sundynix-pets/pets-be/internal/service/community.go

package service

import (
	"encoding/json"

	"gorm.io/datatypes"
	"gorm.io/gorm"

	"github.com/sundynix/pets-be/internal/model"
)

// attachPostImages 把帖子的 ImageFileIDs 解析为可展示的 Images（URL 数组）。
// 机器人帖 ImageFileIDs 为空，保留其 Images（emoji）不变。
func (s *Service) attachPostImages(posts []model.Post) {
	perPost := make([][]string, len(posts))
	all := []string{}
	for i := range posts {
		if len(posts[i].ImageFileIDs) == 0 {
			continue
		}
		var ids []string
		if json.Unmarshal(posts[i].ImageFileIDs, &ids) == nil && len(ids) > 0 {
			perPost[i] = ids
			all = append(all, ids...)
		}
	}
	if len(all) == 0 {
		return
	}
	urlMap := s.fileURLs(all)
	for i := range posts {
		if len(perPost[i]) == 0 {
			continue
		}
		urls := make([]string, 0, len(perPost[i]))
		for _, id := range perPost[i] {
			if u := urlMap[id]; u != "" {
				urls = append(urls, u)
			}
		}
		if b, err := json.Marshal(urls); err == nil {
			posts[i].Images = datatypes.JSON(b)
		}
	}
}

// tabTag 将 feed tab 映射为标签过滤（空表示不过滤）
func tabTag(tab string) string {
	switch tab {
	case "新手求助":
		return "求助"
	case "晒宠":
		return "晒宠"
	case "经验":
		return "经验"
	default: // 推荐 / 关注
		return ""
	}
}

// ListPosts 帖子分页列表。userID 用于「关注」tab 过滤和标记关注状态（可为空）。
func (s *Service) ListPosts(userID, tab string, offset, limit int) ([]model.Post, int64, error) {
	q := s.db.Model(&model.Post{}).Where("status = ?", model.PostPublished)
	if tag := tabTag(tab); tag != "" {
		q = q.Where("JSON_CONTAINS(tags, ?)", `"`+tag+`"`)
	}
	if tab == "关注" {
		ids := s.followeeIDs(userID)
		if len(ids) == 0 {
			// 一个都没关注：返回空列表，而不是退化成「推荐」
			return []model.Post{}, 0, nil
		}
		q = q.Where("user_id IN ?", ids)
	}
	var total int64
	if err := q.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var posts []model.Post
	if err := q.Order("id desc").Offset(offset).Limit(limit).Find(&posts).Error; err != nil {
		return nil, 0, err
	}
	s.attachPostImages(posts)
	s.markFollowed(userID, posts)
	return posts, total, nil
}

// GetPost 帖子详情
func (s *Service) GetPost(postID string) (*model.Post, error) {
	var p model.Post
	if err := s.db.First(&p, postID).Error; err != nil {
		if err == gorm.ErrRecordNotFound {
			return nil, ErrNotFound
		}
		return nil, err
	}
	one := []model.Post{p}
	s.attachPostImages(one)
	return &one[0], nil
}

// PostInput 发帖入参
type PostInput struct {
	PetID        *string
	Identity     string
	Content      string
	Tags         datatypes.JSON
	Images       datatypes.JSON
	ImageFileIDs datatypes.JSON
}

// CreatePost 发帖
func (s *Service) CreatePost(userID string, in PostInput) (*model.Post, error) {
	authorName := "匿名宠友"
	authorEmoji := "🐾"
	switch in.Identity {
	case "official":
		authorName = "肉垫计划官方"
	case "petName":
		if in.PetID != nil {
			var pet model.Pet
			if err := s.db.First(&pet, *in.PetID).Error; err == nil {
				authorName = pet.Name + "的铲屎官"
				authorEmoji = pet.Emoji
			}
		}
	}
	p := model.Post{
		UserID: userID, PetID: in.PetID, AuthorName: authorName, AuthorEmoji: authorEmoji,
		Identity: in.Identity, Content: in.Content, Tags: in.Tags, Images: in.Images,
		ImageFileIDs: in.ImageFileIDs, Status: model.PostPublished,
	}
	if err := s.db.Create(&p).Error; err != nil {
		return nil, err
	}
	one := []model.Post{p}
	s.attachPostImages(one)
	return &one[0], nil
}

// LikePost 点赞（幂等：已赞则不重复计数）
func (s *Service) LikePost(userID, postID string) (int, error) {
	if _, err := s.GetPost(postID); err != nil {
		return 0, err
	}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		like := model.PostLike{PostID: postID, UserID: userID}
		res := tx.Where("post_id = ? AND user_id = ?", postID, userID).FirstOrCreate(&like)
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected == 1 { // 新建才计数
			return tx.Model(&model.Post{}).Where("id = ?", postID).
				UpdateColumn("like_count", gorm.Expr("like_count + 1")).Error
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	return s.postLikeCount(postID)
}

// UnlikePost 取消点赞
func (s *Service) UnlikePost(userID, postID string) (int, error) {
	if _, err := s.GetPost(postID); err != nil {
		return 0, err
	}
	err := s.db.Transaction(func(tx *gorm.DB) error {
		res := tx.Where("post_id = ? AND user_id = ?", postID, userID).Delete(&model.PostLike{})
		if res.Error != nil {
			return res.Error
		}
		if res.RowsAffected == 1 {
			return tx.Model(&model.Post{}).Where("id = ? AND like_count > 0", postID).
				UpdateColumn("like_count", gorm.Expr("like_count - 1")).Error
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	return s.postLikeCount(postID)
}

func (s *Service) postLikeCount(postID string) (int, error) {
	var p model.Post
	if err := s.db.Select("like_count").First(&p, postID).Error; err != nil {
		return 0, err
	}
	return p.LikeCount, nil
}

