package service

import (
	"errors"
	"strings"
	"time"

	"github.com/freefire/jiang13-bbs/model"
	"gorm.io/gorm"
)

// CommentService 评论服务
type CommentService struct {
	db *gorm.DB
}

func NewCommentService(db *gorm.DB) *CommentService {
	return &CommentService{db: db}
}

// ListByPost 获取帖子的评论列表
func (s *CommentService) ListByPost(postID uint) ([]model.Comment, error) {
	var comments []model.Comment
	err := s.db.Where("post_id = ? AND status = ?", postID, model.ContentStatusPublished).
		Order("created_at ASC").
		Preload("User").
		Find(&comments).Error
	return comments, err
}

// Create 创建评论
func (s *CommentService) Create(userID, postID uint, content string) (*model.Comment, error) {
	content = strings.TrimSpace(content)
	if content == "" {
		return nil, errors.New("评论内容不能为空")
	}

	// 检查帖子是否存在且未锁定评论
	var post model.Post
	if err := s.db.First(&post, postID).Error; err != nil {
		return nil, errors.New("帖子不存在")
	}

	comment := &model.Comment{
		PostID:  postID,
		UserID:  userID,
		Content: content,
		Status:  model.ContentStatusPublished,
	}
	if err := s.db.Create(comment).Error; err != nil {
		return nil, err
	}
	// 更新帖子评论数
	s.db.Model(&post).UpdateColumn("comment_count", gorm.Expr("comment_count + 1"))
	// 预加载用户
	s.db.Preload("User").First(comment, comment.ID)
	return comment, nil
}

// UserCommentItem 用户评论列表项（含帖子标题便于跳转）
type UserCommentItem struct {
	ID        uint      `json:"id"`
	PostID    uint      `json:"post_id"`
	PostTitle string    `json:"post_title"`
	Content   string    `json:"content"`
	CreatedAt time.Time `json:"created_at"`
}

// ListByUser 获取指定用户发表的评论（含所属帖子标题）
func (s *CommentService) ListByUser(userID uint, page, size int) ([]UserCommentItem, int64, error) {
	if page < 1 {
		page = 1
	}
	if size < 1 || size > 50 {
		size = 20
	}
	query := s.db.Table("comments").
		Select("comments.id, comments.post_id, posts.title AS post_title, comments.content, comments.created_at").
		Joins("JOIN posts ON posts.id = comments.post_id").
		Where("comments.user_id = ? AND comments.status = ? AND posts.deleted_at IS NULL", userID, model.ContentStatusPublished)

	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var items []UserCommentItem
	offset := (page - 1) * size
	if err := query.Order("comments.created_at DESC").Offset(offset).Limit(size).Scan(&items).Error; err != nil {
		return nil, 0, err
	}
	return items, total, nil
}

// CountByUser 统计用户评论数（仅统计未删除帖子上的评论，与列表保持一致）
func (s *CommentService) CountByUser(userID uint) (int64, error) {
	var total int64
	err := s.db.Table("comments").
		Joins("JOIN posts ON posts.id = comments.post_id").
		Where("comments.user_id = ? AND comments.status = ? AND posts.deleted_at IS NULL", userID, model.ContentStatusPublished).
		Count(&total).Error
	return total, err
}

// Delete 删除评论（仅作者或管理员可操作）
func (s *CommentService) Delete(commentID, userID uint, role string) error {
	var comment model.Comment
	if err := s.db.First(&comment, commentID).Error; err != nil {
		return errors.New("评论不存在")
	}
	// 权限校验：作者本人或管理员
	if comment.UserID != userID && role != RoleAdmin {
		return errors.New("无权限删除此评论")
	}
	// 软删除
	if err := s.db.Delete(&comment).Error; err != nil {
		return err
	}
	// 更新帖子评论数
	s.db.Model(&model.Post{}).Where("id = ?", comment.PostID).
		UpdateColumn("comment_count", gorm.Expr("GREATEST(comment_count - 1, 0)"))
	return nil
}