mce/internal/service/post_service.go

package service

import (
	"bytes"
	"fmt"

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

	"github.com/microcosm-cc/bluemonday"
	"github.com/yuin/goldmark"
)

// sanitizePolicy 纵深防御：对 goldmark 输出的 HTML 再做一层消毒
// goldmark 默认已过滤原始 HTML 和危险链接，但 bluemonday 作为第二道防线
// UGC 策略会剥离 code/pre 的 class 属性，需要显式放行以保留 language-xxx
var sanitizePolicy = func() *bluemonday.Policy {
	p := bluemonday.UGCPolicy()
	p.AllowAttrs("class").OnElements("code", "pre")
	return p
}()

// postStore 帖子服务所需的最小仓储接口（ISP）
type postStore interface {
	Create(post *model.Post) error
	FindByID(id uint) (*model.Post, error)
	FindByIDWithAuthor(id uint) (*model.Post, error)
	FindPageable(keyword string, offset, limit int) ([]model.Post, int64, error)
	FindAdminPageable(keyword, status string, offset, limit int) ([]model.Post, int64, error)
	Update(post *model.Post) error
	SoftDelete(id uint) error
	Restore(id uint) error
}

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

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

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

// renderMarkdown 将 Markdown 文本渲染为安全 HTML
// goldmark（默认安全模式）→ bluemonday（纵深防御）
func (s *PostService) renderMarkdown(body string) (string, error) {
	var buf bytes.Buffer
	if err := s.md.Convert([]byte(body), &buf); err != nil {
		return "", fmt.Errorf("markdown render: %w", err)
	}
	return sanitizePolicy.Sanitize(buf.String()), nil
}

// RenderMarkdown 对外暴露，用于预览 API
func (s *PostService) RenderMarkdown(body string) (string, error) {
	return s.renderMarkdown(body)
}

// Create 创建帖子
func (s *PostService) Create(userID uint, title, body string) (*model.Post, error) {
	bodyHTML, err := s.renderMarkdown(body)
	if err != nil {
		return nil, err
	}

	status := model.PostStatusApproved
	if s.auditEnabled() {
		status = model.PostStatusDraft
	}

	post := &model.Post{
		Title:        title,
		Body:         body,
		BodyHTML:     bodyHTML,
		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) {
	post, err := s.repo.FindByIDWithAuthor(id)
	if err != nil {
		return nil, common.ErrUserNotFound // 复用哨兵表示资源不存在
	}
	return post, nil
}

// 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.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}

	if post.Status == model.PostStatusPending || post.Status == model.PostStatusLocked {
		return fmt.Errorf("当前状态不允许编辑")
	}

	bodyHTML, err := s.renderMarkdown(body)
	if err != nil {
		return err
	}

	post.Title = title
	post.Body = body
	post.BodyHTML = bodyHTML

	// 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.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}
	if post.Status != model.PostStatusDraft && post.Status != model.PostStatusRejected {
		return fmt.Errorf("仅草稿和已退回帖子可提交审核")
	}
	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.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}
	if post.Status != model.PostStatusPending {
		return fmt.Errorf("仅待审核帖子可通过")
	}
	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.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}
	if post.Status != model.PostStatusPending && post.Status != model.PostStatusApproved {
		return fmt.Errorf("仅待审核和已发布帖子可退回")
	}
	post.Status = model.PostStatusRejected
	post.RejectReason = reason
	return s.repo.Update(post)
}

// Lock 锁定：任意状态 → locked
func (s *PostService) Lock(postID uint) error {
	post, err := s.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}
	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.repo.FindByID(postID)
	if err != nil {
		return common.ErrUserNotFound
	}
	if post.Status != model.PostStatusLocked {
		return fmt.Errorf("仅锁定状态可解锁")
	}
	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)
}