Various typespec and compilation improvements

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
2021-09-10 11:27:59 +02:00
parent 029a4ea194
commit de047c8939
125 changed files with 790 additions and 357 deletions
--- a/lib/federation/activity_pub/activity_pub.ex
+++ b/lib/federation/activity_pub/activity_pub.ex
@@ -41,7 +41,7 @@ defmodule Mobilizon.Federation.ActivityPub do

  alias Mobilizon.Federation.ActivityPub.Actor, as: ActivityPubActor

-  alias Mobilizon.Federation.ActivityPub.Types.{Managable, Ownable}
+  alias Mobilizon.Federation.ActivityPub.Types.{Entity, Managable, Ownable}

  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Federation.HTTPSignatures.Signature
@@ -56,11 +56,9 @@ defmodule Mobilizon.Federation.ActivityPub do

  @public_ap_adress "https://www.w3.org/ns/activitystreams#Public"

-  @doc """
-  Wraps an object into an activity
-  """
+  # Wraps an object into an activity
  @spec create_activity(map(), boolean()) :: {:ok, Activity.t()}
-  def create_activity(map, local \\ true) when is_map(map) do
+  defp create_activity(map, local) when is_map(map) do
    with map <- lazy_put_activity_defaults(map) do
      {:ok,
       %Activity{
@@ -168,7 +166,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    * Federates (asynchronously) the activity
    * Returns the activity
  """
-  @spec create(atom(), map(), boolean, map()) :: {:ok, Activity.t(), struct()} | any()
+  @spec create(atom(), map(), boolean, map()) :: {:ok, Activity.t(), Entity.entities()} | any()
  def create(type, args, local \\ false, additional \\ %{}) do
    Logger.debug("creating an activity")
    Logger.debug(inspect(args))
@@ -206,7 +204,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    * Federates (asynchronously) the activity
    * Returns the activity
  """
-  @spec update(struct(), map(), boolean, map()) :: {:ok, Activity.t(), struct()} | any()
+  @spec update(Entity.entities(), map(), boolean, map()) ::
+          {:ok, Activity.t(), Entity.entities()} | any()
  def update(old_entity, args, local \\ false, additional \\ %{}) do
    Logger.debug("updating an activity")
    Logger.debug(inspect(args))
@@ -224,6 +223,12 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @type acceptable_types :: :join | :follow | :invite
+  @type acceptable_entities ::
+          accept_join_entities | accept_follow_entities | accept_invite_entities
+
+  @spec accept(acceptable_types, acceptable_entities, boolean, map) ::
+          {:ok, ActivityStream.t(), acceptable_entities}
  def accept(type, entity, local \\ true, additional \\ %{}) do
    Logger.debug("We're accepting something")

@@ -246,6 +251,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec reject(acceptable_types, acceptable_entities, boolean, map) ::
+          {:ok, ActivityStream.t(), acceptable_entities}
  def reject(type, entity, local \\ true, additional \\ %{}) do
    {:ok, entity, update_data} =
      case type do
@@ -266,6 +273,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec announce(Actor.t(), ActivityStream.t(), String.t() | nil, boolean, boolean) ::
+          {:ok, Activity.t(), ActivityStream.t()}
  def announce(
        %Actor{} = actor,
        object,
@@ -286,6 +295,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec unannounce(Actor.t(), ActivityStream.t(), String.t() | nil, String.t() | nil, boolean) ::
+          {:ok, Activity.t(), ActivityStream.t()}
  def unannounce(
        %Actor{} = actor,
        object,
@@ -306,6 +317,8 @@ defmodule Mobilizon.Federation.ActivityPub do
  @doc """
  Make an actor follow another
  """
+  @spec follow(Actor.t(), Actor.t(), String.t() | nil, boolean, map) ::
+          {:ok, Activity.t(), Follower.t()} | {:error, String.t()}
  def follow(
        %Actor{} = follower,
        %Actor{} = followed,
@@ -336,7 +349,8 @@ defmodule Mobilizon.Federation.ActivityPub do
  @doc """
  Make an actor unfollow another
  """
-  @spec unfollow(Actor.t(), Actor.t(), String.t(), boolean()) :: {:ok, map()} | any()
+  @spec unfollow(Actor.t(), Actor.t(), String.t() | nil, boolean()) ::
+          {:ok, Activity.t(), Follower.t()}
  def unfollow(%Actor{} = follower, %Actor{} = followed, activity_id \\ nil, local \\ true) do
    with {:ok, %Follower{id: follow_id} = follow} <- Actors.unfollow(followed, follower),
         # We recreate the follow activity
@@ -357,6 +371,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec delete(Entity.t(), Actor.t(), boolean, map) :: {:ok, Activity.t(), Entity.t()}
  def delete(object, actor, local \\ true, additional \\ %{}) do
    with {:ok, activity_data, actor, object} <-
           Managable.delete(object, actor, local, additional),
@@ -369,6 +384,9 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec join(Event.t(), Actor.t(), boolean, map) ::
+          {:ok, Activity.t(), Participant.t()} | {:maximum_attendee_capacity, any}
+  @spec join(Actor.t(), Actor.t(), boolean, map) :: {:ok, Activity.t(), Member.t()}
  def join(entity_to_join, actor_joining, local \\ true, additional \\ %{})

  def join(%Event{} = event, %Actor{} = actor, local, additional) do
@@ -397,6 +415,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec leave(Event.t(), Actor.t(), boolean, map) :: {:ok, Activity.t(), Participant.t()}
+  @spec leave(Actor.t(), Actor.t(), boolean, map) :: {:ok, Activity.t(), Member.t()}
  def leave(object, actor, local \\ true, additional \\ %{})

  @doc """
@@ -462,6 +482,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec remove(Member.t(), Actor.t(), Actor.t(), boolean, map) :: {:ok, Activity.t(), Member.t()}
  def remove(
        %Member{} = member,
        %Actor{type: :Group, url: group_url, members_url: group_members_url},
@@ -502,7 +523,7 @@ defmodule Mobilizon.Federation.ActivityPub do
      ) do
    Logger.debug("Handling #{actor_url} invite to #{group_url} sent to #{target_actor_url}")

-    with {:is_able_to_invite, true} <- {:is_able_to_invite, is_able_to_invite(actor, group)},
+    with {:is_able_to_invite, true} <- {:is_able_to_invite, is_able_to_invite?(actor, group)},
         {:ok, %Member{url: member_url} = member} <-
           Actors.create_member(%{
             parent_id: group_id,
@@ -538,7 +559,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

-  defp is_able_to_invite(%Actor{domain: actor_domain, id: actor_id}, %Actor{
+  @spec is_able_to_invite?(Actor.t(), Actor.t()) :: boolean
+  defp is_able_to_invite?(%Actor{domain: actor_domain, id: actor_id}, %Actor{
         domain: group_domain,
         id: group_id
       }) do
@@ -547,12 +569,17 @@ defmodule Mobilizon.Federation.ActivityPub do
      true
    else
      # If local group, we'll send the invite
-      with {:ok, %Member{} = admin_member} <- Actors.get_member(actor_id, group_id) do
-        Member.is_administrator(admin_member)
+      case Actors.get_member(actor_id, group_id) do
+        {:ok, %Member{} = admin_member} ->
+          Member.is_administrator(admin_member)
+
+        _ ->
+          false
      end
    end
  end

