package ws

import (
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
	"github.com/sandrodach/mindsift/internal/domain"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  4096,
	WriteBufferSize: 4096,
	CheckOrigin: func(r *http.Request) bool {
		return true // Self-hosted reverse proxy compatible
	},
}

type Client struct {
	hub             *Hub
	conn            *websocket.Conn
	roomID          string
	userID          string
	send            chan []byte
	subscribedRooms map[string]bool
	sendMu          sync.RWMutex
	closed          bool
}

func (c *Client) closeSend() {
	c.sendMu.Lock()
	defer c.sendMu.Unlock()
	if !c.closed {
		c.closed = true
		close(c.send)
	}
}

func (c *Client) trySend(data []byte) {
	c.sendMu.RLock()
	defer c.sendMu.RUnlock()
	if c.closed {
		return
	}
	select {
	case c.send <- data:
	default:
	}
}

type SSEClient struct {
	id              string
	userID          string
	roomID          string
	send            chan []byte
	subscribedRooms map[string]bool
	sendMu          sync.RWMutex
	closed          bool
}

func (c *SSEClient) closeSend() {
	c.sendMu.Lock()
	defer c.sendMu.Unlock()
	if !c.closed {
		c.closed = true
		close(c.send)
	}
}

func (c *SSEClient) trySend(data []byte) {
	c.sendMu.RLock()
	defer c.sendMu.RUnlock()
	if c.closed {
		return
	}
	select {
	case c.send <- data:
	default:
	}
}

type Hub struct {
	mu           sync.RWMutex
	rooms        map[string]map[*Client]bool
	userRooms    map[string]map[*Client]bool
	allClients   map[*Client]bool
	sseClients   map[*SSEClient]bool
	sseUserRooms map[string]map[*SSEClient]bool
	sseRooms     map[string]map[*SSEClient]bool
	closed       bool
}

func NewHub() *Hub {
	return &Hub{
		rooms:        make(map[string]map[*Client]bool),
		userRooms:    make(map[string]map[*Client]bool),
		allClients:   make(map[*Client]bool),
		sseClients:   make(map[*SSEClient]bool),
		sseUserRooms: make(map[string]map[*SSEClient]bool),
		sseRooms:     make(map[string]map[*SSEClient]bool),
	}
}

func (h *Hub) Register(c *Client) {
	h.mu.Lock()
	h.allClients[c] = true
	if c.roomID != "" {
		if h.rooms[c.roomID] == nil {
			h.rooms[c.roomID] = make(map[*Client]bool)
		}
		h.rooms[c.roomID][c] = true
	}
	if c.userID != "" && c.userID != "anonymous" {
		if h.userRooms[c.userID] == nil {
			h.userRooms[c.userID] = make(map[*Client]bool)
		}
		h.userRooms[c.userID][c] = true
	}
	onlineCount := len(h.allClients) + len(h.sseClients)
	h.mu.Unlock()

	if c.roomID != "" {
		h.Broadcast(c.roomID, "", "USER_PRESENCE", map[string]interface{}{
			"onlineCount": onlineCount,
		})
	}
}

func (h *Hub) Unregister(c *Client) {
	h.mu.Lock()
	delete(h.allClients, c)
	if c.roomID != "" {
		if room, ok := h.rooms[c.roomID]; ok {
			delete(room, c)
			if len(room) == 0 {
				delete(h.rooms, c.roomID)
			}
		}
	}

	if c.subscribedRooms != nil {
		for rID := range c.subscribedRooms {
			if room, ok := h.rooms[rID]; ok {
				delete(room, c)
				if len(room) == 0 {
					delete(h.rooms, rID)
				}
			}
		}
	}

	if c.userID != "" && c.userID != "anonymous" {
		if uRoom, ok := h.userRooms[c.userID]; ok {
			delete(uRoom, c)
			if len(uRoom) == 0 {
				delete(h.userRooms, c.userID)
			}
		}
	}
	c.closeSend()
	h.mu.Unlock()
}

