backend/internal/service/post_service.go

package service

import (
	"context"
	"fmt"
	"log"
	"strconv"
	"strings"
	"time"

	"carrot_bbs/internal/cache"
	"carrot_bbs/internal/model"
	"carrot_bbs/internal/pkg/cursor"
	"carrot_bbs/internal/pkg/hook"
	"carrot_bbs/internal/repository"
)

// 缓存TTL常量
const (
	PostListTTL         = 30 * time.Second // 帖子列表缓存30秒
	PostListNullTTL     = 5 * time.Second
	PostListJitterRatio = 0.15
)

// PostService 帖子服务接口
type PostService interface {
	// 帖子CRUD
	Create(ctx context.Context, userID, title, content string, images []string, channelID *string) (*model.Post, error)
	GetByID(ctx context.Context, id string) (*model.Post, error)
	Update(ctx context.Context, post *model.Post) error
	UpdateWithImages(ctx context.Context, post *model.Post, images *[]string) error
	Delete(ctx context.Context, id string) error

	// 帖子列表
	List(ctx context.Context, page, pageSize int, userID string, includePending bool, channelID *string) ([]*model.Post, int64, error)
	GetLatestPosts(ctx context.Context, page, pageSize int, userID string, channelID *string) ([]*model.Post, int64, error)
	GetLatestPostsForOwner(ctx context.Context, page, pageSize int, userID string, channelID *string) ([]*model.Post, int64, error)
	GetUserPosts(ctx context.Context, userID string, page, pageSize int, includePending bool) ([]*model.Post, int64, error)
	GetFavorites(ctx context.Context, userID string, page, pageSize int) ([]*model.Post, int64, error)
	Search(ctx context.Context, keyword string, page, pageSize int) ([]*model.Post, int64, error)

	// 游标分页方法
	ListByCursor(ctx context.Context, userID string, includePending bool, channelID *string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error)
	SearchByCursor(ctx context.Context, keyword string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error)
	GetUserPostsByCursor(ctx context.Context, userID string, includePending bool, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error)
	GetFollowingPostsByCursor(ctx context.Context, userID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error)
	GetHotPostsByCursor(ctx context.Context, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error)

	// 关注和推荐
	GetFollowingPosts(ctx context.Context, userID string, page, pageSize int) ([]*model.Post, int64, error)
	GetHotPosts(ctx context.Context, page, pageSize int) ([]*model.Post, int64, error)

	// 交互功能
	Like(ctx context.Context, postID, userID string) error
	Unlike(ctx context.Context, postID, userID string) error
	IsLiked(ctx context.Context, postID, userID string) bool
	Favorite(ctx context.Context, postID, userID string) error
	Unfavorite(ctx context.Context, postID, userID string) error
	IsFavorited(ctx context.Context, postID, userID string) bool

	// 交互状态查询
	GetPostInteractionStatus(ctx context.Context, postIDs []string, userID string) (map[string]bool, map[string]bool, error)
	GetPostInteractionStatusSingle(ctx context.Context, postID, userID string) (isLiked, isFavorited bool)

	// 其他
	IncrementViews(ctx context.Context, postID, userID string) error
	// RecordShare 记录分享（仅已发布帖子计数 +1），返回最新 shares_count
	RecordShare(ctx context.Context, postID, userID string) (sharesCount int, err error)

	// 日志服务设置
	SetLogService(logService *LogService)
}

// postServiceImpl 帖子服务实现
type postServiceImpl struct {
	postRepo             repository.PostRepository
	systemMessageService SystemMessageService
	cache                cache.Cache
	postAIService        *PostAIService
	txManager            repository.TransactionManager
	logService           *LogService
	hookManager          *hook.Manager
}

func NewPostService(postRepo repository.PostRepository, systemMessageService SystemMessageService, postAIService *PostAIService, cacheBackend cache.Cache, txManager repository.TransactionManager, hookManager *hook.Manager) PostService {
	return &postServiceImpl{
		postRepo:             postRepo,
		systemMessageService: systemMessageService,
		cache:                cacheBackend,
		postAIService:        postAIService,
		txManager:            txManager,
		logService:           nil,
		hookManager:          hookManager,
	}
}

