From 932b842c8c790605cc8d37f5054b0f12d9184ae9 Mon Sep 17 00:00:00 2001
From: Alexander Strizhakov <alex.strizhakov@gmail.com>
Date: Mon, 30 Dec 2019 11:30:20 +0300
Subject: [PATCH] ActivityPub actions & side-effects in transaction

---
 .gitignore                                   |   2 +
 lib/pleroma/activity.ex                      |   2 +-
 lib/pleroma/object.ex                        |  18 +-
 lib/pleroma/pagination.ex                    |   4 +
 lib/pleroma/upload.ex                        |   1 +
 lib/pleroma/user.ex                          |  11 +-
 lib/pleroma/web/activity_pub/activity_pub.ex | 193 +++++++++++++---
 lib/pleroma/web/activity_pub/utils.ex        |   4 +-
 test/web/activity_pub/activity_pub_test.exs  | 227 +++++++++++++++++--
 9 files changed, 396 insertions(+), 66 deletions(-)

diff --git a/.gitignore b/.gitignore
index 3b0c7d361..198e80139 100644
--- a/.gitignore
+++ b/.gitignore
@@ -47,3 +47,5 @@ docs/generated_config.md
 .idea
 pleroma.iml
 
+# asdf
+.tool-versions
diff --git a/lib/pleroma/activity.ex b/lib/pleroma/activity.ex
index 510d3273c..ff04e02d2 100644
--- a/lib/pleroma/activity.ex
+++ b/lib/pleroma/activity.ex
@@ -309,7 +309,7 @@ defmodule Pleroma.Activity do
 
   def restrict_deactivated_users(query) do
     deactivated_users =
-      from(u in User.Query.build(deactivated: true), select: u.ap_id)
+      from(u in User.Query.build(%{deactivated: true}), select: u.ap_id)
       |> Repo.all()
 
     from(activity in query,
diff --git a/lib/pleroma/object.ex b/lib/pleroma/object.ex
index eb37b95a6..ecb83e438 100644
--- a/lib/pleroma/object.ex
+++ b/lib/pleroma/object.ex
@@ -127,18 +127,18 @@ defmodule Pleroma.Object do
   # Legacy objects can be mutated by anybody
   def authorize_mutation(%Object{}, %User{}), do: true
 
+  @spec get_cached_by_ap_id(String.t()) :: Object.t() | nil
   def get_cached_by_ap_id(ap_id) do
     key = "object:#{ap_id}"
 
-    Cachex.fetch!(:object_cache, key, fn _ ->
-      object = get_by_ap_id(ap_id)
-
-      if object do
-        {:commit, object}
-      else
-        {:ignore, object}
-      end
-    end)
+    with {:ok, nil} <- Cachex.get(:object_cache, key),
+         object when not is_nil(object) <- get_by_ap_id(ap_id),
+         {:ok, true} <- Cachex.put(:object_cache, key, object) do
+      object
+    else
+      {:ok, object} -> object
+      nil -> nil
+    end
   end
 
   def context_mapping(context) do
diff --git a/lib/pleroma/pagination.ex b/lib/pleroma/pagination.ex
index 4535ca7c5..4163660f6 100644
--- a/lib/pleroma/pagination.ex
+++ b/lib/pleroma/pagination.ex
@@ -12,11 +12,14 @@ defmodule Pleroma.Pagination do
 
   alias Pleroma.Repo
 
+  @type type :: :keyset | :offset
+
   @default_limit 20
   @page_keys ["max_id", "min_id", "limit", "since_id", "order"]
 
   def page_keys, do: @page_keys
 
+  @spec fetch_paginated(Ecto.Query.t(), map(), type(), atom() | nil) :: [Ecto.Schema.t()]
   def fetch_paginated(query, params, type \\ :keyset, table_binding \\ nil)
 
   def fetch_paginated(query, %{"total" => true} = params, :keyset, table_binding) do
@@ -57,6 +60,7 @@ defmodule Pleroma.Pagination do
     |> Repo.all()
   end
 
+  @spec paginate(Ecto.Query.t(), map(), type(), atom() | nil) :: [Ecto.Schema.t()]
   def paginate(query, options, method \\ :keyset, table_binding \\ nil)
 
   def paginate(query, options, :keyset, table_binding) do
diff --git a/lib/pleroma/upload.ex b/lib/pleroma/upload.ex
index 2e0986197..440199d19 100644
--- a/lib/pleroma/upload.ex
+++ b/lib/pleroma/upload.ex
@@ -37,6 +37,7 @@ defmodule Pleroma.Upload do
           Plug.Upload.t()
           | (data_uri_string :: String.t())
           | {:from_local, name :: String.t(), id :: String.t(), path :: String.t()}
+          | map()
 