func (h *Hub) RegisterSSE(c *SSEClient) {
	h.mu.Lock()
	h.sseClients[c] = true
	if c.roomID != "" {
		if h.sseRooms[c.roomID] == nil {
			h.sseRooms[c.roomID] = make(map[*SSEClient]bool)
		}
		h.sseRooms[c.roomID][c] = true
	}
	if c.userID != "" && c.userID != "anonymous" {
		if h.sseUserRooms[c.userID] == nil {
			h.sseUserRooms[c.userID] = make(map[*SSEClient]bool)
		}
		h.sseUserRooms[c.userID][c] = true
	}
	if c.subscribedRooms != nil {
		for rID := range c.subscribedRooms {
			if h.sseRooms[rID] == nil {
				h.sseRooms[rID] = make(map[*SSEClient]bool)
			}
			h.sseRooms[rID][c] = true
		}
	}
	onlineCount := len(h.allClients) + len(h.sseClients)
	h.mu.Unlock()

	if c.roomID != "" {
		h.Broadcast(c.roomID, "", "USER_PRESENCE", map[string]interface{}{
			"onlineCount": onlineCount,
		})
	}
}

func (h *Hub) UnregisterSSE(c *SSEClient) {
	h.mu.Lock()
	delete(h.sseClients, c)
	if c.roomID != "" {
		if room, ok := h.sseRooms[c.roomID]; ok {
			delete(room, c)
			if len(room) == 0 {
				delete(h.sseRooms, c.roomID)
			}
		}
	}
	if c.subscribedRooms != nil {
		for rID := range c.subscribedRooms {
			if room, ok := h.sseRooms[rID]; ok {
				delete(room, c)
				if len(room) == 0 {
					delete(h.sseRooms, rID)
				}
			}
		}
	}
	if c.userID != "" && c.userID != "anonymous" {
		if uRoom, ok := h.sseUserRooms[c.userID]; ok {
			delete(uRoom, c)
			if len(uRoom) == 0 {
				delete(h.sseUserRooms, c.userID)
			}
		}
	}
	c.closeSend()
	h.mu.Unlock()
}

func (h *Hub) JoinSSERoomByID(sseID, roomID string) bool {
	h.mu.Lock()
	defer h.mu.Unlock()
	for client := range h.sseClients {
		if client.id == sseID {
			if h.sseRooms[roomID] == nil {
				h.sseRooms[roomID] = make(map[*SSEClient]bool)
			}
			h.sseRooms[roomID][client] = true
			if client.subscribedRooms == nil {
				client.subscribedRooms = make(map[string]bool)
			}
			client.subscribedRooms[roomID] = true
			return true
		}
	}
	return false
}

func (h *Hub) LeaveSSERoomByID(sseID, roomID string) bool {
	h.mu.Lock()
	defer h.mu.Unlock()
	for client := range h.sseClients {
		if client.id == sseID {
			if room, ok := h.sseRooms[roomID]; ok {
				delete(room, client)
				if len(room) == 0 {
					delete(h.sseRooms, roomID)
				}
			}
			if client.subscribedRooms != nil {
				delete(client.subscribedRooms, roomID)
			}
			return true
		}
	}
	return false
}



// Close gracefully disconnects all WebSocket and SSE connections so HTTP shutdown completes immediately.
func (h *Hub) Close() {
	h.mu.Lock()
	if h.closed {
		h.mu.Unlock()
		return
	}
	h.closed = true

	allWsClients := make([]*Client, 0, len(h.allClients))
	for c := range h.allClients {
		allWsClients = append(allWsClients, c)
	}

	allSSEClients := make([]*SSEClient, 0, len(h.sseClients))
	for c := range h.sseClients {
		allSSEClients = append(allSSEClients, c)
	}
	h.mu.Unlock()

	for _, c := range allWsClients {
		_ = c.conn.Close()
		c.closeSend()
	}

	for _, c := range allSSEClients {
		c.closeSend()
	}
}

// Broadcasting Methods

func (h *Hub) BroadcastToAll(event string, payload interface{}) {
	msg := domain.WSMessage{
		Event:     event,
		Payload:   payload,
		Timestamp: domain.NowISO(),
	}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}