// SetLogService 设置日志服务
func (s *postServiceImpl) SetLogService(logService *LogService) {
	s.logService = logService
}

// PostListResult 帖子列表缓存结果
type PostListResult struct {
	Posts []*model.Post
	Total int64
}

// Create 创建帖子
func (s *postServiceImpl) Create(ctx context.Context, userID, title, content string, images []string, channelID *string) (*model.Post, error) {
	post := &model.Post{
		UserID:    userID,
		ChannelID: channelID,
		Title:       title,
		Content:     content,
		Status:      model.PostStatusPending,
	}

	err := s.postRepo.Create(post, images)
	if err != nil {
		return nil, err
	}

	// 记录操作日志
	if s.logService != nil {
		s.logService.OperationLog.RecordOperation(&model.OperationLog{
			UserID:     userID,
			Operation:  string(model.OpPostCreate),
			Module:     "post",
			TargetType: "post",
			TargetID:   post.ID,
			Status:     "success",
		})
	}

	// 失效帖子列表缓存
	cache.InvalidatePostList(s.cache)

	// 异步执行审核流
	go s.reviewPostAsync(post.ID, userID, title, content, images)

	// 重新查询以获取关联的 User 和 Images
	return s.postRepo.GetByID(post.ID)
}

func (s *postServiceImpl) reviewPostAsync(postID, userID, title, content string, images []string) {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("[ERROR] Panic in post moderation async flow, fallback publish post=%s panic=%v", postID, r)
			if err := s.updateModerationStatusWithRetry(postID, model.PostStatusPublished, "", "system"); err != nil {
				log.Printf("[WARN] Failed to publish post %s after panic recovery: %v", postID, err)
				return
			}
			s.invalidatePostCaches(postID)
		}
	}()

	if s.hookManager == nil {
		if err := s.updateModerationStatusWithRetry(postID, model.PostStatusPublished, "", "system"); err != nil {
			log.Printf("[WARN] Failed to publish post without hook manager: %v", err)
		} else {
			s.invalidatePostCaches(postID)
		}
		return
	}

	var authorID uint
	fmt.Sscanf(userID, "%d", &authorID)

	result := &hook.ModerationResult{}
	s.hookManager.TriggerWithMetadata(context.Background(), hook.HookPostPreModerate, authorID, &hook.PostModerateHookData{
		PostID:   postID,
		Title:    title,
		Content:  content,
		Images:   images,
		AuthorID: authorID,
	}, map[string]interface{}{
		"result": result,
	})

	s.hookManager.Trigger(context.Background(), hook.HookPostModerated, authorID, &hook.PostModeratedHookData{
		PostID:       postID,
		AuthorID:     authorID,
		Approved:     result.Approved,
		RejectReason: result.RejectReason,
		ReviewedBy:   result.ReviewedBy,
	})

	if !result.Approved {
		if updateErr := s.updateModerationStatusWithRetry(postID, model.PostStatusRejected, result.RejectReason, result.ReviewedBy); updateErr != nil {
			log.Printf("[WARN] Failed to reject post %s: %v", postID, updateErr)
		} else {
			s.invalidatePostCaches(postID)
		}
		s.notifyModerationRejected(userID, result.RejectReason)
		return
	}

	if err := s.updateModerationStatusWithRetry(postID, model.PostStatusPublished, "", result.ReviewedBy); err != nil {
		log.Printf("[WARN] Failed to publish post %s: %v", postID, err)
		return
	}
	s.invalidatePostCaches(postID)

