3 files changed, 190 insertions, 2 deletions

diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index 65dd251f3..d0c014e9d 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -322,6 +322,32 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
+  def 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),
+         reaction_data <- make_emoji_reaction_data(user, object, emoji, activity_id),
+         {:ok, activity} <- insert(reaction_data, local),
+         {:ok, object} <- add_emoji_reaction_to_object(activity, object),
+         :ok <- maybe_federate(activity) do
+      {:ok, activity, object}
+    end
+  end
+
+  def 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,
+         %Activity{actor: ^user_ap_id} = reaction_activity <- Activity.get_by_ap_id(reaction_id),
+         object <- Object.normalize(reaction_activity),
+         unreact_data <- make_undo_data(user, reaction_activity, activity_id),
+         {:ok, activity} <- insert(unreact_data, local),
+         {:ok, object} <- remove_emoji_reaction_from_object(reaction_activity, object),
+         :ok <- maybe_federate(activity) do
+      {:ok, activity, object}
+    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,
diff --git a/lib/pleroma/web/activity_pub/transmogrifier.ex b/lib/pleroma/web/activity_pub/transmogrifier.ex
index 91a164eff..15612545b 100644
--- a/lib/pleroma/web/activity_pub/transmogrifier.ex
+++ b/lib/pleroma/web/activity_pub/transmogrifier.ex
@@ -566,6 +566,34 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     end
   end
 
+  @misskey_reactions %{
+    "like" => "👍",
+    "love" => "❤️",
+    "laugh" => "😆",
+    "hmm" => "🤔",
+    "surprise" => "😮",
+    "congrats" => "🎉",
+    "angry" => "💢",
+    "confused" => "😥",
+    "rip" => "😇",
+    "pudding" => "🍮",
+    "star" => "⭐"
+  }
+
+  @doc "Rewrite misskey likes into EmojiReactions"
+  def handle_incoming(
+        %{
+          "type" => "Like",
+          "_misskey_reaction" => reaction
+        } = data,
+        options
+      ) do
+    data
+    |> Map.put("type", "EmojiReaction")
+    |> Map.put("content", @misskey_reactions[reaction] || reaction)
+    |> handle_incoming(options)
+  end
+
   def handle_incoming(
         %{"type" => "Like", "object" => object_id, "actor" => _actor, "id" => id} = data,
         _options
@@ -581,6 +609,27 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   end
 
   def handle_incoming(
+        %{
+          "type" => "EmojiReaction",
+          "object" => object_id,
+          "actor" => _actor,
+          "id" => id,
+          "content" => emoji
+        } = data,
+        _options
+      ) do
+    with actor <- Containment.get_actor(data),
+         {:ok, %User{} = actor} <- User.get_or_fetch_by_ap_id(actor),
+         {:ok, object} <- get_obj_helper(object_id),
+         {:ok, activity, _object} <-
+           ActivityPub.react_with_emoji(actor, object, emoji, activity_id: id, local: false) do
+      {:ok, activity}
+    else
+      _e -> :error
+    end
+  end
+
+  def handle_incoming(
         %{"type" => "Announce", "object" => object_id, "actor" => _actor, "id" => id} = data,
         _options
       ) do
@@ -718,6 +767,28 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   def handle_incoming(
         %{
           "type" => "Undo",
+          "object" => %{"type" => "EmojiReaction", "id" => reaction_activity_id},
+          "actor" => _actor,
+          "id" => id
+        } = data,
+        _options
+      ) do
+    with actor <- Containment.get_actor(data),
+         {:ok, %User{} = actor} <- User.get_or_fetch_by_ap_id(actor),
+         {:ok, activity, _} <-
+           ActivityPub.unreact_with_emoji(actor, reaction_activity_id,
+             activity_id: id,
+             local: false
+           ) do
+      {:ok, activity}
+    else
+      _e -> :error
+    end
+  end
+
+  def handle_incoming(
+        %{
+          "type" => "Undo",
           "object" => %{"type" => "Block", "object" => blocked},
           "actor" => blocker,
           "id" => id
@@ -1048,7 +1119,7 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     Map.put(object, "attachment", attachments)
   end
 
-  defp strip_internal_fields(object) do
+  def strip_internal_fields(object) do
     object
     |> Map.drop(Pleroma.Constants.object_internal_fields())
   end
diff --git a/lib/pleroma/web/activity_pub/utils.ex b/lib/pleroma/web/activity_pub/utils.ex
index d812fd734..91cfa2194 100644
--- a/lib/pleroma/web/activity_pub/utils.ex
+++ b/lib/pleroma/web/activity_pub/utils.ex
@@ -255,6 +255,16 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> Repo.one()
   end
 
