defprotocol ProcessHub.Strategy.Distribution.Base do
  @moduledoc """
  The distribution strategy protocol defines behaviour to identify the nodes
  which are responsible for a child process.
  """

  @doc """
  Returns the list of nodes where the child process belongs to.

  The list of nodes is used to determine where the child process should be started
  or migrated to.
  """
  @spec belongs_to(
          strategy :: struct(),
          hub_id :: ProcessHub.hub_id(),
          child_id :: atom() | binary(),
          replication_factor :: pos_integer()
        ) :: [node()]
  def belongs_to(strategy, hub_id, child_id, replication_factor)

  @doc """
  Triggered when coordinator is initialized.

  Could be used to perform initialization.
  """
  @spec init(struct(), ProcessHub.hub_id()) :: any()
  def init(strategy, hub_id)

  @doc """
  Triggered when children are started.

  Could be used to perform validation.
  """
  @spec children_init(struct(), ProcessHub.hub_id(), [map()], keyword()) :: :ok | {:error, any()}
  def children_init(strategy, hub_id, child_specs, opts)
end