+  @spec move(:resource, Resource.t(), map, boolean, map) :: {:ok, Activity.t(), Resource.t()}
  def move(type, old_entity, args, local \\ false, additional \\ %{}) do
    Logger.debug("We're moving something")
    Logger.debug(inspect(args))
@@ -572,6 +599,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec flag(map, boolean, map) :: {:ok, Activity.t(), Report.t()}
  def flag(args, local \\ false, additional \\ %{}) do
    with {report, report_as_data} <- Types.Reports.flag(args, local, additional),
         {:ok, activity} <- create_activity(report_as_data, local),
@@ -615,6 +643,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    end)
  end

+  @spec convert_followers_in_recipients(list(String.t())) :: {list(String.t()), list(String.t())}
  defp convert_followers_in_recipients(recipients) do
    Enum.reduce(recipients, {recipients, []}, fn recipient, {recipients, follower_actors} = acc ->
      case Actors.get_actor_by_followers_url(recipient) do
@@ -678,6 +707,8 @@ defmodule Mobilizon.Federation.ActivityPub do
  @doc """
  Publish an activity to a specific inbox
  """
+  @spec publish_one(%{inbox: String.t(), json: String.t(), actor: Actor.t(), id: String.t()}) ::
+          Tesla.Env.result()
  def publish_one(%{inbox: inbox, json: json, actor: actor, id: id}) do
    Logger.info("Federating #{id} to #{inbox}")
    %URI{host: host, path: path} = URI.parse(inbox)
@@ -711,7 +742,7 @@ defmodule Mobilizon.Federation.ActivityPub do
  @doc """
  Return all public activities (events & comments) for an actor
  """
-  @spec fetch_public_activities_for_actor(Actor.t(), integer(), integer()) :: map()
+  @spec fetch_public_activities_for_actor(Actor.t(), pos_integer(), pos_integer()) :: map()
  def fetch_public_activities_for_actor(%Actor{id: actor_id} = actor, page \\ 1, limit \\ 10) do
    %Actor{id: relay_actor_id} = Relay.get_actor()

@@ -769,6 +800,8 @@ defmodule Mobilizon.Federation.ActivityPub do
  defp check_for_tombstones(%{url: url}), do: Tombstone.find_tombstone(url)
  defp check_for_tombstones(_), do: nil

+  @typep accept_follow_entities :: Follower.t()
+
  @spec accept_follow(Follower.t(), map) :: {:ok, Follower.t(), Activity.t()} | any
  defp accept_follow(%Follower{} = follower, additional) do
    with {:ok, %Follower{} = follower} <- Actors.update_follower(follower, %{approved: true}),
@@ -792,7 +825,10 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

-  @spec accept_join(Participant.t(), map) :: {:ok, Participant.t(), Activity.t()} | any
+  @typep accept_join_entities :: Participant.t() | Member.t()
+
+  @spec accept_join(Participant.t(), map) :: {:ok, Participant.t(), Activity.t()}
+  @spec accept_join(Member.t(), map) :: {:ok, Member.t(), Activity.t()}
  defp accept_join(%Participant{} = participant, additional) do
    with {:ok, %Participant{} = participant} <-
           Events.update_participant(participant, %{role: :participant}),
@@ -820,7 +856,6 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

-  @spec accept_join(Member.t(), map) :: {:ok, Member.t(), Activity.t()} | any
  defp accept_join(%Member{} = member, additional) do
    with {:ok, %Member{} = member} <-
           Actors.update_member(member, %{role: :member}),
@@ -854,6 +889,8 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @typep accept_invite_entities :: Member.t()
+
  @spec accept_invite(Member.t(), map()) :: {:ok, Member.t(), Activity.t()} | any
  defp accept_invite(
         %Member{invited_by_id: invited_by_id, actor_id: actor_id} = member,
@@ -881,6 +918,7 @@ defmodule Mobilizon.Federation.ActivityPub do
    end
  end

+  @spec maybe_refresh_group(Member.t()) :: :ok | nil
  defp maybe_refresh_group(%Member{
         parent: %Actor{domain: parent_domain, url: parent_url},
         actor: %Actor{} = actor
--- a/lib/federation/activity_pub/actor.ex
+++ b/lib/federation/activity_pub/actor.ex
@@ -108,7 +108,7 @@ defmodule Mobilizon.Federation.ActivityPub.Actor do
      {:ok, url} when is_binary(url) ->
        make_actor_from_url(url, preload)

-      _e ->
+      {:error, _e} ->
        {:error, "No ActivityPub URL found in WebFinger"}
    end
  end
--- a/lib/federation/activity_pub/audience.ex
+++ b/lib/federation/activity_pub/audience.ex
@@ -99,6 +99,8 @@ defmodule Mobilizon.Federation.ActivityPub.Audience do
    }
  end

+  @spec get_to_and_cc(Actor.t(), list(), :direct | :private | :public | :unlisted | {:list, any}) ::
+          {list(), list()}
  @doc """
  Determines the full audience based on mentions for an audience

@@ -118,7 +120,6 @@ defmodule Mobilizon.Federation.ActivityPub.Audience do
    * `to` : the mentioned actors and the eventual actor we're replying to
    * `cc` : none
  """
-  @spec get_to_and_cc(Actor.t(), list(), String.t()) :: {list(), list()}
  def get_to_and_cc(%Actor{} = actor, mentions, :public) do
    to = [@ap_public | mentions]
    cc = [actor.followers_url]
@@ -128,7 +129,6 @@ defmodule Mobilizon.Federation.ActivityPub.Audience do
    {to, cc}
  end

-  @spec get_to_and_cc(Actor.t(), list(), String.t()) :: {list(), list()}
  def get_to_and_cc(%Actor{} = actor, mentions, :unlisted) do
    to = [actor.followers_url | mentions]
    cc = [@ap_public]
@@ -138,7 +138,6 @@ defmodule Mobilizon.Federation.ActivityPub.Audience do
    {to, cc}
  end

-  @spec get_to_and_cc(Actor.t(), list(), String.t()) :: {list(), list()}
  def get_to_and_cc(%Actor{} = actor, mentions, :private) do
    {to, cc} = get_to_and_cc(actor, mentions, :direct)

@@ -147,7 +146,6 @@ defmodule Mobilizon.Federation.ActivityPub.Audience do
    {to, cc}
  end

-  @spec get_to_and_cc(Actor.t(), list(), String.t()) :: {list(), list()}
  def get_to_and_cc(_actor, mentions, :direct) do
    {mentions, []}
  end
--- a/lib/federation/activity_pub/permission.ex
+++ b/lib/federation/activity_pub/permission.ex
@@ -13,6 +13,8 @@ defmodule Mobilizon.Federation.ActivityPub.Permission do

  @member_roles [:member, :moderator, :administrator]

+  @type object :: %{id: String.t(), url: String.t()}
+
  @doc """
  Check that actor can access the object
  """
@@ -66,8 +68,8 @@ defmodule Mobilizon.Federation.ActivityPub.Permission do

  @spec can_manage_group_object?(
          existing_object_permissions(),
-          Actor.t(),
-          any()
+          %Actor{url: String.t()},
+          object()
        ) :: boolean()
  defp can_manage_group_object?(permission, %Actor{url: actor_url} = actor, object) do
    if Ownable.group_actor(object) != nil do
@@ -94,7 +96,7 @@ defmodule Mobilizon.Federation.ActivityPub.Permission do
    end
  end

