class ReeDao::OneToOne

def call(list, assoc_dao, **opts)
  return if list.empty?
  dto_class = assoc_dao
    .opts[:schema_mapper]
    .dto(:db_load)
  assoc_name = underscore(demodulize(dto_class.name))
  reverse = opts[:reverse]
  assoc_setter = if opts.key?(:assoc_setter)
    opts[:assoc_setter]
  else
    "set_#{assoc_name}"
  end
  foreign_key = if opts.key?(:foreign_key)
    opts[:foreign_key]
  else
    if reverse
      name = underscore(demodulize(list.first.class.name))
      "#{name}_id".to_sym
    else
      :id
    end
  end
  root_ids = if reverse
    list.map(&:id)
  else
    list.map(&:"#{foreign_key}")
  end
  assoc_by_fk = index_by(assoc_dao.where(foreign_key => root_ids).all) { _1.send(foreign_key) }
  list.each do |item|
    item.send(assoc_setter, assoc_by_fk[item.id])
  end
  nil
end