FEATURE: Import and export themes in a .tar.gz format (#6916)

lib/theme_store/tgz_exporter.rb

@@ -0,0 +1,62 @@
+module ThemeStore; end
+
+class ThemeStore::TgzExporter
+
+  def initialize(theme)
+    @theme = theme
+    @temp_folder = "#{Pathname.new(Dir.tmpdir).realpath}/discourse_theme_#{SecureRandom.hex}"
+    @export_name = "discourse-#{@theme.name.downcase.gsub(/[^0-9a-z.\-]/, '-')}-theme"
+  end
+
+  def package_filename
+    export_package
+  end
+
+  def cleanup!
+    FileUtils.rm_rf(@temp_folder)
+  end
+
+  private
+  def export_to_folder
+    FileUtils.mkdir(@temp_folder)
+
+    Dir.chdir(@temp_folder) do
+      FileUtils.mkdir(@export_name)
+
+      @theme.theme_fields.each do |field|
+        next unless path = field.file_path
+
+        # Belt and braces approach here. All the user input should already be
+        # sanitized, but check for attempts to leave the temp directory anyway
+        pathname = Pathname.new("#{@export_name}/#{path}")
+        folder_path = pathname.parent.realdirpath
+        raise RuntimeError.new("Theme exporter tried to leave directory") unless folder_path.to_s.starts_with?("#{@temp_folder}/#{@export_name}")
+        folder_path.mkpath
+        path = pathname.realdirpath
+        raise RuntimeError.new("Theme exporter tried to leave directory") unless path.to_s.starts_with?("#{@temp_folder}/#{@export_name}")
+
+        if ThemeField.types[field.type_id] == :theme_upload_var
+          filename = Discourse.store.path_for(field.upload)
+          content = filename ? File.read(filename) : Discourse.store.download(object.upload).read
+        else
+          content = field.value
+        end
+        File.write(path, content)
+      end
+
+      File.write("#{@export_name}/about.json", JSON.pretty_generate(@theme.generate_metadata_hash))
+    end
+    @temp_folder
+  end
+
+  def export_package
+    export_to_folder
+    Dir.chdir(@temp_folder) do
+      tar_filename = "#{@export_name}.tar"
+      Discourse::Utils.execute_command('tar', '--create', '--file', tar_filename, @export_name, failure_message: "Failed to tar theme.")
+      Discourse::Utils.execute_command('gzip', '-5', tar_filename, failure_message: "Failed to gzip archive.")
+      "#{@temp_folder}/#{tar_filename}.gz"
+    end
+  end
+
+end