# frozen_string_literal: true

# Responsible for returning a filtered system dashboard
# containing only the default embedded metrics. In future,
# this class may be updated to support filtering to
# alternate metrics/panels.
#
# Why isn't this filtering in a processing stage? By filtering
# here, we ensure the dynamically-determined dashboard is cached.
#
# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
module Gitlab
  module Metrics
    module Dashboard
      class DynamicDashboardService < Gitlab::Metrics::Dashboard::BaseService
        # For the default filtering for embedded metrics,
        # uses the 'id' key in dashboard-yml definition for
        # identification.
        DEFAULT_EMBEDDED_METRICS_IDENTIFIERS = %w(
          system_metrics_kubernetes_container_memory_total
          system_metrics_kubernetes_container_cores_total
        ).freeze

        # Returns a new dashboard with only the matching
        # metrics from the system dashboard, stripped of groups.
        # @return [Hash]
        def raw_dashboard
          panels = panel_groups.each_with_object([]) do |group, panels|
            matched_panels = group['panels'].select { |panel| matching_panel?(panel) }

            panels.concat(matched_panels)
          end

          { 'panel_groups' => [{ 'panels' => panels }] }
        end

        def cache_key
          "dynamic_metrics_dashboard_#{metric_identifiers.join('_')}"
        end

        private

        # Returns an array of the panels groups on the
        # system dashboard
        def panel_groups
          Gitlab::Metrics::Dashboard::SystemDashboardService
            .new(project, nil)
            .raw_dashboard['panel_groups']
        end

        # Identifies a panel as "matching" if any metric ids in
        # the panel is in the list of identifiers to collect.
        def matching_panel?(panel)
          panel['metrics'].any? do |metric|
            metric_identifiers.include?(metric['id'])
          end
        end

        def metric_identifiers
          DEFAULT_EMBEDDED_METRICS_IDENTIFIERS
        end
      end
    end
  end
end