backend/internal/repository/comment_repo.go

package repository

import (
	"errors"

	"with_you/internal/model"
	"with_you/internal/pkg/cursor"
	"context"

	"gorm.io/gorm"
)

// CommentRepository 评论仓储接口
type CommentRepository interface {
	Create(comment *model.Comment) error
	GetByID(id string) (*model.Comment, error)
	Update(comment *model.Comment) error
	UpdateModerationStatus(commentID string, status model.CommentStatus, rejectReason string, reviewedBy string) (*model.Comment, error)
	Delete(id string) error
	GetByPostID(postID string, page, pageSize int) ([]*model.Comment, int64, error)
	GetByPostIDWithReplies(postID string, page, pageSize, replyLimit int) ([]*model.Comment, int64, error)
	GetRepliesByRootID(rootID string, page, pageSize int) ([]*model.Comment, int64, error)
	GetReplies(parentID string) ([]*model.Comment, error)
	Like(commentID, userID string) error
	Unlike(commentID, userID string) error
	IsLiked(commentID, userID string) bool
	IsLikedBatch(commentIDs []string, userID string) map[string]bool
	GetAdminCommentList(filter AdminCommentListFilter) ([]*model.Comment, int64, error)
	GetAdminCommentByID(id string) (*model.Comment, error)
	BatchDelete(ids []string) ([]string, error)
	GetCommentsByPostIDForAdmin(postID string, page, pageSize int) ([]*model.Comment, int64, error)
	GetCommentsByCursor(ctx context.Context, postID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Comment], error)
	GetRepliesByCursor(ctx context.Context, rootID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Comment], error)
}

// commentRepository 评论仓储实现
type commentRepository struct {
	db *gorm.DB
}

// NewCommentRepository 创建评论仓储
func NewCommentRepository(db *gorm.DB) CommentRepository {
	return &commentRepository{db: db}
}

// Create 创建评论
func (r *commentRepository) Create(comment *model.Comment) error {
	return r.db.Create(comment).Error
}

// GetByID 根据ID获取评论
func (r *commentRepository) GetByID(id string) (*model.Comment, error) {
	var comment model.Comment
	err := r.db.Preload("User").First(&comment, "id = ?", id).Error
	if err != nil {
		return nil, err
	}
	return &comment, nil
}

// Update 更新评论（仅内容字段，如 content / segments / images）。
//
// 防御性：评论的 status 字段是计数维护的核心，必须经由 UpdateModerationStatus /
// Delete 等状态转换通道变更，否则会破坏 comments_count / replies_count 一致性。
// 因此本方法显式不更新 status / reviewed_* 等审核字段——即便上层传入的
// comment 结构体 status 为零值或脏值，也不会污染状态机。
func (r *commentRepository) Update(comment *model.Comment) error {
	return r.db.Model(&model.Comment{}).
		Where("id = ?", comment.ID).
		Select("content", "segments", "images", "updated_at").
		Updates(comment).Error
}

// UpdateModerationStatus 更新评论审核状态，并在同一事务内原子地维护
// 帖子评论数 / 父评论回复数等统计字段。
//
// 计数维护统一收敛到 transitionStatus（评论状态变更的唯一通道），
// 因此任何调用方（自动审核、管理端单条 / 批量审核、举报自动隐藏等）
// 都能正确维护计数，避免"评论显示 N 条但计数为 N-1"。
// 同时内置防御：非法状态转换（如 deleted → published）会被拒绝，
// 计数递减使用 CASE WHEN 保证永不为负。
//
// 返回更新后的评论（含 User 关联），便于调用方做缓存失效、通知等后续处理。
func (r *commentRepository) UpdateModerationStatus(commentID string, status model.CommentStatus, rejectReason string, reviewedBy string) (*model.Comment, error) {
	var updated model.Comment
	err := r.db.Transaction(func(tx *gorm.DB) error {
		prev, err := transitionStatus(tx, commentID, status)
		if err != nil {
			return err
		}
		// 状态未变化或仅元数据需补充（reviewed_at / reviewed_by / reject_reason）
		updates := map[string]any{
			"reviewed_at":   gorm.Expr("CURRENT_TIMESTAMP"),
			"reviewed_by":   reviewedBy,
			"reject_reason": rejectReason,
			"updated_at":    gorm.Expr("updated_at"),
		}
		if prev.Status != status {
			updates["status"] = status
		}
		if err := tx.Model(&model.Comment{}).
			Where("id = ?", commentID).
			UpdateColumns(updates).Error; err != nil {
			return err
		}

