feat(share): add Open Graph preview for social media crawlers

Add middleware to intercept social media bot requests and return
OG meta tags for share links, enabling rich previews on platforms
like Facebook, Twitter, Discord, etc.

inventory/share.go

@@ -23,6 +23,14 @@ type (
 	LoadShareUser struct{}
 )
 
+// WithShareEagerLoad returns a context with share eager loading options enabled.
+// This loads the share's associated user and file when querying.
+func WithShareEagerLoad(ctx context.Context) context.Context {
+	ctx = context.WithValue(ctx, LoadShareUser{}, true)
+	ctx = context.WithValue(ctx, LoadShareFile{}, true)
+	return ctx
+}
+
 var (
 	ErrShareLinkExpired  = fmt.Errorf("share link expired")
 	ErrOwnerInactive     = fmt.Errorf("owner is inactive")

middleware/share_preview.go

@@ -0,0 +1,255 @@
+package middleware
+
+import (
+	"bytes"
+	"crypto/subtle"
+	"fmt"
+	"html/template"
+	"net/url"
+	"strings"
+
+	"github.com/cloudreve/Cloudreve/v4/application/dependency"
+	"github.com/cloudreve/Cloudreve/v4/ent"
+	"github.com/cloudreve/Cloudreve/v4/inventory"
+	"github.com/cloudreve/Cloudreve/v4/inventory/types"
+	"github.com/cloudreve/Cloudreve/v4/pkg/cluster/routes"
+	"github.com/cloudreve/Cloudreve/v4/pkg/hashid"
+	"github.com/gin-gonic/gin"
+)
+
+const (
+	ogStatusInvalidLink      = "Invalid Link"
+	ogStatusShareUnavailable = "Share Unavailable"
+	ogStatusPasswordRequired = "Password Required"
+	ogStatusNeedLogin        = "Login Required"
+)
+
+type ogData struct {
+	SiteName    string
+	Title       string
+	Description string
+	ImageURL    string
+	ShareURL    string
+	RedirectURL string
+}
+
+const ogHTMLTemplate = `<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <meta property="og:title" content="{{.Title}}">
+    <meta property="og:description" content="{{.Description}}">
+    <meta property="og:image" content="{{.ImageURL}}">
+    <meta property="og:url" content="{{.ShareURL}}">
+    <meta property="og:type" content="website">
+    <meta property="og:site_name" content="{{.SiteName}}">
+    <meta name="twitter:card" content="summary">
+    <meta name="twitter:title" content="{{.Title}}">
+    <meta name="twitter:description" content="{{.Description}}">
+    <meta name="twitter:image" content="{{.ImageURL}}">
+    <title>{{.Title}} - {{.SiteName}}</title>
+</head>
+<body>
+    <script>window.location.href = "{{.RedirectURL}}";</script>
+    <noscript><a href="{{.RedirectURL}}">{{.Title}}</a></noscript>
+</body>
+</html>`
+
+var ogTemplate = template.Must(template.New("og").Parse(ogHTMLTemplate))
+
+var socialMediaBots = []string{
+	"facebookexternalhit",
+	"facebookcatalog",
+	"facebot",
+	"twitterbot",
+	"linkedinbot",
+	"discordbot",
+	"telegrambot",
+	"slackbot",
+	"whatsapp",
+}
+
+func isSocialMediaBot(ua string) bool {
+	ua = strings.ToLower(ua)
+	for _, bot := range socialMediaBots {
+		if strings.Contains(ua, bot) {
+			return true
+		}
+	}
+	return false
+}
+
+// SharePreview 为社交媒体爬虫渲染OG预览页面
+func SharePreview(dep dependency.Dep) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if !isSocialMediaBot(c.GetHeader("User-Agent")) {
+			c.Next()
+			return
+		}
+
+		id, password := extractShareParams(c)
+		if id == "" {
+			c.Next()
+			return
+		}
+
+		html := renderShareOGPage(c, dep, id, password)
+		c.Header("Content-Type", "text/html; charset=utf-8")
+		c.Header("Cache-Control", "public, no-cache")
+		c.String(200, html)
+		c.Abort()
+	}
+}
+
+func extractShareParams(c *gin.Context) (id, password string) {
+	urlPath := c.Request.URL.Path
+
+	if strings.HasPrefix(urlPath, "/s/") {
+		parts := strings.Split(strings.TrimPrefix(urlPath, "/s/"), "/")
+		if len(parts) >= 1 && parts[0] != "" {
+			id = parts[0]
+			if len(parts) >= 2 {
+				password = parts[1]
+			}
+		}
+	} else if urlPath == "/home" || urlPath == "/home/" {
+		rawPath := c.Query("path")
+		if strings.HasPrefix(rawPath, "cloudreve://") {
