package service

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

	"carrot_bbs/internal/dto"
	"carrot_bbs/internal/model"
	"carrot_bbs/internal/pkg/sse"
	"carrot_bbs/internal/repository"

	"gorm.io/gorm"
)

// 撤回消息的时间限制（2分钟）
const RecallMessageTimeout = 2 * time.Minute

// ChatService 聊天服务接口
type ChatService interface {
	// 会话管理
	GetOrCreateConversation(ctx context.Context, user1ID, user2ID string) (*model.Conversation, error)
	GetConversationList(ctx context.Context, userID string, page, pageSize int) ([]*model.Conversation, int64, error)
	GetConversationByID(ctx context.Context, conversationID string, userID string) (*model.Conversation, error)
	DeleteConversationForSelf(ctx context.Context, conversationID string, userID string) error
	SetConversationPinned(ctx context.Context, conversationID string, userID string, isPinned bool) error

	// 消息操作
	SendMessage(ctx context.Context, senderID string, conversationID string, segments model.MessageSegments, replyToID *string) (*model.Message, error)
	GetMessages(ctx context.Context, conversationID string, userID string, page, pageSize int) ([]*model.Message, int64, error)
	GetMessagesAfterSeq(ctx context.Context, conversationID string, userID string, afterSeq int64, limit int) ([]*model.Message, error)
	GetMessagesBeforeSeq(ctx context.Context, conversationID string, userID string, beforeSeq int64, limit int) ([]*model.Message, error)

	// 已读管理
	MarkAsRead(ctx context.Context, conversationID string, userID string, seq int64) error
	GetUnreadCount(ctx context.Context, conversationID string, userID string) (int64, error)
	GetAllUnreadCount(ctx context.Context, userID string) (int64, error)

	// 消息扩展功能
	RecallMessage(ctx context.Context, messageID string, userID string) error
	DeleteMessage(ctx context.Context, messageID string, userID string) error

	// 实时事件相关
	SendTyping(ctx context.Context, senderID string, conversationID string)

	// 在线状态
	IsUserOnline(userID string) bool

	// 仅保存消息到数据库，不发送实时推送（供群聊等自行推送的场景使用）
	SaveMessage(ctx context.Context, senderID string, conversationID string, segments model.MessageSegments, replyToID *string) (*model.Message, error)
}

// chatServiceImpl 聊天服务实现
type chatServiceImpl struct {
	db        *gorm.DB
	repo      *repository.MessageRepository
	userRepo  *repository.UserRepository
	sensitive SensitiveService
	sseHub    *sse.Hub
}

// NewChatService 创建聊天服务
func NewChatService(
	db *gorm.DB,
	repo *repository.MessageRepository,
	userRepo *repository.UserRepository,
	sensitive SensitiveService,
	sseHub *sse.Hub,
) ChatService {
	return &chatServiceImpl{
		db:        db,
		repo:      repo,
		userRepo:  userRepo,
		sensitive: sensitive,
		sseHub:    sseHub,
	}
}

func (s *chatServiceImpl) publishSSEToUsers(userIDs []string, event string, payload interface{}) {
	if s.sseHub == nil || len(userIDs) == 0 {
		return
	}
	s.sseHub.PublishToUsers(userIDs, event, payload)
}

// GetOrCreateConversation 获取或创建私聊会话
func (s *chatServiceImpl) GetOrCreateConversation(ctx context.Context, user1ID, user2ID string) (*model.Conversation, error) {
	return s.repo.GetOrCreatePrivateConversation(user1ID, user2ID)
}

// GetConversationList 获取用户的会话列表
func (s *chatServiceImpl) GetConversationList(ctx context.Context, userID string, page, pageSize int) ([]*model.Conversation, int64, error) {
	return s.repo.GetConversations(userID, page, pageSize)
}

// GetConversationByID 获取会话详情
func (s *chatServiceImpl) GetConversationByID(ctx context.Context, conversationID string, userID string) (*model.Conversation, error) {
	// 验证用户是否是会话参与者
	participant, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("conversation not found or no permission")
		}
		return nil, fmt.Errorf("failed to get participant: %w", err)
	}

	// 获取会话信息
	conv, err := s.repo.GetConversation(conversationID)
	if err != nil {
		return nil, fmt.Errorf("failed to get conversation: %w", err)
	}

