# Pleroma: A lightweight social networking server
# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Web.Streamer do
  use GenServer
  require Logger
  alias Pleroma.Activity
  alias Pleroma.Config
  alias Pleroma.Conversation.Participation
  alias Pleroma.Notification
  alias Pleroma.Object
  alias Pleroma.User
  alias Pleroma.Web.ActivityPub.ActivityPub
  alias Pleroma.Web.ActivityPub.Visibility
  alias Pleroma.Web.CommonAPI
  alias Pleroma.Web.MastodonAPI.NotificationView

  @keepalive_interval :timer.seconds(30)

  def start_link(_) do
    GenServer.start_link(__MODULE__, %{}, name: __MODULE__)
  end

  def add_socket(topic, socket) do
    GenServer.cast(__MODULE__, %{action: :add, socket: socket, topic: topic})
  end

  def remove_socket(topic, socket) do
    GenServer.cast(__MODULE__, %{action: :remove, socket: socket, topic: topic})
  end

  def stream(topic, item) do
    GenServer.cast(__MODULE__, %{action: :stream, topic: topic, item: item})
  end

  def init(args) do
    Process.send_after(self(), %{action: :ping}, @keepalive_interval)

    {:ok, args}
  end

  def handle_info(%{action: :ping}, topics) do
    topics
    |> Map.values()
    |> List.flatten()
    |> Enum.each(fn socket ->
      Logger.debug("Sending keepalive ping")
      send(socket.transport_pid, {:text, ""})
    end)

    Process.send_after(self(), %{action: :ping}, @keepalive_interval)

    {:noreply, topics}
  end

  def handle_cast(%{action: :stream, topic: "direct", item: item}, topics) do
    recipient_topics =
      User.get_recipients_from_activity(item)
      |> Enum.map(fn %{id: id} -> "direct:#{id}" end)

    Enum.each(recipient_topics || [], fn user_topic ->
      Logger.debug("Trying to push direct message to #{user_topic}\n\n")
      push_to_socket(topics, user_topic, item)
    end)

    {:noreply, topics}
  end

  def handle_cast(%{action: :stream, topic: "participation", item: participation}, topics) do
    user_topic = "direct:#{participation.user_id}"
    Logger.debug("Trying to push a conversation participation to #{user_topic}\n\n")

    push_to_socket(topics, user_topic, participation)

    {:noreply, topics}
  end

  def handle_cast(%{action: :stream, topic: "list", item: item}, topics) do
    # filter the recipient list if the activity is not public, see #270.
    recipient_lists =
      case Visibility.is_public?(item) do
        true ->
          Pleroma.List.get_lists_from_activity(item)

        _ ->
          Pleroma.List.get_lists_from_activity(item)
          |> Enum.filter(fn list ->
            owner = User.get_cached_by_id(list.user_id)

            Visibility.visible_for_user?(item, owner)
          end)
      end

    recipient_topics =
      recipient_lists
      |> Enum.map(fn %{id: id} -> "list:#{id}" end)

    Enum.each(recipient_topics || [], fn list_topic ->
      Logger.debug("Trying to push message to #{list_topic}\n\n")
      push_to_socket(topics, list_topic, item)
    end)

    {:noreply, topics}
  end

  def handle_cast(
        %{action: :stream, topic: topic, item: %Notification{} = item},
        topics
      )
      when topic in ["user", "user:notification"] do
    topics
    |> Map.get("#{topic}:#{item.user_id}", [])
    |> Enum.each(fn socket ->
      with %User{} = user <- User.get_cached_by_ap_id(socket.assigns[:user].ap_id),
           true <- should_send?(user, item) do
        send(
          socket.transport_pid,
          {:text, represent_notification(socket.assigns[:user], item)}
        )
      end
    end)

    {:noreply, topics}
  end

  def handle_cast(%{action: :stream, topic: "user", item: item}, topics) do
    Logger.debug("Trying to push to users")

    recipient_topics =
      User.get_recipients_from_activity(item)
      |> Enum.map(fn %{id: id} -> "user:#{id}" end)

    Enum.each(recipient_topics, fn topic ->
      push_to_socket(topics, topic, item)
    end)

    {:noreply, topics}
  end

  def handle_cast(%{action: :stream, topic: topic, item: item}, topics) do
    Logger.debug("Trying to push to #{topic}")
    Logger.debug("Pushing item to #{topic}")
    push_to_socket(topics, topic, item)
    {:noreply, topics}
  end

  def handle_cast(%{action: :add, topic: topic, socket: socket}, sockets) do
    topic = internal_topic(topic, socket)
    sockets_for_topic = sockets[topic] || []
    sockets_for_topic = Enum.uniq([socket | sockets_for_topic])
    sockets = Map.put(sockets, topic, sockets_for_topic)
    Logger.debug("Got new conn for #{topic}")
    {:noreply, sockets}
  end

  def handle_cast(%{action: :remove, topic: topic, socket: socket}, sockets) do
    topic = internal_topic(topic, socket)
    sockets_for_topic = sockets[topic] || []
    sockets_for_topic = List.delete(sockets_for_topic, socket)
    sockets = Map.put(sockets, topic, sockets_for_topic)
    Logger.debug("Removed conn for #{topic}")
    {:noreply, sockets}
  end