	h.mu.RLock()
	if h.closed {
		h.mu.RUnlock()
		return
	}
	defer h.mu.RUnlock()

	for client := range h.allClients {
		client.trySend(data)
	}
	for sseClient := range h.sseClients {
		sseClient.trySend(data)
	}
}

func (h *Hub) BroadcastToUser(userID, event string, payload interface{}) {
	msg := domain.WSMessage{
		Event:     event,
		Payload:   payload,
		Timestamp: domain.NowISO(),
	}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}

	h.mu.RLock()
	if h.closed {
		h.mu.RUnlock()
		return
	}
	defer h.mu.RUnlock()

	if room, ok := h.userRooms[userID]; ok {
		for client := range room {
			client.trySend(data)
		}
	}
	if sseRoom, ok := h.sseUserRooms[userID]; ok {
		for sseClient := range sseRoom {
			sseClient.trySend(data)
		}
	}
}

func (h *Hub) BroadcastTaskEvent(userID, event string, payload interface{}) {
	h.BroadcastToUser(userID, event, payload)
}

func (h *Hub) BroadcastDocEvent(docID, event string, payload interface{}) {
	if docID != "" {
		h.BroadcastRoom("doc:"+docID, event, payload, nil)
	} else {
		h.BroadcastToAll(event, payload)
	}
}

func (h *Hub) Broadcast(spaceID, listID, event string, payload interface{}) {
	msg := domain.WSMessage{
		Event:     event,
		ListID:    listID,
		Payload:   payload,
		Timestamp: domain.NowISO(),
	}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}

	h.mu.RLock()
	if h.closed {
		h.mu.RUnlock()
		return
	}
	defer h.mu.RUnlock()

	targetRoom := listID
	if targetRoom == "" {
		targetRoom = spaceID
	}

	if room, ok := h.rooms[targetRoom]; ok {
		for client := range room {
			client.trySend(data)
		}
	}
	if sseRoom, ok := h.sseRooms[targetRoom]; ok {
		for sseClient := range sseRoom {
			sseClient.trySend(data)
		}
	}
}

func (h *Hub) BroadcastListEvent(listID, event string, payload interface{}) {
	h.Broadcast("", listID, event, payload)
}

func (h *Hub) JoinRoom(c *Client, roomID string) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if h.rooms[roomID] == nil {
		h.rooms[roomID] = make(map[*Client]bool)
	}
	h.rooms[roomID][c] = true
	if c.subscribedRooms == nil {
		c.subscribedRooms = make(map[string]bool)
	}
	c.subscribedRooms[roomID] = true
}

func (h *Hub) LeaveRoom(c *Client, roomID string) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if room, ok := h.rooms[roomID]; ok {
		delete(room, c)
		if len(room) == 0 {
			delete(h.rooms, roomID)
		}
	}
	if c.subscribedRooms != nil {
		delete(c.subscribedRooms, roomID)
	}
}

func (h *Hub) BroadcastRoom(roomID, event string, payload interface{}, excludeClient *Client) {
	msg := domain.WSMessage{
		Event:     event,
		Payload:   payload,
		Timestamp: domain.NowISO(),
	}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}

	h.mu.RLock()
	if h.closed {
		h.mu.RUnlock()
		return
	}
	defer h.mu.RUnlock()

	if room, ok := h.rooms[roomID]; ok {
		for client := range room {
			if excludeClient != nil && client == excludeClient {
				continue
			}
			client.trySend(data)
		}
	}
	if sseRoom, ok := h.sseRooms[roomID]; ok {
		for sseClient := range sseRoom {
			sseClient.trySend(data)
		}
	}
}

func (c *Client) SendEvent(event string, payload interface{}) {
	msg := domain.WSMessage{
		Event:     event,
		Payload:   payload,
		Timestamp: domain.NowISO(),
	}
	data, err := json.Marshal(msg)
	if err == nil {
		c.trySend(data)
	}
}

func (h *Hub) ServeWS(w http.ResponseWriter, r *http.Request, roomID, userID string) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		slog.Error("WebSocket upgrade error", "room_id", roomID, "user_id", userID, "error", err)
		return
	}

	client := &Client{
		hub:     h,
		conn:    conn,
		roomID:  roomID,
		userID:  userID,
		send:    make(chan []byte, 128),
	}

