FEATURE: Export topics to markdown (#15615)

* FEATURE: Export topics to markdown

The route `/raw/TOPIC_ID` will now export whole topics (paginated to 100
posts) in a markdown format.

See https://meta.discourse.org/t/-/152185/12

app/controllers/posts_controller.rb

@@ -28,6 +28,8 @@ class PostsController < ApplicationController
     :user_posts_feed
   ]
 
+  MARKDOWN_TOPIC_PAGE_SIZE ||= 100
+
   def markdown_id
     markdown Post.find(params[:id].to_i)
   end
@@ -36,8 +38,23 @@ class PostsController < ApplicationController
     if params[:revision].present?
       post_revision = find_post_revision_from_topic_id
       render plain: post_revision.modifications[:raw].last
+    elsif params[:post_number].present?
+      markdown Post.find_by(topic_id: params[:topic_id].to_i, post_number: params[:post_number].to_i)
     else
-      markdown Post.find_by(topic_id: params[:topic_id].to_i, post_number: (params[:post_number] || 1).to_i)
+      opts = params.slice(:page)
+      opts[:limit] = MARKDOWN_TOPIC_PAGE_SIZE
+      topic_view = TopicView.new(params[:topic_id], current_user, opts)
+      content = topic_view.posts.map do |p|
+        <<~HEREDOC
+          #{p.user.username} | #{p.updated_at} | ##{p.post_number}
+
+          #{p.raw}
+
+          -------------------------
+
+        HEREDOC
+      end
+      render plain: content.join
     end
   end
 

spec/requests/posts_controller_spec.rb

@@ -1888,6 +1888,16 @@ describe PostsController do
       expect(response.status).to eq(200)
       expect(response.body).to eq("123456789")
     end
+
+    it "can show whole topics" do
+      topic = Fabricate(:topic)
+      post = Fabricate(:post, topic: topic, post_number: 1, raw: "123456789")
+      post_2 = Fabricate(:post, topic: topic, post_number: 2, raw: "abcdefghij")
+      post.save
+      get "/raw/#{topic.id}"
+      expect(response.status).to eq(200)
+      expect(response.body).to include("123456789", "abcdefghij")
+    end
   end
 
   describe '#short_link' do