub{
		clients:    make(map[*Client]bool),
		register:   make(chan *Client),
		unregister: make(chan *Client),
		broadcast:  make(chan []byte, 256),
	}
	go h.run()
	return h
}

func (h *Hub) run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = true
			h.mu.Unlock()
			log.Printf("[ws] client connected (%d total)", len(h.clients))

		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.send)
			}
			h.mu.Unlock()
			log.Printf("[ws] client disconnected (%d remaining)", len(h.clients))

		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					// Client too slow, skip
				}
			}
			h.mu.RUnlock()
		}
	}
}

// HandleUpgrade upgrades an HTTP connection to WebSocket.
func (h *Hub) HandleUpgrade(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("[ws] upgrade error: %v", err)
		return
	}

	userID := r.URL.Query().Get("user_id")
	if userID == "" {
		userID = "anonymous"
	}

	client := &Client{
		hub:    h,
		conn:   conn,
		send:   make(chan []byte, 64),
		UserID: userID,
	}

	h.register <- client

	go client.writePump()
	go client.readPump()
}

func (c *Client) readPump() {
	defer func() {
		c.hub.unregister <- c
		c.conn.Close()
	}()

	for {
		_, msgBytes, err := c.conn.ReadMessage()
		if err != nil {
			break
		}

		var msg Message
		if err := json.Unmarshal(msgBytes, &msg); err != nil {
			continue
		}

		// Echo back for now (will route to AI-Core later)
		reply := Message{
			Type:      "response",
			Content:   "echo: " + msg.Content,
			SessionID: msg.SessionID,
		}
		replyBytes, _ := json.Marshal(reply)
		c.send <- replyBytes
	}
}

func (c *Client) writePump() {
	defer c.conn.Close()
	for msg := range c.send {
		if err := c.conn.WriteMessage(websocket.TextMessage, msg); err != nil {
			return
		}
	}
}

// Broadcast sends a message to all connected clients.
func (h *Hub) Broadcast(msg Message) error {
	data, err := json.Marshal(msg)
	if err != nil {
		return err
	}
	h.broadcast <- data
	return nil
}

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

// UpgradeHandler returns an http.HandlerFunc for WebSocket upgrades.
func (h *Hub) UpgradeHandler() http.HandlerFunc {
	return h.HandleUpgrade
}