defmodule Actors do
  @moduledoc """
  `Actors` It's the client API for the Spawn actors.
  Through this module we interact with the actors by creating,
  invoking or configuring them.
  """
  use Retry

  require Logger
  require OpenTelemetry.Tracer, as: Tracer

  alias Actors.Actor.Entity, as: ActorEntity
  alias Actors.Actor.Entity.EntityState
  alias Actors.Actor.Entity.Supervisor, as: ActorEntitySupervisor
  alias Actors.Actor.InvocationScheduler

  alias Actors.Registry.{ActorRegistry, HostActor}

  alias Eigr.Functions.Protocol.Actors.{
    Actor,
    ActorId,
    Metadata,
    ActorSettings,
    ActorSystem,
    Registry
  }

  alias Eigr.Functions.Protocol.{
    InvocationRequest,
    ProxyInfo,
    RegistrationRequest,
    RegistrationResponse,
    RequestStatus,
    ServiceInfo,
    SpawnRequest,
    SpawnResponse
  }

  @activate_actors_min_demand 0
  @activate_actors_max_demand 4

  @erpc_timeout 5_000

  @spec get_state(String.t(), String.t()) :: {:ok, term()} | {:error, term()}
  def get_state(system_name, actor_name) do
    retry with: exponential_backoff() |> randomize |> expiry(10_000),
          atoms: [:error, :exit, :noproc, :erpc, :noconnection],
          rescue_only: [ErlangError] do
      do_lookup_action(
        system_name,
        {false, system_name, actor_name, actor_name},
        nil,
        fn actor_ref, _actor_ref_id ->
          ActorEntity.get_state(actor_ref)
        end
      )
    after
      result -> result
    else
      error -> error
    end
  end

  @doc """
  Registers all actors defined in HostActor.

    * `registration` - The RegistrationRequest
    * `opts` - The options to create Actors
  ##
  """
  @spec register(RegistrationRequest.t(), any()) :: {:ok, RegistrationResponse.t()}
  def register(registration, opts \\ [])

  def register(
        %RegistrationRequest{
          service_info: %ServiceInfo{} = _service_info,
          actor_system:
            %ActorSystem{name: _name, registry: %Registry{actors: actors} = _registry} =
              actor_system
        } = _registration,
        opts
      ) do
    hosts =
      Enum.map(Map.values(actors), fn actor -> create_actor_host_pool(actor, opts) end)
      |> List.flatten()

    ActorRegistry.register(hosts)

    spawn(fn ->
      create_actors(actor_system, actors, opts)
    end)

    proxy_info =
      ProxyInfo.new(
        protocol_major_version: 1,
        protocol_minor_version: 2,
        proxy_name: "spawn",
        proxy_version: "0.5.0"
      )

    status = RequestStatus.new(status: :OK, message: "Accepted")
    {:ok, RegistrationResponse.new(proxy_info: proxy_info, status: status)}
  end

  defp create_actor_host_pool(
         %Actor{
           id: %ActorId{system: system, parent: _parent, name: name} = _id,
           settings:
             %ActorSettings{kind: :POOLED, min_pool_size: min_pool, max_pool_size: max_pool} =
               _settings
         } = actor,
         opts
       ) do
    min_pool = if min_pool == 0, do: 1, else: min_pool
    max_pool = if max_pool < min_pool, do: get_defaul_max_pool() + 1, else: max_pool

    case ActorRegistry.get_hosts_by_actor(system, name) do
      {:ok, actor_hosts} ->
        Enum.into(
          min_pool..max_pool,
          [],
          fn index ->
            host = Enum.random(actor_hosts)
            name_alias = "#{name}-#{index}"

            pooled_actor = %Actor{
              actor
              | id: %ActorId{system: system, parent: name_alias, name: name}
            }

            Logger.debug("Creating Pooled Actor #{name} with Alias #{name_alias}")
            %HostActor{node: host.node, actor: pooled_actor, opts: opts}
          end
        )