	// 填充用户的已读位置信息
	_ = participant // 可以用于返回已读位置等信息

	return conv, nil
}

// DeleteConversationForSelf 仅自己删除会话
func (s *chatServiceImpl) DeleteConversationForSelf(ctx context.Context, conversationID string, userID string) error {
	participant, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("conversation not found or no permission")
		}
		return fmt.Errorf("failed to get participant: %w", err)
	}
	if participant.ConversationID == "" {
		return errors.New("conversation not found or no permission")
	}

	if err := s.repo.HideConversationForUser(conversationID, userID); err != nil {
		return fmt.Errorf("failed to hide conversation: %w", err)
	}
	return nil
}

// SetConversationPinned 设置会话置顶（用户维度）
func (s *chatServiceImpl) SetConversationPinned(ctx context.Context, conversationID string, userID string, isPinned bool) error {
	participant, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("conversation not found or no permission")
		}
		return fmt.Errorf("failed to get participant: %w", err)
	}
	if participant.ConversationID == "" {
		return errors.New("conversation not found or no permission")
	}

	if err := s.repo.UpdatePinned(conversationID, userID, isPinned); err != nil {
		return fmt.Errorf("failed to update pinned status: %w", err)
	}
	return nil
}

// SendMessage 发送消息（使用 segments）
func (s *chatServiceImpl) SendMessage(ctx context.Context, senderID string, conversationID string, segments model.MessageSegments, replyToID *string) (*model.Message, error) {
	// 首先验证会话是否存在
	conv, err := s.repo.GetConversation(conversationID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("会话不存在，请重新创建会话")
		}
		return nil, fmt.Errorf("failed to get conversation: %w", err)
	}

	// 拉黑限制：仅拦截“被拉黑方 -> 拉黑人”方向
	if conv.Type == model.ConversationTypePrivate && s.userRepo != nil {
		participants, pErr := s.repo.GetConversationParticipants(conversationID)
		if pErr != nil {
			return nil, fmt.Errorf("failed to get participants: %w", pErr)
		}
		var sentCount *int64
		for _, p := range participants {
			if p.UserID == senderID {
				continue
			}
			blocked, bErr := s.userRepo.IsBlocked(p.UserID, senderID)
			if bErr != nil {
				return nil, fmt.Errorf("failed to check block status: %w", bErr)
			}
			if blocked {
				return nil, ErrUserBlocked
			}

			// 陌生人限制：对方未回关前，只允许发送一条文本消息，且禁止发送图片
			isFollowedBack, fErr := s.userRepo.IsFollowing(p.UserID, senderID)
			if fErr != nil {
				return nil, fmt.Errorf("failed to check follow status: %w", fErr)
			}
			if !isFollowedBack {
				if containsImageSegment(segments) {
					return nil, errors.New("对方未关注你，暂不支持发送图片")
				}
				if sentCount == nil {
					c, cErr := s.repo.CountMessagesBySenderInConversation(conversationID, senderID)
					if cErr != nil {
						return nil, fmt.Errorf("failed to count sender messages: %w", cErr)
					}
					sentCount = &c
				}
				if *sentCount >= 1 {
					return nil, errors.New("对方未关注你前，仅允许发送一条消息")
				}
			}
		}
	}

	// 验证用户是否是会话参与者
	participant, err := s.repo.GetParticipant(conversationID, senderID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("您不是该会话的参与者")
		}
		return nil, fmt.Errorf("failed to get participant: %w", err)
	}

	// 创建消息
	message := &model.Message{
		ConversationID: conversationID,
		SenderID:       senderID, // 直接使用string类型的UUID
		Segments:       segments,
		ReplyToID:      replyToID,
		Status:         model.MessageStatusNormal,
	}

	// 使用事务创建消息并更新seq
	if err := s.repo.CreateMessageWithSeq(message); err != nil {
		return nil, fmt.Errorf("failed to save message: %w", err)
	}

	// 获取会话中的参与者并发送 SSE
	participants, err := s.repo.GetConversationParticipants(conversationID)
	if err == nil {
		targetIDs := make([]string, 0, len(participants))
		for _, p := range participants {
			targetIDs = append(targetIDs, p.UserID)
		}
		detailType := "private"
		if conv.Type == model.ConversationTypeGroup {
			detailType = "group"
		}
		s.publishSSEToUsers(targetIDs, "chat_message", map[string]interface{}{
			"detail_type": detailType,
			"message":     dto.ConvertMessageToResponse(message),
		})
		for _, p := range participants {
			if p.UserID == senderID {
				continue
			}
			if totalUnread, uErr := s.repo.GetAllUnreadCount(p.UserID); uErr == nil {
				s.publishSSEToUsers([]string{p.UserID}, "conversation_unread", map[string]interface{}{
					"conversation_id": conversationID,
					"total_unread":    totalUnread,
				})
			}
		}
	}