-  @spec activity_actor_is_group_member?(Actor.t(), Entity.t(), atom()) :: boolean()
+  @spec activity_actor_is_group_member?(Actor.t(), object(), atom()) :: boolean()
  defp activity_actor_is_group_member?(
         %Actor{id: actor_id, url: actor_url},
         object,
--- a/lib/federation/activity_pub/transmogrifier.ex
+++ b/lib/federation/activity_pub/transmogrifier.ex
@@ -951,7 +951,7 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
  defp do_handle_incoming_reject_invite(invite_object, %Actor{} = actor_rejecting) do
    with {:invite, {:ok, %Member{role: :invited, actor_id: actor_id} = member}} <-
           {:invite, get_member(invite_object)},
-         {:same_actor, true} <- {:same_actor, actor_rejecting.id === actor_id},
+         {:same_actor, true} <- {:same_actor, actor_rejecting.id == actor_id},
         {:ok, activity, member} <-
           ActivityPub.reject(:invite, member, false) do
      {:ok, activity, member}
--- a/lib/federation/activity_pub/types/actors.ex
+++ b/lib/federation/activity_pub/types/actors.ex
@@ -1,10 +1,11 @@
 defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
  @moduledoc false
  alias Mobilizon.Actors
-  alias Mobilizon.Actors.{Actor, Follower, Member}
+  alias Mobilizon.Actors.{Actor, Follower, Member, MemberRole}
  alias Mobilizon.Federation.ActivityPub
  alias Mobilizon.Federation.ActivityPub.{Audience, Permission, Relay}
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.GraphQL.API.Utils, as: APIUtils
  alias Mobilizon.Service.Activity.Group, as: GroupActivity
@@ -17,7 +18,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Actor.t(), ActivityStream.t()}
  def create(args, additional) do
    with args <- prepare_args_for_actor(args),
         {:ok, %Actor{} = actor} <- Actors.create_actor(args),
@@ -35,7 +36,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
  end

  @impl Entity
-  @spec update(Actor.t(), map, map) :: {:ok, Actor.t(), Activity.t()} | any
+  @spec update(Actor.t(), map, map) :: {:ok, Actor.t(), ActivityStream.t()}
  def update(%Actor{} = old_actor, args, additional) do
    with {:ok, %Actor{} = new_actor} <- Actors.update_actor(old_actor, args),
         {:ok, _} <-
@@ -57,6 +58,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
  @public_ap "https://www.w3.org/ns/activitystreams#Public"

  @impl Entity
+  @spec delete(Actor.t(), Actor.t(), boolean, map) ::
+          {:ok, ActivityStream.t(), Actor.t(), Actor.t()}
  def delete(
        %Actor{
          followers_url: followers_url,
@@ -100,10 +103,13 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
    end
  end

+  @spec actor(Actor.t()) :: Actor.t() | nil
  def actor(%Actor{} = actor), do: actor

+  @spec actor(Actor.t()) :: Actor.t() | nil
  def group_actor(%Actor{} = actor), do: actor

+  @spec permissions(Actor.t()) :: Permission.t()
  def permissions(%Actor{} = _group) do
    %Permission{
      access: :member,
@@ -113,7 +119,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
    }
  end

-  @spec join(Actor.t(), Actor.t(), boolean(), map()) :: {:ok, map(), Member.t()}
+  @spec join(Actor.t(), Actor.t(), boolean(), map()) :: {:ok, ActivityStreams.t(), Member.t()}
  def join(%Actor{type: :Group} = group, %Actor{} = actor, _local, additional) do
    with role <-
           additional
@@ -153,6 +159,10 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
    end
  end

+  @spec follow(Actor.t(), Actor.t(), boolean, map) ::
+          {:accept, any}
+          | {:ok, ActivityStreams.t(), Follower.t()}
+          | {:error, :no_person, String.t()}
  def follow(%Actor{} = follower_actor, %Actor{type: type} = followed, _local, additional)
      when type != :Person do
    with {:ok, %Follower{} = follower} <-
@@ -165,6 +175,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do

  def follow(_, _, _, _), do: {:error, :no_person, "Only group and instances can be followed"}

+  @spec prepare_args_for_actor(map) :: map
  defp prepare_args_for_actor(args) do
    args
    |> maybe_sanitize_username()
@@ -191,8 +202,14 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
  defp maybe_sanitize_summary(args), do: args

  # Set the participant to approved if the default role for new participants is :participant
-  @spec approve_if_default_role_is_member(Actor.t(), Actor.t(), map(), Member.t(), atom()) ::
-          {:ok, map(), Member.t()}
+  @spec approve_if_default_role_is_member(
+          Actor.t(),
+          Actor.t(),
+          ActivityStreams.t(),
+          Member.t(),
+          MemberRole.t()
+        ) ::
+          {:ok, ActivityStreams.t(), Member.t()}
  defp approve_if_default_role_is_member(
         %Actor{type: :Group} = group,
         %Actor{} = actor,
@@ -202,7 +219,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
       ) do
    if is_nil(group.domain) && !is_nil(actor.domain) do
      cond do
-        Mobilizon.Actors.get_default_member_role(group) === :member &&
+        Mobilizon.Actors.get_default_member_role(group) == :member &&
            role == :member ->
          {:accept,
           ActivityPub.accept(
@@ -212,7 +229,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
             %{"actor" => group.url}
           )}

-        Mobilizon.Actors.get_default_member_role(group) === :not_approved &&
+        Mobilizon.Actors.get_default_member_role(group) == :not_approved &&
            role == :not_approved ->
          Scheduler.pending_membership_notification(group)
          {:ok, activity_data, member}
@@ -225,6 +242,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Actors do
    end
  end

+  @spec approve_if_manually_approves_followers(Follower.t(), ActivityStreams.t()) ::
+          {:accept, any} | {:ok, ActivityStreams.t(), Follower.t()}
  defp approve_if_manually_approves_followers(
         %Follower{} = follower,
         follow_as_data
--- a/lib/federation/activity_pub/types/comments.ex
+++ b/lib/federation/activity_pub/types/comments.ex
@@ -6,6 +6,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
  alias Mobilizon.Events.{Event, EventOptions}
  alias Mobilizon.Federation.ActivityPub.{Audience, Permission}
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Converter.Utils, as: ConverterUtils
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.GraphQL.API.Utils, as: APIUtils
@@ -20,7 +21,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Comment.t(), ActivityStream.t()}
  def create(args, additional) do
    with args <- prepare_args_for_comment(args),
         :ok <- make_sure_event_allows_commenting(args),
@@ -41,7 +42,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
  end

  @impl Entity
-  @spec update(Comment.t(), map(), map()) :: {:ok, Comment.t(), Activity.t()} | any()
+  @spec update(Comment.t(), map(), map()) :: {:ok, Comment.t(), ActivityStream.t()}
  def update(%Comment{} = old_comment, args, additional) do
    with args <- prepare_args_for_comment_update(args),
         {:ok, %Comment{} = new_comment} <- Discussions.update_comment(old_comment, args),
@@ -60,7 +61,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
  end