		// 重新加载（含 User 关联）供调用方使用
		return tx.Preload("User").First(&updated, "id = ?", commentID).Error
	})
	if err != nil {
		return nil, err
	}
	return &updated, nil
}

// Delete 删除评论（软删除，同时清理关联数据）。
// 删除 = 状态迁移到 deleted，复用 transitionStatus 统一维护计数，
// 保证 Delete 与审核路径的计数行为一致、对称。
func (r *commentRepository) Delete(id string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		// 统一走状态转换层：published → deleted 会自动 -1 计数；非 published 删除则不调整
		if _, err := transitionStatus(tx, id, model.CommentStatusDeleted); err != nil {
			if errors.Is(err, errInvalidStatusTransition) {
				// 已删除的评论重复删除：视为幂等成功
				return nil
			}
			return err
		}

		// 删除评论点赞记录
		if err := tx.Where("comment_id = ?", id).Delete(&model.CommentLike{}).Error; err != nil {
			return err
		}

		// 删除评论（软删除）
		if err := tx.Delete(&model.Comment{}, "id = ?", id).Error; err != nil {
			return err
		}

		return nil
	})
}

// GetByPostID 获取帖子评论
func (r *commentRepository) GetByPostID(postID string, page, pageSize int) ([]*model.Comment, int64, error) {
	var comments []*model.Comment
	var total int64

	r.db.Model(&model.Comment{}).Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished).Count(&total)

	offset := (page - 1) * pageSize
	err := r.db.Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished).
		Preload("User").
		Offset(offset).Limit(pageSize).
		Order("created_at ASC").
		Find(&comments).Error

	return comments, total, err
}

// GetByPostIDWithReplies 获取帖子评论（包含回复，扁平化结构）
// 所有层级的回复都扁平化展示在顶级评论的 replies 中
func (r *commentRepository) GetByPostIDWithReplies(postID string, page, pageSize, replyLimit int) ([]*model.Comment, int64, error) {
	var comments []*model.Comment
	var total int64

	r.db.Model(&model.Comment{}).Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished).Count(&total)

	offset := (page - 1) * pageSize
	err := r.db.Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished).
		Preload("User").
		Offset(offset).Limit(pageSize).
		Order("created_at ASC").
		Find(&comments).Error

	if err != nil {
		return nil, 0, err
	}

	if len(comments) == 0 {
		return comments, total, nil
	}

	rootIDs := make([]string, 0, len(comments))
	commentsByID := make(map[string]*model.Comment, len(comments))
	for _, comment := range comments {
		rootIDs = append(rootIDs, comment.ID)
		commentsByID[comment.ID] = comment
	}

	// 批量加载所有回复，内存中按 root_id 分组并裁剪每个根评论的返回条数
	var allReplies []*model.Comment
	if err := r.db.Where("root_id IN ? AND status = ?", rootIDs, model.CommentStatusPublished).
		Preload("User").
		Order("created_at ASC").
		Find(&allReplies).Error; err != nil {
		return nil, 0, err
	}

	repliesByRoot := make(map[string][]*model.Comment, len(rootIDs))
	for _, reply := range allReplies {
		if reply.RootID == nil {
			continue
		}
		rootID := *reply.RootID
		if replyLimit <= 0 || len(repliesByRoot[rootID]) < replyLimit {
			repliesByRoot[rootID] = append(repliesByRoot[rootID], reply)
		}
	}

	type replyCountRow struct {
		RootID string
		Total  int64
	}
	var replyCountRows []replyCountRow
	if err := r.db.Model(&model.Comment{}).
		Select("root_id, COUNT(*) AS total").
		Where("root_id IN ? AND status = ?", rootIDs, model.CommentStatusPublished).
		Group("root_id").
		Scan(&replyCountRows).Error; err != nil {
		return nil, 0, err
	}

	replyCountMap := make(map[string]int64, len(replyCountRows))
	for _, row := range replyCountRows {
		replyCountMap[row.RootID] = row.Total
	}

	for _, rootID := range rootIDs {
		comment := commentsByID[rootID]
		comment.Replies = repliesByRoot[rootID]
		comment.RepliesCount = int(replyCountMap[rootID])
	}

	return comments, total, nil
}

// GetRepliesByRootID 根据根评论ID分页获取回复（扁平化）
func (r *commentRepository) GetRepliesByRootID(rootID string, page, pageSize int) ([]*model.Comment, int64, error) {
	var replies []*model.Comment
	var total int64

