Gab Social. All are welcome.

app/models/concerns/remotable.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+module Remotable
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def remotable_attachment(attachment_name, limit)
+      attribute_name  = "#{attachment_name}_remote_url".to_sym
+      method_name     = "#{attribute_name}=".to_sym
+      alt_method_name = "reset_#{attachment_name}!".to_sym
+
+      define_method method_name do |url|
+        return if url.blank?
+
+        begin
+          parsed_url = Addressable::URI.parse(url).normalize
+        rescue Addressable::URI::InvalidURIError
+          return
+        end
+
+        return if !%w(http https).include?(parsed_url.scheme) || parsed_url.host.blank? || self[attribute_name] == url
+
+        begin
+          Request.new(:get, url).perform do |response|
+            next if response.code != 200
+
+            content_type = parse_content_type(response.headers.get('content-type').last)
+            extname      = detect_extname_from_content_type(content_type)
+
+            if extname.nil?
+              disposition = response.headers.get('content-disposition').last
+              matches     = disposition&.match(/filename="([^"]*)"/)
+              filename    = matches.nil? ? parsed_url.path.split('/').last : matches[1]
+              extname     = filename.nil? ? '' : File.extname(filename)
+            end
+
+            basename = SecureRandom.hex(8)
+
+            send("#{attachment_name}=", StringIO.new(response.body_with_limit(limit)))
+            send("#{attachment_name}_file_name=", basename + extname)
+
+            self[attribute_name] = url if has_attribute?(attribute_name)
+          end
+        rescue HTTP::TimeoutError, HTTP::ConnectionError, OpenSSL::SSL::SSLError, Paperclip::Errors::NotIdentifiedByImageMagickError, Addressable::URI::InvalidURIError, GabSocial::HostValidationError, GabSocial::LengthValidationError => e
+          Rails.logger.debug "Error fetching remote #{attachment_name}: #{e}"
+          nil
+        rescue Paperclip::Error, GabSocial::DimensionsValidationError => e
+          Rails.logger.debug "Error processing remote #{attachment_name}: #{e}"
+          nil
+        end
+      end
+
+      define_method alt_method_name do
+        url = self[attribute_name]
+
+        return if url.blank?
+
+        self[attribute_name] = ''
+        send(method_name, url)
+      end
+    end
+  end
+
+  private
+
+  def detect_extname_from_content_type(content_type)
+    return if content_type.nil?
+
+    type = MIME::Types[content_type].first
+
+    return if type.nil?
+
+    extname = type.extensions.first
+
+    return if extname.nil?
+
+    ".#{extname}"
+  end
+
+  def parse_content_type(content_type)
+    return if content_type.nil?
+
+    content_type.split(/\s*;\s*/).first
+  end
+end