// ListComments 评论分页
func (s *Service) ListComments(userID, postID string, offset, limit int) ([]model.Comment, int64, error) {
	base := func() *gorm.DB {
		return s.db.Model(&model.Comment{}).Where("post_id = ? AND status = ?", postID, "published")
	}
	// total 是这条帖子的评论总数（含回复），和帖子上显示的数字对得上
	var total int64
	if err := base().Count(&total).Error; err != nil {
		return nil, 0, err
	}
	// 只分页一级评论，回复跟着它爹一起返回
	var roots []model.Comment
	if err := base().Where("parent_id = ? OR parent_id IS NULL", "").
		Order("id desc").Offset(offset).Limit(limit).Find(&roots).Error; err != nil {
		return nil, 0, err
	}
	if len(roots) == 0 {
		return []model.Comment{}, total, nil
	}

	ids := make([]string, 0, len(roots))
	for i := range roots {
		roots[i].IsSelf = roots[i].UserID == userID
		ids = append(ids, roots[i].ID)
	}
	// 一次查完这一页所有一级评论的回复，不要每条一次查询
	var replies []model.Comment
	s.db.Where("parent_id IN ? AND status = ?", ids, "published").Order("id asc").Find(&replies)
	byParent := map[string][]model.Comment{}
	for i := range replies {
		replies[i].IsSelf = replies[i].UserID == userID
		byParent[replies[i].ParentID] = append(byParent[replies[i].ParentID], replies[i])
	}
	for i := range roots {
		list := byParent[roots[i].ID]
		if list == nil {
			list = []model.Comment{} // 空切片而不是 nil，否则 JSON 出来是 null
		}
		roots[i].ReplyN = len(list)
		// 默认只带前 3 条，其余等前端点「展开」再要，避免热门评论一次拉几百条
		if len(list) > 3 {
			list = list[:3]
		}
		roots[i].Replies = list
	}
	return roots, total, nil
}

// ListReplies 展开某条一级评论下的全部回复
func (s *Service) ListReplies(userID, commentID string) ([]model.Comment, error) {
	var list []model.Comment
	if err := s.db.Where("parent_id = ? AND status = ?", commentID, "published").
		Order("id asc").Find(&list).Error; err != nil {
		return nil, err
	}
	for i := range list {
		list[i].IsSelf = list[i].UserID == userID
	}
	return list, nil
}

// CreateComment 评论
func (s *Service) CreateComment(userID, postID string, content string, images []string, parentID string) (*model.Comment, error) {
	if _, err := s.GetPost(postID); err != nil {
		return nil, err
	}
	var user model.User
	name := "宠友"
	if err := s.db.First(&user, userID).Error; err == nil && user.Nickname != "" {
		name = user.Nickname
	}
	// 回复的回复仍然挂到同一条一级评论下，保持两级不塌成深树
	replyTo := ""
	if parentID != "" {
		var parent model.Comment
		if err := s.db.Where("id = ? AND post_id = ?", parentID, postID).First(&parent).Error; err != nil {
			return nil, ErrNotFound
		}
		if parent.ParentID != "" {
			replyTo = parent.AuthorName
			parentID = parent.ParentID
		}
	}

	comment := model.Comment{
		PostID: postID, UserID: userID, AuthorName: name, Content: content,
		Status: "published", ParentID: parentID, ReplyToName: replyTo,
	}
	// 配图存 JSON 数组。空数组也要显式写，否则前端拿到 null 还要额外判空
	if b, err := json.Marshal(images); err == nil && len(images) > 0 {
		comment.Images = b
	}
	if err := s.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(&comment).Error; err != nil {
			return err
		}
		return tx.Model(&model.Post{}).Where("id = ?", postID).
			UpdateColumn("comment_count", gorm.Expr("comment_count + 1")).Error
	}); err != nil {
		return nil, err
	}
	return &comment, nil
}

// DeleteOwnPost 用户删除自己的帖子（软删除，保留数据可追溯）
func (s *Service) DeleteOwnPost(userID, postID string) error {
	var p model.Post
	if err := s.db.Where("id = ?", postID).First(&p).Error; err != nil {
		return ErrNotFound
	}
	if p.UserID != userID {
		return ErrForbidden
	}
	return s.db.Model(&model.Post{}).Where("id = ?", postID).
		Update("status", model.PostDeleted).Error
}

// DeleteOwnComment 用户删除自己的评论，并同步帖子评论数
func (s *Service) DeleteOwnComment(userID, commentID string) error {
	var c model.Comment
	if err := s.db.Where("id = ?", commentID).First(&c).Error; err != nil {
		return ErrNotFound
	}
	if c.UserID != userID {
		return ErrForbidden
	}
	if c.Status == "deleted" {
		return nil // 幂等
	}
	return s.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&model.Comment{}).Where("id = ?", commentID).
			Update("status", "deleted").Error; err != nil {
			return err
		}
		// 删一级评论要连它下面的回复一起删，否则回复会变成挂在空处的孤儿
		n := int64(1)
		if c.ParentID == "" {
			res := tx.Model(&model.Comment{}).
				Where("parent_id = ? AND status = ?", commentID, "published").
				Update("status", "deleted")
			if res.Error != nil {
				return res.Error
			}
			n += res.RowsAffected
		}
		return tx.Model(&model.Post{}).Where("id = ? AND comment_count >= ?", c.PostID, n).
			UpdateColumn("comment_count", gorm.Expr("comment_count - ?", n)).Error
	})
}