  @impl Entity
-  @spec delete(Comment.t(), Actor.t(), boolean, map()) :: {:ok, Comment.t()}
+  @spec delete(Comment.t(), Actor.t(), boolean, map()) ::
+          {:ok, ActivityStream.t(), Actor.t(), Comment.t()}
  def delete(
        %Comment{url: url, id: comment_id},
        %Actor{} = actor,
@@ -91,6 +93,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
    end
  end

+  @spec actor(Comment.t()) :: Actor.t() | nil
  def actor(%Comment{actor: %Actor{} = actor}), do: actor

  def actor(%Comment{actor_id: actor_id}) when not is_nil(actor_id),
@@ -98,6 +101,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do

  def actor(_), do: nil

+  @spec group_actor(Comment.t()) :: Actor.t() | nil
  def group_actor(%Comment{attributed_to: %Actor{} = group}), do: group

  def group_actor(%Comment{attributed_to_id: attributed_to_id}) when not is_nil(attributed_to_id),
@@ -105,6 +109,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do

  def group_actor(_), do: nil

+  @spec permissions(Comment.t()) :: Permission.t()
  def permissions(%Comment{}),
    do: %Permission{
      access: :member,
@@ -114,6 +119,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
    }

  # Prepare and sanitize arguments for comments
+  @spec prepare_args_for_comment(map) :: map
  defp prepare_args_for_comment(args) do
    with in_reply_to_comment <-
           args |> Map.get(:in_reply_to_comment_id) |> Discussions.get_comment_with_preload(),
@@ -150,6 +156,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
    end
  end

+  @spec prepare_args_for_comment_update(map) :: map
  defp prepare_args_for_comment_update(args) do
    with {text, mentions, tags} <-
           APIUtils.make_content_html(
@@ -174,6 +181,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do

  defp handle_event_for_comment(nil), do: nil

+  @spec maybe_publish_graphql_subscription(String.t() | integer() | nil) :: :ok
  defp maybe_publish_graphql_subscription(nil), do: :ok

  defp maybe_publish_graphql_subscription(discussion_id) do
@@ -186,6 +194,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
    end
  end

+  @spec make_sure_event_allows_commenting(%{actor_id: String.t() | integer, event: Event.t()}) ::
+          :ok | {:error, :event_comments_are_closed}
  defp make_sure_event_allows_commenting(%{
         actor_id: actor_id,
         event: %Event{
--- a/lib/federation/activity_pub/types/discussions.ex
+++ b/lib/federation/activity_pub/types/discussions.ex
@@ -6,6 +6,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
  alias Mobilizon.Discussions.{Comment, Discussion}
  alias Mobilizon.Federation.ActivityPub.{Audience, Permission}
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.GraphQL.API.Utils, as: APIUtils
  alias Mobilizon.Service.Activity.Discussion, as: DiscussionActivity
@@ -16,7 +17,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Discussion.t(), ActivityStream.t()}
  def create(%{discussion_id: discussion_id} = args, additional) when not is_nil(discussion_id) do
    with args <- prepare_args(args),
         %Discussion{} = discussion <- Discussions.get_discussion(discussion_id),
@@ -39,7 +40,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
  end

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Discussion.t(), ActivityStream.t()}
  def create(args, additional) do
    with args <- prepare_args(args),
         {:ok, %Discussion{} = discussion} <-
@@ -56,7 +57,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
  end

  @impl Entity
-  @spec update(Discussion.t(), map(), map()) :: {:ok, Discussion.t(), Activity.t()} | any()
+  @spec update(Discussion.t(), map(), map()) :: {:ok, Discussion.t(), ActivityStream.t()}
  def update(%Discussion{} = old_discussion, args, additional) do
    with {:ok, %Discussion{} = new_discussion} <-
           Discussions.update_discussion(old_discussion, args),
@@ -80,7 +81,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
  end

  @impl Entity
-  @spec delete(Discussion.t(), Actor.t(), boolean, map()) :: {:ok, Discussion.t()}
+  @spec delete(Discussion.t(), Actor.t(), boolean, map()) ::
+          {:ok, ActivityStream.t(), Actor.t(), Discussion.t()}
  def delete(
        %Discussion{actor: group, url: url} = discussion,
        %Actor{} = actor,
@@ -106,10 +108,13 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
    end
  end

+  @spec actor(Discussion.t()) :: Actor.t() | nil
  def actor(%Discussion{creator_id: creator_id}), do: Actors.get_actor(creator_id)

+  @spec group_actor(Discussion.t()) :: Actor.t() | nil
  def group_actor(%Discussion{actor_id: actor_id}), do: Actors.get_actor(actor_id)

+  @spec permissions(Discussion.t()) :: Permission.t()
  def permissions(%Discussion{}) do
    %Permission{access: :member, create: :member, update: :moderator, delete: :moderator}
  end
@@ -123,6 +128,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Discussions do
    :ok
  end

+  @spec prepare_args(map) :: map
  defp prepare_args(args) do
    {text, _mentions, _tags} =
      APIUtils.make_content_html(
--- a/lib/federation/activity_pub/types/entity.ex
+++ b/lib/federation/activity_pub/types/entity.ex
@@ -15,7 +15,7 @@ alias Mobilizon.Federation.ActivityPub.Types.{
 }

 alias Mobilizon.Actors.{Actor, Member}
-alias Mobilizon.Events.Event
+alias Mobilizon.Events.{Event, Participant}
 alias Mobilizon.Discussions.{Comment, Discussion}
 alias Mobilizon.Federation.ActivityPub.Permission
 alias Mobilizon.Posts.Post
@@ -28,7 +28,19 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Entity do
  @moduledoc """
  ActivityPub entity behaviour
  """
-  @type t :: %{id: String.t()}
+  @type t :: %{id: String.t(), url: String.t()}
+
+  @type entities ::
+          Actor.t()
+          | Member.t()
+          | Event.t()
+          | Participant.t()
+          | Comment.t()
+          | Discussion.t()
+          | Post.t()
+          | Resource.t()
+          | Todo.t()
+          | TodoList.t()

  @callback create(data :: any(), additionnal :: map()) ::
              {:ok, t(), ActivityStream.t()}
--- a/lib/federation/activity_pub/types/events.ex
+++ b/lib/federation/activity_pub/types/events.ex
@@ -3,8 +3,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  alias Mobilizon.Actors
  alias Mobilizon.Actors.Actor
  alias Mobilizon.Events, as: EventsManager
-  alias Mobilizon.Events.{Event, Participant}
-  alias Mobilizon.Federation.ActivityPub
+  alias Mobilizon.Events.{Event, Participant, ParticipantRole}
+  alias Mobilizon.Federation.{ActivityPub, ActivityStream}
  alias Mobilizon.Federation.ActivityPub.{Audience, Permission}
  alias Mobilizon.Federation.ActivityPub.Types.Entity
  alias Mobilizon.Federation.ActivityStream.Converter.Utils, as: ConverterUtils
@@ -22,7 +22,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Event.t(), ActivityStream.t()}
  def create(args, additional) do
    with args <- prepare_args_for_event(args),
         {:ok, %Event{} = event} <- EventsManager.create_event(args),
@@ -38,7 +38,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  end

  @impl Entity
-  @spec update(Event.t(), map(), map()) :: {:ok, Event.t(), Activity.t()} | any()
+  @spec update(Event.t(), map(), map()) :: {:ok, Event.t(), ActivityStream.t()}
  def update(%Event{} = old_event, args, additional) do
    with args <- prepare_args_for_event(args),
         {:ok, %Event{} = new_event} <- EventsManager.update_event(old_event, args),
@@ -59,7 +59,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  end

