18F/identity-dashboard

class AgencySeeder
  attr_reader :agency_configs

  def initialize(agency_configs = Rails.application.config.agencies)
    @agency_configs = agency_configs
  end

  def run!
    # There are unique indexes on both agency name and agency id so we can't in-place update
    # individual records without potentially causing unique constraint errors. There are also
    # foreign key constraints with the service_providers table, so we can't just delete and recreate
    # records.
    #
    # Our approach is to detect pre-existing records that would conflict, and give them temporary
    # names, then run upserts to match the configuration
    #
    # We do this all inside a transaction to provide continuity for other things that read the rows.
    Agency.transaction do
      agencies_by_id = Agency.where(id: agency_configs.map { |id, _values| id }).to_a
      agencies_by_name = Agency.where(
        name: agency_configs.map { |_id, values| values['name'] },
      ).to_a

      agencies_in_db = (agencies_by_id + agencies_by_name).uniq(&:id)

      # Set temporary names for ones that may collide
      agencies_to_update = agencies_in_db.reject do |agency|
        agency.name == agency_configs[agency.id]['name']
      end
      agencies_to_update.each do |agency|
        agency.update!(name: SecureRandom.uuid)
      end

      # Update everything to match the YAML config
      agency_configs.each do |agency_id, values|
        Agency.new(id: agency_id, name: values['name']).upsert
      end
    end
  end
end