1 files changed, 75 insertions, 0 deletions
diff --git a/lib/gitlab/ci/config/external/file/base.rb b/lib/gitlab/ci/config/external/file/base.rb
new file mode 100644
index 00000000000..15ca47ef60e
--- /dev/null
+++ b/lib/gitlab/ci/config/external/file/base.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class Config
+      module External
+        module File
+          class Base
+            include Gitlab::Utils::StrongMemoize
+
+            attr_reader :location, :opts, :errors
+
+            YAML_WHITELIST_EXTENSION = /.+\.(yml|yaml)$/i.freeze
+
+            def initialize(location, opts = {})
+              @location = location
+              @opts = opts
+              @errors = []
+
+              validate!
+            end
+
+            def invalid_extension?
+              !::File.basename(location).match(YAML_WHITELIST_EXTENSION)
+            end
+
+            def valid?
+              errors.none?
+            end
+
+            def error_message
+              errors.first
+            end
+
+            def content
+              raise NotImplementedError, 'subclass must implement fetching raw content'
+            end
+
+            def to_hash
+              @hash ||= Ci::Config::Loader.new(content).load!
+            rescue Ci::Config::Loader::FormatError
+              nil
+            end
+
+            protected
+
+            def validate!
+              validate_location!
+              validate_content! if errors.none?
+              validate_hash! if errors.none?
+            end
+
+            def validate_location!
+              if invalid_extension?
+                errors.push("Included file `#{location}` does not have YAML extension!")
+              end
+            end
+
+            def validate_content!
+              if content.blank?
+                errors.push("Included file `#{location}` is empty or does not exist!")
+              end
+            end
+
+            def validate_hash!
+              if to_hash.blank?
+                errors.push("Included file `#{location}` does not have valid YAML syntax!")
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end