  @impl Entity
-  @spec delete(Event.t(), Actor.t(), boolean, map()) :: {:ok, Event.t()}
+  @spec delete(Event.t(), Actor.t(), boolean, map()) ::
+          {:ok, ActivityStream.t(), Actor.t(), Event.t()}
  def delete(%Event{url: url} = event, %Actor{} = actor, _local, _additionnal) do
    activity_data = %{
      "type" => "Delete",
@@ -82,6 +83,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
    end
  end

+  @spec actor(Event.t()) :: Actor.t() | nil
  def actor(%Event{organizer_actor: %Actor{} = actor}), do: actor

  def actor(%Event{organizer_actor_id: organizer_actor_id}),
@@ -89,6 +91,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do

  def actor(_), do: nil

+  @spec group_actor(Event.t()) :: Actor.t() | nil
  def group_actor(%Event{attributed_to: %Actor{} = group}), do: group

  def group_actor(%Event{attributed_to_id: attributed_to_id}) when not is_nil(attributed_to_id),
@@ -96,6 +99,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do

  def group_actor(_), do: nil

+  @spec permissions(Event.t()) :: Permission.t()
  def permissions(%Event{draft: draft, attributed_to_id: _attributed_to_id}) do
    %Permission{
      access: if(draft, do: nil, else: :member),
@@ -105,9 +109,12 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
    }
  end

+  @spec join(Event.t(), Actor.t(), boolean, map) ::
+          {:ok, ActivityStreams.t(), Participant.t()}
+          | {:error, :maximum_attendee_capacity_reached}
  def join(%Event{} = event, %Actor{} = actor, _local, additional) do
    with {:maximum_attendee_capacity, true} <-
-           {:maximum_attendee_capacity, check_attendee_capacity(event)},
+           {:maximum_attendee_capacity, check_attendee_capacity?(event)},
         role <-
           additional
           |> Map.get(:metadata, %{})
@@ -133,12 +140,13 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
        role
      )
    else
-      {:maximum_attendee_capacity, err} ->
-        {:maximum_attendee_capacity, err}
+      {:maximum_attendee_capacity, false} ->
+        {:error, :maximum_attendee_capacity_reached}
    end
  end

-  defp check_attendee_capacity(%Event{options: options} = event) do
+  @spec check_attendee_capacity?(Event.t()) :: boolean
+  defp check_attendee_capacity?(%Event{options: options} = event) do
    with maximum_attendee_capacity <-
           Map.get(options, :maximum_attendee_capacity) || 0 do
      maximum_attendee_capacity == 0 ||
@@ -147,6 +155,12 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  end

  # Set the participant to approved if the default role for new participants is :participant
+  @spec approve_if_default_role_is_participant(
+          Event.t(),
+          ActivityStreams.t(),
+          Participant.t(),
+          ParticipantRole.t()
+        ) :: {:ok, ActivityStreams.t(), Participant.t()}
  defp approve_if_default_role_is_participant(event, activity_data, participant, role) do
    case event do
      %Event{attributed_to: %Actor{id: group_id, url: group_url}} ->
@@ -171,9 +185,11 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
    end
  end

+  @spec do_approve(Event.t(), ActivityStreams.t(), Particpant.t(), ParticipantRole.t(), map()) ::
+          {:accept, any} | {:ok, ActivityStreams.t(), Participant.t()}
  defp do_approve(event, activity_data, participant, role, additionnal) do
    cond do
-      Mobilizon.Events.get_default_participant_role(event) === :participant &&
+      Mobilizon.Events.get_default_participant_role(event) == :participant &&
          role == :participant ->
        {:accept,
         ActivityPub.accept(
@@ -183,7 +199,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
           additionnal
         )}

-      Mobilizon.Events.get_default_participant_role(event) === :not_approved &&
+      Mobilizon.Events.get_default_participant_role(event) == :not_approved &&
          role == :not_approved ->
        Scheduler.pending_participation_notification(event)
        {:ok, activity_data, participant}
@@ -194,6 +210,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
  end

  # Prepare and sanitize arguments for events
+  @spec prepare_args_for_event(map) :: map
  defp prepare_args_for_event(args) do
    # If title is not set: we are not updating it
    args =
--- a/lib/federation/activity_pub/types/members.ex
+++ b/lib/federation/activity_pub/types/members.ex
@@ -1,14 +1,15 @@
 defmodule Mobilizon.Federation.ActivityPub.Types.Members do
  @moduledoc false
  alias Mobilizon.Actors
-  alias Mobilizon.Actors.{Actor, Member}
-  alias Mobilizon.Federation.ActivityPub
+  alias Mobilizon.Actors.{Actor, Member, MemberRole}
+  alias Mobilizon.Federation.{ActivityPub, ActivityStream}
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Service.Activity.Member, as: MemberActivity
  alias Mobilizon.Web.Endpoint
  require Logger
  import Mobilizon.Federation.ActivityPub.Utils, only: [make_update_data: 2]

+  @spec update(Member.t(), map, map) :: {:ok, Member.t(), ActivityStream.t()}
  def update(
        %Member{
          parent: %Actor{id: group_id} = group,
@@ -24,7 +25,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Members do
         when moderator_role in [:moderator, :administrator, :creator] <-
           {:has_rights_to_update_role, Actors.get_member(moderator_id, group_id)},
         {:is_only_admin, false} <-
-           {:is_only_admin, check_admins_left(member_id, group_id, current_role, updated_role)},
+           {:is_only_admin, check_admins_left?(member_id, group_id, current_role, updated_role)},
         {:ok, %Member{} = member} <-
           Actors.update_member(old_member, args),
         {:ok, _} <-
@@ -56,6 +57,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Members do
  end

  # Used only when a group is suspended
+  @spec delete(Member.t(), Actor.t(), boolean(), map()) :: {:ok, Activity.t(), Member.t()}
  def delete(
        %Member{parent: %Actor{} = group, actor: %Actor{} = actor} = _member,
        %Actor{},
@@ -66,13 +68,21 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Members do
    ActivityPub.leave(group, actor, local, %{force_member_removal: true})
  end

+  @spec actor(Member.t()) :: Actor.t() | nil
  def actor(%Member{actor_id: actor_id}),
    do: Actors.get_actor(actor_id)

+  @spec group_actor(Member.t()) :: Actor.t() | nil
  def group_actor(%Member{parent_id: parent_id}),
    do: Actors.get_actor(parent_id)

-  defp check_admins_left(member_id, group_id, current_role, updated_role) do
+  @spec check_admins_left?(
+          String.t() | integer,
+          String.t() | integer,
+          MemberRole.t(),
+          MemberRole.t()
+        ) :: boolean
+  defp check_admins_left?(member_id, group_id, current_role, updated_role) do
    Actors.is_only_administrator?(member_id, group_id) && current_role == :administrator &&
      updated_role != :administrator
  end
--- a/lib/federation/activity_pub/types/posts.ex
+++ b/lib/federation/activity_pub/types/posts.ex
@@ -4,6 +4,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
  alias Mobilizon.Actors.Actor
  alias Mobilizon.Federation.ActivityPub.{Audience, Permission}
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Converter.Utils, as: ConverterUtils
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Posts.Post
@@ -17,6 +18,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
  @public_ap "https://www.w3.org/ns/activitystreams#Public"