   @type option ::
           {:type, :avatar | :banner | :background}
diff --git a/lib/pleroma/user.ex b/lib/pleroma/user.ex
index 706aee2ff..166387745 100644
--- a/lib/pleroma/user.ex
+++ b/lib/pleroma/user.ex
@@ -716,9 +716,18 @@ defmodule Pleroma.User do
     Cachex.del(:user_cache, "nickname:#{user.nickname}")
   end
 
+  @spec get_cached_by_ap_id(String.t()) :: User.t() | nil
   def get_cached_by_ap_id(ap_id) do
     key = "ap_id:#{ap_id}"
-    Cachex.fetch!(:user_cache, key, fn _ -> get_by_ap_id(ap_id) end)
+
+    with {:ok, nil} <- Cachex.get(:user_cache, key),
+         user when not is_nil(user) <- get_by_ap_id(ap_id),
+         {:ok, true} <- Cachex.put(:user_cache, key, user) do
+      user
+    else
+      {:ok, user} -> user
+      nil -> nil
+    end
   end
 
   def get_cached_by_id(id) do
diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index 60c9e7e64..30801da0e 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -6,6 +6,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   alias Pleroma.Activity
   alias Pleroma.Activity.Ir.Topics
   alias Pleroma.Config
+  alias Pleroma.Constants
   alias Pleroma.Conversation
   alias Pleroma.Conversation.Participation
   alias Pleroma.Notification
@@ -124,6 +125,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
 
   def increase_poll_votes_if_vote(_create_data), do: :noop
 
+  @spec insert(map(), boolean(), boolean(), boolean()) :: {:ok, Activity.t()} | {:error, any()}
   def insert(map, local \\ true, fake \\ false, bypass_actor_check \\ false) when is_map(map) do
     with nil <- Activity.normalize(map),
          map <- lazy_put_activity_defaults(map, fake),
@@ -231,12 +233,19 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     :noop
   end
 
-  def create(%{to: to, actor: actor, context: context, object: object} = params, fake \\ false) do
+  @spec create(map(), boolean()) :: {:ok, Activity.t()} | {:error, any()}
+  def create(params, fake \\ false) do
+    with {:ok, result} <- Repo.transaction(fn -> do_create(params, fake) end) do
+      result
+    end
+  end
+
+  defp do_create(%{to: to, actor: actor, context: context, object: object} = params, fake) do
     additional = params[:additional] || %{}
     # only accept false as false value
     local = !(params[:local] == false)
     published = params[:published]
-    quick_insert? = Pleroma.Config.get([:env]) == :benchmark
+    quick_insert? = Config.get([:env]) == :benchmark
 
     with create_data <-
            make_create_data(
@@ -259,10 +268,11 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
         {:ok, activity}
 
       {:error, message} ->
-        {:error, message}
+        Repo.rollback(message)
     end
   end
 
+  @spec listen(map()) :: {:ok, Activity.t()} | {:error, any()}
   def listen(%{to: to, actor: actor, context: context, object: object} = params) do
     additional = params[:additional] || %{}
     # only accept false as false value
@@ -277,20 +287,20 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          {:ok, activity} <- insert(listen_data, local),
          :ok <- maybe_federate(activity) do
       {:ok, activity}
-    else
-      {:error, message} ->
-        {:error, message}
     end
   end
 
+  @spec accept(map()) :: {:ok, Activity.t()} | {:error, any()}
   def accept(params) do
     accept_or_reject("Accept", params)
   end
 
+  @spec reject(map()) :: {:ok, Activity.t()} | {:error, any()}
   def reject(params) do
     accept_or_reject("Reject", params)
   end
 
