// pkg/display/events.go
package display

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

	"forge.lthn.ai/core/gui/pkg/window"
	"github.com/gorilla/websocket"
)

// EventType represents the type of event.
// Use: eventType := display.EventWindowFocus
type EventType string

const (
	EventWindowFocus         EventType = "window.focus"
	EventWindowBlur          EventType = "window.blur"
	EventWindowMove          EventType = "window.move"
	EventWindowResize        EventType = "window.resize"
	EventWindowClose         EventType = "window.close"
	EventWindowCreate        EventType = "window.create"
	EventThemeChange         EventType = "theme.change"
	EventScreenChange        EventType = "screen.change"
	EventNotificationClick   EventType = "notification.click"
	EventTrayClick           EventType = "tray.click"
	EventTrayMenuItemClick   EventType = "tray.menuitem.click"
	EventKeybindingTriggered EventType = "keybinding.triggered"
	EventWindowFileDrop      EventType = "window.filedrop"
	EventDockVisibility      EventType = "dock.visibility-changed"
	EventAppStarted          EventType = "app.started"
	EventAppOpenedWithFile   EventType = "app.opened-with-file"
	EventAppWillTerminate    EventType = "app.will-terminate"
	EventAppActive           EventType = "app.active"
	EventAppInactive         EventType = "app.inactive"
	EventSystemPowerChange   EventType = "system.power-change"
	EventSystemSuspend       EventType = "system.suspend"
	EventSystemResume        EventType = "system.resume"
	EventContextMenuClick    EventType = "contextmenu.item-clicked"
	EventWebviewConsole      EventType = "webview.console"
	EventWebviewException    EventType = "webview.exception"
)

// Event represents a display event sent to subscribers.
// Use: evt := display.Event{Type: display.EventWindowFocus, Window: "editor"}
type Event struct {
	Type      EventType      `json:"type"`
	Timestamp int64          `json:"timestamp"`
	Window    string         `json:"window,omitempty"`
	Data      map[string]any `json:"data,omitempty"`
}

// Subscription represents a client subscription to events.
// Use: sub := display.Subscription{ID: "sub-1", EventTypes: []display.EventType{display.EventWindowFocus}}
type Subscription struct {
	ID         string      `json:"id"`
	EventTypes []EventType `json:"eventTypes"`
}

// EventServerInfo summarises the live WebSocket event server state.
// Use: info := display.EventServerInfo{ConnectedClients: 1, Subscriptions: 3}
type EventServerInfo struct {
	ConnectedClients int `json:"connectedClients"`
	Subscriptions    int `json:"subscriptions"`
	BufferedEvents   int `json:"bufferedEvents"`
}

// WSEventManager manages WebSocket connections and event subscriptions.
// Use: events := display.NewWSEventManager()
type WSEventManager struct {
	upgrader    websocket.Upgrader
	clients     map[*websocket.Conn]*clientState
	mu          sync.RWMutex
	nextSubID   int
	eventBuffer chan Event
}

// clientState tracks a client's subscriptions.
// Use: state := &clientState{subscriptions: map[string]*Subscription{}}
type clientState struct {
	subscriptions map[string]*Subscription
	mu            sync.RWMutex
}

// NewWSEventManager creates a new event manager.
// Use: events := display.NewWSEventManager()
func NewWSEventManager() *WSEventManager {
	em := &WSEventManager{
		upgrader: websocket.Upgrader{
			CheckOrigin: func(r *http.Request) bool {
				return true // Allow all origins for local dev
			},
			ReadBufferSize:  1024,
			WriteBufferSize: 1024,
		},
		clients:     make(map[*websocket.Conn]*clientState),
		eventBuffer: make(chan Event, 100),
	}

	// Start event broadcaster
	go em.broadcaster()

	return em
}

// broadcaster sends events to all subscribed clients.
func (em *WSEventManager) broadcaster() {
	for event := range em.eventBuffer {
		em.mu.RLock()
		for conn, state := range em.clients {
			if em.clientSubscribed(state, event.Type) {
				go em.sendEvent(conn, event)
			}
		}
		em.mu.RUnlock()
	}
}

// clientSubscribed checks if a client is subscribed to an event type.
func (em *WSEventManager) clientSubscribed(state *clientState, eventType EventType) bool {
	state.mu.RLock()
	defer state.mu.RUnlock()

	for _, sub := range state.subscriptions {
		for _, et := range sub.EventTypes {
			if et == eventType || et == "*" {
				return true
			}
		}
	}
	return false
}

// sendEvent sends an event to a specific client.
func (em *WSEventManager) sendEvent(conn *websocket.Conn, event Event) {
	em.mu.RLock()
	_, exists := em.clients[conn]
	em.mu.RUnlock()

	if !exists {
		return
	}

	data, err := json.Marshal(event)
	if err != nil {
		return
	}

	conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
	if err := conn.WriteMessage(websocket.TextMessage, data); err != nil {
		em.removeClient(conn)
	}
}

// HandleWebSocket handles WebSocket upgrade and connection.
func (em *WSEventManager) HandleWebSocket(w http.ResponseWriter, r *http.Request) {
	conn, err := em.upgrader.Upgrade(w, r, nil)
	if err != nil {
		return
	}

	em.mu.Lock()
	em.clients[conn] = &clientState{
		subscriptions: make(map[string]*Subscription),
	}
	em.mu.Unlock()

