defmodule EventStore.Storage.Subscription do
  @moduledoc false

  require Logger

  alias EventStore.Sql.Statements
  alias EventStore.Storage.Subscription

  @type t :: %EventStore.Storage.Subscription{
          subscription_id: non_neg_integer(),
          stream_uuid: String.t(),
          subscription_name: String.t(),
          last_seen: non_neg_integer(),
          created_at: DateTime.t()
        }

  defstruct subscription_id: nil,
            stream_uuid: nil,
            subscription_name: nil,
            last_seen: nil,
            created_at: nil

  @doc """
  List all known subscriptions
  """
  def subscriptions(conn, opts \\ []),
    do: Subscription.All.execute(conn, opts)

  def subscribe_to_stream(conn, stream_uuid, subscription_name, start_from, opts \\ []) do
    with {:ok, subscription} <-
           Subscription.Query.execute(conn, stream_uuid, subscription_name, opts) do
      {:ok, subscription}
    else
      {:error, :subscription_not_found} ->
        create_subscription(conn, stream_uuid, subscription_name, start_from, opts)

      reply ->
        reply
    end
  end

  def ack_last_seen_event(conn, stream_uuid, subscription_name, last_seen, opts \\ []) do
    Subscription.Ack.execute(conn, stream_uuid, subscription_name, last_seen, opts)
  end

  def delete_subscription(conn, stream_uuid, subscription_name, opts \\ []),
    do: Subscription.Delete.execute(conn, stream_uuid, subscription_name, opts)

  defp create_subscription(conn, stream_uuid, subscription_name, start_from, opts) do
    case Subscription.Subscribe.execute(conn, stream_uuid, subscription_name, start_from, opts) do
      {:error, :subscription_already_exists} ->
        Subscription.Query.execute(conn, stream_uuid, subscription_name, opts)

      reply ->
        reply
    end
  end

  defmodule All do
    @moduledoc false

    def execute(conn, opts) do
      conn
      |> Postgrex.query(Statements.query_all_subscriptions(), [], opts)
      |> handle_response()
    end

    defp handle_response({:ok, %Postgrex.Result{num_rows: 0}}),
      do: {:ok, []}

    defp handle_response({:ok, %Postgrex.Result{rows: rows}}),
      do: {:ok, Subscription.Adapter.to_subscriptions(rows)}

    defp handle_response({:error, error}), do: {:error, error}
  end

  defmodule Query do
    @moduledoc false

    def execute(conn, stream_uuid, subscription_name, opts) do
      conn
      |> Postgrex.query(
        Statements.query_get_subscription(),
        [stream_uuid, subscription_name],
        opts
      )
      |> handle_response()
    end

    defp handle_response({:ok, %Postgrex.Result{num_rows: 0}}),
      do: {:error, :subscription_not_found}

    defp handle_response({:ok, %Postgrex.Result{rows: rows}}),
      do: {:ok, Subscription.Adapter.to_subscription(rows)}

    defp handle_response({:error, error}), do: {:error, error}
  end

  defmodule Subscribe do
    @moduledoc false

    def execute(conn, stream_uuid, subscription_name, start_from, opts) do
      _ =
        Logger.debug(fn ->
          "Attempting to create subscription on stream " <>
            inspect(stream_uuid) <>
            " named " <> inspect(subscription_name) <> " starting from #" <> inspect(start_from)
        end)

      conn
      |> Postgrex.query(
        Statements.create_subscription(),
        [stream_uuid, subscription_name, start_from],
        opts
      )
      |> handle_response(stream_uuid, subscription_name)
    end

    defp handle_response({:ok, %Postgrex.Result{rows: rows}}, stream_uuid, subscription_name) do
      _ =
        Logger.debug(fn ->
          "Created subscription on stream \"#{stream_uuid}\" named \"#{subscription_name}\""
        end)

      {:ok, Subscription.Adapter.to_subscription(rows)}
    end

    defp handle_response(
           {:error, %Postgrex.Error{postgres: %{code: :unique_violation}}},
           stream_uuid,
           subscription_name
         ) do
      _ =
        Logger.debug(fn ->
          "Failed to create subscription on stream \"#{stream_uuid}\" named \"#{subscription_name}\", already exists"
        end)

      {:error, :subscription_already_exists}
    end

    defp handle_response({:error, error}, stream_uuid, subscription_name) do
      _ =
        Logger.warn(fn ->
          "Failed to create stream create subscription on stream \"#{stream_uuid}\" named \"#{
            subscription_name
          }\" due to: #{error}"
        end)

      {:error, error}
    end
  end

  defmodule Ack do
    @moduledoc false

    def execute(conn, stream_uuid, subscription_name, last_seen, opts) do
      conn
      |> Postgrex.query(
        Statements.ack_last_seen_event(),
        [stream_uuid, subscription_name, last_seen],
        opts
      )
      |> handle_response(stream_uuid, subscription_name)
    end

    defp handle_response({:ok, _result}, _stream_uuid, _subscription_name) do
      :ok
    end

    defp handle_response({:error, error}, stream_uuid, subscription_name) do
      _ =
        Logger.warn(fn ->
          "Failed to ack last seen event on stream \"#{stream_uuid}\" named \"#{subscription_name}\" due to: #{
            error
          }"
        end)

      {:error, error}
    end
  end

  defmodule Delete do
    @moduledoc false

    def execute(conn, stream_uuid, subscription_name, opts) do
      _ =
        Logger.debug(fn ->
          "Attempting to delete subscription on stream \"#{stream_uuid}\" named \"#{
            subscription_name
          }\""
        end)

      conn
      |> Postgrex.query(Statements.delete_subscription(), [stream_uuid, subscription_name], opts)
      |> handle_response(stream_uuid, subscription_name)
    end

    defp handle_response({:ok, _result}, stream_uuid, subscription_name) do
      _ =
        Logger.debug(fn ->
          "Deleted subscription to stream \"#{stream_uuid}\" named \"#{subscription_name}\""
        end)

      :ok
    end

    defp handle_response({:error, error}, stream_uuid, subscription_name) do
      _ =
        Logger.warn(fn ->
          "Failed to delete subscription to stream \"#{stream_uuid}\" named \"#{subscription_name}\" due to: #{
            error
          }"
        end)

      {:error, error}
    end
  end

  defmodule Adapter do
    @moduledoc false

    def to_subscriptions(rows), do: Enum.map(rows, &to_subscription_from_row/1)

    def to_subscription([row | _]), do: to_subscription_from_row(row)

    defp to_subscription_from_row(row) do
      [
        subscription_id,
        stream_uuid,
        subscription_name,
        last_seen,
        created_at
      ] = row

      %Subscription{
        subscription_id: subscription_id,
        stream_uuid: stream_uuid,
        subscription_name: subscription_name,
        last_seen: last_seen,
        created_at: created_at
      }
    end
  end
end