+  @spec accept_or_reject(String.t(), map()) :: {:ok, Activity.t()} | {:error, any()}
   def accept_or_reject(type, %{to: to, actor: actor, object: object} = params) do
     local = Map.get(params, :local, true)
     activity_id = Map.get(params, :activity_id, nil)
@@ -304,6 +314,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
+  @spec update(map()) :: {:ok, Activity.t()} | {:error, any()}
   def update(%{to: to, cc: cc, actor: actor, object: object} = params) do
     local = !(params[:local] == false)
     activity_id = params[:activity_id]
@@ -322,7 +333,16 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
+  @spec react_with_emoji(User.t(), Object.t(), String.t(), keyword()) ::
+          {:ok, Activity.t(), Object.t()} | {:error, any()}
   def react_with_emoji(user, object, emoji, options \\ []) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_react_with_emoji(user, object, emoji, options) end) do
+      result
+    end
+  end
+
+  defp do_react_with_emoji(user, object, emoji, options) do
     with local <- Keyword.get(options, :local, true),
          activity_id <- Keyword.get(options, :activity_id, nil),
          Pleroma.Emoji.is_unicode_emoji?(emoji),
@@ -331,10 +351,21 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          {:ok, object} <- add_emoji_reaction_to_object(activity, object),
          :ok <- maybe_federate(activity) do
       {:ok, activity, object}
+    else
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec unreact_with_emoji(User.t(), String.t(), keyword()) ::
+          {:ok, Activity.t(), Object.t()} | {:error, any()}
   def unreact_with_emoji(user, reaction_id, options \\ []) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_unreact_with_emoji(user, reaction_id, options) end) do
+      result
+    end
+  end
+
+  defp do_unreact_with_emoji(user, reaction_id, options) do
     with local <- Keyword.get(options, :local, true),
          activity_id <- Keyword.get(options, :activity_id, nil),
          user_ap_id <- user.ap_id,
@@ -345,16 +376,26 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          {:ok, object} <- remove_emoji_reaction_from_object(reaction_activity, object),
          :ok <- maybe_federate(activity) do
       {:ok, activity, object}
+    else
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
   # TODO: This is weird, maybe we shouldn't check here if we can make the activity.
-  def like(
-        %User{ap_id: ap_id} = user,
-        %Object{data: %{"id" => _}} = object,
-        activity_id \\ nil,
-        local \\ true
-      ) do
+  @spec like(User.t(), Object.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t(), Object.t()} | {:error, any()}
+  def like(user, object, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <- Repo.transaction(fn -> do_like(user, object, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_like(
+         %User{ap_id: ap_id} = user,
+         %Object{data: %{"id" => _}} = object,
+         activity_id,
+         local
+       ) do
     with nil <- get_existing_like(ap_id, object),
          like_data <- make_like_data(user, object, activity_id),
          {:ok, activity} <- insert(like_data, local),
@@ -362,12 +403,24 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          :ok <- maybe_federate(activity) do
       {:ok, activity, object}
     else
-      %Activity{} = activity -> {:ok, activity, object}
-      error -> {:error, error}
+      %Activity{} = activity ->
+        {:ok, activity, object}
+
+      {:error, error} ->
+        Repo.rollback(error)
     end
   end
 