      _ ->
        Enum.into(
          min_pool..max_pool,
          [],
          fn index ->
            name_alias = "#{name}-#{index}"

            pooled_actor = %Actor{
              actor
              | id: %ActorId{system: system, parent: name_alias, name: name}
            }

            Logger.debug("Creating Pooled Actor #{name} with Alias #{name_alias}")
            %HostActor{node: Node.self(), actor: pooled_actor, opts: opts}
          end
        )
    end
  end

  defp create_actor_host_pool(
         %Actor{settings: %ActorSettings{kind: _kind} = _settings} = actor,
         opts
       ) do
    [%HostActor{node: Node.self(), actor: actor, opts: opts}]
  end

  defp get_defaul_max_pool() do
    length(Node.list() ++ [Node.self()]) * System.schedulers_online()
  end

  @doc """
  Spawn actors defined in HostActor.

    * `registration` - The SpawnRequest
    * `opts` - The options to create Actors

  spawn_actor must be used when you want to create a concrete instance of an actor
  previously registered as abstract.
  That is, when an Actorid is associated with an actor of abstract type.
  This function only registers the metadata of the new actor, not activating it.
  This will occur when the sprite is first invoked.
  ##
  """
  @spec spawn_actor(SpawnRequest.t(), any()) :: {:ok, SpawnResponse.t()}
  def spawn_actor(spawn, opts \\ [])

  def spawn_actor(%SpawnRequest{actors: actors} = _spawn, opts) do
    hosts =
      Enum.map(actors, fn %ActorId{system: system, parent: parent, name: _name} = id ->
        case ActorRegistry.get_hosts_by_actor(system, parent) do
          {:ok, actor_hosts} ->
            Enum.map(actor_hosts, fn %HostActor{
                                       node: node,
                                       actor: %Actor{} = abstract_actor,
                                       opts: _opts
                                     } = _host ->
              spawned_actor = %Actor{abstract_actor | id: id}
              %HostActor{node: node, actor: spawned_actor, opts: opts}
            end)

          _ ->
            raise ArgumentError,
                  "You are trying to create an actor from an Abstract actor that has never been registered before. ActorId: #{inspect(id)}"
        end
      end)
      |> List.flatten()

    ActorRegistry.register(hosts)

    status = RequestStatus.new(status: :OK, message: "Accepted")
    {:ok, SpawnResponse.new(status: status)}
  end

  @doc """
  Makes a request to an actor.

    * `request` - The InvocationRequest
    * `opts` - The options to Invoke Actors
  ##
  """
  @spec invoke(%InvocationRequest{}) :: {:ok, :async} | {:ok, term()} | {:error, term()}
  def invoke(
        %InvocationRequest{} = request,
        opts \\ []
      ) do
    invoke_with_span(request, opts)
  end

  defp invoke_with_span(
         %InvocationRequest{
           actor: %Actor{} = actor,
           system: %ActorSystem{} = system,
           async: async?,
           metadata: metadata,
           caller: caller,
           pooled: pooled?
         } = request,
         opts \\ []
       ) do
    metadata_attributes =
      Enum.map(metadata, fn {key, value} -> {to_existing_atom_or_new(key), value} end) ++
        [{:async, async?}, {"from", get_caller(caller)}, {"target", actor.id.name}]

    {_current, opts} =
      Keyword.get_and_update(opts, :span_ctx, fn v ->
        if is_nil(v), do: {v, OpenTelemetry.Ctx.new()}, else: {v, v}
      end)

    Tracer.with_span opts[:span_ctx], "client invoke", kind: :client do
      Tracer.set_attributes(metadata_attributes)

      retry with: exponential_backoff() |> randomize |> expiry(10_000),
            atoms: [:error, :exit, :noproc, :erpc, :noconnection],
            rescue_only: [ErlangError] do
        Tracer.add_event("lookup", [{"target", actor.id.name}])

        actor_fqdn =
          unless pooled? do
            {pooled?, system.name, actor.id.name, actor.id.name}
          else
            case ActorRegistry.get_hosts_by_actor(system.name, actor.id.name) do
              {:ok, actor_hosts} ->
                host = Enum.random(actor_hosts)
                {pooled?, system.name, host.actor.id.parent, actor.id.name}

