# frozen_string_literal: true

module Karafka
  # Karafka consuming server class
  class Server
    # How long should we sleep between checks on shutting down consumers
    SUPERVISION_SLEEP = 0.1
    # What system exit code should we use when we terminated forcefully
    FORCEFUL_EXIT_CODE = 2
    # This factor allows us to calculate how many times we have to sleep before
    # a forceful shutdown
    SUPERVISION_CHECK_FACTOR = (1 / SUPERVISION_SLEEP)

    private_constant :SUPERVISION_SLEEP, :FORCEFUL_EXIT_CODE, :SUPERVISION_CHECK_FACTOR

    class << self
      # Set of consuming threads. Each consumer thread contains a single consumer
      attr_accessor :listeners

      # Set of workers
      attr_accessor :workers

      # Jobs queue
      attr_accessor :jobs_queue

      # Method which runs app
      def run
        self.listeners = []
        self.workers = []

        # We need to validate this prior to running because it may be executed also from the
        # embedded
        # We cannot validate this during the start because config needs to be populated and routes
        # need to be defined.
        Contracts::ServerCliOptions.new.validate!(
          Karafka::App.config.internal.routing.active.to_h
        )

        process.on_sigint { stop }
        process.on_sigquit { stop }
        process.on_sigterm { stop }
        process.on_sigtstp { quiet }
        process.supervise

        # Start is blocking until stop is called and when we stop, it will wait until
        # all of the things are ready to stop
        start

        # We always need to wait for Karafka to stop here since we should wait for the stop running
        # in a separate thread (or trap context) to indicate everything is closed
        # Since `#start` is blocking, we will get here only after the runner is done. This will
        # not add any performance degradation because of that.
        sleep(0.1) until Karafka::App.terminated?
      # Try its best to shutdown underlying components before re-raising
      # rubocop:disable Lint/RescueException
      rescue Exception => e
        # rubocop:enable Lint/RescueException
        stop

        raise e
      end

      # Starts Karafka with a supervision
      # @note We don't need to sleep because Karafka::Fetcher is locking and waiting to
      # finish loop (and it won't happen until we explicitly want to stop)
      def start
        Karafka::App.run!
        Karafka::Runner.new.call
      end

      # Stops Karafka with a supervision (as long as there is a shutdown timeout)
      # If consumers or workers won't stop in a given time frame, it will force them to exit
      #
      # @note This method is not async. It should not be executed from the workers as it will
      #   lock them forever. If you need to run Karafka shutdown from within workers threads,
      #   please start a separate thread to do so.
      def stop
        # Initialize the stopping process only if Karafka was running
        return if Karafka::App.stopping?
        return if Karafka::App.stopped?
        return if Karafka::App.terminated?

        Karafka::App.stop!

        timeout = Karafka::App.config.shutdown_timeout

        # We check from time to time (for the timeout period) if all the threads finished
        # their work and if so, we can just return and normal shutdown process will take place
        # We divide it by 1000 because we use time in ms.
        ((timeout / 1_000) * SUPERVISION_CHECK_FACTOR).to_i.times do
          return if listeners.count(&:alive?).zero? && workers.count(&:alive?).zero?

          sleep SUPERVISION_SLEEP
        end

        raise Errors::ForcefulShutdownError
      rescue Errors::ForcefulShutdownError => e
        Karafka.monitor.instrument(
          'error.occurred',
          caller: self,
          error: e,
          type: 'app.stopping.error'
        )

        # We're done waiting, lets kill them!
        workers.each(&:terminate)
        listeners.each(&:terminate)
        # We always need to shutdown clients to make sure we do not force the GC to close consumer.
        # This can cause memory leaks and crashes.
        listeners.each(&:shutdown)

        # We also do not forcefully terminate everything when running in the embedded mode,
        # otherwise we would overwrite the shutdown process of the process that started Karafka
        return unless process.supervised?

        # exit! is not within the instrumentation as it would not trigger due to exit
        Kernel.exit!(FORCEFUL_EXIT_CODE)
      ensure
        # We need to check if it wasn't an early exit to make sure that only on stop invocation
        # can change the status after everything is closed
        if timeout
          Karafka::App.stopped!

          # We close producer as the last thing as it can be used in the notification pipeline
          # to dispatch state changes, etc
          Karafka::App.producer.close

          Karafka::App.terminate!
        end
      end

      # Quiets the Karafka server.
      #
      # Karafka will stop processing but won't quit the consumer group, so no rebalance will be
      # triggered until final shutdown.
      def quiet
        # We don't have to safe-guard it with check states as the state transitions work only
        # in one direction
        Karafka::App.quiet!

        # We need one more thread to monitor the process and move to quieted once everything
        # is quiet and no processing is happening anymore
        Thread.new do
          sleep(0.1) until listeners.coordinators.all?(&:finished?)
          Karafka::App.quieted!
        end
      end

      private

      # @return [Karafka::Process] process wrapper instance used to catch system signal calls
      def process
        Karafka::App.config.internal.process
      end
    end
  end
end