+  @spec unlike(User.t(), Object.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t(), Activity.t(), Object.t()} | {:ok, Object.t()} | {:error, any()}
   def unlike(%User{} = actor, %Object{} = object, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_unlike(actor, object, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_unlike(actor, object, activity_id, local) do
     with %Activity{} = like_activity <- get_existing_like(actor.ap_id, object),
          unlike_data <- make_unlike_data(actor, like_activity, activity_id),
          {:ok, unlike_activity} <- insert(unlike_data, local),
@@ -376,10 +429,13 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          :ok <- maybe_federate(unlike_activity) do
       {:ok, unlike_activity, like_activity, object}
     else
-      _e -> {:ok, object}
+      nil -> {:ok, object}
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec announce(User.t(), Object.t(), String.t() | nil, boolean(), boolean()) ::
+          {:ok, Activity.t(), Object.t()} | {:error, any()}
   def announce(
         %User{ap_id: _} = user,
         %Object{data: %{"id" => _}} = object,
@@ -387,6 +443,13 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
         local \\ true,
         public \\ true
       ) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_announce(user, object, activity_id, local, public) end) do
+      result
+    end
+  end
+
+  defp do_announce(user, object, activity_id, local, public) do
     with true <- is_announceable?(object, user, public),
          announce_data <- make_announce_data(user, object, activity_id, public),
          {:ok, activity} <- insert(announce_data, local),
@@ -394,16 +457,26 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          :ok <- maybe_federate(activity) do
       {:ok, activity, object}
     else
-      error -> {:error, error}
+      false -> {:error, false}
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec unannounce(User.t(), Object.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t(), Object.t()} | {:ok, Object.t()} | {:error, any()}
   def unannounce(
         %User{} = actor,
         %Object{} = object,
         activity_id \\ nil,
         local \\ true
       ) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_unannounce(actor, object, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_unannounce(actor, object, activity_id, local) do
     with %Activity{} = announce_activity <- get_existing_announce(actor.ap_id, object),
          unannounce_data <- make_unannounce_data(actor, announce_activity, activity_id),
          {:ok, unannounce_activity} <- insert(unannounce_data, local),
@@ -412,30 +485,61 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          {:ok, object} <- remove_announce_from_object(announce_activity, object) do
       {:ok, unannounce_activity, object}
     else
-      _e -> {:ok, object}
+      nil -> {:ok, object}
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec follow(User.t(), User.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t()} | {:error, any()}
   def follow(follower, followed, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_follow(follower, followed, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_follow(follower, followed, activity_id, local) do
     with data <- make_follow_data(follower, followed, activity_id),
          {:ok, activity} <- insert(data, local),
          :ok <- maybe_federate(activity),
          _ <- User.set_follow_state_cache(follower.ap_id, followed.ap_id, activity.data["state"]) do
       {:ok, activity}
+    else
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec unfollow(User.t(), User.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t()} | nil | {:error, any()}
   def unfollow(follower, followed, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_unfollow(follower, followed, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_unfollow(follower, followed, activity_id, local) do
     with %Activity{} = follow_activity <- fetch_latest_follow(follower, followed),
          {:ok, follow_activity} <- update_follow_state(follow_activity, "cancelled"),
          unfollow_data <- make_unfollow_data(follower, followed, follow_activity, activity_id),
          {:ok, activity} <- insert(unfollow_data, local),
          :ok <- maybe_federate(activity) do
       {:ok, activity}
+    else
+      nil -> nil
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
-  def delete(%User{ap_id: ap_id, follower_address: follower_address} = user) do
+  @spec delete(User.t() | Object.t(), keyword()) :: {:ok, User.t() | Object.t()} | {:error, any()}
+  def delete(entity, options \\ []) do
+    with {:ok, result} <- Repo.transaction(fn -> do_delete(entity, options) end) do
+      result
+    end
+  end
+
+  defp do_delete(%User{ap_id: ap_id, follower_address: follower_address} = user, _) do
     with data <- %{
            "to" => [follower_address],
            "type" => "Delete",
@@ -448,7 +552,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
-  def delete(%Object{data: %{"id" => id, "actor" => actor}} = object, options \\ []) do
+  defp do_delete(%Object{data: %{"id" => id, "actor" => actor}} = object, options) do
     local = Keyword.get(options, :local, true)
     activity_id = Keyword.get(options, :activity_id, nil)
     actor = Keyword.get(options, :actor, actor)
@@ -473,11 +577,22 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          {:ok, _actor} <- decrease_note_count_if_public(user, object),
          :ok <- maybe_federate(activity) do
       {:ok, activity}
+    else
+      {:error, error} ->
+        Repo.rollback(error)
     end
   end
 
-  @spec block(User.t(), User.t(), String.t() | nil, boolean) :: {:ok, Activity.t() | nil}
+  @spec block(User.t(), User.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t()} | {:error, any()}
   def block(blocker, blocked, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_block(blocker, blocked, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_block(blocker, blocked, activity_id, local) do
     outgoing_blocks = Config.get([:activitypub, :outgoing_blocks])
     unfollow_blocked = Config.get([:activitypub, :unfollow_blocked])
 
@@ -492,20 +607,32 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
          :ok <- maybe_federate(activity) do
       {:ok, activity}
     else
-      _e -> {:ok, nil}
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
+  @spec unblock(User.t(), User.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t()} | {:error, any()}
   def unblock(blocker, blocked, activity_id \\ nil, local \\ true) do
+    with {:ok, result} <-
+           Repo.transaction(fn -> do_unblock(blocker, blocked, activity_id, local) end) do
+      result
+    end
+  end
+
+  defp do_unblock(blocker, blocked, activity_id, local) do
     with %Activity{} = block_activity <- fetch_latest_block(blocker, blocked),
          unblock_data <- make_unblock_data(blocker, blocked, block_activity, activity_id),
          {:ok, activity} <- insert(unblock_data, local),
          :ok <- maybe_federate(activity) do
       {:ok, activity}
+    else
+      nil -> nil
+      {:error, error} -> Repo.rollback(error)
     end
   end
 
-  @spec flag(map()) :: {:ok, Activity.t()} | any
+  @spec flag(map()) :: {:ok, Activity.t()} | {:error, any()}
   def flag(
         %{
           actor: actor,
@@ -542,6 +669,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
+  @spec move(User.t(), User.t(), boolean()) :: {:ok, Activity.t()} | {:error, any()}
   def move(%User{} = origin, %User{} = target, local \\ true) do
     params = %{
       "type" => "Move",
@@ -567,7 +695,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   end
 
   defp fetch_activities_for_context_query(context, opts) do
-    public = [Pleroma.Constants.as_public()]
+    public = [Constants.as_public()]
 
     recipients =
       if opts["user"],
@@ -612,10 +740,11 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     |> Repo.one()
   end
 
