defmodule SyntropyWeb.Api.RunController do
  use SyntropyWeb, :controller

  alias Syntropy.Persistence
  alias SyntropyWeb.Api.{ControllerHelpers, Listing, RunJSON, RunRequest}

  @memory_scan_limit 1_000

  @spec index(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def index(conn, params) do
    case Listing.parse_opts(params, [:status, :kind, :q]) do
      {:ok, opts} ->
        page = runs_page(opts)

        json(conn, %{
          data: Enum.map(page.entries, &RunJSON.run/1),
          meta: Listing.meta(page)
        })

      {:error, :invalid_cursor} ->
        ControllerHelpers.invalid_request(conn, "Invalid cursor.", [])
    end
  end

  @spec show(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def show(conn, %{"id" => run_id}) do
    case Syntropy.run(run_id) || Persistence.get_run_envelope(run_id) do
      nil -> ControllerHelpers.not_found(conn, "Run", run_id)
      run -> json(conn, %{data: RunJSON.run(run)})
    end
  end

  @spec create(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def create(conn, params) do
    with {:ok, %{prompt: prompt, opts: opts}} <- RunRequest.parse(params),
         {:ok, run} <- Syntropy.start_run(prompt, opts) do
      conn
      |> put_status(:accepted)
      |> json(%{data: RunJSON.run(run)})
    else
      {:error, errors} when is_list(errors) ->
        ControllerHelpers.invalid_request(conn, "Invalid run request.", errors)

      {:error, reason} ->
        ControllerHelpers.task_failure(conn, reason)
    end
  end

  @spec cancel(Plug.Conn.t(), map()) :: Plug.Conn.t()
  def cancel(conn, %{"id" => run_id}) do
    case Syntropy.cancel_run(run_id) do
      {:ok, run} ->
        json(conn, %{data: RunJSON.run(run)})

      {:error, :not_found} ->
        ControllerHelpers.not_found(conn, "Run", run_id)

      {:error, :not_cancellable} ->
        ControllerHelpers.conflict(
          conn,
          "not_cancellable",
          "Run #{run_id} already reached a terminal state."
        )
    end
  end

  defp runs_page(opts) do
    if Persistence.enabled?() do
      Persistence.list_run_envelopes(opts)
    else
      @memory_scan_limit
      |> Syntropy.recent_runs()
      |> Listing.filter_runs(opts)
      |> Listing.paginate(opts, :updated_at)
    end
  end
end