package service

import (
	"context"
	"errors"
	"fmt"
	"time"

	"carrot_bbs/internal/dto"
	"carrot_bbs/internal/model"
	"carrot_bbs/internal/pkg/websocket"
	"carrot_bbs/internal/repository"
)

// 推送相关常量
const (
	// DefaultPushTimeout 默认推送超时时间
	DefaultPushTimeout = 30 * time.Second
	// MaxRetryCount 最大重试次数
	MaxRetryCount = 3
	// DefaultExpiredTime 默认消息过期时间（24小时）
	DefaultExpiredTime = 24 * time.Hour
	// PushQueueSize 推送队列大小
	PushQueueSize = 1000
)

// PushPriority 推送优先级
type PushPriority int

const (
	PriorityLow      PushPriority = 1  // 低优先级（营销消息等）
	PriorityNormal   PushPriority = 5  // 普通优先级（系统通知）
	PriorityHigh     PushPriority = 8  // 高优先级（聊天消息）
	PriorityCritical PushPriority = 10 // 最高优先级（重要系统通知）
)

// PushService 推送服务接口
type PushService interface {
	// 推送核心方法
	PushMessage(ctx context.Context, userID string, message *model.Message) error
	PushToUser(ctx context.Context, userID string, message *model.Message, priority int) error

	// 系统消息推送
	PushSystemMessage(ctx context.Context, userID string, msgType, title, content string, data map[string]interface{}) error
	PushNotification(ctx context.Context, userID string, notification *websocket.NotificationMessage) error
	PushAnnouncement(ctx context.Context, announcement *websocket.AnnouncementMessage) error

	// 系统通知推送（新接口，使用独立的 SystemNotification 模型）
	PushSystemNotification(ctx context.Context, userID string, notification *model.SystemNotification) error

	// 设备管理
	RegisterDevice(ctx context.Context, userID string, deviceID string, deviceType model.DeviceType, pushToken string) error
	UnregisterDevice(ctx context.Context, deviceID string) error
	UpdateDeviceToken(ctx context.Context, deviceID string, newPushToken string) error

	// 推送记录管理
	CreatePushRecord(ctx context.Context, userID string, messageID string, channel model.PushChannel) (*model.PushRecord, error)
	GetPendingPushes(ctx context.Context, userID string) ([]*model.PushRecord, error)

	// 后台任务
	StartPushWorker(ctx context.Context)
	StopPushWorker()
}

// pushServiceImpl 推送服务实现
type pushServiceImpl struct {
	pushRepo    *repository.PushRecordRepository
	deviceRepo  *repository.DeviceTokenRepository
	messageRepo *repository.MessageRepository
	wsManager   *websocket.WebSocketManager

	// 推送队列
	pushQueue chan *pushTask
	stopChan  chan struct{}
}

// pushTask 推送任务
type pushTask struct {
	userID   string
	message  *model.Message
	priority int
}

// NewPushService 创建推送服务
func NewPushService(
	pushRepo *repository.PushRecordRepository,
	deviceRepo *repository.DeviceTokenRepository,
	messageRepo *repository.MessageRepository,
	wsManager *websocket.WebSocketManager,
) PushService {
	return &pushServiceImpl{
		pushRepo:    pushRepo,
		deviceRepo:  deviceRepo,
		messageRepo: messageRepo,
		wsManager:   wsManager,
		pushQueue:   make(chan *pushTask, PushQueueSize),
		stopChan:    make(chan struct{}),
	}
}

// PushMessage 推送消息给用户
func (s *pushServiceImpl) PushMessage(ctx context.Context, userID string, message *model.Message) error {
	return s.PushToUser(ctx, userID, message, int(PriorityNormal))
}

