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, 145 insertions, 0 deletions

diff --git a/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb b/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb
new file mode 100644
index 00000000000..53b7497ae21
--- /dev/null
+++ b/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb
@@ -0,0 +1,145 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Metrics::Dashboard::CustomMetricEmbedService do
+  include MetricsDashboardHelpers
+
+  set(:project) { build(:project) }
+  set(:user) { create(:user) }
+  set(:environment) { create(:environment, project: project) }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  let(:dashboard_path) { system_dashboard_path }
+  let(:group) { business_metric_title }
+  let(:title) { 'title' }
+  let(:y_label) { 'y_label' }
+
+  describe '.valid_params?' do
+    let(:valid_params) do
+      {
+        embedded: true,
+        dashboard_path: dashboard_path,
+        group: group,
+        title: title,
+        y_label: y_label
+      }
+    end
+
+    subject { described_class.valid_params?(params) }
+
+    let(:params) { valid_params }
+
+    it { is_expected.to be_truthy }
+
+    context 'not embedded' do
+      let(:params) { valid_params.except(:embedded) }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'non-system dashboard' do
+      let(:dashboard_path) { '.gitlab/dashboards/test.yml' }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'undefined dashboard' do
+      let(:params) { valid_params.except(:dashboard_path) }
+
+      it { is_expected.to be_truthy }
+    end
+
+    context 'non-custom metric group' do
+      let(:group) { 'Different Group' }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'missing group' do
+      let(:group) { nil }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'missing title' do
+      let(:title) { nil }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'undefined y-axis label' do
+      let(:params) { valid_params.except(:y_label) }
+
+      it { is_expected.to be_falsey }
+    end
+  end
+
+  describe '#get_dashboard' do
+    let(:service_params) do
+      [
+        project,
+        user,
+        {
+          embedded: true,
+          environment: environment,
+          dashboard_path: dashboard_path,
+          group: group,
+          title: title,
+          y_label: y_label
+        }
+      ]
+    end
+
+    let(:service_call) { described_class.new(*service_params).get_dashboard }
+
+    it_behaves_like 'misconfigured dashboard service response', :not_found
+    it_behaves_like 'raises error for users with insufficient permissions'
+
+    context 'the custom metric exists' do
+      let!(:metric) { create(:prometheus_metric, project: project) }
+
+      it_behaves_like 'valid embedded dashboard service response'
+
+      it 'does not cache the unprocessed dashboard' do
+        expect(Gitlab::Metrics::Dashboard::Cache).not_to receive(:fetch)
+
+        described_class.new(*service_params).get_dashboard
+      end
+
+      context 'multiple metrics meet criteria' do
+        let!(:metric_2) { create(:prometheus_metric, project: project, query: 'avg(metric_2)') }
+
+        it_behaves_like 'valid embedded dashboard service response'
+
+        it 'includes both metrics' do
+          result = service_call
+          included_queries = all_queries(result[:dashboard])
+
+          expect(included_queries).to include('avg(metric_2)', 'avg(metric)')
+        end
+      end
+    end
+
+    context 'when the metric exists in another project' do
+      let!(:metric) { create(:prometheus_metric, project: create(:project)) }
+
+      it_behaves_like 'misconfigured dashboard service response', :not_found
+    end
+  end
+
+  private
+
+  def all_queries(dashboard)
+    dashboard[:panel_groups].flat_map do |group|
+      group[:panels].flat_map do |panel|
+        panel[:metrics].map do |metric|
+          metric[:query_range]
+        end
+      end
+    end
+  end
+end