Set Open Graph image to first image for diary entries

app/controllers/diary_entries_controller.rb

@@ -68,6 +68,7 @@ class DiaryEntriesController < ApplicationController
     @entry = entries.find_by(:id => params[:id])
     if @entry
       @title = t ".title", :user => params[:display_name], :title => @entry.title
+      @og_image = @entry.body.image
       @comments = can?(:unhidecomment, DiaryEntry) ? @entry.comments : @entry.visible_comments
     else
       @title = t "diary_entries.no_such_entry.title", :id => params[:id]

app/helpers/open_graph_helper.rb

@@ -1,10 +1,10 @@
 module OpenGraphHelper
-  def opengraph_tags(title = nil)
+  def opengraph_tags(title = nil, og_image = nil)
     tags = {
       "og:site_name" => t("layouts.project_name.title"),
       "og:title" => [title, t("layouts.project_name.title")].compact.join(" | "),
       "og:type" => "website",
-      "og:image" => image_url("osm_logo_256.png"),
+      "og:image" => og_image || image_url("osm_logo_256.png"),
       "og:url" => url_for(:only_path => false),
       "og:description" => t("layouts.intro_text")
     }

app/models/diary_entry.rb

@@ -50,7 +50,7 @@ class DiaryEntry < ApplicationRecord
   after_save :spam_check
 
   def body
-    RichText.new(self[:body_format], self[:body])
+    @body ||= RichText.new(self[:body_format], self[:body])
   end
 
   private

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) %>
+<%= opengraph_tags(@title, @og_image) %>
 <% if flash[:matomo_goal] -%>
 <%= tag.meta :name => "matomo-goal", :content => flash[:matomo_goal] %>
 <% end -%>

test/controllers/diary_entries_controller_test.rb

@@ -752,6 +752,17 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     end
   end
 
+  def test_show_og_image
+    user = create(:user)
+    diary_entry = create(:diary_entry, :user => user, :body => "![some picture](https://example.com/picture.jpg)")
+
+    get diary_entry_path(user, diary_entry)
+    assert_response :success
+    assert_dom "head meta[property='og:image']" do
+      assert_dom "> @content", "https://example.com/picture.jpg"
+    end
+  end
+
   def test_hide
     user = create(:user)
     diary_entry = create(:diary_entry, :user => user)