plugins: added the article Jekyll plugin

This plugin adds og:type related tags depending on whether the given page is a
website or an article.

Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>

4 files changed, 113 insertions, 12 deletions

diff --git a/_layouts/default.html b/_layouts/default.html
index 4053b9b..5668661 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -43,7 +43,8 @@
     {% endif %}
     <meta property="og:title" content="{{ title }}" />
     <meta property="og:description" content="{{ description }}" />
-    <meta property="og:type" content="website" />
+
+    {% render_type_tags %}
 
     {% comment %}<!-- Twitter stuff -->{% endcomment %}
     <meta name="twitter:card" content="summary_large_image" />
diff --git a/_plugins/article.rb b/_plugins/article.rb
new file mode 100644
index 0000000..3107b4a
--- /dev/null
+++ b/_plugins/article.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+# Copyright (C) 2019 Miquel Sabaté Solà <mikisabate@gmail.com>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+require "time"
+require_relative "render_helper"
+
+module Jekyll
+  # Render og:type related tags.
+  class RenderTypeTags < Liquid::Tag
+    include ::Jekyll::RenderHelper
+
+    def render(context)
+      if ["posts"].include?(context["page"]["collection"])
+        render_article_tags(context["page"])
+      else
+        '<meta property="og:type" content="website" />'
+      end
+    end
+
+    protected
+
+    # Render all the tags related to the article og:type.
+    def render_article_tags(page)
+      tags = page["tags"].inject("") { |acc, t| acc + render_meta("article:tag", t) }
+
+      '<meta property="og:type" content="article" />' +
+        render_meta("og:author", "Miquel Sabaté Solà") +
+        render_meta("profile:first_name", "Miquel") +
+        render_meta("profile:last_name", "Sabaté Solà") +
+        render_meta("profile:username", "mssola") +
+        render_meta("profile:gender", "male") +
+        render_meta("article:section", page["collection"]) +
+        render_meta("article:published_time", published_time(page)) +
+        render_meta("article:modified_time", modified_time(page)) +
+        tags
+    end
+
+    # Returns the published time of the given page.
+    def published_time(page)
+      # We could do fancy stuff like using DateTime.strptime and so on, but
+      # Jekyll completely disregards the hour, minutes, etc., so why bother.
+      page["date"].to_s.split.first
+    end
+
+    # Returns the modified time of the given page.
+    def modified_time(page)
+      path = File.expand_path(File.join(File.dirname(__FILE__), "..", page["path"]))
+      out  = `git log -n 1 --pretty='format:%cd' --date=iso8601-strict -- #{path}`
+
+      begin
+        Time.iso8601(out)
+        out
+      rescue ArgumentError => e
+        puts "[WARNING] Could not parse the given modified time from Git: #{e}"
+        nil
+      end
+    end
+  end
+end
+
+Liquid::Template.register_tag("render_type_tags", Jekyll::RenderTypeTags)
diff --git a/_plugins/render_helper.rb b/_plugins/render_helper.rb
new file mode 100644
index 0000000..dc18ba4
--- /dev/null
+++ b/_plugins/render_helper.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+# Copyright (C) 2019 Miquel Sabaté Solà <mikisabate@gmail.com>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+module Jekyll
+  # RenderHelper implements methods that help other plugins to render HTML code.
+  module RenderHelper
+    # Render an HTML meta tag with the given property and content
+    # attributes. You may optionally pass a `name` argument. When true, it will
+    # use "name" instead of "property". Defaults to nil.
+    def render_meta(property, content, name: nil)
+      if name
+        "<meta name=\"#{property}\" content=\"#{content}\" />"
+      else
+        "<meta property=\"#{property}\" content=\"#{content}\" />"
+      end
+    end
+  end
+end
diff --git a/_plugins/twitter.rb b/_plugins/twitter.rb
index e65831b..e04eecc 100644
--- a/_plugins/twitter.rb
+++ b/_plugins/twitter.rb
@@ -15,9 +15,13 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+require_relative "render_helper"
+
 module Jekyll
   # Render the OG image meta HTML tag for the currently rendered page.
   class RenderOGImageTag < Liquid::Tag
+    include ::Jekyll::RenderHelper
+
     # The path to be used when the current page does not have a specific image.
     DEFAULT_PATH = "/images/default.png"
 
@@ -44,17 +48,6 @@ module Jekyll
     def normalize(str)
       str.gsub(/\s/, "-").downcase
     end
-
-    # Render an HTML meta tag with the given property and content
-    # attributes. You may optionally pass a `name` argument. When true, it will
-    # use "name" instead of "property". Defaults to nil.
-    def render_meta(property, content, name: nil)
-      if name
-        "<meta name=\"#{property}\" content=\"#{content}\" />"
-      else
-        "<meta property=\"#{property}\" content=\"#{content}\" />"
-      end
-    end
   end
 end