# frozen_string_literal: true

module Gitlab
  module Ci
    module Pipeline
      class Logger
        include ::Gitlab::Utils::StrongMemoize

        def self.current_monotonic_time
          ::Gitlab::Metrics::System.monotonic_time
        end

        def initialize(project:, destination: Gitlab::AppJsonLogger)
          @started_at = current_monotonic_time
          @project = project
          @destination = destination
          @log_conditions = []

          yield(self) if block_given?
        end

        def log_when(&block)
          log_conditions.push(block)
        end

        def instrument(operation)
          return yield unless enabled?

          raise ArgumentError, 'block not given' unless block_given?

          op_started_at = current_monotonic_time

          result = yield

          observe("#{operation}_duration_s", current_monotonic_time - op_started_at)

          result
        end

        def instrument_with_sql(operation, &block)
          op_start_db_counters = current_db_counter_payload

          result = instrument(operation, &block)

          observe_sql_counters(operation, op_start_db_counters, current_db_counter_payload)

          result
        end

        def observe(operation, value)
          return unless enabled?

          observations[operation.to_s].push(value)
        end

        def commit(pipeline:, caller:)
          return unless log?

          attributes = {
            class: self.class.name.to_s,
            pipeline_creation_caller: caller,
            project_id: project&.id, # project is not available when called from `/ci/lint`
            pipeline_persisted: pipeline.persisted?,
            pipeline_source: pipeline.source,
            pipeline_creation_service_duration_s: age
          }

          if pipeline.persisted?
            attributes[:pipeline_builds_tags_count] = pipeline.tags_count
            attributes[:pipeline_builds_distinct_tags_count] = pipeline.distinct_tags_count
            attributes[:pipeline_id] = pipeline.id
          end

          attributes.compact!
          attributes.stringify_keys!
          attributes.merge!(observations_hash)

          destination.info(attributes)
        end

        def observations_hash
          observations.transform_values do |values|
            next if values.empty?

            {
              'count' => values.size,
              'min' => values.min,
              'max' => values.max,
              'avg' => values.sum / values.size
            }
          end.compact
        end

        private

        attr_reader :project, :destination, :started_at, :log_conditions

        delegate :current_monotonic_time, to: :class

        def age
          current_monotonic_time - started_at
        end

        def log?
          return false unless enabled?
          return true if log_conditions.empty?

          log_conditions.any? { |cond| cond.call(observations) }
        end

        def enabled?
          strong_memoize(:enabled) do
            ::Feature.enabled?(:ci_pipeline_creation_logger, project, type: :ops, default_enabled: :yaml)
          end
        end

        def observations
          @observations ||= Hash.new { |hash, key| hash[key] = [] }
        end

        def observe_sql_counters(operation, start_db_counters, end_db_counters)
          end_db_counters.each do |key, value|
            result = value - start_db_counters.fetch(key, 0)
            next if result == 0

            observe("#{operation}_#{key}", result)
          end
        end

        def current_db_counter_payload
          ::Gitlab::Metrics::Subscribers::ActiveRecord.db_counter_payload
        end
      end
    end
  end
end