package ws

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

	"github.com/ThreeDotsLabs/watermill"
	"github.com/ThreeDotsLabs/watermill/message"
	"github.com/ThreeDotsLabs/watermill-redisstream/pkg/redisstream"
	"github.com/redis/go-redis/v9"

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

// Subscriber bridges Watermill PubSub events to WebSocket push notifications.
// It subscribes to relevant Watermill topics (message, conversation, contact events)
// and forwards the events to the appropriate WebSocket rooms via the Hub.
//
// Architecture mapping:
//   Chatwoot ActionCable broadcasts  → Watermill subscriber → Hub.SendToAccount/SendToConversationJSON
//   Each GoChat instance runs its own subscriber, so events are delivered to
//   locally-connected WebSocket clients. Multi-instance delivery relies on Redis
//   PubSub (each instance receives the event and pushes to its own clients).
//
// Reference: P2E §3 — Real-time communication via Redis Pub/Sub
type Subscriber struct {
	hub          *Hub
	subscriber   *redisstream.Subscriber
	router       *message.Router
	redisClient  redis.UniversalClient
}

// NewSubscriber creates a PubSub-to-WebSocket bridge subscriber.
func NewSubscriber(hub *Hub, redisClient redis.UniversalClient) (*Subscriber, error) {
	loggerAdapter := &watermillZapAdapter{}

	wmSubscriber, err := redisstream.NewSubscriber(
		redisstream.SubscriberConfig{
			Client:        redisClient,
			ConsumerGroup: "ws-gateway-" + watermill.NewUUID(),
		},
		loggerAdapter,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create watermill subscriber: %w", err)
	}

	router, err := message.NewRouter(message.RouterConfig{}, loggerAdapter)
	if err != nil {
		return nil, fmt.Errorf("failed to create watermill router: %w", err)
	}

	s := &Subscriber{
		hub:         hub,
		subscriber:  wmSubscriber,
		router:      router,
		redisClient: redisClient,
	}

	// Register handler functions for each event topic
	s.registerHandlers()

	return s, nil
}

// registerHandlers sets up Watermill router handlers that forward PubSub events
// to WebSocket clients via the Hub.
func (s *Subscriber) registerHandlers() {
	// --- Message events → Account room + Conversation room ---
	// Using AddNoPublisherHandler because these handlers push directly to WS, not to an output topic.
	s.router.AddNoPublisherHandler(
		"ws-message-created-handler",
		"gochat.message.created",
		s.subscriber,
		s.forwardToAccountAndConversation(EventMessageCreated),
	)

	s.router.AddNoPublisherHandler(
		"ws-message-updated-handler",
		"gochat.message.updated",
		s.subscriber,
		s.forwardToAccountAndConversation(EventMessageUpdated),
	)

	s.router.AddNoPublisherHandler(
		"ws-message-deleted-handler",
		"gochat.message.deleted",
		s.subscriber,
		s.forwardToAccountAndConversation(EventMessageDeleted),
	)

	// --- Conversation events → Account room ---
	s.router.AddNoPublisherHandler(
		"ws-conversation-created-handler",
		"gochat.conversation.created",
		s.subscriber,
		s.forwardToAccount(EventConversationCreated),
	)

	s.router.AddNoPublisherHandler(
		"ws-conversation-updated-handler",
		"gochat.conversation.updated",
		s.subscriber,
		s.forwardToAccountAndConversation(EventConversationUpdated),
	)

	s.router.AddNoPublisherHandler(
		"ws-conversation-resolved-handler",
		"gochat.conversation.resolved",
		s.subscriber,
		s.forwardToAccountAndConversation(EventConversationResolved),
	)

	s.router.AddNoPublisherHandler(
		"ws-conversation-assigned-handler",
		"gochat.conversation.assigned",
		s.subscriber,
		s.forwardToAccountAndConversation(EventConversationAssigned),
	)

	// --- Contact events → Account room ---
	s.router.AddNoPublisherHandler(
		"ws-contact-created-handler",
		"gochat.contact.created",
		s.subscriber,
		s.forwardToAccount(EventContactCreated),
	)

	s.router.AddNoPublisherHandler(
		"ws-contact-updated-handler",
		"gochat.contact.updated",
		s.subscriber,
		s.forwardToAccount(EventContactUpdated),
	)

	// --- Agent typing events → Conversation room ---
	s.router.AddNoPublisherHandler(
		"ws-agent-typing-on-handler",
		"gochat.agent.typing_on",
		s.subscriber,
		s.forwardToConversation(EventAgentTypingOn),
	)

	s.router.AddNoPublisherHandler(
		"ws-agent-typing-off-handler",
		"gochat.agent.typing_off",
		s.subscriber,
		s.forwardToConversation(EventAgentTypingOff),
	)

	// --- Inbox events → Account room ---
	s.router.AddNoPublisherHandler(
		"ws-inbox-created-handler",
		"gochat.inbox.created",
		s.subscriber,
		s.forwardToAccount(EventInboxCreated),
	)

	s.router.AddNoPublisherHandler(
		"ws-inbox-updated-handler",
		"gochat.inbox.updated",
		s.subscriber,
		s.forwardToAccount(EventInboxUpdated),
	)

	// --- Notification events → Account room (P4 M8 Notification+Webhook) ---
	s.router.AddNoPublisherHandler(
		"ws-notification-created-handler",
		"gochat.notification.created",
		s.subscriber,
		s.forwardToAccount(EventNotificationCreated),
	)
}

