Merge branch 'follow-pipeline' into 'develop'

Handle `Follow` activities with the pipeline

See merge request pleroma/pleroma!2734

diff --combined lib/pleroma/web/activity_pub/side_effects.ex
index 70746f341d0a9541d98aa5d0f01cbcf5f2cd579e,de02baf0f8db15e3bfa8a024755ec388e846dc66..1d2c296a5c001a99d02c8ae72256d61029aa1dd4
--- 1/lib/pleroma/web/activity_pub/side_effects.ex
--- 2/lib/pleroma/web/activity_pub/side_effects.ex
+++ b/lib/pleroma/web/activity_pub/side_effects.ex
@@@ -9,6 -9,7 +9,7 @@@ defmodule Pleroma.Web.ActivityPub.SideE
    alias Pleroma.Activity.Ir.Topics
    alias Pleroma.Chat
    alias Pleroma.Chat.MessageReference
+   alias Pleroma.FollowingRelationship
    alias Pleroma.Notification
    alias Pleroma.Object
    alias Pleroma.Repo
@@@ -21,6 -22,69 +22,69 @@@
  
    def handle(object, meta \\ [])
  
+   # Tasks this handle
+   # - Follows if possible
+   # - Sends a notification
+   # - Generates accept or reject if appropriate
+   def handle(
+         %{
+           data: %{
+             "id" => follow_id,
+             "type" => "Follow",
+             "object" => followed_user,
+             "actor" => following_user
+           }
+         } = object,
+         meta
+       ) do
+     with %User{} = follower <- User.get_cached_by_ap_id(following_user),
+          %User{} = followed <- User.get_cached_by_ap_id(followed_user),
+          {_, {:ok, _}, _, _} <-
+            {:following, User.follow(follower, followed, :follow_pending), follower, followed} do
+       if followed.local && !followed.locked do
+         Utils.update_follow_state_for_all(object, "accept")
+         FollowingRelationship.update(follower, followed, :follow_accept)
+         User.update_follower_count(followed)
+         User.update_following_count(follower)
+ 
+         %{
+           to: [following_user],
+           actor: followed,
+           object: follow_id,
+           local: true
+         }
+         |> ActivityPub.accept()
+       end
+     else
+       {:following, {:error, _}, follower, followed} ->
+         Utils.update_follow_state_for_all(object, "reject")
+         FollowingRelationship.update(follower, followed, :follow_reject)
+ 
+         if followed.local do
+           %{
+             to: [follower.ap_id],
+             actor: followed,
+             object: follow_id,
+             local: true
+           }
+           |> ActivityPub.reject()
+         end
+ 
+       _ ->
+         nil
+     end
+ 
+     {:ok, notifications} = Notification.create_notifications(object, do_send: false)
+ 
+     meta =
+       meta
+       |> add_notifications(notifications)
+ 
+     updated_object = Activity.get_by_ap_id(follow_id)
+ 
+     {:ok, updated_object, meta}
+   end
+ 
    # Tasks this handles:
    # - Unfollow and block
    def handle(
@@@ -209,20 -273,14 +273,20 @@@
      {:ok, object}
    end
  
 -  def handle_undoing(%{data: %{"type" => "Like"}} = object) do
 -    with %Object{} = liked_object <- Object.get_by_ap_id(object.data["object"]),
 -         {:ok, _} <- Utils.remove_like_from_object(object, liked_object),
 -         {:ok, _} <- Repo.delete(object) do
 -      :ok
 +  defp undo_like(nil, object), do: delete_object(object)
 +
 +  defp undo_like(%Object{} = liked_object, object) do
 +    with {:ok, _} <- Utils.remove_like_from_object(object, liked_object) do
 +      delete_object(object)
      end
    end
  
 +  def handle_undoing(%{data: %{"type" => "Like"}} = object) do
 +    object.data["object"]
 +    |> Object.get_by_ap_id()
 +    |> undo_like(object)
 +  end
 +
    def handle_undoing(%{data: %{"type" => "EmojiReact"}} = object) do
      with %Object{} = reacted_object <- Object.get_by_ap_id(object.data["object"]),
           {:ok, _} <- Utils.remove_emoji_reaction_from_object(object, reacted_object),
@@@ -252,11 -310,6 +316,11 @@@
  
    def handle_undoing(object), do: {:error, ["don't know how to handle", object]}
  
 +  @spec delete_object(Object.t()) :: :ok | {:error, Ecto.Changeset.t()}
 +  defp delete_object(object) do
 +    with {:ok, _} <- Repo.delete(object), do: :ok
 +  end
 +
    defp send_notifications(meta) do
      Keyword.get(meta, :notifications, [])
      |> Enum.each(fn notification ->