+  @spec fetch_public_activities(map(), Pagination.type()) :: [Activity.t()]
   def fetch_public_activities(opts \\ %{}, pagination \\ :keyset) do
     opts = Map.drop(opts, ["user"])
 
-    [Pleroma.Constants.as_public()]
+    [Constants.as_public()]
     |> fetch_activities_query(opts)
     |> restrict_unlisted()
     |> Pagination.fetch_paginated(opts, pagination)
@@ -775,7 +904,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
       |> Map.put("instance", params["instance"])
       |> Map.put("whole_db", true)
 
-    fetch_activities([Pleroma.Constants.as_public()], params, :offset)
+    fetch_activities([Constants.as_public()], params, :offset)
     |> Enum.reverse()
   end
 
@@ -785,9 +914,9 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
 
   defp user_activities_recipients(%{"reading_user" => reading_user}) do
     if reading_user do
-      [Pleroma.Constants.as_public()] ++ [reading_user.ap_id | User.following(reading_user)]
+      [Constants.as_public()] ++ [reading_user.ap_id | User.following(reading_user)]
     else
-      [Pleroma.Constants.as_public()]
+      [Constants.as_public()]
     end
   end
 
@@ -994,7 +1123,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
         fragment(
           "not (coalesce(?->'cc', '{}'::jsonb) \\?| ?)",
           activity.data,
-          ^[Pleroma.Constants.as_public()]
+          ^[Constants.as_public()]
         )
     )
   end
@@ -1168,7 +1297,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   @doc """
   Fetch favorites activities of user with order by sort adds to favorites
   """
-  @spec fetch_favourites(User.t(), map(), atom()) :: list(Activity.t())
+  @spec fetch_favourites(User.t(), map(), Pagination.type()) :: list(Activity.t())
   def fetch_favourites(user, params \\ %{}, pagination \\ :keyset) do
     user.ap_id
     |> Activity.Queries.by_actor()
@@ -1206,7 +1335,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
       where:
         fragment("? && ?", activity.recipients, ^recipients) or
           (fragment("? && ?", activity.recipients, ^recipients_with_public) and
-             ^Pleroma.Constants.as_public() in activity.recipients)
+             ^Constants.as_public() in activity.recipients)
     )
   end
 
@@ -1222,6 +1351,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     |> Enum.reverse()
   end
 
+  @spec upload(Upload.source(), keyword()) :: {:ok, Object.t()} | {:error, any()}
   def upload(file, opts \\ []) do
     with {:ok, data} <- Upload.store(file, opts) do
       obj_data =
@@ -1319,8 +1449,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   defp normalize_counter(_), do: 0
 
   defp maybe_update_follow_information(data) do
-    with {:enabled, true} <-
-           {:enabled, Pleroma.Config.get([:instance, :external_user_synchronization])},
+    with {:enabled, true} <- {:enabled, Config.get([:instance, :external_user_synchronization])},
          {:ok, info} <- fetch_follow_information_for_user(data) do
       info = Map.merge(data[:info] || %{}, info)
       Map.put(data, :info, info)
diff --git a/lib/pleroma/web/activity_pub/utils.ex b/lib/pleroma/web/activity_pub/utils.ex
index db7084246..76d72886a 100644
--- a/lib/pleroma/web/activity_pub/utils.ex
+++ b/lib/pleroma/web/activity_pub/utils.ex
@@ -45,7 +45,7 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     Map.put(params, "actor", get_ap_id(params["actor"]))
   end
 
-  @spec determine_explicit_mentions(map()) :: map()
+  @spec determine_explicit_mentions(map()) :: list()
   def determine_explicit_mentions(%{"tag" => tag} = _) when is_list(tag) do
     Enum.flat_map(tag, fn
       %{"type" => "Mention", "href" => href} -> [href]
@@ -312,7 +312,7 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> Map.put("content", emoji)
   end
 