	_ = participant // 避免未使用变量警告

	return message, nil
}

func containsImageSegment(segments model.MessageSegments) bool {
	for _, seg := range segments {
		if seg.Type == string(model.ContentTypeImage) || seg.Type == "image" {
			return true
		}
	}
	return false
}

// GetMessages 获取消息历史（分页）
func (s *chatServiceImpl) GetMessages(ctx context.Context, conversationID string, userID string, page, pageSize int) ([]*model.Message, int64, error) {
	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, 0, errors.New("conversation not found or no permission")
		}
		return nil, 0, fmt.Errorf("failed to get participant: %w", err)
	}

	return s.repo.GetMessages(conversationID, page, pageSize)
}

// GetMessagesAfterSeq 获取指定seq之后的消息（用于增量同步）
func (s *chatServiceImpl) GetMessagesAfterSeq(ctx context.Context, conversationID string, userID string, afterSeq int64, limit int) ([]*model.Message, error) {
	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("conversation not found or no permission")
		}
		return nil, fmt.Errorf("failed to get participant: %w", err)
	}

	if limit <= 0 {
		limit = 100
	}

	return s.repo.GetMessagesAfterSeq(conversationID, afterSeq, limit)
}

// GetMessagesBeforeSeq 获取指定seq之前的历史消息（用于下拉加载更多）
func (s *chatServiceImpl) GetMessagesBeforeSeq(ctx context.Context, conversationID string, userID string, beforeSeq int64, limit int) ([]*model.Message, error) {
	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("conversation not found or no permission")
		}
		return nil, fmt.Errorf("failed to get participant: %w", err)
	}

	if limit <= 0 {
		limit = 20
	}

	return s.repo.GetMessagesBeforeSeq(conversationID, beforeSeq, limit)
}

// MarkAsRead 标记已读
func (s *chatServiceImpl) MarkAsRead(ctx context.Context, conversationID string, userID string, seq int64) error {
	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("conversation not found or no permission")
		}
		return fmt.Errorf("failed to get participant: %w", err)
	}

	// 更新参与者的已读位置
	err = s.repo.UpdateLastReadSeq(conversationID, userID, seq)
	if err != nil {
		return fmt.Errorf("failed to update last read seq: %w", err)
	}

	participants, pErr := s.repo.GetConversationParticipants(conversationID)
	if pErr == nil {
		detailType := "private"
		groupID := ""
		if conv, convErr := s.repo.GetConversation(conversationID); convErr == nil && conv.Type == model.ConversationTypeGroup {
			detailType = "group"
			if conv.GroupID != nil {
				groupID = *conv.GroupID
			}
		}
		targetIDs := make([]string, 0, len(participants))
		for _, p := range participants {
			targetIDs = append(targetIDs, p.UserID)
		}
		s.publishSSEToUsers(targetIDs, "message_read", map[string]interface{}{
			"detail_type":     detailType,
			"conversation_id": conversationID,
			"group_id":        groupID,
			"user_id":         userID,
			"seq":             seq,
		})
	}
	if totalUnread, uErr := s.repo.GetAllUnreadCount(userID); uErr == nil {
		s.publishSSEToUsers([]string{userID}, "conversation_unread", map[string]interface{}{
			"conversation_id": conversationID,
			"total_unread":    totalUnread,
		})
	}

	return nil
}

// GetUnreadCount 获取指定会话的未读消息数
func (s *chatServiceImpl) GetUnreadCount(ctx context.Context, conversationID string, userID string) (int64, error) {
	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return 0, errors.New("conversation not found or no permission")
		}
		return 0, fmt.Errorf("failed to get participant: %w", err)
	}

	return s.repo.GetUnreadCount(conversationID, userID)
}

// GetAllUnreadCount 获取所有会话的未读消息总数
func (s *chatServiceImpl) GetAllUnreadCount(ctx context.Context, userID string) (int64, error) {
	return s.repo.GetAllUnreadCount(userID)
}

// RecallMessage 撤回消息（2分钟内）
func (s *chatServiceImpl) RecallMessage(ctx context.Context, messageID string, userID string) error {
	// 获取消息
	var message model.Message
	err := s.db.First(&message, "id = ?", messageID).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("message not found")
		}
		return fmt.Errorf("failed to get message: %w", err)
	}

	// 验证是否是消息发送者
	if message.SenderIDStr() != userID {
		return errors.New("can only recall your own messages")
	}

	// 验证消息是否已被撤回
	if message.Status == model.MessageStatusRecalled {
		return errors.New("message already recalled")
	}

	// 验证是否在2分钟内
	if time.Since(message.CreatedAt) > RecallMessageTimeout {
		return errors.New("message recall timeout (2 minutes)")
	}