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

func (h *Hub) ServeSSE(w http.ResponseWriter, r *http.Request, roomID, userID string, initialRooms []string) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "Streaming unsupported!", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache, no-transform")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")
	w.Header().Set("Access-Control-Allow-Origin", "*")

	client := &SSEClient{
		id:              domain.NewID("sse"),
		userID:          userID,
		roomID:          roomID,
		send:            make(chan []byte, 128),
		subscribedRooms: make(map[string]bool),
	}

	for _, room := range initialRooms {
		if strings.TrimSpace(room) != "" {
			client.subscribedRooms[strings.TrimSpace(room)] = true
		}
	}

	h.RegisterSSE(client)
	defer h.UnregisterSSE(client)

	// Send initial connected comment and event
	fmt.Fprintf(w, ": connected (transport: sse, id: %s)\n\n", client.id)
	connectedMsg, _ := json.Marshal(domain.WSMessage{
		Event: "SSE_CONNECTED",
		Payload: map[string]interface{}{
			"sseId":     client.id,
			"transport": "sse",
			"userId":    userID,
		},
		Timestamp: domain.NowISO(),
	})
	fmt.Fprintf(w, "data: %s\n\n", connectedMsg)
	flusher.Flush()

	ticker := time.NewTicker(15 * time.Second)
	defer ticker.Stop()

	notify := r.Context().Done()

	for {
		select {
		case <-notify:
			return
		case msg, ok := <-client.send:
			if !ok {
				return
			}
			fmt.Fprintf(w, "data: %s\n\n", msg)
			flusher.Flush()
		case <-ticker.C:
			// Periodic ping comment to keep HTTP connection alive and prevent proxy timeouts
			fmt.Fprintf(w, ": ping\n\n")
			flusher.Flush()
		}
	}
}

func (c *Client) readPump() {
	defer func() {
		c.hub.Unregister(c)
		_ = c.conn.Close()
	}()

	c.conn.SetReadLimit(4 * 1024 * 1024) // 4MB for large document CRDT updates
	_ = c.conn.SetReadDeadline(time.Now().Add(60 * time.Second))
	c.conn.SetPongHandler(func(string) error {
		_ = c.conn.SetReadDeadline(time.Now().Add(60 * time.Second))
		return nil
	})

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

		// Handle client-initiated lock, CRDT, room subscription, and presence messages
		var incoming struct {
			Event   string          `json:"event"`
			DocID   string          `json:"docId"`
			Room    string          `json:"room"`
			Payload json.RawMessage `json:"payload"`
		}
		if json.Unmarshal(message, &incoming) == nil && c.userID != "" && c.userID != "anonymous" {
			docID := incoming.DocID
			if docID == "" && len(incoming.Payload) > 0 {
				var p struct {
					DocID string `json:"docId"`
				}
				_ = json.Unmarshal(incoming.Payload, &p)
				docID = p.DocID
			}

			// Room subscription without requiring docID
			if incoming.Event == "JOIN_ROOM" {
				room := incoming.Room
				if room == "" {
					room = docID
				}
				if room != "" {
					c.hub.JoinRoom(c, room)
				}
			} else if incoming.Event == "LEAVE_ROOM" {
				room := incoming.Room
				if room == "" {
					room = docID
				}
				if room != "" {
					c.hub.LeaveRoom(c, room)
				}
			}
		}
	}
}

func (c *Client) writePump() {
	ticker := time.NewTicker(30 * time.Second)
	defer func() {
		ticker.Stop()
		_ = c.conn.Close()
	}()

	for {
		select {
		case message, ok := <-c.send:
			_ = c.conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
			if !ok {
				_ = c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}
			if err := c.conn.WriteMessage(websocket.TextMessage, message); err != nil {
				return
			}
		case <-ticker.C:
			_ = c.conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}