feat: add fediverse_creator handle for Mastodon attribution

Expose a per-post fediverse_creator frontmatter field plus a site-wide
default in config.toml ([site].fediverse_creator). The handle is returned
in the post and site payloads, rendered as <dc:creator> in the RSS feed
and as authors[].name in the JSON feed, so a front-end can drop it into
<meta name="fediverse:creator"> on rendered pages. Per-post value
overrides the site default. Validated against a simple @user@host regex.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

lib/volumen/config.rb

@@ -18,7 +18,8 @@ module Volumen
         "description" => "A blog powered by volumen.",
         "base_url" => "https://example.com",
         "language" => "en",
-        "author" => "Anonymous"
+        "author" => "Anonymous",
+        "fediverse_creator" => nil
       }.freeze,
       "admin" => {
         "password_hash" => "",
@@ -46,6 +47,9 @@ module Volumen
       base_url = "https://example.com"
       language = "en"
       author = "Anonymous"
+      # Default fediverse handle surfaced in <meta name="fediverse:creator">
+      # by frontends consuming the API. Leave empty to disable.
+      fediverse_creator = ""
 
       [admin]
       # Bootstrap admin login: paste a hash from `volumen hash-password` to sign

lib/volumen/post.rb

@@ -7,6 +7,8 @@ require_relative "markdown"
 module Volumen
   # A single blog post: TOML frontmatter metadata plus a Markdown body.
   class Post
+    FEDIVERSE_CREATOR_REGEX = /\A@[^@\s]+@[^@\s]+\z/
+
     attr_reader :metadata, :body
     attr_accessor :path
 
@@ -56,6 +58,18 @@ module Volumen
       metadata["cover"]
     end
 
+    def fediverse_creator
+      value = metadata["fediverse_creator"]
+      return nil if value.nil?
+
+      text = value.to_s.strip
+      text.empty? ? nil : text
+    end
+
+    def valid_fediverse_creator?
+      fediverse_creator&.match?(FEDIVERSE_CREATOR_REGEX)
+    end
+
     def publish_at
       metadata["publish_at"]
     end
@@ -112,6 +126,7 @@ module Volumen
         "lang" => lang,
         "tags" => tags,
         "author" => author,
+        "fediverse_creator" => fediverse_creator,
         "cover" => cover,
         "reading_time" => reading_time,
         "translations" => translations,

lib/volumen/server.rb

@@ -84,7 +84,12 @@ module Volumen
     end
 
     def site_payload
-      config.site.slice("title", "description", "base_url", "language", "author")
+      config.site.slice("title", "description", "base_url", "language", "author",
+                        "fediverse_creator")
+    end
+
+    def site_fediverse_creator
+      config.site["fediverse_creator"]
     end
 
     def posts_payload
@@ -146,7 +151,7 @@ module Volumen
       items = published_posts.first(20).map { |post| feed_item(post) }.join("\n")
       <<~XML
         <?xml version="1.0" encoding="UTF-8"?>
-        <rss version="2.0">
+        <rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/">
           <channel>
             <title>#{escape(site["title"])}</title>
             <link>#{escape(base_url)}</link>
@@ -165,12 +170,14 @@ module Volumen
             else
               ""
             end
+      creator = post.fediverse_creator
+      creator_tag = creator ? "\n      <dc:creator>#{escape(creator)}</dc:creator>" : ""
       <<~XML.chomp
         <item>
           <title>#{escape(post.title)}</title>
           <link>#{escape(link)}</link>
           <guid>#{escape(link)}</guid>
-          <description>#{escape(post.excerpt)}</description>#{pub}
+          <description>#{escape(post.excerpt)}</description>#{pub}#{creator_tag}
         </item>
       XML
     end
@@ -208,6 +215,8 @@ module Volumen
         "date_published" => iso_date(post.metadata["date"]),
         "tags" => post.tags
       }
+      author = post.fediverse_creator || site_fediverse_creator
+      item["authors"] = [{ "name" => author }] if author
       item.reject { |_k, v| v.nil? || v == "" || v == [] }
     end
 
@@ -401,7 +410,15 @@ module Volumen
       existing = store.find(params["slug"])
       halt(404, "Not found") if existing.nil?
 
-      store.save(post_from_params(params, existing: existing))
+      post = post_from_params(params, existing: existing)
+      error = fediverse_creator_error(post)
+      if error
+        @mode = :edit
+        @post = post
+        @error = error
+        return erb(:form)
+      end
+      store.save(post)
       redirect to("/admin/")
     end
 
@@ -410,7 +427,7 @@ module Volumen
       return "Invalid slug." unless post.slug.match?(SLUG_REGEX)
       return "A post with that slug already exists." if store.find(post.slug)
 
-      nil
+      fediverse_creator_error(post)
     end
 
     def post_from_params(http_params, existing: nil)
@@ -419,6 +436,7 @@ module Volumen
         "slug" => presence(http_params["slug"]) || existing&.slug,
         "lang" => presence(http_params["lang"]),
         "author" => presence(http_params["author"]),
+        "fediverse_creator" => presence(http_params["fediverse_creator"]),
         "date" => parse_date(http_params["date"]),
         "publish_at" => parse_date(http_params["publish_at"]),
         "tags" => parse_tags(http_params["tags"]),
@@ -432,6 +450,17 @@ module Volumen
       post
     end
 
+    def fediverse_creator_error(post)
+      value = post.metadata["fediverse_creator"]
+      return nil if value.nil?
+
+      if Post::FEDIVERSE_CREATOR_REGEX.match?(value.to_s)
+        nil
+      else
+        "Fediverse creator must look like @user@host."
+      end
+    end
+
     def clean_metadata(metadata)
       metadata.reject { |_key, value| value.nil? || value == "" || value == [] || value == false }
     end

lib/volumen/web/views/form.erb

@@ -16,6 +16,10 @@
     </label>
     <label>Language <input type="text" name="lang" value="<%= h(@post.lang) %>"></label>
     <label>Author <input type="text" name="author" value="<%= h(@post.author) %>"></label>
+    <label>Fediverse creator
+      <input type="text" name="fediverse_creator" value="<%= h(@post.fediverse_creator) %>"
+             placeholder="@user@instance.tld">
+    </label>
     <label>Date <input type="date" name="date" value="<%= h(@post.date_string) %>"></label>
     <label>Publish at
       <input type="date" name="publish_at"