Set og:description meta tag to diary entry description

app/controllers/diary_entries_controller.rb

@@ -68,8 +68,11 @@ def show
     @entry = entries.find_by(:id => params[:id])
     if @entry
       @title = t ".title", :user => params[:display_name], :title => @entry.title
-      @og_image = @entry.body.image
-      @og_image_alt = @entry.body.image_alt
+      @opengraph_properties = {
+        "og:image" => @entry.body.image,
+        "og:image:alt" => @entry.body.image_alt,
+        "og:description" => @entry.body.description
+      }
       @comments = can?(:unhide, DiaryComment) ? @entry.comments : @entry.visible_comments
     else
       @title = t "diary_entries.no_such_entry.title", :id => params[:id]

app/helpers/open_graph_helper.rb

@@ -1,15 +1,15 @@
 module OpenGraphHelper
   require "addressable/uri"
 
-  def opengraph_tags(title = nil, og_image = nil, og_image_alt = nil)
+  def opengraph_tags(title, properties)
     tags = {
       "og:site_name" => t("layouts.project_name.title"),
       "og:title" => title || t("layouts.project_name.title"),
       "og:type" => "website",
       "og:url" => url_for(:only_path => false),
-      "og:description" => t("layouts.intro_text")
+      "og:description" => properties["og:description"] || t("layouts.intro_text")
     }.merge(
-      opengraph_image_properties(og_image, og_image_alt)
+      opengraph_image_properties(properties)
     )
 
     safe_join(tags.map do |property, content|
@@ -19,13 +19,13 @@ def opengraph_tags(title = nil, og_image = nil, og_image_alt = nil)
 
   private
 
-  def opengraph_image_properties(og_image, og_image_alt)
+  def opengraph_image_properties(properties)
     begin
-      if og_image
-        properties = {}
-        properties["og:image"] = Addressable::URI.join(root_url, og_image).normalize
-        properties["og:image:alt"] = og_image_alt if og_image_alt
-        return properties
+      if properties["og:image"]
+        image_properties = {}
+        image_properties["og:image"] = Addressable::URI.join(root_url, properties["og:image"]).normalize
+        image_properties["og:image:alt"] = properties["og:image:alt"] if properties["og:image:alt"]
+        return image_properties
       end
     rescue Addressable::URI::InvalidURIError
       # return default image

app/views/layouts/_meta.html.erb

@@ -21,7 +21,7 @@
 <% end -%>
 <%= tag.link :rel => "search", :type => "application/opensearchdescription+xml", :title => "OpenStreetMap Search", :href => asset_path("osm.xml") %>
 <%= tag.meta :name => "description", :content => "OpenStreetMap is the free wiki world map." %>
-<%= opengraph_tags(@title, @og_image, @og_image_alt) %>
+<%= opengraph_tags(@title, @opengraph_properties || {}) %>
 <% if flash[:matomo_goal] -%>
 <%= tag.meta :name => "matomo-goal", :content => flash[:matomo_goal] %>
 <% end -%>

lib/rich_text.rb

@@ -3,6 +3,8 @@ module RichText
     "Business Description:", "Additional Keywords:"
   ].freeze
 
+  MAX_DESCRIPTION_LENGTH = 500
+
   def self.new(format, text)
     case format
     when "html" then HTML.new(text || "")
@@ -57,6 +59,10 @@ def image_alt
       nil
     end
 
+    def description
+      nil
+    end
+
     protected
 
     def simple_format(text)
@@ -105,6 +111,12 @@ def image_alt
       @image_element.attr["alt"] if @image_element
     end
 
+    def description
+      return @description if defined? @description
+
+      @description = first_truncated_text_content(document.root)
+    end
+
     private
 
     def document
@@ -120,9 +132,44 @@ def first_image_element(element)
       end
     end
 
+    def first_truncated_text_content(element)
+      if paragraph?(element)
+        truncated_text_content(element)
+      else
+        element.children.find do |child|
+          text = first_truncated_text_content(child)
+          break text unless text.nil?
+        end
+      end
+    end
+
+    def truncated_text_content(element)
+      text = ""
+
+      append_text = lambda do |child|
+        if child.type == :text
+          text << child.value
+        else
+          child.children.each do |c|
+            append_text.call(c)
+            break if text.length > MAX_DESCRIPTION_LENGTH
+          end
+        end
+      end
+      append_text.call(element)
+
+      return nil if text.blank?
+
+      text.truncate(MAX_DESCRIPTION_LENGTH)
+    end
+
     def image?(element)
       element.type == :img || (element.type == :html_element && element.value == "img")
     end
+
+    def paragraph?(element)
+      element.type == :p || (element.type == :html_element && element.value == "p")
+    end
   end
 
   class Text < Base

test/controllers/diary_entries_controller_test.rb

@@ -744,6 +744,28 @@ def test_show_og_image_without_alt
     assert_dom "head meta[property='og:image:alt']", :count => 0
   end
 