  def handle_cast(m, state) do
    Logger.info("Unknown: #{inspect(m)}, #{inspect(state)}")
    {:noreply, state}
  end

  defp represent_update(%Activity{} = activity, %User{} = user) do
    %{
      event: "update",
      payload:
        Pleroma.Web.MastodonAPI.StatusView.render(
          "status.json",
          activity: activity,
          for: user
        )
        |> Jason.encode!()
    }
    |> Jason.encode!()
  end

  defp represent_update(%Activity{} = activity) do
    %{
      event: "update",
      payload:
        Pleroma.Web.MastodonAPI.StatusView.render(
          "status.json",
          activity: activity
        )
        |> Jason.encode!()
    }
    |> Jason.encode!()
  end

  def represent_conversation(%Participation{} = participation) do
    %{
      event: "conversation",
      payload:
        Pleroma.Web.MastodonAPI.ConversationView.render("participation.json", %{
          participation: participation,
          user: participation.user
        })
        |> Jason.encode!()
    }
    |> Jason.encode!()
  end

  @spec represent_notification(User.t(), Notification.t()) :: binary()
  defp represent_notification(%User{} = user, %Notification{} = notify) do
    %{
      event: "notification",
      payload:
        NotificationView.render(
          "show.json",
          %{notification: notify, for: user}
        )
        |> Jason.encode!()
    }
    |> Jason.encode!()
  end

  defp should_send?(%User{} = user, %Activity{} = item) do
    blocks = user.info.blocks || []
    mutes = user.info.mutes || []
    reblog_mutes = user.info.muted_reblogs || []
    domain_blocks = Pleroma.Web.ActivityPub.MRF.subdomains_regex(user.info.domain_blocks)

    with parent when not is_nil(parent) <- Object.normalize(item),
         true <- Enum.all?([blocks, mutes, reblog_mutes], &(item.actor not in &1)),
         true <- Enum.all?([blocks, mutes], &(parent.data["actor"] not in &1)),
         %{host: item_host} <- URI.parse(item.actor),
         %{host: parent_host} <- URI.parse(parent.data["actor"]),
         false <- Pleroma.Web.ActivityPub.MRF.subdomain_match?(domain_blocks, item_host),
         false <- Pleroma.Web.ActivityPub.MRF.subdomain_match?(domain_blocks, parent_host),
         true <- thread_containment(item, user),
         false <- CommonAPI.thread_muted?(user, item) do
      true
    else
      _ -> false
    end
  end

  defp should_send?(%User{} = user, %Notification{activity: activity}) do
    should_send?(user, activity)
  end

  def push_to_socket(topics, topic, %Activity{data: %{"type" => "Announce"}} = item) do
    Enum.each(topics[topic] || [], fn socket ->
      # Get the current user so we have up-to-date blocks etc.
      if socket.assigns[:user] do
        user = User.get_cached_by_ap_id(socket.assigns[:user].ap_id)

        if should_send?(user, item) do
          send(socket.transport_pid, {:text, represent_update(item, user)})
        end
      else
        send(socket.transport_pid, {:text, represent_update(item)})
      end
    end)
  end

  def push_to_socket(topics, topic, %Participation{} = participation) do
    Enum.each(topics[topic] || [], fn socket ->
      send(socket.transport_pid, {:text, represent_conversation(participation)})
    end)
  end

  def push_to_socket(topics, topic, %Activity{
        data: %{"type" => "Delete", "deleted_activity_id" => deleted_activity_id}
      }) do
    Enum.each(topics[topic] || [], fn socket ->
      send(
        socket.transport_pid,
        {:text, %{event: "delete", payload: to_string(deleted_activity_id)} |> Jason.encode!()}
      )
    end)
  end

  def push_to_socket(_topics, _topic, %Activity{data: %{"type" => "Delete"}}), do: :noop

  def push_to_socket(topics, topic, item) do
    Enum.each(topics[topic] || [], fn socket ->
      # Get the current user so we have up-to-date blocks etc.
      if socket.assigns[:user] do
        user = User.get_cached_by_ap_id(socket.assigns[:user].ap_id)
        blocks = user.info.blocks || []
        mutes = user.info.mutes || []

        with true <- Enum.all?([blocks, mutes], &(item.actor not in &1)),
             true <- thread_containment(item, user) do
          send(socket.transport_pid, {:text, represent_update(item, user)})
        end
      else
        send(socket.transport_pid, {:text, represent_update(item)})
      end
    end)
  end

  defp internal_topic(topic, socket) when topic in ~w[user user:notification direct] do
    "#{topic}:#{socket.assigns[:user].id}"
  end

  defp internal_topic(topic, _), do: topic

  @spec thread_containment(Activity.t(), User.t()) :: boolean()
  defp thread_containment(_activity, %User{info: %{skip_thread_containment: true}}), do: true

  defp thread_containment(activity, user) do
    if Config.get([:instance, :skip_thread_containment]) do
      true
    else
      ActivityPub.contain_activity(activity, user)
    end
  end
end