# frozen_string_literal: true

require "sidekiq"
require "sidekiq/component"

module Sidekiq # :nodoc:
  class BasicFetch
    include Sidekiq::Component
    # We want the fetch operation to timeout every few seconds so the thread
    # can check if the process is shutting down.
    TIMEOUT = 2

    UnitOfWork = Struct.new(:queue, :job, :config) {
      def acknowledge
        # nothing to do
      end

      def queue_name
        queue.delete_prefix("queue:")
      end

      def requeue
        config.redis do |conn|
          conn.rpush(queue, job)
        end
      end
    }

    def initialize(config)
      raise ArgumentError, "missing queue list" unless config[:queues]
      @config = config
      @strictly_ordered_queues = !!@config[:strict]
      @queues = @config[:queues].map { |q| "queue:#{q}" }
      if @strictly_ordered_queues
        @queues.uniq!
        @queues << TIMEOUT
      end
    end

    def retrieve_work
      qs = queues_cmd
      # 4825 Sidekiq Pro with all queues paused will return an
      # empty set of queues with a trailing TIMEOUT value.
      if qs.size <= 1
        sleep(TIMEOUT)
        return nil
      end

      queue, job = redis { |conn| conn.brpop(*qs) }
      UnitOfWork.new(queue, job, config) if queue
    end

    def bulk_requeue(inprogress, options)
      return if inprogress.empty?

      logger.debug { "Re-queueing terminated jobs" }
      jobs_to_requeue = {}
      inprogress.each do |unit_of_work|
        jobs_to_requeue[unit_of_work.queue] ||= []
        jobs_to_requeue[unit_of_work.queue] << unit_of_work.job
      end

      redis do |conn|
        conn.pipelined do |pipeline|
          jobs_to_requeue.each do |queue, jobs|
            pipeline.rpush(queue, jobs)
          end
        end
      end
      logger.info("Pushed #{inprogress.size} jobs back to Redis")
    rescue => ex
      logger.warn("Failed to requeue #{inprogress.size} jobs: #{ex.message}")
    end

    # Creating the Redis#brpop command takes into account any
    # configured queue weights. By default Redis#brpop returns
    # data from the first queue that has pending elements. We
    # recreate the queue command each time we invoke Redis#brpop
    # to honor weights and avoid queue starvation.
    def queues_cmd
      if @strictly_ordered_queues
        @queues
      else
        permute = @queues.shuffle
        permute.uniq!
        permute << TIMEOUT
        permute
      end
    end
  end
end