defmodule PromptRunner.Rendering.Sinks.CallbackSink do
  @moduledoc """
  A sink that forwards events to a callback function.
  """

  @behaviour PromptRunner.Rendering.Sink

  @impl true
  def init(opts) do
    case Keyword.fetch(opts, :callback) do
      {:ok, callback} when is_function(callback, 2) -> {:ok, %{callback: callback}}
      {:ok, _} -> {:error, "callback must be a 2-arity function"}
      :error -> {:error, "callback option is required"}
    end
  end

  @impl true
  def write(_iodata, state), do: {:ok, state}

  @impl true
  def write_event(event, iodata, state) do
    state.callback.(event, iodata)
    {:ok, state}
  end

  @impl true
  def flush(state), do: {:ok, state}

  @impl true
  def close(_state), do: :ok
end