// forwardToAccountAndConversation creates a handler that pushes an event to both
// the account room and the conversation room (if the payload contains conversation_id).
// Used for message events and conversation update events that are relevant at both levels.
func (s *Subscriber) forwardToAccountAndConversation(eventType string) func(msg *message.Message) error {
	return func(msg *message.Message) error {
		payload, err := extractPayload(msg)
		if err != nil {
			logger.L().Errorf("ws: failed to extract payload for %s: %v", eventType, err)
			return nil // don't retry — bad payload
		}

		accountID := payload.AccountID
		if accountID == 0 {
			logger.L().Warnf("ws: event %s missing account_id", eventType)
			return nil
		}

		// Build the event frame
		frame := EventFrame{
			Type:    ServerEvent,
			Event:   eventType,
			Payload: payload.Data,
		}
		frameData, err := json.Marshal(frame)
		if err != nil {
			logger.L().Errorf("ws: failed to marshal event frame for %s: %v", eventType, err)
			return nil
		}

		// Push to account room
		s.hub.SendToAccount(accountID, frameData)

		// Also push to conversation room if conversation_id is present
		if payload.ConversationID > 0 {
			s.hub.SendToAccountConversation(accountID, payload.ConversationID, frameData)
		}

		return nil
	}
}

// forwardToAccount creates a handler that pushes an event only to the account room.
// Used for conversation/contact/inbox creation events that don't target a specific conversation.
func (s *Subscriber) forwardToAccount(eventType string) func(msg *message.Message) error {
	return func(msg *message.Message) error {
		payload, err := extractPayload(msg)
		if err != nil {
			logger.L().Errorf("ws: failed to extract payload for %s: %v", eventType, err)
			return nil
		}

		accountID := payload.AccountID
		if accountID == 0 {
			logger.L().Warnf("ws: event %s missing account_id", eventType)
			return nil
		}

		frame := EventFrame{
			Type:    ServerEvent,
			Event:   eventType,
			Payload: payload.Data,
		}
		frameData, err := json.Marshal(frame)
		if err != nil {
			logger.L().Errorf("ws: failed to marshal event frame for %s: %v", eventType, err)
			return nil
		}

		s.hub.SendToAccount(accountID, frameData)
		return nil
	}
}

// forwardToConversation creates a handler that pushes an event only to the conversation room.
// Used for typing events that only need to reach clients viewing that conversation.
func (s *Subscriber) forwardToConversation(eventType string) func(msg *message.Message) error {
	return func(msg *message.Message) error {
		payload, err := extractPayload(msg)
		if err != nil {
			logger.L().Errorf("ws: failed to extract payload for %s: %v", eventType, err)
			return nil
		}

		accountID := payload.AccountID
		conversationID := payload.ConversationID
		if accountID == 0 || conversationID == 0 {
			logger.L().Warnf("ws: event %s missing account_id or conversation_id", eventType)
			return nil
		}

		frame := EventFrame{
			Type:    ServerEvent,
			Event:   eventType,
			Payload: payload.Data,
		}
		frameData, err := json.Marshal(frame)
		if err != nil {
			logger.L().Errorf("ws: failed to marshal event frame for %s: %v", eventType, err)
			return nil
		}

		s.hub.SendToAccountConversation(accountID, conversationID, frameData)
		return nil
	}
}

// --- Event Payload Extraction ---

// EventPayload represents the common structure of PubSub event messages.
// Watermill message payloads are JSON-encoded with account_id, conversation_id,
// and an arbitrary data field.
type EventPayload struct {
	AccountID      uint        `json:"account_id"`
	ConversationID uint        `json:"conversation_id,omitempty"`
	Data           interface{} `json:"data"`
}

// extractPayload parses a Watermill message payload into an EventPayload.
func extractPayload(msg *message.Message) (*EventPayload, error) {
	var payload EventPayload
	if err := json.Unmarshal(msg.Payload, &payload); err != nil {
		return nil, fmt.Errorf("json unmarshal failed: %w", err)
	}
	return &payload, nil
}

// --- Watermill Zap Logger Adapter ---
// Reuses the same pattern as pubsub/event_bus.go's zapLoggerAdapter.

type watermillZapAdapter struct{}

func (l *watermillZapAdapter) Error(msg string, err error, fields watermill.LogFields) {
	if err != nil {
		logger.L().Errorf("watermill-ws: %s err=%v fields=%v", msg, err, fields)
	} else {
		logger.L().Errorf("watermill-ws: %s fields=%v", msg, fields)
	}
}

func (l *watermillZapAdapter) Info(msg string, fields watermill.LogFields) {
	logger.L().Infof("watermill-ws: %s fields=%v", msg, fields)
}

func (l *watermillZapAdapter) Debug(msg string, fields watermill.LogFields) {
	// Skip debug logs to reduce noise
}

func (l *watermillZapAdapter) Trace(msg string, fields watermill.LogFields) {
	// Skip trace logs
}

func (l *watermillZapAdapter) With(fields watermill.LogFields) watermill.LoggerAdapter {
	return l
}

// --- Lifecycle Management ---

// Run starts the Watermill router (blocking). Should be called in a goroutine.
func (s *Subscriber) Run(ctx context.Context) error {
	logger.L().Info("ws: starting PubSub subscriber router")
	return s.router.Run(ctx)
}

// Close gracefully shuts down the Watermill router and subscriber.
func (s *Subscriber) Close() error {
	logger.L().Info("ws: shutting down PubSub subscriber")
	if err := s.router.Close(); err != nil {
		logger.L().Errorf("ws: router close error: %v", err)
		return err
	}
	if err := s.subscriber.Close(); err != nil {
		if !strings.Contains(err.Error(), "already closed") {
			logger.L().Errorf("ws: subscriber close error: %v", err)
			return err
		}
	}
	return nil
}

// Running returns whether the router is currently running.
func (s *Subscriber) Running() bool {
	return s.router.IsRunning()
}