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.

6 files changed, 126 insertions, 23 deletions

diff --git a/lib/gitlab/metrics/dashboard/defaults.rb b/lib/gitlab/metrics/dashboard/defaults.rb
new file mode 100644
index 00000000000..3c39a7c6911
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/defaults.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Central point for managing default attributes from within
+# the metrics dashboard module.
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Defaults
+        DEFAULT_PANEL_TYPE = 'area-chart'
+        DEFAULT_PANEL_WEIGHT = 0
+      end
+    end
+  end
+end
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
diff --git a/lib/gitlab/metrics/dashboard/finder.rb b/lib/gitlab/metrics/dashboard/finder.rb
index 1373830844b..66c4d662a6c 100644
--- a/lib/gitlab/metrics/dashboard/finder.rb
+++ b/lib/gitlab/metrics/dashboard/finder.rb
@@ -12,21 +12,37 @@ module Gitlab
           # @param project [Project]
           # @param user [User]
           # @param environment [Environment]
-          # @param opts - dashboard_path [String] Path at which the
-          #         dashboard can be found. Nil values will
-          #         default to the system dashboard.
-          # @param opts - embedded [Boolean] Determines whether the
+          # @param options - embedded [Boolean] Determines whether the
           #         dashboard is to be rendered as part of an
           #         issue or location other than the primary
           #         metrics dashboard UI. Returns only the
           #         Memory/CPU charts of the system dash.
+          # @param options - dashboard_path [String] Path at which the
+          #         dashboard can be found. Nil values will
+          #         default to the system dashboard.
+          # @param options - group [String] Title of the group
+          #         to which a panel might belong. Used by
+          #         embedded dashboards.
+          # @param options - title [String] Title of the panel.
+          #         Used by embedded dashboards.
+          # @param options - y_label [String] Y-Axis label of
+          #         a panel. Used by embedded dashboards.
           # @return [Hash]
-          def find(project, user, environment, dashboard_path: nil, embedded: false)
-            service_for_path(dashboard_path, embedded: embedded)
-              .new(project, user, environment: environment, dashboard_path: dashboard_path)
+          def find(project, user, environment, options = {})
+            service_for(options)
+              .new(project, user, options.merge(environment: environment))
               .get_dashboard
           end
 
+          # Returns a dashboard without any supplemental info.
+          # Returns only full, yml-defined dashboards.
+          # @return [Hash]
+          def find_raw(project, dashboard_path: nil)
+            service_for(dashboard_path: dashboard_path)
+              .new(project, nil, dashboard_path: dashboard_path)
+              .raw_dashboard
+          end
+
           # Summary of all known dashboards.
           # @return [Array<Hash>] ex) [{ path: String,
           #                              display_name: String,
@@ -46,13 +62,6 @@ module Gitlab
 
           private
 
-          def service_for_path(dashboard_path, embedded:)
-            return embed_service if embedded
-            return system_service if system_dashboard?(dashboard_path)
-
-            project_service
-          end
-
           def system_service
             ::Metrics::Dashboard::SystemDashboardService
           end
@@ -61,12 +70,8 @@ module Gitlab
             ::Metrics::Dashboard::ProjectDashboardService
           end
 
-          def embed_service
-            ::Metrics::Dashboard::DefaultEmbedService
-          end
-
-          def system_dashboard?(filepath)
-            !filepath || system_service.system_dashboard?(filepath)
+          def service_for(options)
+            Gitlab::Metrics::Dashboard::ServiceSelector.call(options)
           end
         end
       end
diff --git a/lib/gitlab/metrics/dashboard/service_selector.rb b/lib/gitlab/metrics/dashboard/service_selector.rb
new file mode 100644
index 00000000000..934ba9145a2
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/service_selector.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+# Responsible for determining which dashboard service should
+# be used to fetch or generate a dashboard hash.
+# The services can be considered in two categories - embeds
+# and dashboards. Embeds are all portions of dashboards.
+module Gitlab
+  module Metrics
+    module Dashboard
+      class ServiceSelector
+        SERVICES = ::Metrics::Dashboard
+
+        class << self
+          include Gitlab::Utils::StrongMemoize
+
+          # Returns a class which inherits from the BaseService
+          # class that can be used to obtain a dashboard.
+          # @return [Gitlab::Metrics::Dashboard::Services::BaseService]
+          def call(params)
+            return SERVICES::CustomMetricEmbedService if custom_metric_embed?(params)
+            return SERVICES::DynamicEmbedService if dynamic_embed?(params)
+            return SERVICES::DefaultEmbedService if params[:embedded]
+            return SERVICES::SystemDashboardService if system_dashboard?(params[:dashboard_path])
+            return SERVICES::ProjectDashboardService if params[:dashboard_path]
+
+            default_service
+          end
+
+          private
+
+          def default_service
+            SERVICES::SystemDashboardService
+          end
+
+          def system_dashboard?(filepath)
+            SERVICES::SystemDashboardService.system_dashboard?(filepath)
+          end
+
+          def custom_metric_embed?(params)
+            SERVICES::CustomMetricEmbedService.valid_params?(params)
+          end
+
+          def dynamic_embed?(params)
+            SERVICES::DynamicEmbedService.valid_params?(params)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/dashboard/stages/base_stage.rb b/lib/gitlab/metrics/dashboard/stages/base_stage.rb
index 0db7b176e8d..514ed50e58d 100644
--- a/lib/gitlab/metrics/dashboard/stages/base_stage.rb
+++ b/lib/gitlab/metrics/dashboard/stages/base_stage.rb
@@ -5,11 +5,11 @@ module Gitlab
     module Dashboard
       module Stages
         class BaseStage
+          include Gitlab::Metrics::Dashboard::Defaults
+
           DashboardProcessingError = Class.new(StandardError)
           LayoutError = Class.new(DashboardProcessingError)
 
-          DEFAULT_PANEL_TYPE = 'area-chart'
-
           attr_reader :project, :environment, :dashboard
 
           def initialize(project, environment, dashboard)
diff --git a/lib/gitlab/metrics/dashboard/stages/project_metrics_inserter.rb b/lib/gitlab/metrics/dashboard/stages/project_metrics_inserter.rb
index 221610a14d1..643be309992 100644
--- a/lib/gitlab/metrics/dashboard/stages/project_metrics_inserter.rb
+++ b/lib/gitlab/metrics/dashboard/stages/project_metrics_inserter.rb
@@ -97,7 +97,7 @@ module Gitlab
           end
 
           def new_metric(metric)
-            metric.queries.first.merge(metric_id: metric.id)
+            metric.to_metric_hash
           end
         end
       end