Add FlatHub link inline macro

gems/lib/asciidoctor/flathub-link-inline-macro/README.adoc

@@ -0,0 +1,28 @@
+= Flathub link inline macro
+:toc:
+
+
+A shorthand for linking applications from link:https://flathub.org[FlatHub].
+
+
+== Synopsis
+
+[source, asciidoc]
+----
+flathub:$APP_ID[$CAPTION]
+----
+
+Where...
+
+- `$APP_ID` is the application ID of the program on Flathub.
+
+- `$CAPTION` is the link text to be used.
+By default, it will get the appstream metadata from FlatHub and use the display name.
+Take note it creates an additional network request to get the name.
+
+
+== Example usage
+
+- `flathub:org.gnome.design.IconLibrary[]` links to the link:https://flathub.org/apps/org.gnome.design.IconLibrary[FlatHub page of GNOME Icon Library] with `Icon Library` as the link text.
+
+- `flathub:org.gnome.design.IconLibrary[GNOME Icon Library]` is the same as the previous list item but with its link text replaced with `GNOME Icon Library`.

gems/lib/asciidoctor/flathub-link-inline-macro/extension.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require 'json'
+require 'open-uri'
+require 'open-uri/cached'
+
+class FlathubLinkInlineMacro < Asciidoctor::Extensions::InlineMacroProcessor
+  use_dsl
+
+  named :flathub
+  name_positional_attributes 'caption'
+
+  def process(parent, target, attrs)
+    doc = parent.document
+
+    # FlatHub API seems to have no documentation aside from the source code.
+    # You can easily infer the API with its source code at
+    # https://github.com/flathub/website.
+    app_id = target
+    app_metadata_uri = %(https://flathub.org/api/v2/appstream/#{app_id})
+
+    headers = {
+      'Accept' => 'application/json',
+      'User-Agent' => ::Asciidoctor::FoodogsquaredCustomExtensions::USER_AGENT
+    }
+
+    if attrs['caption'].nil?
+      metadata = OpenURI.open_uri(app_metadata_uri, headers) { |f| JSON.parse(f.read) }
+      attrs['caption'] = metadata['name']
+    end
+
+    url = %(https://flathub.org/apps/#{app_id})
+    doc.register :links, url
+    create_anchor parent, attrs['caption'], type: :link, target: url
+  end
+end

gems/lib/asciidoctor/foodogsquared-extensions.rb

@@ -18,6 +18,7 @@ require_relative 'wikipedia-inline-macro/extension'
 require_relative 'package-indices-link-macro/extension'
 require_relative 'fdroid-link-inline-macro/extension'
 require_relative 'musicbrainz-link-inline-macro/extension'
+require_relative 'flathub-link-inline-macro/extension'
 require_relative 'repology-link-inline-macro/extension'
 
 Asciidoctor::Extensions.register do
@@ -38,12 +39,16 @@ Asciidoctor::Extensions.register do
 
   inline_macro WikipediaInlineMacro
 
+  # Package indices
   inline_macro CtanLinkInlineMacro
   inline_macro PypiLinkInlineMacro
   inline_macro CratesIOLinkInlineMacro
+
+  # App stores
   inline_macro FDroidLinkInlineMacro
+  inline_macro FlathubLinkInlineMacro
 
+  # Databases
   inline_macro MusicBrainzLinkInlineMacro
-
   inline_macro RepologyLinkInlineMacro
 end