defmodule Actors.Actor.Entity.Lifecycle.StreamInitiator do
  @moduledoc """
  Handles lifecycle functions for Actor Entity that interacts with Event Source mechanisms
  """
  require Logger

  alias Actors.Actor.Entity.Lifecycle.StreamConsumer

  alias Spawn.Actors.Actor
  alias Spawn.Actors.ProjectionSettings
  alias Spawn.Actors.ProjectionSubject

  alias Google.Protobuf.Timestamp

  alias Spawn.Utils.Nats
  alias Gnat.Jetstream.API.Stream, as: NatsStream
  alias Gnat.Jetstream.API.Consumer

  @consumer_not_found_code 10014
  @one_day_in_ms :timer.hours(24)
  @stream_not_found_code 10059

  @spec init_projection_stream(module()) :: :ignore | {:error, any()} | {:ok, pid()}
  def init_projection_stream(%Actor{} = actor) do
    name = "#{actor.id.system}:#{actor.id.name}"

    with {:create_stream, :ok} <- {:create_stream, create_stream(actor, true)},
         {:create_consumer, :ok} <-
           {:create_consumer, create_consumer(actor, deliver_policy: :all)} do
      start_pipeline(actor)
    else
      {:create_stream, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [create_stream]. Details: #{inspect(error)}"
        )

        {:error, error}

      {:create_consumer, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [create_consumer]. Details: #{inspect(error)}"
        )

        {:error, error}

      error ->
        Logger.error(
          "Error on start Projection #{name}. During phase [start_pipeline]. Details: #{inspect(error)}"
        )

        {:error, error}
    end
  end

  def init_sourceable_stream(%Actor{} = actor), do: create_stream(actor, false)

  def replay(stream_pid, actor, call_opts) do
    # TODO: Necessary avoid naming conflicts using actor system and actor name to build name of stream
    name = "#{actor.id.system}:#{actor.id.name}"

    with {:stop_pipeline, :ok} <- {:stop_pipeline, stop_pipeline(stream_pid)},
         {:destroy_consumer, :ok} <- {:destroy_consumer, destroy_consumer(actor)},
         {:recreate_consumer, :ok} <- {:recreate_consumer, create_consumer(actor, call_opts)},
         {:start_pipeline, {:ok, newpid}} <- {:start_pipeline, start_pipeline(actor)} do
      {:ok, newpid}
    else
      {:stop_pipeline, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [stop_pipeline]. Details: #{inspect(error)}"
        )

        {:error, error}

      {:destroy_consumer, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [destroy_consumer]. Details: #{inspect(error)}"
        )

        {:error, error}

      {:recreate_consumer, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [recreate_consumer]. Details: #{inspect(error)}"
        )

        {:error, error}

      {:start_pipeline, error} ->
        Logger.error(
          "Error on start Projection #{name}. During phase [start_pipeline]. Details: #{inspect(error)}"
        )

        {:error, error}
    end
  end

  defp build_consumer(stream_name, consumer_name, opts) do
    deliver_policy = Keyword.get(opts, :deliver_policy, :all)
    build_consumer_by_deliver(deliver_policy, stream_name, consumer_name, opts)
  end

  defp build_consumer_by_deliver(:by_start_time, stream_name, consumer_name, opts) do
    ten_minutes =
      DateTime.utc_now()
      |> DateTime.add(-@one_day_in_ms, :second)

    start_time = Keyword.get(opts, :opt_start_time, ten_minutes)

    %Consumer{
      stream_name: stream_name,
      durable_name: consumer_name,
      deliver_policy: :by_start_time,
      opt_start_time: start_time
    }
  end

  defp build_consumer_by_deliver(:all, stream_name, consumer_name, _opts) do
    %Consumer{stream_name: stream_name, durable_name: consumer_name, deliver_policy: :all}
  end

  defp build_sources(%ProjectionSettings{} = settings) do
    settings.subjects
    |> Enum.map(fn %ProjectionSubject{} = subject ->
      opt_start_time =
        case subject.start_time do
          nil ->
            DateTime.from_unix!(0, :second)

          %Timestamp{seconds: start_at} ->
            DateTime.from_unix!(start_at, :second)
        end

      %{
        name: subject.actor,
        filter_subject: "actors.#{subject.actor}.*.#{subject.action}",
        opt_start_time: opt_start_time
      }
    end)
  end

  defp build_stream_max_age(%ProjectionSettings{} = settings) do
    case Map.get(settings.events_retention_strategy, :strategy, {:duration_ms, @one_day_in_ms}) do
      {:infinite, true} -> 0
      # ms to ns
      {:duration_ms, max_age} -> max_age * 1_000_000
    end
  end

  defp conn, do: Nats.connection_name()

  defp create_stream(actor, true) do
    # TODO: Necessary avoid naming conflicts using actor system and actor name to build name of stream
    stream_name = actor.id.name
    max_age = build_stream_max_age(actor.settings.projection_settings)

    stream =
      %NatsStream{
        name: stream_name,
        subjects: [],
        sources: build_sources(actor.settings.projection_settings),
        duplicate_window: max_age,
        max_age: max_age
      }

    case NatsStream.info(conn(), stream_name) do
      {:ok, _info} ->
        # TODO: Make sure to update the stream if it already exists and sources is changed
        :ok

      {:error, %{"code" => 404, "err_code" => @stream_not_found_code}} ->
        {:ok, %{created: _}} = NatsStream.create(conn(), stream)
        :ok

      error ->
        error
    end
  end

  defp create_stream(actor, false) do
    # TODO: Necessary avoid naming conflicts using actor system and actor name to build name of stream
    stream_name = actor.id.name

    max_age = build_stream_max_age(actor.settings.projection_settings)

    stream = %NatsStream{
      name: stream_name,
      subjects: ["actors.#{stream_name}.>"],
      max_age: max_age,
      duplicate_window: max_age
    }

    case NatsStream.info(conn(), stream_name) do
      {:ok, _info} ->
        :ok

      {:error, %{"code" => 404, "err_code" => @stream_not_found_code}} ->
        {:ok, %{created: _}} = NatsStream.create(conn(), stream)
        :ok

      error ->
        error
    end
  end

  defp create_consumer(actor, opts) do
    # TODO: Necessary avoid naming conflicts using actor system and actor name to build name of stream
    stream_name = actor.id.name
    consumer_name = actor.id.name

    case Consumer.info(conn(), stream_name, consumer_name) do
      {:ok, _info} ->
        :ok

      {:error,
       %{
         "code" => 404,
         "description" => "consumer not found",
         "err_code" => @consumer_not_found_code
       }} ->
        {:ok, %{created: _}} =
          Consumer.create(conn(), build_consumer(stream_name, consumer_name, opts))

        :ok

      error ->
        error
    end
  end

  defp destroy_consumer(actor) do
    stream_name = actor.id.name
    consumer_name = actor.id.name

    case Consumer.info(conn(), stream_name, consumer_name) do
      {:ok, _info} ->
        Consumer.delete(conn(), stream_name, consumer_name)

      {:error,
       %{
         "code" => 404,
         "description" => "consumer not found",
         "err_code" => @consumer_not_found_code
       }} ->
        :ok

      error ->
        error
    end
  end

  defp start_pipeline(actor),
    do:
      StreamConsumer.start_link(%{
        actor_name: actor.id.name,
        projection_pid: self(),
        strict_ordering: actor.settings.projection_settings.strict_events_ordering
      })

  defp stop_pipeline(pid), do: Broadway.stop(pid)
end