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diff --git a/lib/pleroma/web/mastodon_api/websocket_handler.ex b/lib/pleroma/web/mastodon_api/websocket_handler.ex
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+++ b/lib/pleroma/web/mastodon_api/websocket_handler.ex
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+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.MastodonAPI.WebsocketHandler do
+  require Logger
+
+  alias Pleroma.Repo
+  alias Pleroma.User
+  alias Pleroma.Web.OAuth.Token
+  alias Pleroma.Web.Streamer
+
+  @behaviour :cowboy_websocket
+
+  # Client ping period.
+  @tick :timer.seconds(30)
+  # Cowboy timeout period.
+  @timeout :timer.seconds(60)
+  # Hibernate every X messages
+  @hibernate_every 100
+
+  def init(%{qs: qs} = req, state) do
+    with params <- Enum.into(:cow_qs.parse_qs(qs), %{}),
+         sec_websocket <- :cowboy_req.header("sec-websocket-protocol", req, nil),
+         access_token <- Map.get(params, "access_token"),
+         {:ok, user, oauth_token} <- authenticate_request(access_token, sec_websocket),
+         {:ok, topic} <- Streamer.get_topic(params["stream"], user, oauth_token, params) do
+      req =
+        if sec_websocket do
+          :cowboy_req.set_resp_header("sec-websocket-protocol", sec_websocket, req)
+        else
+          req
+        end
+
+      {:cowboy_websocket, req,
+       %{user: user, topic: topic, oauth_token: oauth_token, count: 0, timer: nil},
+       %{idle_timeout: @timeout}}
+    else
+      {:error, :bad_topic} ->
+        Logger.debug("#{__MODULE__} bad topic #{inspect(req)}")
+        req = :cowboy_req.reply(404, req)
+        {:ok, req, state}
+
+      {:error, :unauthorized} ->
+        Logger.debug("#{__MODULE__} authentication error: #{inspect(req)}")
+        req = :cowboy_req.reply(401, req)
+        {:ok, req, state}
+    end
+  end
+
+  def websocket_init(state) do
+    Logger.debug(
+      "#{__MODULE__} accepted websocket connection for user #{(state.user || %{id: "anonymous"}).id}, topic #{state.topic}"
+    )
+
+    Streamer.add_socket(state.topic, state.oauth_token)
+    {:ok, %{state | timer: timer()}}
+  end
+
+  # Client's Pong frame.
+  def websocket_handle(:pong, state) do
+    if state.timer, do: Process.cancel_timer(state.timer)
+    {:ok, %{state | timer: timer()}}
+  end
+
+  # We only receive pings for now
+  def websocket_handle(:ping, state), do: {:ok, state}
+
+  def websocket_handle(frame, state) do
+    Logger.error("#{__MODULE__} received frame: #{inspect(frame)}")
+    {:ok, state}
+  end
+
+  def websocket_info({:render_with_user, view, template, item}, state) do
+    user = %User{} = User.get_cached_by_ap_id(state.user.ap_id)
+
+    unless Streamer.filtered_by_user?(user, item) do
+      websocket_info({:text, view.render(template, item, user)}, %{state | user: user})
+    else
+      {:ok, state}
+    end
+  end
+
+  def websocket_info({:text, message}, state) do
+    # If the websocket processed X messages, force an hibernate/GC.
+    # We don't hibernate at every message to balance CPU usage/latency with RAM usage.
+    if state.count > @hibernate_every do
+      {:reply, {:text, message}, %{state | count: 0}, :hibernate}
+    else
+      {:reply, {:text, message}, %{state | count: state.count + 1}}
+    end
+  end
+
+  # Ping tick. We don't re-queue a timer there, it is instead queued when :pong is received.
+  # As we hibernate there, reset the count to 0.
+  # If the client misses :pong, Cowboy will automatically timeout the connection after
+  # `@idle_timeout`.
+  def websocket_info(:tick, state) do
+    {:reply, :ping, %{state | timer: nil, count: 0}, :hibernate}
+  end
+
+  def websocket_info(:close, state) do
+    {:stop, state}
+  end
+
+  # State can be `[]` only in case we terminate before switching to websocket,
+  # we already log errors for these cases in `init/1`, so just do nothing here
+  def terminate(_reason, _req, []), do: :ok
+
+  def terminate(reason, _req, state) do
+    Logger.debug(
+      "#{__MODULE__} terminating websocket connection for user #{(state.user || %{id: "anonymous"}).id}, topic #{state.topic || "?"}: #{inspect(reason)}"
+    )
+
+    Streamer.remove_socket(state.topic)
+    :ok
+  end
+
+  # Public streams without authentication.
+  defp authenticate_request(nil, nil) do
+    {:ok, nil, nil}
+  end
+
+  # Authenticated streams.
+  defp authenticate_request(access_token, sec_websocket) do
+    token = access_token || sec_websocket
+
+    with true <- is_bitstring(token),
+         oauth_token = %Token{user_id: user_id} <- Repo.get_by(Token, token: token),
+         user = %User{} <- User.get_cached_by_id(user_id) do
+      {:ok, user, oauth_token}
+    else
+      _ -> {:error, :unauthorized}
+    end
+  end
+
+  defp timer do
+    Process.send_after(self(), :tick, @tick)
+  end
+end