use Croma

defmodule RaftFleet.LeaderPidCache do
  @table_name :raft_fleet_leader_pid_cache

  defun init :: :ok do
    _table_id = :ets.new(@table_name, [:public, :named_table, {:read_concurrency, true}])
    :ok
  end

  defun get(name :: atom) :: nil | pid do
    case :ets.lookup(@table_name, name) do
      []         -> nil
      [{_, pid}] -> pid
    end
  end

  defun set(name :: atom, leader :: nil | pid) :: :ok do
    :ets.insert(@table_name, {name, leader})
    :ok
  end

  defun unset(name :: atom) :: :ok do
    :ets.delete(@table_name, name)
    :ok
  end

  defun keys :: [atom] do
    case :ets.first(@table_name) do
      :"$end_of_table" -> []
      k                -> keys_impl(k, [k])
    end
  end

  defp keys_impl(k, acc) do
    case :ets.next(@table_name, k) do
      :"$end_of_table" -> acc
      k                -> keys_impl(k, [k | acc])
    end
  end
end