}

func (s *postServiceImpl) updateModerationStatusWithRetry(postID string, status model.PostStatus, rejectReason string, reviewedBy string) error {
	const maxAttempts = 3
	const retryDelay = 200 * time.Millisecond

	var lastErr error
	for attempt := 1; attempt <= maxAttempts; attempt++ {
		if err := s.postRepo.UpdateModerationStatus(postID, status, rejectReason, reviewedBy); err != nil {
			lastErr = err
			if attempt < maxAttempts {
				log.Printf("[WARN] UpdateModerationStatus failed post=%s attempt=%d/%d err=%v", postID, attempt, maxAttempts, err)
				time.Sleep(time.Duration(attempt) * retryDelay)
				continue
			}
		} else {
			return nil
		}
	}
	return lastErr
}

func (s *postServiceImpl) invalidatePostCaches(postID string) {
	cache.InvalidatePostDetail(s.cache, postID)
	cache.InvalidatePostList(s.cache)
}

func (s *postServiceImpl) notifyModerationRejected(userID, reason string) {
	if s.systemMessageService == nil || strings.TrimSpace(userID) == "" {
		return
	}

	content := "您发布的帖子未通过AI审核，请修改后重试。"
	if strings.TrimSpace(reason) != "" {
		content = fmt.Sprintf("您发布的帖子未通过AI审核，原因：%s。请修改后重试。", reason)
	}

	go func() {
		if err := s.systemMessageService.SendSystemAnnouncement(
			context.Background(),
			[]string{userID},
			"帖子审核未通过",
			content,
		); err != nil {
			log.Printf("[WARN] Failed to send moderation reject notification: %v", err)
		}
	}()
}

// GetByID 根据ID获取帖子
func (s *postServiceImpl) GetByID(ctx context.Context, id string) (*model.Post, error) {
	return s.postRepo.GetByID(id)
}

// Update 更新帖子
func (s *postServiceImpl) Update(ctx context.Context, post *model.Post) error {
	return s.UpdateWithImages(ctx, post, nil)
}

// UpdateWithImages 更新帖子并可选更新图片（images=nil 表示不更新图片）
func (s *postServiceImpl) UpdateWithImages(ctx context.Context, post *model.Post, images *[]string) error {
	err := s.postRepo.UpdateWithImages(post, images)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存和列表缓存
	cache.InvalidatePostDetail(s.cache, post.ID)
	cache.InvalidatePostList(s.cache)

	return nil
}

// Delete 删除帖子
func (s *postServiceImpl) Delete(ctx context.Context, id string) error {
	err := s.postRepo.Delete(id)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存和列表缓存
	cache.InvalidatePostDetail(s.cache, id)
	cache.InvalidatePostList(s.cache)

	return nil
}

// List 获取帖子列表（带缓存）
func (s *postServiceImpl) List(ctx context.Context, page, pageSize int, userID string, includePending bool, channelID *string) ([]*model.Post, int64, error) {
	cacheSettings := cache.GetSettings()
	postListTTL := cacheSettings.PostListTTL
	if postListTTL <= 0 {
		postListTTL = PostListTTL
	}
	nullTTL := cacheSettings.NullTTL
	if nullTTL <= 0 {
		nullTTL = PostListNullTTL
	}
	jitter := cacheSettings.JitterRatio
	if jitter <= 0 {
		jitter = PostListJitterRatio
	}

	// 生成缓存键（包含 userID 维度与可见性维度，避免作者视角污染公开视角）
	visibilityUserKey := userID
	if includePending && userID != "" {
		visibilityUserKey = "owner:" + userID
	}
	if channelID != nil && *channelID != "" {
		visibilityUserKey += ":channel:" + *channelID
	}
	cacheKey := cache.PostListKey("latest", visibilityUserKey, page, pageSize)

	result, err := cache.GetOrLoadTyped(
		s.cache,
		cacheKey,
		postListTTL,
		jitter,
		nullTTL,
		func() (*PostListResult, error) {
			posts, total, err := s.postRepo.List(page, pageSize, userID, includePending, channelID)
			if err != nil {
				return nil, err
			}
			return &PostListResult{Posts: posts, Total: total}, nil
		},
	)
	if err != nil {
		return nil, 0, err
	}
	if result == nil {
		return []*model.Post{}, 0, nil
	}