// PushToUser 带优先级的推送
func (s *pushServiceImpl) PushToUser(ctx context.Context, userID string, message *model.Message, priority int) error {
	// 首先尝试WebSocket推送（实时推送）
	if s.pushViaWebSocket(ctx, userID, message) {
		// WebSocket推送成功，记录推送状态
		record, err := s.CreatePushRecord(ctx, userID, message.ID, model.PushChannelWebSocket)
		if err != nil {
			return fmt.Errorf("failed to create push record: %w", err)
		}
		record.MarkPushed()
		if err := s.pushRepo.Update(record); err != nil {
			return fmt.Errorf("failed to update push record: %w", err)
		}
		return nil
	}

	// WebSocket推送失败，加入推送队列等待移动端推送
	select {
	case s.pushQueue <- &pushTask{
		userID:   userID,
		message:  message,
		priority: priority,
	}:
		return nil
	default:
		// 队列已满，直接创建待推送记录
		_, err := s.CreatePushRecord(ctx, userID, message.ID, model.PushChannelFCM)
		if err != nil {
			return fmt.Errorf("failed to create pending push record: %w", err)
		}
		return errors.New("push queue is full, message queued for later delivery")
	}
}

// pushViaWebSocket 通过WebSocket推送消息
// 返回true表示推送成功，false表示用户不在线
func (s *pushServiceImpl) pushViaWebSocket(ctx context.Context, userID string, message *model.Message) bool {
	if s.wsManager == nil {
		return false
	}

	if !s.wsManager.IsUserOnline(userID) {
		return false
	}

	// 判断是否为系统消息/通知消息
	if message.IsSystemMessage() || message.Category == model.CategoryNotification {
		// 使用 NotificationMessage 格式推送系统通知
		// 从 segments 中提取文本内容
		content := dto.ExtractTextContentFromModel(message.Segments)

		notification := &websocket.NotificationMessage{
			ID:        fmt.Sprintf("%s", message.ID),
			Type:      string(message.SystemType),
			Content:   content,
			Extra:     make(map[string]interface{}),
			CreatedAt: message.CreatedAt.UnixMilli(),
		}

		// 填充额外数据
		if message.ExtraData != nil {
			notification.Extra["actor_id"] = message.ExtraData.ActorID
			notification.Extra["actor_name"] = message.ExtraData.ActorName
			notification.Extra["avatar_url"] = message.ExtraData.AvatarURL
			notification.Extra["target_id"] = message.ExtraData.TargetID
			notification.Extra["target_type"] = message.ExtraData.TargetType
			notification.Extra["action_url"] = message.ExtraData.ActionURL
			notification.Extra["action_time"] = message.ExtraData.ActionTime

			// 设置触发用户信息
			if message.ExtraData.ActorID > 0 {
				notification.TriggerUser = &websocket.NotificationUser{
					ID:       fmt.Sprintf("%d", message.ExtraData.ActorID),
					Username: message.ExtraData.ActorName,
					Avatar:   message.ExtraData.AvatarURL,
				}
			}
		}

		wsMsg := websocket.CreateWSMessage(websocket.MessageTypeNotification, notification)
		s.wsManager.SendToUser(userID, wsMsg)
		return true
	}

	// 构建普通聊天消息的 WebSocket 消息 - 使用新的 WSEventResponse 格式
	// 获取会话类型 (private/group)
	detailType := "private"
	if message.ConversationID != "" {
		// 从会话中获取类型，需要查询数据库或从消息中判断
		// 这里暂时默认为 private，group 类型需要额外逻辑
	}

	// 直接使用 message.Segments
	segments := message.Segments

	event := &dto.WSEventResponse{
		ID:         fmt.Sprintf("%s", message.ID),
		Time:       message.CreatedAt.UnixMilli(),
		Type:       "message",
		DetailType: detailType,
		Seq:        fmt.Sprintf("%d", message.Seq),
		Segments:   segments,
		SenderID:   message.SenderID,
	}

	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeMessage, event)
	s.wsManager.SendToUser(userID, wsMsg)
	return true
}