-  @spec update_element_in_object(String.t(), list(any), Object.t()) ::
+  @spec update_element_in_object(String.t(), list(any) | map(), Object.t()) ::
           {:ok, Object.t()} | {:error, Ecto.Changeset.t()}
   def update_element_in_object(property, element, object) do
     length =
diff --git a/test/web/activity_pub/activity_pub_test.exs b/test/web/activity_pub/activity_pub_test.exs
index ad6b9810c..8538c0dce 100644
--- a/test/web/activity_pub/activity_pub_test.exs
+++ b/test/web/activity_pub/activity_pub_test.exs
@@ -8,6 +8,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
 
   alias Pleroma.Activity
   alias Pleroma.Builders.ActivityBuilder
+  alias Pleroma.Config
   alias Pleroma.Notification
   alias Pleroma.Object
   alias Pleroma.User
@@ -15,6 +16,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   alias Pleroma.Web.ActivityPub.Utils
   alias Pleroma.Web.AdminAPI.AccountView
   alias Pleroma.Web.CommonAPI
+  alias Pleroma.Web.Federator
 
   import Pleroma.Factory
   import Tesla.Mock
@@ -224,7 +226,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
 
   describe "insertion" do
     test "drops activities beyond a certain limit" do
-      limit = Pleroma.Config.get([:instance, :remote_limit])
+      limit = Config.get([:instance, :remote_limit])
 
       random_text =
         :crypto.strong_rand_bytes(limit + 1)
@@ -385,6 +387,27 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "create activities" do
+    test "it reverts create" do
+      user = insert(:user)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} =
+          ActivityPub.create(%{
+            to: ["user1", "user2"],
+            actor: user,
+            context: "",
+            object: %{
+              "to" => ["user1", "user2"],
+              "type" => "Note",
+              "content" => "testing"
+            }
+          })
+      end
+
+      assert Repo.aggregate(Activity, :count, :id) == 0
+      assert Repo.aggregate(Object, :count, :id) == 0
+    end
+
     test "removes doubled 'to' recipients" do
       user = insert(:user)
 
@@ -852,8 +875,8 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "react to an object" do
-    test_with_mock "sends an activity to federation", Pleroma.Web.Federator, [:passthrough], [] do
-      Pleroma.Config.put([:instance, :federating], true)
+    test_with_mock "sends an activity to federation", Federator, [:passthrough], [] do
+      Config.put([:instance, :federating], true)
       user = insert(:user)
       reactor = insert(:user)
       {:ok, activity} = CommonAPI.post(user, %{"status" => "YASSSS queen slay"})
@@ -861,7 +884,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
 
       {:ok, reaction_activity, _object} = ActivityPub.react_with_emoji(reactor, object, "🔥")
 
-      assert called(Pleroma.Web.Federator.publish(reaction_activity))
+      assert called(Federator.publish(reaction_activity))
     end
 
     test "adds an emoji reaction activity to the db" do
@@ -883,11 +906,26 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       assert object.data["reaction_count"] == 1
       assert object.data["reactions"]["🔥"] == [reactor.ap_id]
     end
+
+    test "reverts emoji reaction on error" do
+      [user, reactor] = insert_list(2, :user)
+
+      {:ok, activity} = CommonAPI.post(user, %{"status" => "Status"})
+      object = Object.normalize(activity)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.react_with_emoji(reactor, object, "😀")
+      end
+
+      object = Object.get_by_ap_id(object.data["id"])
+      refute object.data["reaction_count"]
+      refute object.data["reactions"]
+    end
   end
 
   describe "unreacting to an object" do
-    test_with_mock "sends an activity to federation", Pleroma.Web.Federator, [:passthrough], [] do
-      Pleroma.Config.put([:instance, :federating], true)
+    test_with_mock "sends an activity to federation", Federator, [:passthrough], [] do
+      Config.put([:instance, :federating], true)
       user = insert(:user)
       reactor = insert(:user)
       {:ok, activity} = CommonAPI.post(user, %{"status" => "YASSSS queen slay"})
@@ -895,12 +933,12 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
 
       {:ok, reaction_activity, _object} = ActivityPub.react_with_emoji(reactor, object, "🔥")
 
-      assert called(Pleroma.Web.Federator.publish(reaction_activity))
+      assert called(Federator.publish(reaction_activity))
 
       {:ok, unreaction_activity, _object} =
         ActivityPub.unreact_with_emoji(reactor, reaction_activity.data["id"])
 