+  @doc """
+  Returns like activities targeting an object
+  """
+  def get_object_likes(%{data: %{"id" => id}}) do
+    id
+    |> Activity.Queries.by_object_id()
+    |> Activity.Queries.by_type("Like")
+    |> Repo.all()
+  end
+
   @spec make_like_data(User.t(), map(), String.t()) :: map()
   def make_like_data(
         %User{ap_id: ap_id} = actor,
@@ -286,13 +296,30 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> maybe_put("id", activity_id)
   end
 
+  def make_emoji_reaction_data(user, object, emoji, activity_id) do
+    make_like_data(user, object, activity_id)
+    |> Map.put("type", "EmojiReaction")
+    |> Map.put("content", emoji)
+  end
+
   @spec update_element_in_object(String.t(), list(any), Object.t()) ::
           {:ok, Object.t()} | {:error, Ecto.Changeset.t()}
   def update_element_in_object(property, element, object) do
+    length =
+      if is_map(element) do
+        element
+        |> Map.values()
+        |> List.flatten()
+        |> length()
+      else
+        element
+        |> length()
+      end
+
     data =
       Map.merge(
         object.data,
-        %{"#{property}_count" => length(element), "#{property}s" => element}
+        %{"#{property}_count" => length, "#{property}s" => element}
       )
 
     object
@@ -300,6 +327,38 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> Object.update_and_set_cache()
   end
 
+  @spec add_emoji_reaction_to_object(Activity.t(), Object.t()) ::
+          {:ok, Object.t()} | {:error, Ecto.Changeset.t()}
+
+  def add_emoji_reaction_to_object(
+        %Activity{data: %{"content" => emoji, "actor" => actor}},
+        object
+      ) do
+    reactions = object.data["reactions"] || %{}
+    emoji_actors = reactions[emoji] || []
+    new_emoji_actors = [actor | emoji_actors] |> Enum.uniq()
+    new_reactions = Map.put(reactions, emoji, new_emoji_actors)
+    update_element_in_object("reaction", new_reactions, object)
+  end
+
+  def remove_emoji_reaction_from_object(
+        %Activity{data: %{"content" => emoji, "actor" => actor}},
+        object
+      ) do
+    reactions = object.data["reactions"] || %{}
+    emoji_actors = reactions[emoji] || []
+    new_emoji_actors = List.delete(emoji_actors, actor)
+
+    new_reactions =
+      if new_emoji_actors == [] do
+        Map.delete(reactions, emoji)
+      else
+        Map.put(reactions, emoji, new_emoji_actors)
+      end
+
+    update_element_in_object("reaction", new_reactions, object)
+  end
+
   @spec add_like_to_object(Activity.t(), Object.t()) ::
           {:ok, Object.t()} | {:error, Ecto.Changeset.t()}
   def add_like_to_object(%Activity{data: %{"actor" => actor}}, object) do
@@ -397,6 +456,19 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> Repo.one()
   end
 
+  def get_latest_reaction(internal_activity_id, %{ap_id: ap_id}, emoji) do
+    %{data: %{"object" => object_ap_id}} = Activity.get_by_id(internal_activity_id)
+
+    "EmojiReaction"
+    |> Activity.Queries.by_type()
+    |> where(actor: ^ap_id)
+    |> where([activity], fragment("?->>'content' = ?", activity.data, ^emoji))
+    |> Activity.Queries.by_object_id(object_ap_id)
+    |> order_by([activity], fragment("? desc nulls last", activity.id))
+    |> limit(1)
+    |> Repo.one()
+  end
+
   #### Announce-related helpers
 
   @doc """
@@ -489,6 +561,25 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> maybe_put("id", activity_id)
   end
 
+  def make_undo_data(
+        %User{ap_id: actor, follower_address: follower_address},
+        %Activity{
+          data: %{"id" => undone_activity_id, "context" => context},
+          actor: undone_activity_actor
+        },
+        activity_id \\ nil
+      ) do
+    %{
+      "type" => "Undo",
+      "actor" => actor,
+      "object" => undone_activity_id,
+      "to" => [follower_address, undone_activity_actor],
+      "cc" => [Pleroma.Constants.as_public()],
+      "context" => context
+    }
+    |> maybe_put("id", activity_id)
+  end
+
   @spec add_announce_to_object(Activity.t(), Object.t()) ::
           {:ok, Object.t()} | {:error, Ecto.Changeset.t()}
   def add_announce_to_object(