Versioned definition for a precise, asynchronous operational procedure.

A Work owns no process and receives no open goal. Its callbacks are short, deterministic reducers; registered operations run separately through the shared operational runtime.

defmodule MyApp.ReadPages do
  use Spectre.Work,
    id: :read_pages,
    version: 1,
    input: :map,
    state: :map,
    update: :map,
    budget: [steps: 500, attempts: 750]

  operation :fetch_page, {MyApp.Pages, :fetch},
    input: :map,
    output: :map,
    side_effect: :idempotent,
    retry: [max_attempts: 3]

  @impl true
  def init(input, _context), do: {:ok, %{queue: input.urls, pages: []}}

  @impl true
  def next(%{queue: [url | _]}, _context),
    do: run(:fetch_page, %{url: url}, phase: :reading)

  @impl true
  def apply_result(state, _request, result, _context) do
    [_url | rest] = state.queue
    {:ok, %{state | queue: rest, pages: [result.value | state.pages]}}
  end

  @impl true
  def complete(%{queue: []} = state, _context), do: complete(Enum.reverse(state.pages))
  def complete(_state, _context), do: :continue
end