+  def test_show_no_og_description
+    user = create(:user)
+    diary_entry = create(:diary_entry, :user => user, :body => "![nope](https://example.com/nope.jpg)")
+
+    get diary_entry_path(user, diary_entry)
+    assert_response :success
+    assert_dom "head meta[property='og:description']" do
+      assert_dom "> @content", I18n.t("layouts.intro_text")
+    end
+  end
+
+  def test_show_og_description
+    user = create(:user)
+    diary_entry = create(:diary_entry, :user => user, :body => "# Hello\n\n![hello](https://example.com/hello.jpg)\n\nFirst paragraph.\n\nSecond paragraph.")
+
+    get diary_entry_path(user, diary_entry)
+    assert_response :success
+    assert_dom "head meta[property='og:description']" do
+      assert_dom "> @content", "First paragraph."
+    end
+  end
+
   def test_hide
     user = create(:user)
     diary_entry = create(:diary_entry, :user => user)

test/lib/rich_text_test.rb

@@ -250,16 +250,18 @@ def test_text_spam_score
     assert_equal 141, r.spam_score.round
   end
 
-  def test_text_no_image
+  def test_text_no_opengraph_properties
     r = RichText.new("text", "foo https://example.com/ bar")
     assert_nil r.image
     assert_nil r.image_alt
+    assert_nil r.description
   end
 
-  def test_html_no_image
+  def test_html_no_opengraph_properties
     r = RichText.new("html", "foo <a href='https://example.com/'>bar</a> baz")
     assert_nil r.image
     assert_nil r.image_alt
+    assert_nil r.description
   end
 
   def test_markdown_no_image
@@ -328,6 +330,52 @@ def test_markdown_skip_html_image_without_src
     assert_equal "have src", r.image_alt
   end
 
+  def test_markdown_no_description
+    r = RichText.new("markdown", "#Nope")
+    assert_nil r.description
+  end
+
+  def test_markdown_description
+    r = RichText.new("markdown", "This is an article about something.")
+    assert_equal "This is an article about something.", r.description
+  end
+
+  def test_markdown_description_after_heading
+    r = RichText.new("markdown", "#Heading\n\nHere starts the text.")
+    assert_equal "Here starts the text.", r.description
+  end
+
+  def test_markdown_description_after_image
+    r = RichText.new("markdown", "![bar](https://example.com/image.jpg)\n\nThis is below the image.")
+    assert_equal "This is below the image.", r.description
+  end
+
+  def test_markdown_description_only_first_paragraph
+    r = RichText.new("markdown", "This thing.\n\nMaybe also that thing.")
+    assert_equal "This thing.", r.description
+  end
+
+  def test_markdown_description_elements
+    r = RichText.new("markdown", "*Something* **important** [here](https://example.com/).")
+    assert_equal "Something important here.", r.description
+  end
+
+  def test_markdown_html_description
+    r = RichText.new("markdown", "<p>Can use HTML tags.</p>")
+    assert_equal "Can use HTML tags.", r.description
+  end
+
+  def test_markdown_description_max_length
+    r = RichText.new("markdown", "x" * RichText::MAX_DESCRIPTION_LENGTH)
+    assert_equal "x" * RichText::MAX_DESCRIPTION_LENGTH, r.description
+
+    r = RichText.new("markdown", "y" * (RichText::MAX_DESCRIPTION_LENGTH + 1))
+    assert_equal "#{'y' * (RichText::MAX_DESCRIPTION_LENGTH - 3)}...", r.description
+
+    r = RichText.new("markdown", "*zzzzzzzzz*z" * ((RichText::MAX_DESCRIPTION_LENGTH + 1) / 10.0).ceil)
+    assert_equal "#{'z' * (RichText::MAX_DESCRIPTION_LENGTH - 3)}...", r.description
+  end
+
   private
 
   def assert_html(richtext, &block)