Add post tags, with a tag page and two side-column modules

Posts can now carry tags, set on the post form as a checklist of the
blog's existing tags plus a comma-separated box for new ones (no JS).
A tag is a name and a unique slug, so "Go" and "go" are one tag and
Greek tags get readable URLs; tags no post uses any more are deleted.

On the blog, tags appear under the post date and link to /tag/<slug>,
which lists the published posts from every page, paginated like a page.
Two new layout modules show them: a Tags list (with counts, by use) and
a Tag cloud (alphabetical, sized by use). Both are only fetched when a
visible module needs them.

The article loop and pager move to a shared postlist partial; while
there, the pager stops adding a trailing slash — /news/?p=2 was a 404
because a {page} wildcard never matches one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 23 insertions, 2 deletions

diff --git a/internal/web/handlers_posts.go b/internal/web/handlers_posts.go
index d38c5f2..16d9cf2 100644
--- a/internal/web/handlers_posts.go
+++ b/internal/web/handlers_posts.go
@@ -54,6 +54,11 @@ func (s *Server) handlePostForm(w http.ResponseWriter, r *http.Request) {
 		s.serverError(w, err)
 		return
 	}
+	allTags, err := blogStore(r).ListTags(r.Context())
+	if err != nil {
+		s.serverError(w, err)
+		return
+	}
 	p := &store.Post{Published: true, CreatedAt: time.Now()}
 	if r.PathValue("id") != "" {
 		if p = s.loadPost(w, r); p == nil {
@@ -64,7 +69,7 @@ func (s *Server) handlePostForm(w http.ResponseWriter, r *http.Request) {
 	} else if hp, err := blogStore(r).HomePage(r.Context()); err == nil {
 		p.PageID = hp.ID
 	}
-	s.render(w, r, "dashboard/post_form.html", map[string]any{"post": p, "pages": pages})
+	s.render(w, r, "dashboard/post_form.html", map[string]any{"post": p, "pages": pages, "allTags": allTags, "tagged": tagSet(p.Tags), "newTags": ""})
 }
 
 func (s *Server) handlePostSave(w http.ResponseWriter, r *http.Request) {
@@ -74,6 +79,11 @@ func (s *Server) handlePostSave(w http.ResponseWriter, r *http.Request) {
 		s.serverError(w, err)
 		return
 	}
+	allTags, err := blogStore(r).ListTags(r.Context())
+	if err != nil {
+		s.serverError(w, err)
+		return
+	}
 	p := &store.Post{CreatedAt: time.Now()}
 	if r.PathValue("id") != "" {
 		if p = s.loadPost(w, r); p == nil {
@@ -85,12 +95,16 @@ func (s *Server) handlePostSave(w http.ResponseWriter, r *http.Request) {
 	p.BodyMD = strings.ReplaceAll(r.FormValue("body"), "\r\n", "\n")
 	p.Published = r.FormValue("published") == "on"
 	p.PageID, _ = strconv.ParseInt(r.FormValue("page_id"), 10, 64)
+	// The ticked existing tags and the comma-separated new ones are one list.
+	tags, tagsOK := parseTags(append(r.Form["tag"], strings.Split(r.FormValue("new_tags"), ",")...))
+	p.Tags = tags
 	autoSlug := p.Slug == ""
 	if autoSlug {
 		p.Slug = slug.Make(p.Title)
 	}
 	fail := func(status int, msg string) {
-		s.renderStatus(w, r, status, "dashboard/post_form.html", map[string]any{"post": p, "pages": pages, "error": msg})
+		s.renderStatus(w, r, status, "dashboard/post_form.html", map[string]any{"post": p, "pages": pages, "error": msg,
+			"allTags": allTags, "tagged": tagSet(p.Tags), "newTags": r.FormValue("new_tags")})
 	}
 	if at := strings.TrimSpace(r.FormValue("posted_at")); at != "" { // blank keeps the current date
 		var ok bool
@@ -124,6 +138,9 @@ func (s *Server) handlePostSave(w http.ResponseWriter, r *http.Request) {
 	case len(p.BodyMD) > 200_000:
 		fail(http.StatusBadRequest, s.tr(r, "Post is too long (200 KB max)."))
 		return
+	case !tagsOK:
+		fail(http.StatusBadRequest, s.tr(r, "Tags: at most 20 per post, 40 characters each."))
+		return
 	}
 	p.BodyHTML = markdown.Render(p.BodyMD)
 	base := p.Slug
@@ -149,6 +166,10 @@ func (s *Server) handlePostSave(w http.ResponseWriter, r *http.Request) {
 		s.serverError(w, err)
 		return
 	}
+	if err := blogStore(r).SetPostTags(r.Context(), p.ID, tags); err != nil {
+		s.serverError(w, err)
+		return
+	}
 	redirectOK(w, r, "/b/"+blog.Subdomain+"/posts/"+strconv.FormatInt(p.ID, 10)+"/edit", s.tr(r, "Saved. Refresh your blog to see it."))
 }