require 'json'

# See http://doc.gitlab.com/ce/development/migration_style_guide.html
# for more information on how to write migrations for GitLab.

class MigrateSidekiqQueuesFromDefault < ActiveRecord::Migration[4.2]
  include Gitlab::Database::MigrationHelpers

  DOWNTIME = true

  DOWNTIME_REASON = <<-EOF
  Moving Sidekiq jobs from queues requires Sidekiq to be stopped. Not stopping
  Sidekiq will result in the loss of jobs that are scheduled after this
  migration completes.
  EOF

  disable_ddl_transaction!

  # Jobs for which the queue names have been changed (e.g. multiple workers
  # using the same non-default queue).
  #
  # The keys are the old queue names, the values the jobs to move and their new
  # queue names.
  RENAMED_QUEUES = {
    gitlab_shell: {
      'GitGarbageCollectorWorker' => :git_garbage_collector,
      'ProjectExportWorker'       => :project_export,
      'RepositoryForkWorker'      => :repository_fork,
      'RepositoryImportWorker'    => :repository_import
    },
    project_web_hook: {
      'ProjectServiceWorker' => :project_service
    },
    incoming_email: {
      'EmailReceiverWorker' => :email_receiver
    },
    mailers: {
      'EmailsOnPushWorker' => :emails_on_push
    },
    default: {
      'AdminEmailWorker'                        => :cronjob,
      'BuildCoverageWorker'                     => :build,
      'BuildEmailWorker'                        => :build,
      'BuildFinishedWorker'                     => :build,
      'BuildHooksWorker'                        => :build,
      'BuildSuccessWorker'                      => :build,
      'ClearDatabaseCacheWorker'                => :clear_database_cache,
      'DeleteUserWorker'                        => :delete_user,
      'ExpireBuildArtifactsWorker'              => :cronjob,
      'ExpireBuildInstanceArtifactsWorker'      => :expire_build_instance_artifacts,
      'GroupDestroyWorker'                      => :group_destroy,
      'ImportExportProjectCleanupWorker'        => :cronjob,
      'IrkerWorker'                             => :irker,
      'MergeWorker'                             => :merge,
      'NewNoteWorker'                           => :new_note,
      'PipelineHooksWorker'                     => :pipeline,
      'PipelineMetricsWorker'                   => :pipeline,
      'PipelineProcessWorker'                   => :pipeline,
      'PipelineSuccessWorker'                   => :pipeline,
      'PipelineUpdateWorker'                    => :pipeline,
      'ProjectCacheWorker'                      => :project_cache,
      'ProjectDestroyWorker'                    => :project_destroy,
      'PruneOldEventsWorker'                    => :cronjob,
      'RemoveExpiredGroupLinksWorker'           => :cronjob,
      'RemoveExpiredMembersWorker'              => :cronjob,
      'RepositoryArchiveCacheWorker'            => :cronjob,
      'RepositoryCheck::BatchWorker'            => :cronjob,
      'RepositoryCheck::ClearWorker'            => :repository_check,
      'RepositoryCheck::SingleRepositoryWorker' => :repository_check,
      'RequestsProfilesWorker'                  => :cronjob,
      'StuckCiBuildsWorker'                     => :cronjob,
      'UpdateMergeRequestsWorker'               => :update_merge_requests
    }
  }.freeze

  def up
    Sidekiq.redis do |redis|
      RENAMED_QUEUES.each do |queue, jobs|
        migrate_from_queue(redis, queue, jobs)
      end
    end
  end

  def down
    Sidekiq.redis do |redis|
      RENAMED_QUEUES.each do |dest_queue, jobs|
        jobs.each do |worker, from_queue|
          migrate_from_queue(redis, from_queue, worker => dest_queue)
        end
      end
    end
  end

  def migrate_from_queue(redis, queue, job_mapping)
    while job = redis.lpop("queue:#{queue}")
      payload = JSON.parse(job)
      new_queue = job_mapping[payload['class']]

      # If we have no target queue to migrate to we're probably dealing with
      # some ancient job for which the worker no longer exists. In that case
      # there's no sane option we can take, other than just dropping the job.
      next unless new_queue

      payload['queue'] = new_queue

      redis.lpush("queue:#{new_queue}", JSON.dump(payload))
    end
  end
end