	// 兼容历史脏缓存：旧缓存序列化会丢失 Post.User，导致前端显示“匿名用户”
	// 这里检测并回源重建一次缓存，避免在 TTL 内持续返回缺失作者的数据。
	missingAuthor := false
	for _, post := range result.Posts {
		if post != nil && post.UserID != "" && post.User == nil {
			missingAuthor = true
			break
		}
	}
	if missingAuthor {
		posts, total, loadErr := s.postRepo.List(page, pageSize, userID, includePending, channelID)
		if loadErr != nil {
			return nil, 0, loadErr
		}
		result = &PostListResult{Posts: posts, Total: total}
		cache.SetWithJitter(s.cache, cacheKey, result, postListTTL, jitter)
	}

	return result.Posts, result.Total, nil
}

// GetLatestPosts 获取最新帖子（语义化别名）
func (s *postServiceImpl) GetLatestPosts(ctx context.Context, page, pageSize int, userID string, channelID *string) ([]*model.Post, int64, error) {
	return s.List(ctx, page, pageSize, userID, false, channelID)
}

// GetLatestPostsForOwner 获取作者视角帖子列表（包含待审核）
func (s *postServiceImpl) GetLatestPostsForOwner(ctx context.Context, page, pageSize int, userID string, channelID *string) ([]*model.Post, int64, error) {
	return s.List(ctx, page, pageSize, userID, true, channelID)
}

// GetUserPosts 获取用户帖子
func (s *postServiceImpl) GetUserPosts(ctx context.Context, userID string, page, pageSize int, includePending bool) ([]*model.Post, int64, error) {
	return s.postRepo.GetUserPosts(userID, page, pageSize, includePending)
}

// Like 点赞
func (s *postServiceImpl) Like(ctx context.Context, postID, userID string) error {
	// 获取帖子信息用于发送通知
	post, err := s.postRepo.GetByID(postID)
	if err != nil {
		return err
	}

	err = s.postRepo.Like(postID, userID)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存
	cache.InvalidatePostDetail(s.cache, postID)

	// 发送点赞通知（不给自己发通知）
	if s.systemMessageService != nil && post.UserID != userID {
		go func() {
			notifyErr := s.systemMessageService.SendLikeNotification(context.Background(), post.UserID, userID, postID)
			if notifyErr != nil {
				log.Printf("[ERROR] Error sending like notification: %v", notifyErr)
			}
		}()
	}

	return nil
}

// Unlike 取消点赞
func (s *postServiceImpl) Unlike(ctx context.Context, postID, userID string) error {
	err := s.postRepo.Unlike(postID, userID)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存
	cache.InvalidatePostDetail(s.cache, postID)

	return nil
}

// IsLiked 检查是否点赞
func (s *postServiceImpl) IsLiked(ctx context.Context, postID, userID string) bool {
	return s.postRepo.IsLiked(postID, userID)
}

// Favorite 收藏
func (s *postServiceImpl) Favorite(ctx context.Context, postID, userID string) error {
	// 获取帖子信息用于发送通知
	post, err := s.postRepo.GetByID(postID)
	if err != nil {
		return err
	}

	err = s.postRepo.Favorite(postID, userID)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存
	cache.InvalidatePostDetail(s.cache, postID)

	// 发送收藏通知（不给自己发通知）
	if s.systemMessageService != nil && post.UserID != userID {
		go func() {
			notifyErr := s.systemMessageService.SendFavoriteNotification(context.Background(), post.UserID, userID, postID)
			if notifyErr != nil {
				log.Printf("[ERROR] Error sending favorite notification: %v", notifyErr)
			}
		}()
	}

	return nil
}

// Unfavorite 取消收藏
func (s *postServiceImpl) Unfavorite(ctx context.Context, postID, userID string) error {
	err := s.postRepo.Unfavorite(postID, userID)
	if err != nil {
		return err
	}

	// 失效帖子详情缓存
	cache.InvalidatePostDetail(s.cache, postID)

	return nil
}

// IsFavorited 检查是否收藏
func (s *postServiceImpl) IsFavorited(ctx context.Context, postID, userID string) bool {
	return s.postRepo.IsFavorited(postID, userID)
}