	// 统计总数
	r.db.Model(&model.Comment{}).Where("root_id = ? AND status = ?", rootID, model.CommentStatusPublished).Count(&total)

	// 分页查询
	offset := (page - 1) * pageSize
	err := r.db.Where("root_id = ? AND status = ?", rootID, model.CommentStatusPublished).
		Preload("User").
		Order("created_at ASC").
		Offset(offset).
		Limit(pageSize).
		Find(&replies).Error

	return replies, total, err
}

// GetReplies 获取回复
func (r *commentRepository) GetReplies(parentID string) ([]*model.Comment, error) {
	var comments []*model.Comment
	err := r.db.Where("parent_id = ? AND status = ?", parentID, model.CommentStatusPublished).
		Preload("User").
		Order("created_at ASC").
		Find(&comments).Error
	return comments, err
}

// Like 点赞评论（使用事务保证数据一致性）
func (r *commentRepository) Like(commentID, userID string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		// 检查是否已经点赞
		var existing model.CommentLike
		err := tx.Where("comment_id = ? AND user_id = ?", commentID, userID).First(&existing).Error
		if err == nil {
			// 已经点赞
			return nil
		}
		if err != gorm.ErrRecordNotFound {
			return err
		}

		// 创建点赞记录
		like := &model.CommentLike{
			CommentID: commentID,
			UserID:    userID,
		}
		if err := tx.Create(like).Error; err != nil {
			return err
		}

		// 增加评论点赞数
		return tx.Model(&model.Comment{}).Where("id = ?", commentID).
			UpdateColumn("likes_count", gorm.Expr("likes_count + 1")).Error
	})
}

// Unlike 取消点赞评论（使用事务保证数据一致性）
func (r *commentRepository) Unlike(commentID, userID string) error {
	return r.db.Transaction(func(tx *gorm.DB) error {
		result := tx.Where("comment_id = ? AND user_id = ?", commentID, userID).Delete(&model.CommentLike{})
		if result.Error != nil {
			return result.Error
		}
		if result.RowsAffected > 0 {
			// 减少评论点赞数
			return tx.Model(&model.Comment{}).Where("id = ?", commentID).
				UpdateColumn("likes_count", gorm.Expr("likes_count - 1")).Error
		}
		return nil
	})
}

// IsLiked 检查是否已点赞
func (r *commentRepository) IsLiked(commentID, userID string) bool {
	var count int64
	r.db.Model(&model.CommentLike{}).Where("comment_id = ? AND user_id = ?", commentID, userID).Count(&count)
	return count > 0
}

// IsLikedBatch 批量检查是否点赞（解决 N+1 问题）
// 返回 map[commentID]bool
func (r *commentRepository) IsLikedBatch(commentIDs []string, userID string) map[string]bool {
	result := make(map[string]bool)
	if len(commentIDs) == 0 || userID == "" {
		return result
	}

	// 初始化所有 commentID 为 false
	for _, commentID := range commentIDs {
		result[commentID] = false
	}

	// 一次性查询所有点赞记录
	var likedCommentIDs []string
	r.db.Model(&model.CommentLike{}).
		Where("comment_id IN ? AND user_id = ?", commentIDs, userID).
		Pluck("comment_id", &likedCommentIDs)

	// 更新已点赞的评论
	for _, commentID := range likedCommentIDs {
		result[commentID] = true
	}

	return result
}

// AdminCommentListFilter 管理端评论列表筛选条件
type AdminCommentListFilter struct {
	Keyword   string
	PostID    string
	AuthorID  string
	Status    string
	StartDate string
	EndDate   string
	Page      int
	PageSize  int
}

// GetAdminCommentList 获取管理端评论列表
func (r *commentRepository) GetAdminCommentList(filter AdminCommentListFilter) ([]*model.Comment, int64, error) {
	var comments []*model.Comment
	var total int64

	query := r.db.Model(&model.Comment{}).Preload("User")

	// 应用筛选条件
	if filter.Keyword != "" {
		query = query.Where("content LIKE ?", "%"+filter.Keyword+"%")
	}
	if filter.PostID != "" {
		query = query.Where("post_id = ?", filter.PostID)
	}
	if filter.AuthorID != "" {
		query = query.Where("user_id = ?", filter.AuthorID)
	}
	if filter.Status != "" {
		query = query.Where("status = ?", filter.Status)
	}
	if filter.StartDate != "" {
		query = query.Where("created_at >= ?", filter.StartDate)
	}
	if filter.EndDate != "" {
		query = query.Where("created_at <= ?", filter.EndDate+" 23:59:59")
	}