              _ ->
                {pooled?, system.name, "#{actor.id.name}-1", actor.id.name}
            end
          end

        do_lookup_action(system.name, actor_fqdn, system, fn actor_ref, actor_ref_id ->
          %InvocationRequest{
            actor: %Actor{} = actor
          } = request

          request_params = %InvocationRequest{request | actor: %Actor{actor | id: actor_ref_id}}

          if is_nil(request.scheduled_to) || request.scheduled_to == 0 do
            maybe_invoke_async(async?, actor_ref, request_params, opts)
          else
            InvocationScheduler.schedule_invoke(request_params)

            {:ok, :async}
          end
        end)
      after
        result -> result
      else
        error -> error
      end
    end
  end

  defp get_caller(nil), do: "external"
  defp get_caller(caller), do: caller.name

  defp do_lookup_action(
         system_name,
         {pooled, system_name, parent, actor_name} = actor_fqdn,
         system,
         action_fun
       ) do
    Tracer.with_span "actor-lookup" do
      Tracer.set_attributes([{:actor_fqdn, actor_fqdn}])

      case Spawn.Cluster.Node.Registry.lookup(Actors.Actor.Entity, parent) do
        [{actor_ref, _}] ->
          Tracer.add_event("actor-status", [{"alive", true}])
          Tracer.set_attributes([{"actor-pid", "#{inspect(actor_ref)}"}])
          Logger.debug("Lookup Actor #{actor_name}. PID: #{inspect(actor_ref)}")

          actor_ref_id =
            try do
              %EntityState{actor: %Actor{id: %ActorId{} = actor_ref_id}} =
                :sys.get_state(actor_ref, 1000)
                |> EntityState.unpack()

              actor_ref_id
            catch
              e ->
                Logger.warning(
                  "Failure during get_state to actor #{actor_name}. Error #{inspect(e)}"
                )
            end

          if pooled,
            # Ensures that the name change will not affect the host function call
            do: action_fun.(actor_ref, %ActorId{actor_ref_id | name: actor_name}),
            else: action_fun.(actor_ref, actor_ref_id)

        _ ->
          Tracer.add_event("actor-status", [{"alive", false}])

          Tracer.with_span "actor-reactivation" do
            Tracer.set_attributes([{:system_name, system_name}])
            Tracer.set_attributes([{:actor_name, actor_name}])

            with {:ok, %HostActor{node: node, actor: actor, opts: opts}} <-
                   ActorRegistry.lookup(system_name, actor_name,
                     filter_by_parent: pooled,
                     parent: parent
                   ),
                 {:ok, actor_ref} =
                   :erpc.call(
                     node,
                     __MODULE__,
                     :try_reactivate_actor,
                     [system, actor, opts],
                     @erpc_timeout
                   ) do
              Tracer.set_attributes([{"actor-pid", "#{inspect(actor_ref)}"}])

              Tracer.add_event("try-reactivate-actor", [
                {"reactivation-on-node", "#{inspect(node)}"}
              ])

              if pooled,
                # Ensures that the name change will not affect the host function call
                do: action_fun.(actor_ref, %ActorId{actor.id | name: actor_name}),
                else: action_fun.(actor_ref, actor.id)
            else
              {:not_found, _} ->
                Logger.error("Actor #{actor_name} not found on ActorSystem #{system_name}")

                Tracer.add_event("reactivation-failure", [
                  {:cause, "not_found"}
                ])

                {:error, "Actor #{actor_name} not found on ActorSystem #{system_name}"}

              {:erpc, :timeout} ->
                Logger.error(
                  "Failed to invoke Actor #{actor_name} on ActorSystem #{system_name}: Node connection timeout"
                )

                Tracer.add_event("reactivation-failure", [
                  {:cause, "timeout"}
                ])