// GetPostInteractionStatus 批量获取帖子的交互状态（点赞、收藏）
func (s *postServiceImpl) GetPostInteractionStatus(ctx context.Context, postIDs []string, userID string) (map[string]bool, map[string]bool, error) {
	isLikedMap := make(map[string]bool)
	isFavoritedMap := make(map[string]bool)

	if userID == "" || len(postIDs) == 0 {
		return isLikedMap, isFavoritedMap, nil
	}

	// 使用批量查询替代循环中的单个查询，解决 N+1 问题
	isLikedMap = s.postRepo.IsLikedBatch(postIDs, userID)
	isFavoritedMap = s.postRepo.IsFavoritedBatch(postIDs, userID)

	return isLikedMap, isFavoritedMap, nil
}

// GetPostInteractionStatusSingle 获取单个帖子的交互状态
func (s *postServiceImpl) GetPostInteractionStatusSingle(ctx context.Context, postID, userID string) (isLiked, isFavorited bool) {
	if userID == "" {
		return false, false
	}
	return s.postRepo.IsLiked(postID, userID), s.postRepo.IsFavorited(postID, userID)
}

// IncrementViews 增加帖子观看量
func (s *postServiceImpl) IncrementViews(ctx context.Context, postID, userID string) error {
	if err := s.postRepo.IncrementViews(postID); err != nil {
		return err
	}

	return nil
}

// RecordShare 记录分享：仅已发布帖子增加 shares_count，并失效帖子详情与列表缓存
func (s *postServiceImpl) RecordShare(ctx context.Context, postID, userID string) (int, error) {
	n, err := s.postRepo.IncrementShares(postID)
	if err != nil {
		return 0, err
	}
	if s.cache != nil {
		cache.InvalidatePostDetail(s.cache, postID)
		cache.InvalidatePostList(s.cache)
	}
	return n, nil
}

// GetFavorites 获取收藏列表
func (s *postServiceImpl) GetFavorites(ctx context.Context, userID string, page, pageSize int) ([]*model.Post, int64, error) {
	return s.postRepo.GetFavorites(userID, page, pageSize)
}

// Search 搜索帖子
func (s *postServiceImpl) Search(ctx context.Context, keyword string, page, pageSize int) ([]*model.Post, int64, error) {
	return s.postRepo.Search(keyword, page, pageSize)
}

// GetFollowingPosts 获取关注用户的帖子（带缓存）
func (s *postServiceImpl) GetFollowingPosts(ctx context.Context, userID string, page, pageSize int) ([]*model.Post, int64, error) {
	cacheSettings := cache.GetSettings()
	postListTTL := cacheSettings.PostListTTL
	if postListTTL <= 0 {
		postListTTL = PostListTTL
	}
	nullTTL := cacheSettings.NullTTL
	if nullTTL <= 0 {
		nullTTL = PostListNullTTL
	}
	jitter := cacheSettings.JitterRatio
	if jitter <= 0 {
		jitter = PostListJitterRatio
	}

	// 生成缓存键
	cacheKey := cache.PostListKey("follow", userID, page, pageSize)

	result, err := cache.GetOrLoadTyped[*PostListResult](
		s.cache,
		cacheKey,
		postListTTL,
		jitter,
		nullTTL,
		func() (*PostListResult, error) {
			posts, total, err := s.postRepo.GetFollowingPosts(userID, page, pageSize)
			if err != nil {
				return nil, err
			}
			return &PostListResult{Posts: posts, Total: total}, nil
		},
	)
	if err != nil {
		return nil, 0, err
	}
	if result == nil {
		return []*model.Post{}, 0, nil
	}
	return result.Posts, result.Total, nil
}

