// Package ws provides the EventPublisher that unifies real-time event delivery
// across WebSocket Hub and SSE fallback channels. Services call PublishEvent
// after mutations (CreateConversation, SendMessage, etc.) to push events to
// all connected clients, mirroring Chatwoot's ActionCable broadcast pattern.
package ws

import (
	"context"
	"encoding/json"
	"fmt"

	applogger "github.com/gochat/gochat/pkg/logger"
)

// EventPublisher routes business events to both WebSocket and SSE clients.
// It is the central point that services call after mutations to push real-time
// updates, matching Chatwoot's pattern where controllers broadcast events
// after create/update/delete actions via Wisper → ActionCable.
//
// Architecture:
//   Service.CreateX() → EventPublisher.PublishEvent(accountID, eventType, payload)
//     → Hub.SendToAccount (WebSocket local delivery)
//     → SSERegistry.SendToAccount (SSE local delivery)
//     → BroadcastRelay.Publish (Redis Pub/Sub cross-instance delivery)
//
// Reference: Chatwoot uses Wisper (in-process pub/sub) + ActionCable (WebSocket)
// + Redis Pub/Sub for cross-instance. GoChat uses EventPublisher as the unified
// entry point, with Hub and SSERegistry as local delivery targets, and Redis
// Pub/Sub relay for multi-instance fan-out.
type EventPublisher struct {
	hub   MessageHandler   // WebSocket Hub (local delivery)
	sse   *SSERegistry     // SSE registry (local delivery)
	relay *BroadcastRelay  // Redis Pub/Sub relay (cross-instance delivery)
}

// NewEventPublisher creates an EventPublisher with all delivery targets.
func NewEventPublisher(hub MessageHandler, sse *SSERegistry, relay *BroadcastRelay) *EventPublisher {
	return &EventPublisher{
		hub:   hub,
		sse:   sse,
		relay: relay,
	}
}

// NewEventPublisherLocal creates an EventPublisher with only local delivery
// (no Redis relay). Used for development/testing without Redis.
func NewEventPublisherLocal(hub MessageHandler, sse *SSERegistry) *EventPublisher {
	return &EventPublisher{
		hub: hub,
		sse: sse,
	}
}

// PublishEvent publishes a real-time event to all delivery targets.
// This is the primary API that services call after business mutations.
//
// Parameters:
//   - accountID: the account scope for the event (each client only sees their account's events)
//   - eventType: dot-separated event name (e.g. "message.created", "conversation.updated")
//   - payload: event data (will be JSON-encoded for transport)
//
// The event is routed to:
//   1. WebSocket Hub → all locally connected WS clients for that account
//   2. SSE Registry → all locally connected SSE clients for that account
//   3. Redis Pub/Sub relay → all other GoChat instances (cross-instance delivery)
//
// Reference: Chatwoot controllers call broadcast_event after mutations,
// which triggers Wisper → ActionCable → Redis Pub/Sub relay.
func (p *EventPublisher) PublishEvent(accountID uint, eventType string, payload interface{}) {
	// Build the wire-format message (matching Chatwoot ActionCable event format)
	wsMsg := &WSMessage{
		Event:     eventType,
		Data:      payload,
		AccountID: accountID,
	}

	data, err := json.Marshal(wsMsg)
	if err != nil {
		applogger.L().Warnf("event publisher: failed to marshal event %s: %v", eventType, err)
		return
	}

	// 1. Deliver to WebSocket Hub (local clients)
	if p.hub != nil {
		p.hub.SendToAccount(accountID, data)
	}

	// 2. Deliver to SSE registry (local clients)
	if p.sse != nil {
		p.sse.SendToAccount(accountID, SSEEvent{
			Type:    eventType,
			Payload: payload,
		})
	}

	// 3. Publish to Redis Pub/Sub relay (cross-instance delivery)
	if p.relay != nil {
		room := accountRoomNameHelper(accountID)
		if err := p.relay.Publish(context.Background(), room, wsMsg); err != nil {
			applogger.L().Warnf("event publisher: redis publish failed for %s: %v", eventType, err)
		}
	}
}

// PublishConversationEvent publishes a real-time event scoped to a specific
// conversation within an account. This is used for events that should only
// reach clients viewing that conversation (e.g. typing indicators, message updates).
//
// Reference: Chatwoot ConversationChannel — events broadcast to clients
// subscribed to a specific conversation's channel.
func (p *EventPublisher) PublishConversationEvent(accountID uint, conversationID uint, eventType string, payload interface{}) {
	wsMsg := &WSMessage{
		Event:     eventType,
		Data:      payload,
		AccountID: accountID,
	}

	data, err := json.Marshal(wsMsg)
	if err != nil {
		applogger.L().Warnf("event publisher: failed to marshal conversation event %s: %v", eventType, err)
		return
	}

	// 1. Deliver to WebSocket Hub (both account room and conversation room)
	if p.hub != nil {
		p.hub.SendToAccount(accountID, data)
		convRoom := conversationRoomNameHelper(accountID, conversationID)
		p.hub.SendToRoom(convRoom, data)
	}

	// 2. Deliver to SSE registry (conversation-filtered channels)
	if p.sse != nil {
		p.sse.SendToConversation(accountID, conversationID, SSEEvent{
			Type:    eventType,
			Payload: payload,
		})
	}

	// 3. Publish to Redis Pub/Sub relay (both account and conversation channels)
	if p.relay != nil {
		room := accountRoomNameHelper(accountID)
		if err := p.relay.Publish(context.Background(), room, wsMsg); err != nil {
			applogger.L().Warnf("event publisher: redis publish failed for %s: %v", eventType, err)
		}
	}
}

// accountRoomNameHelper generates the room name for an account channel.
func accountRoomNameHelper(accountID uint) string {
	return fmt.Sprintf("account_%d", accountID)
}

// conversationRoomNameHelper generates the room name for a conversation channel.
func conversationRoomNameHelper(accountID uint, conversationID uint) string {
	return fmt.Sprintf("account_%d_conversation_%d", accountID, conversationID)
}