	// 统计总数
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, err
	}

	// 分页查询
	offset := (filter.Page - 1) * filter.PageSize
	if err := query.Offset(offset).Limit(filter.PageSize).Order("created_at DESC").Find(&comments).Error; err != nil {
		return nil, 0, err
	}

	return comments, total, nil
}

// GetAdminCommentByID 获取管理端评论详情（包含关联信息）
func (r *commentRepository) GetAdminCommentByID(id string) (*model.Comment, error) {
	var comment model.Comment
	err := r.db.Preload("User").First(&comment, "id = ?", id).Error
	if err != nil {
		return nil, err
	}
	return &comment, nil
}

// BatchDelete 批量删除评论。
// 逐条复用 transitionStatus 完成 published → deleted 的状态迁移，
// 统一维护 comments_count 与父评论 replies_count（修复此前批量删除漏减 replies_count 的问题）。
// 返回失败 ID 列表（当前实现下事务整体回滚，故失败时返回全部 ids）。
func (r *commentRepository) BatchDelete(ids []string) ([]string, error) {
	if len(ids) == 0 {
		return nil, nil
	}

	err := r.db.Transaction(func(tx *gorm.DB) error {
		for _, id := range ids {
			// 统一走状态转换层：幂等处理已删除评论，已发布评论自动 -1 计数 + 父回复数
			if _, terr := transitionStatus(tx, id, model.CommentStatusDeleted); terr != nil {
				if errors.Is(terr, errInvalidStatusTransition) {
					continue // 已删除：幂等跳过
				}
				return terr
			}
		}

		// 批量删除评论点赞记录
		if err := tx.Where("comment_id IN ?", ids).Delete(&model.CommentLike{}).Error; err != nil {
			return err
		}

		// 批量删除评论（软删除）
		if err := tx.Where("id IN ?", ids).Delete(&model.Comment{}).Error; err != nil {
			return err
		}
		return nil
	})

	if err != nil {
		return ids, err
	}
	return nil, nil
}

// GetCommentsByPostIDForAdmin 管理端获取帖子的评论列表（包含所有状态）
func (r *commentRepository) GetCommentsByPostIDForAdmin(postID string, page, pageSize int) ([]*model.Comment, int64, error) {
	var comments []*model.Comment
	var total int64

	r.db.Model(&model.Comment{}).Where("post_id = ?", postID).Count(&total)

	offset := (page - 1) * pageSize
	err := r.db.Where("post_id = ?", postID).
		Preload("User").
		Offset(offset).Limit(pageSize).
		Order("created_at DESC").
		Find(&comments).Error

	return comments, total, err
}

// ========== Cursor Pagination Methods ==========

// GetCommentsByCursor 游标分页获取帖子评论（包含回复）
// 排序方式：created_at ASC（最早发布的为一楼）
func (r *commentRepository) GetCommentsByCursor(ctx context.Context, postID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Comment], error) {
	// 构建基础查询 - 只查询顶级评论
	query := r.db.WithContext(ctx).Model(&model.Comment{}).
		Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished)

	// 使用游标构建器
	builder := cursor.NewBuilder(query, cursor.SortByCreatedAtAsc).
		WithCursor(req.Cursor, req.Direction).
		WithPageSize(req.PageSize)

	if builder.Error() != nil {
		// 无效游标，返回空列表
		return cursor.NewCursorPageResult([]*model.Comment{}, "", "", false), nil
	}

	// 执行查询
	var comments []*model.Comment
	query = builder.Build().Preload("User")
	if err := query.Find(&comments).Error; err != nil {
		return nil, err
	}

	// 构建响应
	pageSize := builder.GetPageSize()
	hasMore := cursor.HasMore(len(comments), pageSize)
	if hasMore {
		comments = comments[:pageSize]
	}

	// 加载每个评论的回复（默认加载前3条）
	if len(comments) > 0 {
		r.loadRepliesForComments(comments, 3)
	}