// GetHotPosts 获取热门帖子（优先分层缓存 top_ids → Redis ZSET，未就绪时回源 DB 按最新排序）
func (s *postServiceImpl) GetHotPosts(ctx context.Context, page, pageSize int) ([]*model.Post, int64, error) {
	offset := (page - 1) * pageSize
	if posts, total, ok, err := s.tryHotPostsFromTopIDsCache(offset, pageSize); ok {
		return posts, total, err
	} else if err != nil {
		return nil, 0, err
	}
	if posts, total, ok, err := s.tryHotPostsFromZSet(ctx, offset, pageSize); ok {
		return posts, total, err
	} else if err != nil {
		return nil, 0, err
	}
	return s.getHotPostsFromDB(ctx, page, pageSize)
}

// tryHotPostsFromTopIDsCache 从热门榜有序 ID 列表取帖（命中 LayeredCache 本地层时可不访问 Redis）
func (s *postServiceImpl) tryHotPostsFromTopIDsCache(offset, pageSize int) (posts []*model.Post, total int64, ok bool, err error) {
	if s.cache == nil || pageSize <= 0 {
		return nil, 0, false, nil
	}
	ids, hit := cache.GetTyped[[]string](s.cache, cache.HotRankTopIDsKey())
	if !hit || len(ids) == 0 {
		return nil, 0, false, nil
	}
	if offset >= len(ids) {
		return []*model.Post{}, int64(len(ids)), true, nil
	}
	end := offset + pageSize
	if end > len(ids) {
		end = len(ids)
	}
	pageIDs := ids[offset:end]
	posts, err = s.postRepo.GetByIDs(pageIDs)
	if err != nil {
		return nil, 0, false, err
	}
	return posts, int64(len(ids)), true, nil
}

// tryHotPostsFromZSet 从定时任务写入的 ZSET 按排名取帖；ok=false 表示应回源
func (s *postServiceImpl) tryHotPostsFromZSet(ctx context.Context, offset, pageSize int) (posts []*model.Post, total int64, ok bool, err error) {
	if s.cache == nil || pageSize <= 0 {
		return nil, 0, false, nil
	}
	key := cache.HotRankZSetKey()
	card, zerr := s.cache.ZCard(ctx, key)
	if zerr != nil || card == 0 {
		return nil, 0, false, nil
	}
	stop := int64(offset + pageSize - 1)
	ids, zerr := s.cache.ZRevRange(ctx, key, int64(offset), stop)
	if zerr != nil || len(ids) == 0 {
		return nil, 0, false, nil
	}
	posts, err = s.postRepo.GetByIDs(ids)
	if err != nil {
		return nil, 0, false, err
	}
	return posts, card, true, nil
}

// getHotPostsFromDB 热门未就绪时按最新发布降级
func (s *postServiceImpl) getHotPostsFromDB(ctx context.Context, page, pageSize int) ([]*model.Post, int64, error) {
	posts, total, err := s.postRepo.GetHotPosts(page, pageSize)
	if err != nil {
		return nil, 0, err
	}
	return posts, total, nil
}

// ========== 事务管理器示例方法 ==========

// DeletePostWithTransaction 使用事务管理器删除帖子（示例）
// 此方法展示如何在 Service 层使用事务管理器控制跨多个 Repository 的事务
// 当需要在一个事务中执行多个 Repository 操作时，可以使用此模式
func (s *postServiceImpl) DeletePostWithTransaction(ctx context.Context, postID string) error {
	// 使用事务管理器执行事务
	return s.txManager.RunInTransaction(ctx, func(ctx context.Context) error {
		// 在同一个事务中执行删除操作
		// Repository 方法会通过 context 获取事务 TX
		return s.postRepo.DeleteWithContext(ctx, postID)
	})
}

// ========== 游标分页方法 ==========

// ListByCursor 游标分页获取帖子列表
func (s *postServiceImpl) ListByCursor(ctx context.Context, userID string, includePending bool, channelID *string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	// 规范化请求参数
	req.Normalize()

	return s.postRepo.GetPostsByCursor(ctx, userID, includePending, channelID, req)
}

