mce/internal/service/post_service.go

package service

import (
	"errors"
	"fmt"
	"regexp"
	"strings"
	"unicode/utf8"

	"metazone.cc/metalab/internal/common"
	"metazone.cc/metalab/internal/config"
	"metazone.cc/metalab/internal/model"

	"gorm.io/gorm"
)

// mdPatterns Markdown 语法正则（用于生成纯文本摘要）
var mdPatterns = []*regexp.Regexp{
	// 代码块 ```...```
	regexp.MustCompile("(?s)```[^`]*```"),
	// 行内代码 `...`
	regexp.MustCompile("`[^`]+`"),
	// 图片 ![alt](url)
	regexp.MustCompile(`!\[.*?\]\(.*?\)`),
	// 链接 [text](url)
	regexp.MustCompile(`\[([^\]]*)\]\(.*?\)`),
	// 标题标记 #
	regexp.MustCompile(`^#{1,6}\s+`),
	// 粗体/斜体/删除线标记
	regexp.MustCompile(`\*{1,3}|_{1,3}|~~`),
	// 引用 >
	regexp.MustCompile(`^>\s?`),
	// 列表标记
	regexp.MustCompile(`^[\s]*[-*+]\s+`),
	regexp.MustCompile(`^[\s]*\d+\.\s+`),
	// 分割线
	regexp.MustCompile(`^[-*_]{3,}\s*$`),
}

// generateExcerpt 从 Markdown 生成纯文本摘要（最多 300 字符）
// MD 作为纯文本存储无 XSS 风险，前端由 Vditor 渲染
func generateExcerpt(md string) string {
	text := md

	// 按行处理，保留行结构
	lines := strings.Split(text, "\n")
	var cleaned []string
	for _, line := range lines {
		cleanedLine := line
		for _, re := range mdPatterns {
			if re == mdPatterns[2] {
				// 链接保留文字: [text](url) → text
				cleanedLine = re.ReplaceAllString(cleanedLine, "$1")
			} else {
				cleanedLine = re.ReplaceAllString(cleanedLine, "")
			}
		}
		cleanedLine = strings.TrimSpace(cleanedLine)
		if cleanedLine != "" {
			cleaned = append(cleaned, cleanedLine)
		}
	}

	result := strings.Join(cleaned, " ")

	// 按 rune 截断，不切中文字符
	const maxChars = 300
	if utf8.RuneCountInString(result) > maxChars {
		runes := []rune(result)
		result = string(runes[:maxChars]) + "..."
	}

	return result
}

// PostService 帖子业务逻辑
type PostService struct {
	repo postStore
	ss   *config.SiteSettings
}

// NewPostService 构造函数
func NewPostService(repo postStore, ss *config.SiteSettings) *PostService {
	return &PostService{
		repo: repo,
		ss:   ss,
	}
}

// auditEnabled 审核是否开启
func (s *PostService) auditEnabled() bool {
	return s.ss.IsAuditEnabled()
}

// findPost 按 ID 查找帖子，区分"未找到"和"数据库错误"
func (s *PostService) findPost(id uint) (*model.Post, error) {
	post, err := s.repo.FindByID(id)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, common.ErrPostNotFound
		}
		return nil, fmt.Errorf("查询帖子失败: %w", err)
	}
	return post, nil
}

// findPostWithAuthor 按 ID 查找帖子（含作者名），区分"未找到"和"数据库错误"
func (s *PostService) findPostWithAuthor(id uint) (*model.Post, error) {
	post, err := s.repo.FindByIDWithAuthor(id)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, common.ErrPostNotFound
		}
		return nil, fmt.Errorf("查询帖子失败: %w", err)
	}
	return post, nil
}

// Create 创建帖子
// body 为 Vditor 输出的 Markdown，后端直接存储不做 HTML 消毒
// MD 是纯文本，无 XSS 注入风险；前端渲染时由 Vditor 转 HTML
func (s *PostService) Create(userID uint, title, body string) (*model.Post, error) {
	status := model.PostStatusApproved
	if s.auditEnabled() {
		status = model.PostStatusDraft
	}

	post := &model.Post{
		Title:        title,
		Body:         body,
		Excerpt:      generateExcerpt(body),
		UserID:       userID,
		Status:       status,
		AllowComment: true,
	}
	if err := s.repo.Create(post); err != nil {
		return nil, err
	}
	return post, nil
}

// GetByID 按 ID 获取帖子（含作者名，仅 approved 公开可见）
func (s *PostService) GetByID(id uint) (*model.Post, error) {
	return s.findPostWithAuthor(id)
}

// List 公开帖子列表（仅 approved）
func (s *PostService) List(keyword string, page, pageSize int) ([]model.Post, int64, error) {
	p := common.Pagination{Page: page, PageSize: pageSize}
	p.DefaultPagination()
	return s.repo.FindPageable(keyword, p.Offset(), p.PageSize)
}

// ListAdmin 管理后台帖子列表（全状态）
func (s *PostService) ListAdmin(keyword, status string, page, pageSize int) ([]model.Post, int64, error) {
	p := common.Pagination{Page: page, PageSize: pageSize}
	p.DefaultPagination()
	return s.repo.FindAdminPageable(keyword, status, p.Offset(), p.PageSize)
}

// Update 编辑帖子（权限在 controller 层检查）
func (s *PostService) Update(postID uint, title, body string) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}

	if post.Status == model.PostStatusPending || post.Status == model.PostStatusLocked {
		return common.ErrPostCannotEdit
	}

	post.Title = title
	post.Body = body
	post.Excerpt = generateExcerpt(body)

	// rejected 状态编辑后自动重置为 draft
	if post.Status == model.PostStatusRejected {
		post.Status = model.PostStatusDraft
		post.RejectReason = ""
	}

	return s.repo.Update(post)
}

// Delete 软删除（权限在 controller 层检查）
func (s *PostService) Delete(postID uint) error {
	return s.repo.SoftDelete(postID)
}

// SubmitForAudit 提交审核：draft → pending
func (s *PostService) SubmitForAudit(postID uint) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}
	if post.Status != model.PostStatusDraft && post.Status != model.PostStatusRejected {
		return common.ErrPostCannotSubmit
	}
	post.Status = model.PostStatusPending
	return s.repo.Update(post)
}

// Approve 审核通过：pending → approved
func (s *PostService) Approve(postID uint) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}
	if post.Status != model.PostStatusPending {
		return common.ErrPostCannotApprove
	}
	post.Status = model.PostStatusApproved
	post.RejectReason = ""
	return s.repo.Update(post)
}

// Reject 退回：pending/approved → rejected
func (s *PostService) Reject(postID uint, reason string) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}
	if post.Status != model.PostStatusPending && post.Status != model.PostStatusApproved {
		return common.ErrPostCannotReject
	}
	post.Status = model.PostStatusRejected
	post.RejectReason = reason
	return s.repo.Update(post)
}

// Lock 锁定：任意状态 → locked（管理员可随时锁定）
func (s *PostService) Lock(postID uint) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}
	post.Status = model.PostStatusLocked
	return s.repo.Update(post)
}

// Unlock 解锁：locked → 草稿
func (s *PostService) Unlock(postID uint) error {
	post, err := s.findPost(postID)
	if err != nil {
		return err
	}
	if post.Status != model.PostStatusLocked {
		return common.ErrPostCannotUnlock
	}
	post.Status = model.PostStatusDraft
	return s.repo.Update(post)
}

// Restore 恢复软删除
func (s *PostService) Restore(postID uint) error {
	return s.repo.Restore(postID)
}