-      assert called(Pleroma.Web.Federator.publish(unreaction_activity))
+      assert called(Federator.publish(unreaction_activity))
     end
 
     test "adds an undo activity to the db" do
@@ -921,18 +959,36 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       assert object.data["reaction_count"] == 0
       assert object.data["reactions"] == %{}
     end
+
+    test "reverts emoji unreact on error" do
+      [user, reactor] = insert_list(2, :user)
+      {:ok, activity} = CommonAPI.post(user, %{"status" => "Status"})
+      object = Object.normalize(activity)
+
+      {:ok, reaction_activity, _object} = ActivityPub.react_with_emoji(reactor, object, "😀")
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} =
+          ActivityPub.unreact_with_emoji(reactor, reaction_activity.data["id"])
+      end
+
+      object = Object.get_by_ap_id(object.data["id"])
+
+      assert object.data["reaction_count"] == 1
+      assert object.data["reactions"]["😀"] == [reactor.ap_id]
+    end
   end
 
   describe "like an object" do
-    test_with_mock "sends an activity to federation", Pleroma.Web.Federator, [:passthrough], [] do
-      Pleroma.Config.put([:instance, :federating], true)
+    test_with_mock "sends an activity to federation", Federator, [:passthrough], [] do
+      Config.put([:instance, :federating], true)
       note_activity = insert(:note_activity)
       assert object_activity = Object.normalize(note_activity)
 
       user = insert(:user)
 
       {:ok, like_activity, _object} = ActivityPub.like(user, object_activity)
-      assert called(Pleroma.Web.Federator.publish(like_activity))
+      assert called(Federator.publish(like_activity))
     end
 
     test "returns exist activity if object already liked" do
@@ -947,6 +1003,19 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       assert like_activity == like_activity_exist
     end
 
+    test "reverts like activity on error" do
+      note_activity = insert(:note_activity)
+      object = Object.normalize(note_activity)
+      user = insert(:user)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.like(user, object)
+      end
+
+      assert Repo.aggregate(Activity, :count, :id) == 1
+      assert Repo.get(Object, object.id) == object
+    end
+
     test "adds a like activity to the db" do
       note_activity = insert(:note_activity)
       assert object = Object.normalize(note_activity)
@@ -977,15 +1046,15 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "unliking" do
-    test_with_mock "sends an activity to federation", Pleroma.Web.Federator, [:passthrough], [] do
-      Pleroma.Config.put([:instance, :federating], true)
+    test_with_mock "sends an activity to federation", Federator, [:passthrough], [] do
+      Config.put([:instance, :federating], true)
 
       note_activity = insert(:note_activity)
       object = Object.normalize(note_activity)
       user = insert(:user)
 
       {:ok, object} = ActivityPub.unlike(user, object)
-      refute called(Pleroma.Web.Federator.publish())
+      refute called(Federator.publish())
 
       {:ok, _like_activity, object} = ActivityPub.like(user, object)
       assert object.data["like_count"] == 1
@@ -993,7 +1062,24 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       {:ok, unlike_activity, _, object} = ActivityPub.unlike(user, object)
       assert object.data["like_count"] == 0
 
-      assert called(Pleroma.Web.Federator.publish(unlike_activity))
+      assert called(Federator.publish(unlike_activity))
+    end
+
+    test "reverts unliking on error" do
+      note_activity = insert(:note_activity)
+      object = Object.normalize(note_activity)
+      user = insert(:user)
+
+      {:ok, like_activity, object} = ActivityPub.like(user, object)
+      assert object.data["like_count"] == 1
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.unlike(user, object)
+      end
+
+      assert Object.get_by_ap_id(object.data["id"]) == object
+      assert object.data["like_count"] == 1
+      assert Activity.get_by_id(like_activity.id)
     end
 
     test "unliking a previously liked object" do
@@ -1035,6 +1121,21 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       assert announce_activity.data["actor"] == user.ap_id
       assert announce_activity.data["context"] == object.data["context"]
     end
+
+    test "reverts annouce from object on error" do
+      note_activity = insert(:note_activity)
+      object = Object.normalize(note_activity)
+      user = insert(:user)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.announce(user, object)
+      end
+
+      reloaded_object = Object.get_by_ap_id(object.data["id"])
+      assert reloaded_object == object
+      refute reloaded_object.data["announcement_count"]
+      refute reloaded_object.data["announcements"]
+    end
   end
 
   describe "announcing a private object" do
@@ -1077,8 +1178,8 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       user = insert(:user)
 
       # Unannouncing an object that is not announced does nothing
-      # {:ok, object} = ActivityPub.unannounce(user, object)
-      # assert object.data["announcement_count"] == 0
+      {:ok, object} = ActivityPub.unannounce(user, object)
+      refute object.data["announcement_count"]
 