	// Handle incoming messages
	go em.handleMessages(conn)
}

// handleMessages processes incoming WebSocket messages.
func (em *WSEventManager) handleMessages(conn *websocket.Conn) {
	defer em.removeClient(conn)

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

		var msg struct {
			Action     string      `json:"action"`
			ID         string      `json:"id,omitempty"`
			EventTypes []EventType `json:"eventTypes,omitempty"`
		}

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

		switch msg.Action {
		case "subscribe":
			em.subscribe(conn, msg.ID, msg.EventTypes)
		case "unsubscribe":
			em.unsubscribe(conn, msg.ID)
		case "list":
			em.listSubscriptions(conn)
		}
	}
}

// subscribe adds a subscription for a client.
func (em *WSEventManager) subscribe(conn *websocket.Conn, id string, eventTypes []EventType) {
	em.mu.RLock()
	state, exists := em.clients[conn]
	em.mu.RUnlock()

	if !exists {
		return
	}

	// Generate ID if not provided
	if id == "" {
		em.mu.Lock()
		em.nextSubID++
		id = fmt.Sprintf("sub-%d", em.nextSubID)
		em.mu.Unlock()
	}

	state.mu.Lock()
	state.subscriptions[id] = &Subscription{
		ID:         id,
		EventTypes: eventTypes,
	}
	state.mu.Unlock()

	// Send confirmation
	response := map[string]any{
		"type":       "subscribed",
		"id":         id,
		"eventTypes": eventTypes,
	}
	data, _ := json.Marshal(response)
	conn.WriteMessage(websocket.TextMessage, data)
}

// unsubscribe removes a subscription for a client.
func (em *WSEventManager) unsubscribe(conn *websocket.Conn, id string) {
	em.mu.RLock()
	state, exists := em.clients[conn]
	em.mu.RUnlock()

	if !exists {
		return
	}

	state.mu.Lock()
	delete(state.subscriptions, id)
	state.mu.Unlock()

	// Send confirmation
	response := map[string]any{
		"type": "unsubscribed",
		"id":   id,
	}
	data, _ := json.Marshal(response)
	conn.WriteMessage(websocket.TextMessage, data)
}

// listSubscriptions sends a list of active subscriptions to a client.
func (em *WSEventManager) listSubscriptions(conn *websocket.Conn) {
	em.mu.RLock()
	state, exists := em.clients[conn]
	em.mu.RUnlock()

	if !exists {
		return
	}

	state.mu.RLock()
	subs := make([]*Subscription, 0, len(state.subscriptions))
	for _, sub := range state.subscriptions {
		subs = append(subs, sub)
	}
	state.mu.RUnlock()

	response := map[string]any{
		"type":          "subscriptions",
		"subscriptions": subs,
	}
	data, _ := json.Marshal(response)
	conn.WriteMessage(websocket.TextMessage, data)
}

// removeClient removes a client and its subscriptions.
func (em *WSEventManager) removeClient(conn *websocket.Conn) {
	em.mu.Lock()
	delete(em.clients, conn)
	em.mu.Unlock()
	conn.Close()
}

// Emit sends an event to all subscribed clients.
func (em *WSEventManager) Emit(event Event) {
	event.Timestamp = time.Now().UnixMilli()
	select {
	case em.eventBuffer <- event:
	default:
		// Buffer full, drop event
	}
}

// EmitWindowEvent is a helper to emit window-related events.
func (em *WSEventManager) EmitWindowEvent(eventType EventType, windowName string, data map[string]any) {
	em.Emit(Event{
		Type:   eventType,
		Window: windowName,
		Data:   data,
	})
}

// ConnectedClients returns the number of connected WebSocket clients.
func (em *WSEventManager) ConnectedClients() int {
	em.mu.RLock()
	defer em.mu.RUnlock()
	return len(em.clients)
}

// Info returns a snapshot of the WebSocket event server state.
func (em *WSEventManager) Info() EventServerInfo {
	em.mu.RLock()
	defer em.mu.RUnlock()

	info := EventServerInfo{
		ConnectedClients: len(em.clients),
		BufferedEvents:   len(em.eventBuffer),
	}
	for _, state := range em.clients {
		state.mu.RLock()
		info.Subscriptions += len(state.subscriptions)
		state.mu.RUnlock()
	}
	return info
}

// Close shuts down the event manager.
func (em *WSEventManager) Close() {
	em.mu.Lock()
	for conn := range em.clients {
		conn.Close()
	}
	em.clients = make(map[*websocket.Conn]*clientState)
	em.mu.Unlock()
	close(em.eventBuffer)
}

// AttachWindowListeners attaches event listeners to a specific window.
// Accepts window.PlatformWindow instead of *application.WebviewWindow.
func (em *WSEventManager) AttachWindowListeners(pw window.PlatformWindow) {
	if pw == nil {
		return
	}

	pw.OnWindowEvent(func(e window.WindowEvent) {
		em.EmitWindowEvent(EventType("window."+e.Type), e.Name, e.Data)
	})
}