// pushViaFCM 通过FCM推送（预留接口）
func (s *pushServiceImpl) pushViaFCM(ctx context.Context, deviceToken *model.DeviceToken, message *model.Message) error {
	// TODO: 实现FCM推送
	// 1. 构建FCM消息
	// 2. 调用Firebase Admin SDK发送消息
	// 3. 处理发送结果
	return errors.New("FCM push not implemented")
}

// pushViaAPNs 通过APNs推送（预留接口）
func (s *pushServiceImpl) pushViaAPNs(ctx context.Context, deviceToken *model.DeviceToken, message *model.Message) error {
	// TODO: 实现APNs推送
	// 1. 构建APNs消息
	// 2. 调用APNs SDK发送消息
	// 3. 处理发送结果
	return errors.New("APNs push not implemented")
}

// RegisterDevice 注册设备
func (s *pushServiceImpl) RegisterDevice(ctx context.Context, userID string, deviceID string, deviceType model.DeviceType, pushToken string) error {
	deviceToken := &model.DeviceToken{
		UserID:     userID,
		DeviceID:   deviceID,
		DeviceType: deviceType,
		PushToken:  pushToken,
		IsActive:   true,
	}
	deviceToken.UpdateLastUsed()

	return s.deviceRepo.Upsert(deviceToken)
}

// UnregisterDevice 注销设备
func (s *pushServiceImpl) UnregisterDevice(ctx context.Context, deviceID string) error {
	return s.deviceRepo.Deactivate(deviceID)
}

// UpdateDeviceToken 更新设备Token
func (s *pushServiceImpl) UpdateDeviceToken(ctx context.Context, deviceID string, newPushToken string) error {
	deviceToken, err := s.deviceRepo.GetByDeviceID(deviceID)
	if err != nil {
		return fmt.Errorf("device not found: %w", err)
	}

	deviceToken.PushToken = newPushToken
	deviceToken.Activate()

	return s.deviceRepo.Update(deviceToken)
}

// CreatePushRecord 创建推送记录
func (s *pushServiceImpl) CreatePushRecord(ctx context.Context, userID string, messageID string, channel model.PushChannel) (*model.PushRecord, error) {
	expiredAt := time.Now().Add(DefaultExpiredTime)
	record := &model.PushRecord{
		UserID:      userID,
		MessageID:   messageID,
		PushChannel: channel,
		PushStatus:  model.PushStatusPending,
		MaxRetry:    MaxRetryCount,
		ExpiredAt:   &expiredAt,
	}

	if err := s.pushRepo.Create(record); err != nil {
		return nil, fmt.Errorf("failed to create push record: %w", err)
	}

	return record, nil
}

// GetPendingPushes 获取待推送记录
func (s *pushServiceImpl) GetPendingPushes(ctx context.Context, userID string) ([]*model.PushRecord, error) {
	return s.pushRepo.GetByUserID(userID, 100, 0)
}

// StartPushWorker 启动推送工作协程
func (s *pushServiceImpl) StartPushWorker(ctx context.Context) {
	go s.processPushQueue()
	go s.retryFailedPushes()
}

// StopPushWorker 停止推送工作协程
func (s *pushServiceImpl) StopPushWorker() {
	close(s.stopChan)
}

// processPushQueue 处理推送队列
func (s *pushServiceImpl) processPushQueue() {
	for {
		select {
		case <-s.stopChan:
			return
		case task := <-s.pushQueue:
			s.processPushTask(task)
		}
	}
}

// processPushTask 处理单个推送任务
func (s *pushServiceImpl) processPushTask(task *pushTask) {
	ctx, cancel := context.WithTimeout(context.Background(), DefaultPushTimeout)
	defer cancel()

	// 获取用户活跃设备
	devices, err := s.deviceRepo.GetActiveByUserID(task.userID)
	if err != nil || len(devices) == 0 {
		// 没有可用设备，创建待推送记录
		s.CreatePushRecord(ctx, task.userID, task.message.ID, model.PushChannelFCM)
		return
	}