       {:ok, announce_activity, object} = ActivityPub.announce(user, object)
       assert object.data["announcement_count"] == 1
@@ -1098,6 +1199,22 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
 
       assert Activity.get_by_id(announce_activity.id) == nil
     end
+
+    test "reverts unannouncing on error" do
+      note_activity = insert(:note_activity)
+      object = Object.normalize(note_activity)
+      user = insert(:user)
+
+      {:ok, _announce_activity, object} = ActivityPub.announce(user, object)
+      assert object.data["announcement_count"] == 1
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.unannounce(user, object)
+      end
+
+      object = Object.get_by_ap_id(object.data["id"])
+      assert object.data["announcement_count"] == 1
+    end
   end
 
   describe "uploading files" do
@@ -1132,6 +1249,35 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "following / unfollowing" do
+    test "it reverts follow activity" do
+      follower = insert(:user)
+      followed = insert(:user)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.follow(follower, followed)
+      end
+
+      assert Repo.aggregate(Activity, :count, :id) == 0
+      assert Repo.aggregate(Object, :count, :id) == 0
+    end
+
+    test "it reverts unfollow activity" do
+      follower = insert(:user)
+      followed = insert(:user)
+
+      {:ok, follow_activity} = ActivityPub.follow(follower, followed)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.unfollow(follower, followed)
+      end
+
+      activity = Activity.get_by_id(follow_activity.id)
+      assert activity.data["type"] == "Follow"
+      assert activity.data["actor"] == follower.ap_id
+
+      assert activity.data["object"] == followed.ap_id
+    end
+
     test "creates a follow activity" do
       follower = insert(:user)
       followed = insert(:user)
@@ -1161,6 +1307,17 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "blocking / unblocking" do
+    test "reverts block activity on error" do
+      [blocker, blocked] = insert_list(2, :user)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.block(blocker, blocked)
+      end
+
+      assert Repo.aggregate(Activity, :count, :id) == 0
+      assert Repo.aggregate(Object, :count, :id) == 0
+    end
+
     test "creates a block activity" do
       blocker = insert(:user)
       blocked = insert(:user)
@@ -1172,6 +1329,21 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
       assert activity.data["object"] == blocked.ap_id
     end
 
+    test "reverts unblock activity on error" do
+      [blocker, blocked] = insert_list(2, :user)
+      {:ok, block_activity} = ActivityPub.block(blocker, blocked)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.unblock(blocker, blocked)
+      end
+
+      assert block_activity.data["type"] == "Block"
+      assert block_activity.data["actor"] == blocker.ap_id
+
+      assert Repo.aggregate(Activity, :count, :id) == 1
+      assert Repo.aggregate(Object, :count, :id) == 1
+    end
+
     test "creates an undo activity for the last block" do
       blocker = insert(:user)
       blocked = insert(:user)
@@ -1191,6 +1363,19 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   describe "deletion" do
+    test "it reverts deletion on error" do
+      note = insert(:note_activity)
+      object = Object.normalize(note)
+
+      with_mock(Utils, [:passthrough], maybe_federate: fn _ -> {:error, :reverted} end) do
+        assert {:error, :reverted} = ActivityPub.delete(object)
+      end
+
+      assert Repo.aggregate(Activity, :count, :id) == 1
+      assert Repo.get(Object, object.id) == object
+      assert Activity.get_by_id(note.id) == note
+    end
+
     test "it creates a delete activity and deletes the original object" do
       note = insert(:note_activity)
       object = Object.normalize(note)
@@ -1294,10 +1479,10 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
     end
 
     test "it passes delete activity through MRF before deleting the object" do
-      rewrite_policy = Pleroma.Config.get([:instance, :rewrite_policy])
-      Pleroma.Config.put([:instance, :rewrite_policy], Pleroma.Web.ActivityPub.MRF.DropPolicy)
+      rewrite_policy = Config.get([:instance, :rewrite_policy])
+      Config.put([:instance, :rewrite_policy], Pleroma.Web.ActivityPub.MRF.DropPolicy)
 
-      on_exit(fn -> Pleroma.Config.put([:instance, :rewrite_policy], rewrite_policy) end)
+      on_exit(fn -> Config.put([:instance, :rewrite_policy], rewrite_policy) end)
 
       note = insert(:note_activity)
       object = Object.normalize(note)
@@ -1385,7 +1570,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   end
 
   test "returned pinned statuses" do
-    Pleroma.Config.put([:instance, :max_pinned_statuses], 3)
+    Config.put([:instance, :max_pinned_statuses], 3)
     user = insert(:user)
 
     {:ok, activity_one} = CommonAPI.post(user, %{"status" => "HI!!!"})