3 files changed, 93 insertions, 0 deletions
diff --git a/lib/gitlab/ci/external/file/base.rb b/lib/gitlab/ci/external/file/base.rb
new file mode 100644
index 00000000000..f4da07b0b02
--- /dev/null
+++ b/lib/gitlab/ci/external/file/base.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module External
+      module File
+        class Base
+          YAML_WHITELIST_EXTENSION = /(yml|yaml)$/i.freeze
+
+          def initialize(location, opts = {})
+            @location = location
+          end
+
+          def valid?
+            location.match(YAML_WHITELIST_EXTENSION) && content
+          end
+
+          def content
+            raise NotImplementedError, 'content must be implemented and return a string or nil'
+          end
+
+          def error_message
+            raise NotImplementedError, 'error_message must be implemented and return a string'
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/ci/external/file/local.rb b/lib/gitlab/ci/external/file/local.rb
new file mode 100644
index 00000000000..1aa7f687507
--- /dev/null
+++ b/lib/gitlab/ci/external/file/local.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module External
+      module File
+        class Local < Base
+          attr_reader :location, :project, :sha
+
+          def initialize(location, opts = {})
+            super
+
+            @project = opts.fetch(:project)
+            @sha = opts.fetch(:sha)
+          end
+
+          def content
+            @content ||= fetch_local_content
+          end
+
+          def error_message
+            "Local file '#{location}' is not valid."
+          end
+
+          private
+
+          def fetch_local_content
+            project.repository.blob_data_at(sha, location)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/ci/external/file/remote.rb b/lib/gitlab/ci/external/file/remote.rb
new file mode 100644
index 00000000000..59bb3e8999e
--- /dev/null
+++ b/lib/gitlab/ci/external/file/remote.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module External
+      module File
+        class Remote < Base
+          include Gitlab::Utils::StrongMemoize
+          attr_reader :location
+
+          def content
+            return @content if defined?(@content)
+
+            @content = strong_memoize(:content) do
+              begin
+                Gitlab::HTTP.get(location)
+              rescue Gitlab::HTTP::Error, Timeout::Error, SocketError, Gitlab::HTTP::BlockedUrlError
+                nil
+              end
+            end
+          end
+
+          def error_message
+            "Remote file '#{location}' is not valid."
+          end
+        end
+      end
+    end
+  end
+end