Support dashboard params for metrics dashboard

https://gitlab.com/gitlab-org/gitlab-ce/issues/62971

Adds support to EnvironmentsController#metrics_dashboard
for the following params: group, title, y_label
These params are used to uniquely identify a panel on
the metrics dashboard.

Metrics are stored in several places, so this adds
utilities to find a specific panel from the database
or filesystem depending on the metric specified.

Also moves some shared utilities into separate classes,
notably default values and errors.

1 files changed, 34 insertions, 0 deletions

diff --git a/lib/gitlab/metrics/dashboard/errors.rb b/lib/gitlab/metrics/dashboard/errors.rb
new file mode 100644
index 00000000000..1739a4e6738
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/errors.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+# Central point for managing errors from within the metrics
+# dashboard module. Handles errors from dashboard retrieval
+# and processing steps, as well as defines shared error classes.
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Errors
+        PanelNotFoundError = Class.new(StandardError)
+
+        PROCESSING_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
+        NOT_FOUND_ERROR = Gitlab::Template::Finders::RepoTemplateFinder::FileNotFoundError
+
+        def handle_errors(error)
+          case error
+          when PROCESSING_ERROR
+            error(error.message, :unprocessable_entity)
+          when NOT_FOUND_ERROR
+            error("#{dashboard_path} could not be found.", :not_found)
+          when PanelNotFoundError
+            error(error.message, :not_found)
+          else
+            raise error
+          end
+        end
+
+        def panels_not_found!(opts)
+          raise PanelNotFoundError.new("No panels matching properties #{opts}")
+        end
+      end
+    end
+  end
+end