# frozen_string_literal: true

module CronSchedulable
  extend ActiveSupport::Concern
  include Schedulable

  def set_next_run_at
    self.next_run_at = calculate_next_run_at
  end

  private

  ##
  # The `next_run_at` column is set to the actual execution date of worker that
  # triggers the schedule. This way, a schedule like `*/1 * * * *` won't be triggered
  # in a short interval when the worker runs irregularly by Sidekiq Memory Killer.
  def calculate_next_run_at(start_time = Time.zone.now)
    ideal_next_run = ideal_next_run_from(start_time)

    if ideal_next_run == cron_worker_next_run_from(start_time)
      ideal_next_run
    else
      cron_worker_next_run_from(ideal_next_run)
    end
  end

  def ideal_next_run_from(start_time)
    next_time_from(start_time, cron, cron_timezone)
  end

  def cron_worker_next_run_from(start_time)
    next_time_from(start_time, worker_cron_expression, Time.zone.name)
  end

  def next_time_from(start_time, cron, cron_timezone)
    Gitlab::Ci::CronParser
      .new(cron, cron_timezone)
      .next_time_from(start_time)
  end

  def worker_cron_expression
    raise NotImplementedError
  end
end