  @impl Entity
+  @spec create(map(), map()) :: {:ok, Post.t(), ActivityStream.t()}
  def create(args, additional) do
    with args <- prepare_args(args),
         {:ok, %Post{attributed_to_id: group_id, author_id: creator_id} = post} <-
@@ -37,6 +39,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
  end

  @impl Entity
+  @spec update(Post.t(), map(), map()) :: {:ok, Post.t(), ActivityStream.t()}
  def update(%Post{} = post, args, additional) do
    with args <- prepare_args(args),
         {:ok, %Post{attributed_to_id: group_id, author_id: creator_id} = post} <-
@@ -60,6 +63,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
  end

  @impl Entity
+  @spec delete(Post.t(), Actor.t(), boolean, map) ::
+          {:ok, ActivityStream.t(), Actor.t(), Post.t()}
  def delete(
        %Post{
          url: url,
@@ -86,12 +91,15 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
    end
  end

+  @spec actor(Post.t()) :: Actor.t() | nil
  def actor(%Post{author_id: author_id}),
    do: Actors.get_actor(author_id)

+  @spec group_actor(Post.t()) :: Actor.t() | nil
  def group_actor(%Post{attributed_to_id: attributed_to_id}),
    do: Actors.get_actor(attributed_to_id)

+  @spec permissions(Post.t()) :: Permission.t()
  def permissions(%Post{}) do
    %Permission{
      access: :member,
@@ -101,6 +109,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Posts do
    }
  end

+  @spec prepare_args(map()) :: map
  defp prepare_args(args) do
    args
    |> Map.update(:tags, [], &ConverterUtils.fetch_tags/1)
--- a/lib/federation/activity_pub/types/reports.ex
+++ b/lib/federation/activity_pub/types/reports.ex
@@ -2,11 +2,13 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Reports do
  @moduledoc false
  alias Mobilizon.{Actors, Discussions, Reports}
  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Reports.Report
  alias Mobilizon.Service.Formatter.HTML
  require Logger

+  @spec flag(map(), boolean(), map()) :: {Report.t(), ActivityStream.t()}
  def flag(args, local \\ false, _additional \\ %{}) do
    with {:build_args, args} <- {:build_args, prepare_args_for_report(args)},
         {:create_report, {:ok, %Report{} = report}} <-
@@ -18,6 +20,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Reports do
    end
  end

+  @spec prepare_args_for_report(map()) :: map()
  defp prepare_args_for_report(args) do
    with {:reporter, %Actor{} = reporter_actor} <-
           {:reporter, Actors.get_actor!(args.reporter_id)},
--- a/lib/federation/activity_pub/types/resources.ex
+++ b/lib/federation/activity_pub/types/resources.ex
@@ -4,6 +4,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
  alias Mobilizon.Actors.Actor
  alias Mobilizon.Federation.ActivityPub.Permission
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Resources.Resource
  alias Mobilizon.Service.Activity.Resource, as: ResourceActivity
@@ -16,6 +17,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
  @behaviour Entity

  @impl Entity
+  @spec create(map(), map()) :: {:ok, Resource.t(), ActivityStream.t()}
  def create(%{type: type} = args, additional) do
    args =
      case type do
@@ -66,6 +68,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
  end

  @impl Entity
+  @spec update(Resource.t(), map(), map()) :: {:ok, Resource.t(), ActivityStream.t()}
  def update(
        %Resource{parent_id: old_parent_id} = old_resource,
        %{parent_id: parent_id} = args,
@@ -104,6 +107,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
    end
  end

+  @spec update(Resource.t(), map(), map()) :: {:ok, Resource.t(), ActivityStream.t()}
  def move(
        %Resource{parent_id: old_parent_id} = old_resource,
        %{parent_id: _new_parent_id} = args,
@@ -142,6 +146,8 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
  end

  @impl Entity
+  @spec delete(Resource.t(), Actor.t(), boolean, map()) ::
+          {:ok, ActivityStream.t(), Actor.t(), Resource.t()}
  def delete(
        %Resource{url: url, actor: %Actor{url: group_url, members_url: members_url}} = resource,
        %Actor{url: actor_url} = actor,
@@ -166,11 +172,14 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Resources do
    end
  end

+  @spec actor(Todo.t()) :: Actor.t() | nil
  def actor(%Resource{creator_id: creator_id}),
    do: Actors.get_actor(creator_id)

+  @spec group_actor(Todo.t()) :: Actor.t() | nil
  def group_actor(%Resource{actor_id: actor_id}), do: Actors.get_actor(actor_id)

+  @spec permissions(TodoList.t()) :: Permission.t()
  def permissions(%Resource{}) do
    %Permission{access: :member, create: :member, update: :member, delete: :member}
  end
--- a/lib/federation/activity_pub/types/todo_lists.ex
+++ b/lib/federation/activity_pub/types/todo_lists.ex
@@ -13,7 +13,9 @@ defmodule Mobilizon.Federation.ActivityPub.Types.TodoLists do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) ::
+          {:ok, TodoList.t(), ActivityStream.t()}
+          | {:error, :group_not_found | Ecto.Changeset.t()}
  def create(args, additional) do
    with {:ok, %TodoList{actor_id: group_id} = todo_list} <- Todos.create_todo_list(args),
         {:ok, %Actor{} = group} <- Actors.get_group_by_actor_id(group_id),
@@ -26,7 +28,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.TodoLists do
  end

  @impl Entity
-  @spec update(TodoList.t(), map, map) :: {:ok, TodoList.t(), Activity.t()} | any
+  @spec update(TodoList.t(), map, map) :: {:ok, TodoList.t(), ActivityStream.t()} | any
  def update(%TodoList{} = old_todo_list, args, additional) do
    with {:ok, %TodoList{actor_id: group_id} = todo_list} <-
           Todos.update_todo_list(old_todo_list, args),
@@ -65,10 +67,13 @@ defmodule Mobilizon.Federation.ActivityPub.Types.TodoLists do
    end
  end

+  @spec actor(TodoList.t()) :: nil
  def actor(%TodoList{}), do: nil

+  @spec group_actor(TodoList.t()) :: Actor.t() | nil
  def group_actor(%TodoList{actor_id: actor_id}), do: Actors.get_actor(actor_id)

+  @spec permissions(TodoList.t()) :: Permission.t()
  def permissions(%TodoList{}) do
    %Permission{access: :member, create: :member, update: :member, delete: :member}
  end
--- a/lib/federation/activity_pub/types/todos.ex
+++ b/lib/federation/activity_pub/types/todos.ex
@@ -4,6 +4,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Todos do
  alias Mobilizon.Actors.Actor
  alias Mobilizon.Federation.ActivityPub.Permission
  alias Mobilizon.Federation.ActivityPub.Types.Entity
+  alias Mobilizon.Federation.ActivityStream
  alias Mobilizon.Federation.ActivityStream.Convertible
  alias Mobilizon.Todos.{Todo, TodoList}
  import Mobilizon.Federation.ActivityPub.Utils, only: [make_create_data: 2, make_update_data: 2]
@@ -12,7 +13,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Todos do
  @behaviour Entity

