# frozen_string_literal: true

require 'rails_autoscale_agent/logger'

module WorkerAdapters
  class DelayedJob
    include RailsAutoscaleAgent::Logger
    include Singleton

    class << self
      attr_accessor :queues
    end

    def initialize
      # Track the known queues so we can continue reporting on queues that don't
      # currently have enqueued jobs.
      self.class.queues = Set.new

      install if enabled?
    end

    def enabled?
      defined? ::Delayed
    end

    def collect!(store)
      log_msg = String.new('DelayedJob latency ')
      t = Time.now

      sql = 'SELECT queue, min(run_at) FROM delayed_jobs GROUP BY queue'
      run_at_by_queue = Hash[ActiveRecord::Base.connection.select_rows(sql)]
      queues = self.class.queues | run_at_by_queue.keys

      queues.each do |queue|
        run_at = run_at_by_queue[queue]
        run_at = Time.parse(run_at) if run_at.is_a?(String)
        latency_ms = run_at ? ((t - run_at)*1000).ceil : 0
        store.push latency_ms, t, queue
        log_msg << "#{queue}=#{latency_ms} "
      end

      logger.debug log_msg
    end

    private

    def install
      plugin = Class.new(Delayed::Plugin) do
        require 'delayed_job'

        callbacks do |lifecycle|
          lifecycle.before(:enqueue) do |job, &block|
            queue = job.queue || 'default'
            WorkerAdapters::DelayedJob.queues.add queue
          end
        end
      end

      Delayed::Worker.plugins << plugin
    end
  end
end