+			u, err := url.Parse(rawPath)
+			if err != nil {
+				return "", ""
+			}
+			if strings.ToLower(u.Host) != "share" || u.User == nil {
+				return "", ""
+			}
+			id = u.User.Username()
+			password, _ = u.User.Password()
+		}
+	}
+
+	if len(id) > 32 || len(password) > 32 {
+		return "", ""
+	}
+	return id, password
+}
+
+func renderShareOGPage(c *gin.Context, dep dependency.Dep, id, password string) string {
+	settings := dep.SettingProvider()
+	siteBasic := settings.SiteBasic(c)
+	pwa := settings.PWA(c)
+	base := settings.SiteURL(c)
+
+	data := &ogData{
+		SiteName:    siteBasic.Name,
+		Title:       siteBasic.Name,
+		Description: siteBasic.Description,
+		ShareURL:    routes.MasterShareUrl(base, id, "").String(),
+		RedirectURL: routes.MasterShareLongUrl(id, password).String(),
+	}
+
+	if pwa.LargeIcon != "" {
+		data.ImageURL = resolveURL(base, pwa.LargeIcon)
+	} else if pwa.MediumIcon != "" {
+		data.ImageURL = resolveURL(base, pwa.MediumIcon)
+	}
+
+	shareID, err := dep.HashIDEncoder().Decode(id, hashid.ShareID)
+	if err != nil {
+		data.Description = ogStatusInvalidLink
+		return renderOGHTML(data)
+	}
+
+	share, err := loadShareForOG(c, dep, shareID)
+	if err != nil {
+		if ent.IsNotFound(err) {
+			data.Description = ogStatusInvalidLink
+		} else {
+			data.Description = ogStatusShareUnavailable
+		}
+		return renderOGHTML(data)
+	}
+
+	if err := inventory.IsValidShare(share); err != nil {
+		data.Description = ogStatusShareUnavailable
+		return renderOGHTML(data)
+	}
+
+	if !canAnonymousAccessShare(c, dep) {
+		data.Description = ogStatusNeedLogin
+		return renderOGHTML(data)
+	}
+
+	if share.Password != "" && subtle.ConstantTimeCompare([]byte(share.Password), []byte(password)) != 1 {
+		data.Description = ogStatusPasswordRequired
+		return renderOGHTML(data)
+	}
+
+	targetFile := share.Edges.File
+	if targetFile != nil {
+		fileName := targetFile.Name
+		fileType := types.FileType(targetFile.Type)
+
+		data.Title = fileName
+		if fileType == types.FileTypeFolder {
+			data.Description = "Folder"
+		} else {
+			data.Description = formatFileSize(targetFile.Size)
+		}
+
+		if share.Edges.User != nil && share.Edges.User.Nick != "" {
+			data.Description += " · " + share.Edges.User.Nick
+		}
+	}
+
+	return renderOGHTML(data)
+}
+
+func loadShareForOG(c *gin.Context, dep dependency.Dep, shareID int) (*ent.Share, error) {
+	ctx := inventory.WithShareEagerLoad(c)
+	return dep.ShareClient().GetByID(ctx, shareID)
+}
+
+func canAnonymousAccessShare(c *gin.Context, dep dependency.Dep) bool {
+	anonymousGroup, err := dep.GroupClient().AnonymousGroup(c)
+	if err != nil {
+		return false
+	}
+	return anonymousGroup.Permissions.Enabled(int(types.GroupPermissionShareDownload))
+}
+
+func renderOGHTML(data *ogData) string {
+	var buf bytes.Buffer
+	if err := ogTemplate.Execute(&buf, data); err != nil {
+		return ""
+	}
+	return buf.String()
+}
+
+func resolveURL(base *url.URL, path string) string {
+	if strings.HasPrefix(path, "http://") || strings.HasPrefix(path, "https://") {
+		return path
+	}
+	return base.ResolveReference(&url.URL{Path: path}).String()
+}
+
+func formatFileSize(size int64) string {
+	const (
+		KB = 1024
+		MB = 1024 * KB
+		GB = 1024 * MB
+		TB = 1024 * GB
+	)
+
+	switch {
+	case size >= TB:
+		return fmt.Sprintf("%.2f TB", float64(size)/TB)
+	case size >= GB:
+		return fmt.Sprintf("%.2f GB", float64(size)/GB)
+	case size >= MB:
+		return fmt.Sprintf("%.2f MB", float64(size)/MB)
+	case size >= KB:
+		return fmt.Sprintf("%.2f KB", float64(size)/KB)
+	default:
+		return fmt.Sprintf("%d B", size)
+	}
+}

routers/router.go

@@ -208,6 +208,7 @@ func initMasterRouter(dep dependency.Dep) *gin.Engine {
 		静态资源
 	*/
 	r.Use(gzip.Gzip(gzip.DefaultCompression, gzip.WithExcludedPaths([]string{"/api/"})))
+	r.Use(middleware.SharePreview(dep))
 	r.Use(middleware.FrontendFileHandler(dep))
 	r.GET("manifest.json", controllers.Manifest)