Implement ActivityPub remote follow form

activityPubTools.go

@@ -1,8 +1,14 @@
 package main
 
 import (
+	"encoding/json"
+	"fmt"
+	"io"
 	"net/http"
+	"net/url"
+	"strings"
 
+	"github.com/carlmjohnson/requests"
 	"github.com/go-chi/chi/v5"
 )
 
@@ -25,3 +31,67 @@ func (a *goBlog) apShowFollowers(w http.ResponseWriter, r *http.Request) {
 		},
 	})
 }
+
+func (a *goBlog) apRemoteFollow(w http.ResponseWriter, r *http.Request) {
+	blogName := chi.URLParam(r, "blog")
+	blog, ok := a.cfg.Blogs[blogName]
+	if !ok || blog == nil {
+		a.serveError(w, r, "Blog not found", http.StatusNotFound)
+		return
+	}
+	if user := r.FormValue("user"); user != "" {
+		// Parse instance
+		userParts := strings.Split(user, "@")
+		if len(userParts) < 2 {
+			a.serveError(w, r, "User must be of the form user@example.org or @user@example.org", http.StatusBadRequest)
+			return
+		}
+		user = userParts[len(userParts)-2]
+		instance := userParts[len(userParts)-1]
+		if user == "" || instance == "" {
+			a.serveError(w, r, "User or instance are empty", http.StatusBadRequest)
+			return
+		}
+		// Get webfinger
+		type webfingerLinkType struct {
+			Rel      string `json:"rel"`
+			Template string `json:"template"`
+		}
+		type webfingerType struct {
+			Links []*webfingerLinkType `json:"links"`
+		}
+		webfinger := &webfingerType{}
+		err := requests.URL(fmt.Sprintf("https://%s/.well-known/webfinger?resource=acct:%s@%s", instance, user, instance)).
+			Client(a.httpClient).
+			UserAgent(appUserAgent).
+			Handle(func(resp *http.Response) error {
+				defer resp.Body.Close()
+				return json.NewDecoder(io.LimitReader(resp.Body, 1000*1000)).Decode(webfinger)
+			}).
+			Fetch(r.Context())
+		if err != nil {
+			a.serveError(w, r, "Failed to query webfinger", http.StatusInternalServerError)
+			return
+		}
+		// Check webfinger and find template
+		template := ""
+		for _, link := range webfinger.Links {
+			if link.Rel == "http://ostatus.org/schema/1.0/subscribe" {
+				template = link.Template
+				break
+			}
+		}
+		if template == "" {
+			a.serveError(w, r, "Instance does not support subscribe schema version 1.0", http.StatusInternalServerError)
+			return
+		}
+		// Build redirect
+		redirect := strings.ReplaceAll(template, "{uri}", url.PathEscape(a.apIri(blog)))
+		http.Redirect(w, r, redirect, http.StatusFound)
+		return
+	}
+	// Render remote follow form
+	a.render(w, r, a.renderActivityPubRemoteFollow, &renderData{
+		BlogString: blogName,
+	})
+}

httpRouters.go

@@ -42,8 +42,11 @@ func (a *goBlog) activityPubRouter(r chi.Router) {
 	if ap := a.cfg.ActivityPub; ap != nil && ap.Enabled {
 		r.Route("/activitypub", func(r chi.Router) {
 			r.Post("/inbox/{blog}", a.apHandleInbox)
-			r.Post("/{blog}/inbox", a.apHandleInbox)
+			r.Post("/{blog}/inbox", a.apHandleInbox) // old
 			r.With(a.authMiddleware).Get("/{blog}/followers", a.apShowFollowers)
+			r.With(a.authMiddleware).Get("/followers/{blog}", a.apShowFollowers) // old
+			r.With(a.cacheMiddleware).Get("/remote_follow/{blog}", a.apRemoteFollow)
+			r.Post("/remote_follow/{blog}", a.apRemoteFollow)
 		})
 		r.Group(func(r chi.Router) {
 			r.Use(cacheLoggedIn, a.cacheMiddleware)

strings/de.yaml

@@ -23,6 +23,8 @@ editorpostdesc: "💡 Leere Parameter werden automatisch entfernt. Mehr möglich
 editorusetemplate: "Benutze Vorlage"
 emailopt: "E-Mail (optional)"
 fileuses: "Datei-Verwendungen"
+follow: "Folgen"
+followusingactivitypub: "Mit ActivityPub folgen"
 general: "Allgemein"
 gentts: "Text-To-Speech-Audio erzeugen"
 gpxhelper: "GPX-Helfer"

strings/default.yaml

@@ -30,6 +30,8 @@ editorusetemplate: "Use template"
 emailopt: "Email (optional)"
 feed: "Feed"
 fileuses: "file uses"
+follow: "Follow"
+followusingactivitypub: "Follow using ActivityPub"
 general: "General"
 gentts: "Generate Text-To-Speech audio"
 gpxhelper: "GPX helper"

ui.go

@@ -1631,6 +1631,33 @@ func (a *goBlog) renderActivityPubFollowers(hb *htmlbuilder.HtmlBuilder, rd *ren
 			}
 			hb.WriteElementClose("tbody")
 			hb.WriteElementClose("table")
+
+			hb.WriteElementClose("main")
+		},
+	)
+}
+
+func (a *goBlog) renderActivityPubRemoteFollow(hb *htmlbuilder.HtmlBuilder, rd *renderData) {
+	a.renderBase(
+		hb, rd,
+		func(hb *htmlbuilder.HtmlBuilder) {
+			a.renderTitleTag(hb, rd.Blog, a.ts.GetTemplateStringVariant(rd.Blog.Lang, "apfollowers"))
+		},
+		func(hb *htmlbuilder.HtmlBuilder) {
+			hb.WriteElementOpen("main")
+
+			// Title
+			hb.WriteElementOpen("h1")
+			hb.WriteEscaped(a.ts.GetTemplateStringVariant(rd.Blog.Lang, "followusingactivitypub"))
+			hb.WriteElementClose("h1")
+
+			// Form
+			hb.WriteElementOpen("form", "class", "fw p", "method", "post")
+			hb.WriteElementOpen("input", "type", "text", "name", "user", "placeholder", "user@example.org")
+			hb.WriteElementOpen("input", "type", "submit", "value", a.ts.GetTemplateStringVariant(rd.Blog.Lang, "follow"))
+			hb.WriteElementClose("form")
+
+			hb.WriteElementClose("main")
 		},
 	)
 }