#399

backend/app/controllers/preview_controller.rb

@@ -38,6 +38,27 @@ class PreviewController < ApplicationController
     render_unprocessable_entity(e.message)
   end
 
+  def image
+    return render_bad_request('URL は必須です．') if params[:url].blank?
+
+    attachment = Post.resized_thumbnail_attachment(
+        StringIO.new(Preview::ThumbnailFetcher.fetch_image_response(params[:url]).body))
+    attachment[:io].rewind
+    send_data attachment[:io].read,
+              type: attachment[:content_type],
+              disposition: 'inline'
+  rescue Preview::UrlSafety::UnsafeUrl => e
+    render_bad_request(e.message)
+  rescue Preview::HttpFetcher::FetchTimeout => e
+    render_preview_error(e.message, :gateway_timeout)
+  rescue Preview::HttpFetcher::ResponseTooLarge => e
+    render_preview_error(e.message, :payload_too_large)
+  rescue Preview::HttpFetcher::FetchFailed => e
+    render_preview_error(e.message, :bad_gateway)
+  rescue Preview::ThumbnailFetcher::GenerationFailed, MiniMagick::Error => e
+    render_unprocessable_entity(e.message)
+  end
+
   private
 
   def require_member!