	// 对每个设备创建推送记录并尝试推送
	for _, device := range devices {
		record, err := s.CreatePushRecord(ctx, task.userID, task.message.ID, s.getChannelForDevice(device))
		if err != nil {
			continue
		}

		var pushErr error
		switch {
		case device.IsIOS():
			pushErr = s.pushViaAPNs(ctx, device, task.message)
		case device.IsAndroid():
			pushErr = s.pushViaFCM(ctx, device, task.message)
		default:
			// Web设备只支持WebSocket
			continue
		}

		if pushErr != nil {
			record.MarkFailed(pushErr.Error())
		} else {
			record.MarkPushed()
		}
		s.pushRepo.Update(record)
	}
}

// getChannelForDevice 根据设备类型获取推送通道
func (s *pushServiceImpl) getChannelForDevice(device *model.DeviceToken) model.PushChannel {
	switch device.DeviceType {
	case model.DeviceTypeIOS:
		return model.PushChannelAPNs
	case model.DeviceTypeAndroid:
		return model.PushChannelFCM
	default:
		return model.PushChannelWebSocket
	}
}

// retryFailedPushes 重试失败的推送
func (s *pushServiceImpl) retryFailedPushes() {
	ticker := time.NewTicker(5 * time.Minute)
	defer ticker.Stop()

	for {
		select {
		case <-s.stopChan:
			return
		case <-ticker.C:
			s.doRetry()
		}
	}
}

// doRetry 执行重试
func (s *pushServiceImpl) doRetry() {
	ctx := context.Background()

	// 获取失败待重试的推送
	records, err := s.pushRepo.GetFailedPushesForRetry(100)
	if err != nil {
		return
	}

	for _, record := range records {
		// 检查是否过期
		if record.IsExpired() {
			record.MarkExpired()
			s.pushRepo.Update(record)
			continue
		}

		// 获取消息
		message, err := s.messageRepo.GetMessageByID(record.MessageID)
		if err != nil {
			record.MarkFailed("message not found")
			s.pushRepo.Update(record)
			continue
		}

		// 尝试WebSocket推送
		if s.pushViaWebSocket(ctx, record.UserID, message) {
			record.MarkDelivered()
			s.pushRepo.Update(record)
			continue
		}

		// 获取设备并尝试移动端推送
		if record.DeviceToken != "" {
			device, err := s.deviceRepo.GetByPushToken(record.DeviceToken)
			if err != nil {
				record.MarkFailed("device not found")
				s.pushRepo.Update(record)
				continue
			}

			var pushErr error
			switch {
			case device.IsIOS():
				pushErr = s.pushViaAPNs(ctx, device, message)
			case device.IsAndroid():
				pushErr = s.pushViaFCM(ctx, device, message)
			}

			if pushErr != nil {
				record.MarkFailed(pushErr.Error())
			} else {
				record.MarkPushed()
			}
			s.pushRepo.Update(record)
		}
	}
}

// PushSystemMessage 推送系统消息
func (s *pushServiceImpl) PushSystemMessage(ctx context.Context, userID string, msgType, title, content string, data map[string]interface{}) error {
	// 首先尝试WebSocket推送
	if s.pushSystemViaWebSocket(ctx, userID, msgType, title, content, data) {
		return nil
	}

	// 用户不在线，创建待推送记录（移动端上线后可通过其他方式获取）
	// 系统消息通常不需要离线推送，客户端上线后会主动拉取
	return errors.New("user is offline, system message will be available on next sync")
}

// pushSystemViaWebSocket 通过WebSocket推送系统消息
func (s *pushServiceImpl) pushSystemViaWebSocket(ctx context.Context, userID string, msgType, title, content string, data map[string]interface{}) bool {
	if s.wsManager == nil {
		return false
	}

	if !s.wsManager.IsUserOnline(userID) {
		return false
	}

	sysMsg := &websocket.SystemMessage{
		Type:      msgType,
		Title:     title,
		Content:   content,
		Data:      data,
		CreatedAt: time.Now().UnixMilli(),
	}