	// 生成游标
	var nextCursor, prevCursor string
	if len(comments) > 0 {
		// 下一页游标
		if hasMore {
			lastComment := comments[len(comments)-1]
			nextCursor = cursor.NewCursor(
				cursor.FormatTime(lastComment.CreatedAt),
				lastComment.ID,
				cursor.SortByCreatedAtAsc,
			).Encode()
		}
		// 上一页游标
		firstComment := comments[0]
		prevCursor = cursor.NewCursor(
			cursor.FormatTime(firstComment.CreatedAt),
			firstComment.ID,
			cursor.SortByCreatedAtAsc,
		).Encode()
	}

	return cursor.NewCursorPageResult(comments, nextCursor, prevCursor, hasMore), nil
}

// loadRepliesForComments 为评论列表加载回复
func (r *commentRepository) loadRepliesForComments(comments []*model.Comment, replyLimit int) {
	if len(comments) == 0 {
		return
	}

	rootIDs := make([]string, 0, len(comments))
	commentsByID := make(map[string]*model.Comment, len(comments))
	for _, comment := range comments {
		rootIDs = append(rootIDs, comment.ID)
		commentsByID[comment.ID] = comment
	}

	// 批量加载所有回复
	var allReplies []*model.Comment
	if err := r.db.Where("root_id IN ? AND status = ?", rootIDs, model.CommentStatusPublished).
		Preload("User").
		Order("created_at ASC").
		Find(&allReplies).Error; err != nil {
		return
	}

	// 按 root_id 分组并裁剪
	repliesByRoot := make(map[string][]*model.Comment, len(rootIDs))
	for _, reply := range allReplies {
		if reply.RootID == nil {
			continue
		}
		rootID := *reply.RootID
		if replyLimit <= 0 || len(repliesByRoot[rootID]) < replyLimit {
			repliesByRoot[rootID] = append(repliesByRoot[rootID], reply)
		}
	}

	// 查询每个根评论的回复总数
	type replyCountRow struct {
		RootID string
		Total  int64
	}
	var replyCountRows []replyCountRow
	if err := r.db.Model(&model.Comment{}).
		Select("root_id, COUNT(*) AS total").
		Where("root_id IN ? AND status = ?", rootIDs, model.CommentStatusPublished).
		Group("root_id").
		Scan(&replyCountRows).Error; err != nil {
		return
	}

	replyCountMap := make(map[string]int64, len(replyCountRows))
	for _, row := range replyCountRows {
		replyCountMap[row.RootID] = row.Total
	}

	// 设置回复和回复数
	for _, rootID := range rootIDs {
		comment := commentsByID[rootID]
		comment.Replies = repliesByRoot[rootID]
		comment.RepliesCount = int(replyCountMap[rootID])
	}
}

// GetRepliesByCursor 游标分页获取根评论的回复
// 排序方式：created_at ASC（回复按时间正序）
func (r *commentRepository) GetRepliesByCursor(ctx context.Context, rootID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Comment], error) {
	// 构建基础查询
	query := r.db.WithContext(ctx).Model(&model.Comment{}).
		Where("root_id = ? AND status = ?", rootID, model.CommentStatusPublished)

	// 使用游标构建器（回复按时间升序）
	builder := cursor.NewBuilder(query, cursor.SortByCreatedAtAsc).
		WithCursor(req.Cursor, req.Direction).
		WithPageSize(req.PageSize)

	if builder.Error() != nil {
		// 无效游标，返回空列表
		return cursor.NewCursorPageResult([]*model.Comment{}, "", "", false), nil
	}

	// 执行查询
	var replies []*model.Comment
	query = builder.Build().Preload("User")
	if err := query.Find(&replies).Error; err != nil {
		return nil, err
	}

	// 构建响应
	pageSize := builder.GetPageSize()
	hasMore := cursor.HasMore(len(replies), pageSize)
	if hasMore {
		replies = replies[:pageSize]
	}

	// 生成游标
	var nextCursor, prevCursor string
	if len(replies) > 0 {
		// 下一页游标
		if hasMore {
			lastReply := replies[len(replies)-1]
			nextCursor = cursor.NewCursor(
				cursor.FormatTime(lastReply.CreatedAt),
				lastReply.ID,
				cursor.SortByCreatedAtAsc,
			).Encode()
		}
		// 上一页游标
		firstReply := replies[0]
		prevCursor = cursor.NewCursor(
			cursor.FormatTime(firstReply.CreatedAt),
			firstReply.ID,
			cursor.SortByCreatedAtAsc,
		).Encode()
	}

	return cursor.NewCursorPageResult(replies, nextCursor, prevCursor, hasMore), nil
}