defmodule Vela.Distributed.RPC do
  @moduledoc """
  Thin wrapper around `:erpc` for remote procedure calls.

  Provides a consistent interface with timeout handling and
  error normalization for Vela's distributed topologies.
  """

  @default_timeout 5_000

  @doc """
  Synchronous call to a function on a remote node.
  Returns `{:ok, result}` or `{:error, reason}`.
  """
  @spec call(node(), module(), atom(), [term()], timeout()) ::
          {:ok, term()} | {:error, term()}
  def call(node, mod, fun, args, timeout \\ @default_timeout) do
    {:ok, :erpc.call(node, mod, fun, args, timeout)}
  rescue
    e in ErlangError ->
      {:error, {:rpc_failed, node, e}}
  catch
    :exit, reason ->
      {:error, {:rpc_exit, node, reason}}
  end

  @doc """
  Asynchronous cast to a function on a remote node.
  Fire-and-forget — does not wait for a result.
  """
  @spec cast(node(), module(), atom(), [term()]) :: :ok
  def cast(node, mod, fun, args) do
    :erpc.cast(node, mod, fun, args)
    :ok
  end

  @doc """
  Calls a function on multiple nodes in parallel.
  Returns a map of `%{node => {:ok, result} | {:error, reason}}`.
  """
  @spec multi_call([node()], module(), atom(), [term()], timeout()) ::
          %{node() => {:ok, term()} | {:error, term()}}
  def multi_call(nodes, mod, fun, args, timeout \\ @default_timeout) do
    nodes
    |> Enum.map(fn target ->
      {target, Task.async(fn -> call(target, mod, fun, args, timeout) end)}
    end)
    |> Enum.map(fn {target, task} ->
      {target, Task.await(task, timeout + 1_000)}
    end)
    |> Map.new()
  end
end