	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeSystem, sysMsg)
	s.wsManager.SendToUser(userID, wsMsg)
	return true
}

// PushNotification 推送通知消息
func (s *pushServiceImpl) PushNotification(ctx context.Context, userID string, notification *websocket.NotificationMessage) error {
	// 首先尝试WebSocket推送
	if s.pushNotificationViaWebSocket(ctx, userID, notification) {
		return nil
	}

	// 用户不在线，创建待推送记录
	// 通知消息可以等用户上线后拉取
	return errors.New("user is offline, notification will be available on next sync")
}

// pushNotificationViaWebSocket 通过WebSocket推送通知消息
func (s *pushServiceImpl) pushNotificationViaWebSocket(ctx context.Context, userID string, notification *websocket.NotificationMessage) bool {
	if s.wsManager == nil {
		return false
	}

	if !s.wsManager.IsUserOnline(userID) {
		return false
	}

	if notification.CreatedAt == 0 {
		notification.CreatedAt = time.Now().UnixMilli()
	}

	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeNotification, notification)
	s.wsManager.SendToUser(userID, wsMsg)
	return true
}

// PushAnnouncement 广播公告消息
func (s *pushServiceImpl) PushAnnouncement(ctx context.Context, announcement *websocket.AnnouncementMessage) error {
	if s.wsManager == nil {
		return errors.New("websocket manager not available")
	}

	if announcement.CreatedAt == 0 {
		announcement.CreatedAt = time.Now().UnixMilli()
	}

	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeAnnouncement, announcement)
	s.wsManager.Broadcast(wsMsg)
	return nil
}

// PushSystemNotification 推送系统通知（使用独立的 SystemNotification 模型）
func (s *pushServiceImpl) PushSystemNotification(ctx context.Context, userID string, notification *model.SystemNotification) error {
	// 首先尝试WebSocket推送
	if s.pushSystemNotificationViaWebSocket(ctx, userID, notification) {
		return nil
	}

	// 用户不在线，系统通知已存储在数据库中，用户上线后会主动拉取
	return nil
}

// pushSystemNotificationViaWebSocket 通过WebSocket推送系统通知
func (s *pushServiceImpl) pushSystemNotificationViaWebSocket(ctx context.Context, userID string, notification *model.SystemNotification) bool {
	if s.wsManager == nil {
		return false
	}

	if !s.wsManager.IsUserOnline(userID) {
		return false
	}

	// 构建 WebSocket 通知消息
	wsNotification := &websocket.NotificationMessage{
		ID:        fmt.Sprintf("%d", notification.ID),
		Type:      string(notification.Type),
		Title:     notification.Title,
		Content:   notification.Content,
		Extra:     make(map[string]interface{}),
		CreatedAt: notification.CreatedAt.UnixMilli(),
	}

	// 填充额外数据
	if notification.ExtraData != nil {
		wsNotification.Extra["actor_id_str"] = notification.ExtraData.ActorIDStr
		wsNotification.Extra["actor_name"] = notification.ExtraData.ActorName
		wsNotification.Extra["avatar_url"] = notification.ExtraData.AvatarURL
		wsNotification.Extra["target_id"] = notification.ExtraData.TargetID
		wsNotification.Extra["target_type"] = notification.ExtraData.TargetType
		wsNotification.Extra["action_url"] = notification.ExtraData.ActionURL
		wsNotification.Extra["action_time"] = notification.ExtraData.ActionTime

		// 设置触发用户信息
		if notification.ExtraData.ActorIDStr != "" {
			wsNotification.TriggerUser = &websocket.NotificationUser{
				ID:       notification.ExtraData.ActorIDStr,
				Username: notification.ExtraData.ActorName,
				Avatar:   notification.ExtraData.AvatarURL,
			}
		}
	}

	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeNotification, wsNotification)
	s.wsManager.SendToUser(userID, wsMsg)
	return true
}