	// 更新消息状态为已撤回，并清空原始消息内容，仅保留撤回占位
	err = s.db.Model(&message).Updates(map[string]interface{}{
		"status":   model.MessageStatusRecalled,
		"segments": model.MessageSegments{},
	}).Error
	if err != nil {
		return fmt.Errorf("failed to recall message: %w", err)
	}

	if participants, pErr := s.repo.GetConversationParticipants(message.ConversationID); pErr == nil {
		detailType := "private"
		groupID := ""
		if conv, convErr := s.repo.GetConversation(message.ConversationID); convErr == nil && conv.Type == model.ConversationTypeGroup {
			detailType = "group"
			if conv.GroupID != nil {
				groupID = *conv.GroupID
			}
		}
		targetIDs := make([]string, 0, len(participants))
		for _, p := range participants {
			targetIDs = append(targetIDs, p.UserID)
		}
		s.publishSSEToUsers(targetIDs, "message_recall", map[string]interface{}{
			"detail_type":     detailType,
			"conversation_id": message.ConversationID,
			"group_id":        groupID,
			"message_id":      messageID,
			"sender_id":       userID,
		})
	}

	return nil
}

// DeleteMessage 删除消息（仅对自己可见）
func (s *chatServiceImpl) DeleteMessage(ctx context.Context, messageID string, userID string) error {
	// 获取消息
	var message model.Message
	err := s.db.First(&message, "id = ?", messageID).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("message not found")
		}
		return fmt.Errorf("failed to get message: %w", err)
	}

	// 验证用户是否是会话参与者
	_, err = s.repo.GetParticipant(message.ConversationID, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return errors.New("no permission to delete this message")
		}
		return fmt.Errorf("failed to get participant: %w", err)
	}

	// 对于删除消息，我们使用软删除，但需要确保只对当前用户隐藏
	// 这里简化处理：只有发送者可以删除自己的消息
	if message.SenderIDStr() != userID {
		return errors.New("can only delete your own messages")
	}

	// 更新消息状态为已删除
	err = s.db.Model(&message).Update("status", model.MessageStatusDeleted).Error
	if err != nil {
		return fmt.Errorf("failed to delete message: %w", err)
	}

	return nil
}

// SendTyping 发送正在输入状态
func (s *chatServiceImpl) SendTyping(ctx context.Context, senderID string, conversationID string) {
	if s.sseHub == nil {
		return
	}

	// 验证用户是否是会话参与者
	_, err := s.repo.GetParticipant(conversationID, senderID)
	if err != nil {
		return
	}

	// 获取会话中的其他参与者
	participants, err := s.repo.GetConversationParticipants(conversationID)
	if err != nil {
		return
	}

	detailType := "private"
	if conv, convErr := s.repo.GetConversation(conversationID); convErr == nil && conv.Type == model.ConversationTypeGroup {
		detailType = "group"
	}
	for _, p := range participants {
		if p.UserID == senderID {
			continue
		}
		if s.sseHub != nil {
			s.sseHub.PublishToUser(p.UserID, "typing", map[string]interface{}{
				"detail_type":     detailType,
				"conversation_id": conversationID,
				"user_id":         senderID,
				"is_typing":       true,
			})
		}
	}
}

// IsUserOnline 检查用户是否在线
func (s *chatServiceImpl) IsUserOnline(userID string) bool {
	if s.sseHub != nil {
		return s.sseHub.HasSubscribers(userID)
	}
	return false
}

// SaveMessage 仅保存消息到数据库，不发送实时推送
// 适用于群聊等由调用方自行负责推送的场景
func (s *chatServiceImpl) SaveMessage(ctx context.Context, senderID string, conversationID string, segments model.MessageSegments, replyToID *string) (*model.Message, error) {
	// 验证会话是否存在
	_, err := s.repo.GetConversation(conversationID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("会话不存在，请重新创建会话")
		}
		return nil, fmt.Errorf("failed to get conversation: %w", err)
	}

	// 验证用户是否是会话参与者
	_, err = s.repo.GetParticipant(conversationID, senderID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("您不是该会话的参与者")
		}
		return nil, fmt.Errorf("failed to get participant: %w", err)
	}

	message := &model.Message{
		ConversationID: conversationID,
		SenderID:       senderID,
		Segments:       segments,
		ReplyToID:      replyToID,
		Status:         model.MessageStatusNormal,
	}

	if err := s.repo.CreateMessageWithSeq(message); err != nil {
		return nil, fmt.Errorf("failed to save message: %w", err)
	}

	return message, nil
}