  @impl Entity
-  @spec create(map(), map()) :: {:ok, map()}
+  @spec create(map(), map()) :: {:ok, Todo.t(), ActivityStream.t()}
  def create(args, additional) do
    with {:ok, %Todo{todo_list_id: todo_list_id, creator_id: creator_id} = todo} <-
           Todos.create_todo(args),
@@ -30,7 +31,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Todos do
  end

  @impl Entity
-  @spec update(Todo.t(), map, map) :: {:ok, Todo.t(), Activity.t()} | any
+  @spec update(Todo.t(), map, map) :: {:ok, Todo.t(), ActivityStream.t()}
  def update(%Todo{} = old_todo, args, additional) do
    with {:ok, %Todo{todo_list_id: todo_list_id} = todo} <- Todos.update_todo(old_todo, args),
         %TodoList{actor_id: group_id} = todo_list <- Todos.get_todo_list(todo_list_id),
@@ -69,8 +70,10 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Todos do
    end
  end

+  @spec actor(Todo.t()) :: Actor.t() | nil
  def actor(%Todo{creator_id: creator_id}), do: Actors.get_actor(creator_id)

+  @spec group_actor(Todo.t()) :: Actor.t() | nil
  def group_actor(%Todo{todo_list_id: todo_list_id}) do
    case Todos.get_todo_list(todo_list_id) do
      %TodoList{actor_id: group_id} ->
@@ -81,6 +84,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Todos do
    end
  end

+  @spec permissions(TodoList.t()) :: Permission.t()
  def permissions(%Todo{}) do
    %Permission{access: :member, create: :member, update: :member, delete: :member}
  end
--- a/lib/federation/activity_stream/converter/actor.ex
+++ b/lib/federation/activity_stream/converter/actor.ex
@@ -29,7 +29,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Actor do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map()) :: {:ok, map()}
+  @spec as_to_model_data(map()) :: map() | {:error, :actor_not_allowed_type}
  def as_to_model_data(%{"type" => type} = data) when type in @allowed_types do
    avatar =
      download_picture(get_in(data, ["icon", "url"]), get_in(data, ["icon", "name"]), "avatar")
@@ -64,7 +64,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Actor do
    }
  end

-  def as_to_model_data(_), do: :error
+  def as_to_model_data(_), do: {:error, :actor_not_allowed_type}

  @doc """
  Convert an actor struct to an ActivityStream representation.
@@ -135,7 +135,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Actor do
    end
  end

-  @spec download_picture(String.t() | nil, String.t(), String.t()) :: map()
+  @spec download_picture(String.t() | nil, String.t(), String.t()) :: map() | nil
  defp download_picture(nil, _name, _default_name), do: nil

  defp download_picture(url, name, default_name) do
--- a/lib/federation/activity_stream/converter/comment.ex
+++ b/lib/federation/activity_stream/converter/comment.ex
@@ -38,7 +38,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Comment do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
+  @spec as_to_model_data(map) :: map | {:error, any()}
  def as_to_model_data(object) do
    Logger.debug("We're converting raw ActivityStream data to a comment entity")
    Logger.debug(inspect(object))
--- a/lib/federation/activity_stream/converter/converter.ex
+++ b/lib/federation/activity_stream/converter/converter.ex
@@ -8,6 +8,6 @@ defmodule Mobilizon.Federation.ActivityStream.Converter do

  @type model_data :: map()

-  @callback as_to_model_data(as_data :: ActivityStream.t()) :: model_data()
+  @callback as_to_model_data(as_data :: ActivityStream.t()) :: model_data() | {:error, any()}
  @callback model_to_as(model :: struct()) :: ActivityStream.t()
 end
--- a/lib/federation/activity_stream/converter/discussion.ex
+++ b/lib/federation/activity_stream/converter/discussion.ex
@@ -12,6 +12,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Discussion do
  alias Mobilizon.Federation.ActivityStream.{Converter, Convertible}
  alias Mobilizon.Federation.ActivityStream.Converter.Discussion, as: DiscussionConverter
  alias Mobilizon.Storage.Repo
+  import Mobilizon.Service.Guards, only: [is_valid_string: 1]

  require Logger

@@ -45,20 +46,27 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Discussion do
  end

  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
-  def as_to_model_data(%{"type" => "Note", "name" => name} = object) when not is_nil(name) do
-    with creator_url <- Map.get(object, "actor"),
-         {:ok, %Actor{id: creator_id, suspended: false}} <-
+  @spec as_to_model_data(map) :: map() | {:error, any()}
+  def as_to_model_data(%{"type" => "Note", "name" => name} = object) when is_valid_string(name) do
+    case extract_actors(object) do
+      %{actor_id: actor_id, creator_id: creator_id} ->
+        %{actor_id: actor_id, creator_id: creator_id, title: name, url: object["id"]}
+
+      {:error, error} ->
+        {:error, error}
+    end
+  end
+
+  @spec extract_actors(map()) :: %{actor_id: String.t(), creator_id: String.t()} | {:error, any()}
+  defp extract_actors(%{"actor" => creator_url, "attributedTo" => actor_url} = _object)
+       when is_valid_string(creator_url) and is_valid_string(actor_url) do
+    with {:ok, %Actor{id: creator_id, suspended: false}} <-
           ActivityPubActor.get_or_fetch_actor_by_url(creator_url),
-         actor_url <- Map.get(object, "attributedTo"),
         {:ok, %Actor{id: actor_id, suspended: false}} <-
           ActivityPubActor.get_or_fetch_actor_by_url(actor_url) do
-      %{
-        title: name,
-        actor_id: actor_id,
-        creator_id: creator_id,
-        url: object["id"]
-      }
+      %{actor_id: actor_id, creator_id: creator_id}
+    else
+      {:error, error} -> {:error, error}
    end
  end
 end
--- a/lib/federation/activity_stream/converter/event.ex
+++ b/lib/federation/activity_stream/converter/event.ex
@@ -45,7 +45,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Event do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map()} | {:error, any()}
+  @spec as_to_model_data(map) :: map() | {:error, any()} | :error
  def as_to_model_data(object) do
    with {%Actor{id: actor_id}, attributed_to} <-
           maybe_fetch_actor_and_attributed_to_id(object),
--- a/lib/federation/activity_stream/converter/member.ex
+++ b/lib/federation/activity_stream/converter/member.ex
@@ -33,6 +33,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Member do
    }
  end

+  @spec as_to_model_data(map()) :: map()
  def as_to_model_data(%{
        "type" => "Member",
        "actor" => actor,
--- a/lib/federation/activity_stream/converter/post.ex
+++ b/lib/federation/activity_stream/converter/post.ex
@@ -18,6 +18,8 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Post do
      process_pictures: 2
    ]

+  import Mobilizon.Service.Guards, only: [is_valid_string: 1]
+
  @behaviour Converter

  defimpl Convertible, for: Post do
@@ -63,15 +65,15 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Post do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
+  @spec as_to_model_data(map) :: map() | {:error, any()}
  def as_to_model_data(
        %{"type" => "Article", "actor" => creator, "attributedTo" => group_uri} = object
      ) do
    with {:ok, %Actor{id: attributed_to_id} = group} <- get_actor(group_uri),
-         {:ok, %Actor{id: author_id}} <- get_actor(creator),
-         {:visibility, visibility} <- {:visibility, get_visibility(object, group)},
-         [description: description, picture_id: picture_id, medias: medias] <-
-           process_pictures(object, attributed_to_id) do
+         {:ok, %Actor{id: author_id}} <- get_actor(creator) do
+      [description: description, picture_id: picture_id, medias: medias] =
+        process_pictures(object, attributed_to_id)
+
      %{
        title: object["name"],
        body: description,
@@ -82,7 +84,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Post do
        publish_at: object["published"],
        picture_id: picture_id,
        medias: medias,
-        visibility: visibility,
+        visibility: get_visibility(object, group),
        draft: object["draft"] == true
      }
    else
@@ -92,11 +94,12 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Post do
  end

