defmodule ExESDB.Commanded.Adapter do
  @moduledoc """
    An adapter for Commanded to use ExESDB as the event store.
    for reference, see: https://hexdocs.pm/commanded/Commanded.EventStore.Adapter.html
  """
  @behaviour Commanded.EventStore.Adapter

  require Logger

  alias ExESDB.Snapshots, as: Snapshots
  alias ExESDB.StreamsWriter, as: StreamsWriter
  alias ExESDB.StreamsReader, as: StreamsReader
  alias ExESDB.SubscriptionsWriter, as: SubscriptionsWriter

  alias ExESDB.Commanded.Mapper, as: Mapper

  @type adapter_meta :: map()
  @type application :: Commanded.Application.t()
  @type config :: Keyword.t()
  @type stream_uuid :: String.t()
  @type start_from :: :origin | :current | integer
  @type expected_version :: :any_version | :no_stream | :stream_exists | non_neg_integer
  @type subscription_name :: String.t()
  @type subscription :: any
  @type subscriber :: pid
  @type source_uuid :: String.t()
  @type error :: term

  @spec ack_event(
          adapter_meta(),
          pid(),
          Commanded.EventStore.EventData.t()
        ) :: :ok | {:error, error()}
  @impl Commanded.EventStore.Adapter
  def ack_event(meta, pid, event) do
    Logger.warning(
      "ack_event/3 is not implemented for #{inspect(meta)}, #{inspect(pid)}, #{inspect(event)}"
    )

    :ok
  end

  @doc """
    Append one or more events to a stream atomically.
  """
  @spec append_to_stream(
          adapter_meta :: map(),
          stream_uuid :: String.t(),
          expected_version :: integer(),
          events :: list(Commanded.EventStore.EventData.t()),
          opts :: Keyword.t()
        ) ::
          :ok | {:error, :wrong_expected_version} | {:error, term()}
  @impl Commanded.EventStore.Adapter
  def append_to_stream(%{store_id: store}, stream_uuid, expected_version, events, _opts) do
    new_events =
      events
      |> Enum.map(&Mapper.to_new_event/1)

    store
    |> StreamsWriter.append_events(stream_uuid, expected_version, new_events)
  end

  @doc """
    Return a child spec defining all processes required by the event store.
  """
  @spec child_spec(
          application(),
          Keyword.t()
        ) ::
          {:ok, [:supervisor.child_spec() | {Module.t(), term} | Module.t()], adapter_meta}
  @impl Commanded.EventStore.Adapter
  def child_spec(application, opts) do
    meta =
      opts
      |> Keyword.put(:application, application)
      |> Map.new()

    {:ok, [ExESDB.System.child_spec(opts)], meta}
  end

  @doc """
    Delete a snapshot of the current state of the event store.
  """
  @spec delete_snapshot(
          adapter_meta :: adapter_meta,
          source_uuid :: source_uuid
        ) :: :ok | {:error, error}
  @impl Commanded.EventStore.Adapter
  def delete_snapshot(%{store_id: store}, source_uuid) do
    case store
         |> Snapshots.delete_snapshot(source_uuid) do
      {:ok, _} ->
        :ok

      {:error, reason} ->
        {:error, reason}
    end
  end

  @doc """
    Delete a subscription.
  """
  @spec delete_subscription(
          adapter_meta :: adapter_meta,
          selector :: stream_uuid,
          subscription_name :: subscription_name
        ) :: :ok | {:error, error}
  @impl Commanded.EventStore.Adapter
  def delete_subscription(%{store_id: store}, stream_uuid, subscription_name) do
    case store
         |> SubscriptionsWriter.delete_subscription(stream_uuid, subscription_name) do
      {:ok, _} -> :ok
      {:error, reason} -> {:error, reason}
    end
  end

  @impl Commanded.EventStore.Adapter
  def read_snapshot(%{store_id: store}, source_uuid) do
    case store
         |> Snapshots.read_snapshot(source_uuid) do
      {:ok, snapshot_record} ->
        {:ok, Mapper.to_snapshot_data(snapshot_record)}

      {:error, reason} ->
        {:error, reason}
    end
  end

  @doc """
    Record a snapshot of the current state of the event store.
  """
  @spec record_snapshot(
          adapter_meta :: adapter_meta,
          snapshot_data :: any
        ) :: :ok | {:error, error}
  @impl Commanded.EventStore.Adapter
  def record_snapshot(%{store_id: store}, snapshot_data) do
    record = Mapper.to_snapshot_record(snapshot_data)

    store
    |> Snapshots.record_snapshot(record)
  end

  @doc """
    Streams events from the given stream, in the order in which they were
    originally written.
  """
  @spec stream_forward(
          adapter_meta :: adapter_meta,
          stream_uuid :: stream_uuid,
          start_version :: non_neg_integer,
          read_batch_size :: non_neg_integer
        ) ::
          Enumerable.t()
          | {:error, :stream_not_found}
          | {:error, error}
  @impl Commanded.EventStore.Adapter
  def stream_forward(adapter_meta, stream_uuid, start_version, read_batch_size) do
    store = Map.get(adapter_meta, :store_id)

    case store
         |> StreamsReader.stream_forward(stream_uuid, start_version, read_batch_size) do
      {:ok, stream} ->
        stream
        |> Stream.map(&Mapper.to_recorded_event/1)

      {:error, :stream_not_found} ->
        {:error, :stream_not_found}

      {:error, reason} ->
        {:error, reason}
    end
  end

  @doc """
    Create a transient subscription to a single event stream.

    The event store will publish any events appended to the given stream to the
    `subscriber` process as an `{:events, events}` message.

    The subscriber does not need to acknowledge receipt of the events.
  """
  @spec subscribe(
          adapter_meta :: adapter_meta,
          stream :: String.t()
        ) ::
          :ok | {:error, error}

  @impl Commanded.EventStore.Adapter
  def subscribe(adapter_meta, stream) do
    Logger.warning(
      "subscribe/2 is not implemented for #{inspect(adapter_meta)}, #{inspect(stream)}"
    )

    store = Map.get(adapter_meta, :store_id)

    store
    |> SubscriptionsWriter.subscribe(stream)
  end

  @doc """
    Create a persistent subscription to an event stream.
  """
  @spec subscribe_to(
          adapter_meta :: adapter_meta,
          stream :: String.t(),
          subscription_name :: String.t(),
          subscriber :: pid,
          start_from :: :origin | :current | non_neg_integer,
          opts :: Keyword.t()
        ) ::
          {:ok, subscription}
          | {:error, :subscription_already_exists}
          | {:error, error}

  @impl Commanded.EventStore.Adapter
  def subscribe_to(adapter_meta, stream, subscription_name, subscriber, start_from, opts) do
    Logger.warning(
      "subscribe_to/7 is ROUGHLY implemented for #{inspect(adapter_meta)}, #{inspect(stream)}, #{inspect(subscription_name)}, #{inspect(subscriber)}, #{inspect(start_from)}, #{inspect(opts)}"
    )

    store = Map.get(adapter_meta, :store_id)

    store
    |> SubscriptionsWriter.subscribe_to(stream, subscription_name, subscriber, start_from, opts)

    {:error, :not_implemented}
  end

  @impl Commanded.EventStore.Adapter
  def unsubscribe(adapter_meta, subscription_name) do
    Logger.warning(
      "unsubscribe/3 is not implemented for #{inspect(adapter_meta)}, #{inspect(subscription_name)}"
    )

    {:error, :not_implemented}
  end
end