// Fail2ban UI - A Swiss made, management interface for Fail2ban.
//
// Copyright (C) 2025 Swissmakers GmbH (https://swissmakers.ch)
//
// Licensed under the GNU General Public License, Version 3 (GPL-3.0)
// You may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.gnu.org/licenses/gpl-3.0.en.html
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package web

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

	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"
	"github.com/swissmakers/fail2ban-ui/internal/storage"
)

const (
	// Time allowed to write a message to the peer
	writeWait = 10 * time.Second

	// Time allowed to read the next pong message from the peer
	pongWait = 60 * time.Second

	// Send pings to peer with this period (must be less than pongWait)
	pingPeriod = (pongWait * 9) / 10
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin: func(r *http.Request) bool {
		// Allow all origins for now - can be restricted in production
		return true
	},
}

// Client represents a WebSocket connection
type Client struct {
	hub  *Hub
	conn *websocket.Conn
	send chan []byte
}

// Hub maintains the set of active clients and broadcasts messages to them
type Hub struct {
	// Registered clients
	clients map[*Client]bool

	// Inbound messages from clients
	broadcast chan []byte

	// Register requests from clients
	register chan *Client

	// Unregister requests from clients
	unregister chan *Client

	// Mutex for thread-safe operations
	mu sync.RWMutex
}

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

// Run starts the hub's main loop
func (h *Hub) Run() {
	// Start heartbeat ticker
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = true
			h.mu.Unlock()
			log.Printf("WebSocket client connected. Total clients: %d", 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("WebSocket client disconnected. Total clients: %d", len(h.clients))

		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					close(client.send)
					delete(h.clients, client)
				}
			}
			h.mu.RUnlock()

		case <-ticker.C:
			// Send heartbeat to all clients
			h.sendHeartbeat()
		}
	}
}

// sendHeartbeat sends a heartbeat message to all connected clients
func (h *Hub) sendHeartbeat() {
	message := map[string]interface{}{
		"type":   "heartbeat",
		"time":   time.Now().UTC().Unix(),
		"status": "healthy",
	}
	data, err := json.Marshal(message)
	if err != nil {
		log.Printf("Error marshaling heartbeat: %v", err)
		return
	}

	h.mu.RLock()
	for client := range h.clients {
		select {
		case client.send <- data:
		default:
			close(client.send)
			delete(h.clients, client)
		}
	}
	h.mu.RUnlock()
}

// BroadcastBanEvent broadcasts a ban event to all connected clients
func (h *Hub) BroadcastBanEvent(event storage.BanEventRecord) {
	message := map[string]interface{}{
		"type": "ban_event",
		"data": event,
	}
	data, err := json.Marshal(message)
	if err != nil {
		log.Printf("Error marshaling ban event: %v", err)
		return
	}

	select {
	case h.broadcast <- data:
	default:
		log.Printf("Broadcast channel full, dropping ban event")
	}
}

// readPump pumps messages from the WebSocket connection to the hub
func (c *Client) readPump() {
	defer func() {
		c.hub.unregister <- c
		c.conn.Close()
	}()

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

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

// 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)

			// Add queued messages to the current websocket message
			n := len(c.send)
			for i := 0; i < n; i++ {
				w.Write([]byte{'\n'})
				w.Write(<-c.send)
			}

			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
			}
		}
	}
}

// serveWS handles WebSocket requests from clients
func serveWS(hub *Hub, c *gin.Context) {
	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		log.Printf("WebSocket upgrade error: %v", err)
		return
	}

	client := &Client{
		hub:  hub,
		conn: conn,
		send: make(chan []byte, 256),
	}

	client.hub.register <- client

	// Allow collection of memory referenced by the caller by doing all work in new goroutines
	go client.writePump()
	go client.readPump()
}

// WebSocketHandler is the Gin handler for WebSocket connections
func WebSocketHandler(hub *Hub) gin.HandlerFunc {
	return func(c *gin.Context) {
		serveWS(hub, c)
	}
}