                {:error, "Node connection timeout"}

              {:error, reason} ->
                Logger.error(
                  "Failed to invoke Actor #{actor_name} on ActorSystem #{system_name}: #{inspect(reason)}"
                )

                Tracer.add_event("reactivation-failure", [
                  {:cause, "#{inspect(reason)}"}
                ])

                {:error, reason}

              _ ->
                Logger.error("Failed to invoke Actor #{actor_name} on ActorSystem #{system_name}")

                Tracer.add_event("reactivation-failure", [
                  {:cause, "unknown"}
                ])

                {:error, "Failed to invoke Actor #{actor_name} on ActorSystem #{system_name}"}
            end
          end
      end
    end
  end

  defp maybe_invoke_async(true, actor_ref, request, opts) do
    ActorEntity.invoke_async(actor_ref, request, opts)

    {:ok, :async}
  end

  defp maybe_invoke_async(false, actor_ref, request, opts) do
    ActorEntity.invoke(actor_ref, request, opts)
  end

  @spec try_reactivate_actor(ActorSystem.t(), Actor.t(), any()) :: {:ok, any()} | {:error, any()}
  def try_reactivate_actor(system, actor, opts \\ [])

  def try_reactivate_actor(
        %ActorSystem{} = system,
        %Actor{id: %ActorId{name: name} = _id} = actor,
        opts
      ) do
    case ActorEntitySupervisor.lookup_or_create_actor(system, actor, opts) do
      {:ok, actor_ref} ->
        Logger.debug("Actor #{name} reactivated. ActorRef PID: #{inspect(actor_ref)}")
        {:ok, actor_ref}

      reason ->
        Logger.error("Failed to reactivate actor #{name}: #{inspect(reason)}")
        {:error, reason}
    end
  end

  # To lookup all actors
  def try_reactivate_actor(nil, %Actor{id: %ActorId{name: name} = _id} = actor, opts) do
    case ActorEntitySupervisor.lookup_or_create_actor(nil, actor, opts) do
      {:ok, actor_ref} ->
        Logger.debug("Actor #{name} reactivated. ActorRef PID: #{inspect(actor_ref)}")
        {:ok, actor_ref}

      reason ->
        Logger.error("Failed to reactivate actor #{name}: #{inspect(reason)}")
        {:error, reason}
    end
  end

  defp create_actors(actor_system, actors, opts) when is_map(actors) do
    actors
    |> Flow.from_enumerable(
      min_demand: @activate_actors_min_demand,
      max_demand: @activate_actors_max_demand
    )
    |> Flow.filter(fn {_actor_name,
                       %Actor{
                         metadata: %Metadata{channel_group: channel},
                         settings: %ActorSettings{stateful: stateful, kind: kind}
                       } = _actor} ->
      cond do
        kind == :POOLED ->
          false

        match?(true, stateful) and kind != :ABSTRACT ->
          true

        not is_nil(channel) and byte_size(channel) > 0 ->
          true

        true ->
          false
      end
    end)
    |> Flow.map(fn {actor_name, actor} ->
      {time, result} = :timer.tc(&lookup_actor/4, [actor_system, actor_name, actor, opts])

      Logger.info(
        "Actor #{actor_name} Activated on Node #{inspect(Node.self())} in #{inspect(time)}ms"
      )

      result
    end)
    |> Flow.run()
  end

  @spec lookup_actor(ActorSystem.t(), String.t(), Actor.t(), any()) ::
          {:ok, pid()} | {:error, String.t()}
  defp lookup_actor(actor_system, actor_name, actor, opts) do
    case ActorEntitySupervisor.lookup_or_create_actor(actor_system, actor, opts) do
      {:ok, pid} ->
        {:ok, pid}

      _ ->
        Logger.debug("Failed to register Actor #{actor_name}")
        {:error, "Failed to register Actor #{actor_name}"}
    end
  end

  defp to_existing_atom_or_new(string) do
    String.to_existing_atom(string)
  rescue
    _e ->
      String.to_atom(string)
  end
end