package service

import (
	"context"
	"log/slog"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/dto"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqldao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqlmodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/redisdao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/errcode"
)

// LikeService 点赞业务服务。
type LikeService struct {
	likeDao   *mysqldao.LikeDao
	outfitDao *mysqldao.OutfitDao
}

// NewLikeService 创建点赞服务。
func NewLikeService() *LikeService {
	return &LikeService{
		likeDao:   mysqldao.NewLikeDao(),
		outfitDao: mysqldao.NewOutfitDao(),
	}
}

// LikeCreate 点赞或取消点赞社区穿搭。
func (s *LikeService) LikeCreate(ctx context.Context, userID int64, request *dto.LikeCreateRequest) (*dto.LikeResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.LikeLikeCreate")
	defer span.End()

	outfit, cerr := s.getPublicOutfit(ctx, userID, request.TargetUUID)
	if cerr != nil {
		return nil, cerr
	}
	targetID := outfit.ID

	existing, err := s.likeDao.LikeGetByTargetAndUser(ctx, LikeTypeOutfit, targetID, userID)
	notExist := false
	if err != nil {
		if isNotFound(err) {
			notExist = true
		} else {
			slog.ErrorContext(ctx, "like: query record failed", "target_id", targetID, "user_id", userID, "error", err)
			return nil, errcode.DatabaseError
		}
	}

	switch request.Action {
	case ActionDo: // 点赞
		if cerr := s.likeDao.LikeUpsertOn(ctx, &mysqlmodel.Like{
			LikeType: LikeTypeOutfit,
			TargetID: targetID,
			UserID:   userID,
			Status:   InteractStatusOn,
		}); cerr != nil {
			slog.ErrorContext(ctx, "like: upsert record failed", "target_id", targetID, "user_id", userID, "error", cerr)
			return nil, errcode.LikeFailed
		}
		if rerr := redisdao.LikeAdd(ctx, LikeTypeOutfit, targetID, userID); rerr != nil {
			slog.WarnContext(ctx, "like: redis add failed, counter may undercount",
				"target_id", targetID, "user_id", userID, "error", rerr)
		}

		// 仅在「首次点赞」时发通知（likes 表此前无记录）。
		// 取消点赞只把 status 置为已取消、不删行，因此 notExist 可稳定表达
		// 「此前从未赞过该穿搭」；取消后再点赞不再重复通知，避免频繁点赞/取消把拥有者刷屏。
		if notExist && outfit.UserID != userID {
			sendNotification(ctx, outfit.UserID, userID, NotificationTypeLike, "收到新的点赞", "你的穿搭「"+outfit.OutfitName+"」收到了一个赞")
		}

	case ActionCancel: // 取消点赞
		if !notExist && existing.Status == InteractStatusOn {
			if uerr := s.likeDao.LikeUpdateStatus(ctx, existing.ID, InteractStatusOff); uerr != nil {
				slog.ErrorContext(ctx, "like: update status failed", "target_id", targetID, "user_id", userID, "error", uerr)
				return nil, errcode.LikeFailed
			}
			if rerr := redisdao.LikeRemove(ctx, LikeTypeOutfit, targetID, userID); rerr != nil {
				slog.WarnContext(ctx, "like: redis remove failed, counter may overcount",
					"target_id", targetID, "user_id", userID, "error", rerr)
			}
		}
	}

	return &dto.LikeResponse{}, nil
}

// GetByTargetID 查询穿搭点赞状态与点赞数（Redis 优先）。
func (s *LikeService) GetByTargetID(ctx context.Context, userID int64, request *dto.LikeGetByTargetIDRequest) (*dto.LikeGetByTargetIDResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.LikeGetByTargetID")
	defer span.End()

	outfit, cerr := s.getPublicOutfit(ctx, userID, request.TargetUUID)
	if cerr != nil {
		return nil, cerr
	}
	targetID := outfit.ID

	// 是否已点赞：以 MySQL 为权威。
	// Redis 集合带 TTL，过期后会被后续写入重建为「仅含新成员」，导致 SIsMember/SCard 长期低估，
	// 因此只在 DB 异常时用 Redis 兜底（降级可用性优先于精确性）。
	isLiked := false
	if rec, derr := s.likeDao.LikeGetByTargetAndUser(ctx, LikeTypeOutfit, targetID, userID); derr == nil {
		isLiked = rec.Status == InteractStatusOn
	} else if !isNotFound(derr) {
		slog.WarnContext(ctx, "query like record failed, fallback to redis",
			"target_id", targetID, "user_id", userID, "error", derr)
		if v, rerr := redisdao.LikeIsMember(ctx, LikeTypeOutfit, targetID, userID); rerr == nil {
			isLiked = v
		} else {
			slog.DebugContext(ctx, "like: redis fallback read failed",
				"target_id", targetID, "user_id", userID, "error", rerr)
		}
	}

	// 点赞总数：以 MySQL 为权威（同上，Redis 仅在 DB 异常时兜底）。
	count, derr := s.likeDao.LikeCountByTarget(ctx, LikeTypeOutfit, targetID)
	if derr != nil {
		slog.WarnContext(ctx, "count like failed, fallback to redis",
			"target_id", targetID, "error", derr)
		if rcnt, rerr := redisdao.LikeCount(ctx, LikeTypeOutfit, targetID); rerr == nil {
			count = rcnt
		}
	}

	return &dto.LikeGetByTargetIDResponse{
		UserIsLiked: isLiked,
		LikeCount:   count,
	}, nil
}

// getPublicOutfit 按 UUID 查询社区穿搭（须存在），非本人仅可操作公开可见的穿搭。
func (s *LikeService) getPublicOutfit(ctx context.Context, userID int64, outfitUUID string) (*mysqlmodel.Outfit, *errcode.Error) {
	outfit, err := s.outfitDao.OutfitGetByUUID(ctx, outfitUUID)
	if err != nil {
		if isNotFound(err) {
			return nil, errcode.TargetNotFound
		}
		slog.ErrorContext(ctx, "like: query outfit failed", "outfit_uuid", outfitUUID, "user_id", userID, "error", err)
		return nil, errcode.DatabaseError
	}
	if outfit.UserID != userID && !isOutfitPublicVisible(outfit) {
		return nil, errcode.OutfitNoPermission
	}
	return outfit, nil
}