# frozen_string_literal: true

module Gitlab
  module Database
    module Reindexing
      class Coordinator
        include AsyncDdlExclusiveLeaseGuard

        # Maximum lease time for the global Redis lease
        # This should be higher than the maximum time for any
        # long running step in the reindexing process (compare with
        # statement timeouts).
        TIMEOUT_PER_ACTION = 1.day

        attr_reader :index, :notifier

        def initialize(index, notifier = GrafanaNotifier.new)
          @index = index
          @notifier = notifier
        end

        def perform
          return if too_late_for_reindexing?

          # This obtains a global lease such that there's
          # only one live reindexing process at a time.
          try_obtain_lease do
            action = ReindexAction.create_for(index)

            with_notifications(action) do
              perform_for(index, action)
            end
          end
        end

        def drop
          return if too_late_for_reindexing?

          try_obtain_lease do
            Gitlab::AppLogger.info("Removing index #{index.identifier} which is a leftover, temporary index from previous reindexing activity")

            retries = Gitlab::Database::WithLockRetriesOutsideTransaction.new(
              connection: connection,
              timing_configuration: REMOVE_INDEX_RETRY_CONFIG,
              klass: self.class,
              logger: Gitlab::AppLogger
            )

            retries.run(raise_on_exhaustion: false) do
              connection.execute("DROP INDEX CONCURRENTLY IF EXISTS #{full_index_name}")
            end
          end
        end

        private

        delegate :connection, :connection_db_config, to: :index

        def with_notifications(action)
          notifier.notify_start(action)
          yield
        ensure
          notifier.notify_end(action)
        end

        def perform_for(index, action)
          ReindexConcurrently.new(index).perform
        rescue StandardError
          action.state = :failed

          raise
        ensure
          action.finish
        end

        def lease_timeout
          TIMEOUT_PER_ACTION
        end

        def full_index_name
          [
            connection.quote_table_name(index.schema),
            connection.quote_table_name(index.name)
          ].join('.')
        end

        # We need to check the time explicitly because we execute 4 reindexing
        # action per rake invocation and one action can take up to 24 hours.
        # This means that it can span for more than the weekend.
        def too_late_for_reindexing?
          !Time.current.on_weekend?
        end
      end
    end
  end
end