  @spec get_actor(String.t() | map() | nil) :: {:ok, Actor.t()} | {:error, String.t()}
-  defp get_actor(nil), do: {:error, "nil property found for actor data"}
-
-  defp get_actor(actor),
+  defp get_actor(actor) when is_valid_string(actor),
    do: actor |> Utils.get_url() |> ActivityPubActor.get_or_fetch_actor_by_url()

+  defp get_actor(_), do: {:error, "nil property found for actor data"}
+
+  @spec to_date(DateTime.t() | NaiveDateTime.t() | nil) :: String.t() | nil
  defp to_date(nil), do: nil
  defp to_date(%DateTime{} = date), do: DateTime.to_iso8601(date)
  defp to_date(%NaiveDateTime{} = date), do: NaiveDateTime.to_iso8601(date)
--- a/lib/federation/activity_stream/converter/resource.ex
+++ b/lib/federation/activity_stream/converter/resource.ex
@@ -56,18 +56,17 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Resource do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
+  @spec as_to_model_data(map) :: map() | {:error, any()}
  def as_to_model_data(%{"type" => type, "actor" => creator, "attributedTo" => group} = object) do
    with {:ok, %Actor{id: actor_id, resources_url: resources_url}} <- get_actor(group),
-         {:ok, %Actor{id: creator_id}} <- get_actor(creator),
-         parent_id <- get_parent_id(object["context"], resources_url) do
+         {:ok, %Actor{id: creator_id}} <- get_actor(creator) do
      data = %{
        title: object["name"],
        summary: object["summary"],
        url: object["id"],
        actor_id: actor_id,
        creator_id: creator_id,
-        parent_id: parent_id,
+        parent_id: get_parent_id(object["context"], resources_url),
        published_at: object["published"]
      }

--- a/lib/federation/activity_stream/converter/todo.ex
+++ b/lib/federation/activity_stream/converter/todo.ex
@@ -47,7 +47,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Todo do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
+  @spec as_to_model_data(map) :: map() | {:error, any()}
  def as_to_model_data(
        %{"type" => "Todo", "actor" => actor_url, "todoList" => todo_list_url} = object
      ) do
--- a/lib/federation/activity_stream/converter/todo_list.ex
+++ b/lib/federation/activity_stream/converter/todo_list.ex
@@ -37,7 +37,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.TodoList do
  Converts an AP object data to our internal data structure.
  """
  @impl Converter
-  @spec as_to_model_data(map) :: {:ok, map} | {:error, any()}
+  @spec as_to_model_data(map) :: map() | {:error, :group_not_found}
  def as_to_model_data(%{"type" => "TodoList", "actor" => actor_url} = object) do
    case ActivityPubActor.get_or_fetch_actor_by_url(actor_url) do
      {:ok, %Actor{type: :Group, id: group_id} = _group} ->
--- a/lib/federation/http_signatures/signature.ex
+++ b/lib/federation/http_signatures/signature.ex
@@ -19,7 +19,7 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do

  @spec key_id_to_actor_url(String.t()) :: String.t()
  def key_id_to_actor_url(key_id) do
-    %{path: path} =
+    %URI{path: path} =
      uri =
      key_id
      |> URI.parse()
@@ -29,7 +29,7 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do
      if is_nil(path) do
        uri
      else
-        Map.put(uri, :path, String.trim_trailing(path, "/publickey"))
+        %URI{uri | path: String.trim_trailing(path, "/publickey")}
      end

    URI.to_string(uri)
@@ -78,6 +78,9 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do
    end
  end

+  @spec fetch_public_key(Plug.Conn.t()) ::
+          {:ok, String.t()}
+          | {:error, :actor_fetch_error | :actor_not_fetchable | :pem_decode_error}
  def fetch_public_key(conn) do
    with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
         actor_id <- key_id_to_actor_url(kid),
@@ -87,6 +90,9 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do
    end
  end

+  @spec refetch_public_key(Plug.Conn.t()) ::
+          {:ok, String.t()}
+          | {:error, :actor_fetch_error | :actor_not_fetchable | :pem_decode_error}
  def refetch_public_key(conn) do
    with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
         actor_id <- key_id_to_actor_url(kid),
@@ -97,6 +103,7 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do
    end
  end

+  @spec sign(Actor.t(), map()) :: String.t()
  def sign(%Actor{domain: domain, keys: keys} = actor, headers) when is_nil(domain) do
    Logger.debug("Signing a payload on behalf of #{actor.url}")
    Logger.debug("headers")
@@ -112,14 +119,17 @@ defmodule Mobilizon.Federation.HTTPSignatures.Signature do
    raise ArgumentError, message: "Can't do a signature on remote actor #{url}"
  end

+  @spec generate_date_header :: String.t()
  def generate_date_header, do: generate_date_header(NaiveDateTime.utc_now())

  def generate_date_header(%NaiveDateTime{} = date) do
    Timex.format!(date, "{WDshort}, {0D} {Mshort} {YYYY} {h24}:{m}:{s} GMT")
  end

+  @spec generate_request_target(String.t(), String.t()) :: String.t()
  def generate_request_target(method, path), do: "#{method} #{path}"

+  @spec build_digest(String.t()) :: String.t()
  def build_digest(body) do
    "SHA-256=#{:sha256 |> :crypto.hash(body) |> Base.encode64()}"
  end
--- a/lib/federation/web_finger/web_finger.ex
+++ b/lib/federation/web_finger/web_finger.ex
@@ -66,10 +66,10 @@ defmodule Mobilizon.Federation.WebFinger do
    end
  end

-  @spec represent_actor(Actor.t()) :: struct()
+  @spec represent_actor(Actor.t()) :: map()
+  @spec represent_actor(Actor.t(), String.t()) :: map()
  def represent_actor(%Actor{} = actor), do: represent_actor(actor, "JSON")

-  @spec represent_actor(Actor.t(), String.t()) :: struct()
  def represent_actor(%Actor{} = actor, "JSON") do
    links =
      [
@@ -141,11 +141,15 @@ defmodule Mobilizon.Federation.WebFinger do
  @doc """
  Fetches the Extensible Resource Descriptor endpoint `/.well-known/host-meta` to find the Webfinger endpoint (usually `/.well-known/webfinger?resource=`)
  """
-  @spec find_webfinger_endpoint(String.t()) :: String.t()
+  @spec find_webfinger_endpoint(String.t()) ::
+          {:ok, String.t()} | {:error, :link_not_found} | {:error, any()}
  def find_webfinger_endpoint(domain) when is_binary(domain) do
    with {:ok, %{body: body}} <- fetch_document("http://#{domain}/.well-known/host-meta"),
         link_template when is_binary(link_template) <- find_link_from_template(body) do
      {:ok, link_template}
+    else
+      {:error, :link_not_found} -> {:error, :link_not_found}
+      {:error, error} -> {:error, error}
    end
  end