// SearchByCursor 游标分页搜索帖子
func (s *postServiceImpl) SearchByCursor(ctx context.Context, keyword string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	// 规范化请求参数
	req.Normalize()

	return s.postRepo.SearchPostsByCursor(ctx, keyword, req)
}

// GetUserPostsByCursor 游标分页获取用户帖子
func (s *postServiceImpl) GetUserPostsByCursor(ctx context.Context, userID string, includePending bool, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	// 规范化请求参数
	req.Normalize()

	return s.postRepo.GetUserPostsByCursor(ctx, userID, includePending, req)
}

// GetFollowingPostsByCursor 游标分页获取关注用户的帖子
func (s *postServiceImpl) GetFollowingPostsByCursor(ctx context.Context, userID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	// 规范化请求参数
	req.Normalize()

	return s.postRepo.GetFollowingPostsByCursor(ctx, userID, req)
}

// GetHotPostsByCursor 游标分页获取热门帖子
func (s *postServiceImpl) GetHotPostsByCursor(ctx context.Context, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	// 规范化请求参数
	req.Normalize()

	return s.getHotPostsByCursorFromDB(ctx, req)
}

// getHotPostsByCursorFromDB 热门游标：优先 ZSET（一次多取 1 条判断 hasMore），否则回源 DB
func (s *postServiceImpl) getHotPostsByCursorFromDB(ctx context.Context, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Post], error) {
	offset := 0
	if req.Cursor != "" {
		if parsed, err := strconv.Atoi(req.Cursor); err == nil && parsed >= 0 {
			offset = parsed
		}
	}

	if s.cache != nil {
		if ids, hit := cache.GetTyped[[]string](s.cache, cache.HotRankTopIDsKey()); hit && len(ids) > 0 {
			if offset < len(ids) {
				stop := offset + req.PageSize + 1
				if stop > len(ids) {
					stop = len(ids)
				}
				slice := ids[offset:stop]
				hasMore := len(slice) > req.PageSize
				if hasMore {
					slice = slice[:req.PageSize]
				}
				posts, gerr := s.postRepo.GetByIDs(slice)
				if gerr != nil {
					return nil, gerr
				}
				nextCursor := ""
				if hasMore {
					nextCursor = strconv.Itoa(offset + req.PageSize)
				}
				return &cursor.CursorPageResult[*model.Post]{
					Items:      posts,
					NextCursor: nextCursor,
					PrevCursor: "",
					HasMore:    hasMore,
				}, nil
			}
			return &cursor.CursorPageResult[*model.Post]{
				Items:      []*model.Post{},
				NextCursor: "",
				PrevCursor: "",
				HasMore:    false,
			}, nil
		}

		key := cache.HotRankZSetKey()
		card, zerr := s.cache.ZCard(ctx, key)
		if zerr == nil && card > 0 {
			stop := int64(offset + req.PageSize)
			ids, rerr := s.cache.ZRevRange(ctx, key, int64(offset), stop)
			if rerr == nil && len(ids) > 0 {
				hasMore := len(ids) > req.PageSize
				if hasMore {
					ids = ids[:req.PageSize]
				}
				posts, gerr := s.postRepo.GetByIDs(ids)
				if gerr != nil {
					return nil, gerr
				}
				nextCursor := ""
				if hasMore {
					nextCursor = strconv.Itoa(offset + req.PageSize)
				}
				return &cursor.CursorPageResult[*model.Post]{
					Items:      posts,
					NextCursor: nextCursor,
					PrevCursor: "",
					HasMore:    hasMore,
				}, nil
			}
		}
	}

	page := offset/req.PageSize + 1
	posts, _, err := s.postRepo.GetHotPosts(page, req.PageSize+1)
	if err != nil {
		return nil, err
	}

	hasMore := len(posts) > req.PageSize
	if hasMore {
		posts = posts[:req.PageSize]
	}

	nextCursor := ""
	if hasMore {
		nextCursor = strconv.Itoa(offset + req.PageSize)
	}

	return &cursor.CursorPageResult[*model.Post]{
		Items:      posts,
		NextCursor: nextCursor,
		PrevCursor: "",
		HasMore:    hasMore,
	}, nil
}