From 2316c5d41db1c0cf68804c3b4dee53469bbec0a9 Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Wed, 2 Oct 2019 09:47:04 -0400
Subject: [PATCH] Handle follow activities

---
 lib/clacks/activitypub.ex                     | 11 +++++
 lib/clacks/inbox.ex                           | 49 +++++++++++++++----
 .../controllers/inbox_controller.ex           | 16 ++++--
 3 files changed, 63 insertions(+), 13 deletions(-)

diff --git a/lib/clacks/activitypub.ex b/lib/clacks/activitypub.ex
index e667f2c..751e339 100644
--- a/lib/clacks/activitypub.ex
+++ b/lib/clacks/activitypub.ex
@@ -95,6 +95,17 @@ defmodule Clacks.ActivityPub do
     }
   end
 
+  @spec accept_follow(follow_activity :: map()) :: map()
+  def accept_follow(%{"type" => "Follow", "object" => followed} = follow_activity) do
+    %{
+      "@context" => @context,
+      "type" => "Accept",
+      "id" => activity_id(Ecto.UUID.generate()),
+      "actor" => followed,
+      "object" => follow_activity
+    }
+  end
+
   @spec object_id(id :: String.t()) :: String.t()
   def object_id(id) do
     url = Application.get_env(:clacks, ClacksWeb.Endpoint)[:url]
diff --git a/lib/clacks/inbox.ex b/lib/clacks/inbox.ex
index 154f690..6abfbbe 100644
--- a/lib/clacks/inbox.ex
+++ b/lib/clacks/inbox.ex
@@ -1,24 +1,53 @@
 defmodule Clacks.Inbox do
-  alias Clacks.{Repo, Activity, Object, Actor}
-
-  def handle_create(%{"type" => "Create", "object" => object, "actor" => actor} = activity) do
-    changeset = Object.changeset(%Object{}, %{data: object})
-    {:ok, _object} = Repo.insert(changeset)
+  require Logger
+  alias Clacks.{Repo, Activity, Object, Actor, ActivityPub}
 
+  defp store_activity(%{"actor" => actor} = activity, local \\ false) when is_binary(actor) do
     changeset =
       Activity.changeset(%Activity{}, %{
         data: activity,
-        local: false,
+        local: local,
         actor: actor
       })
 
-    {:ok, _activity} = Repo.insert(changeset)
+    Repo.insert(changeset)
   end
 
-  def handle_follow(%{"type" => "Follow", "object" => followed_id, "actor" => follower})
+  def handle_create(%{"type" => "Create", "object" => object} = activity) do
+    changeset = Object.changeset(%Object{}, %{data: object})
+    {:ok, _object} = Repo.insert(changeset)
+
+    {:ok, _activity} = store_activity(activity)
+  end
+
+  @spec handle_follow(activity :: map()) :: :ok | {:error, reason :: any()}
+  def handle_follow(
+        %{"type" => "Follow", "object" => followed_id, "actor" => follower_id} = activity
+      )
       when is_binary(followed_id) do
     followed = Actor.get_by_ap_id(followed_id)
-    changeset = Actor.changeset(followed, %{followers: [follower | followed.followers]})
-    {:ok, _followed} = Repo.update(changeset)
+    follower = Actor.get_by_ap_id(follower_id)
+
+    store_activity(activity)
+
+    changeset = Actor.changeset(followed, %{followers: [follower_id | followed.followers]})
+
+    case Repo.update(changeset) do
+      {:error, changeset} ->
+        Logger.error("Couldn't store Follow activity: #{inspect(changeset)}")
+        {:error, "Couldn't store Follow activity"}
+
+      {:ok, _followed} ->
+        accept = ActivityPub.accept_follow(activity)
+
+        case store_activity(accept, true) do
+          {:error, changeset} ->
+            Logger.error("Couldn't store Accept activity: #{inspect(changeset)}")
+            {:error, "Couldn't store Accept activity"}
+
+          {:ok, _accept} ->
+            ActivityPub.Federator.federate(accept, follower.data["inbox"])
+        end
+    end
   end
 end
diff --git a/lib/clacks_web/controllers/inbox_controller.ex b/lib/clacks_web/controllers/inbox_controller.ex
index 30f2589..573d175 100644
--- a/lib/clacks_web/controllers/inbox_controller.ex
+++ b/lib/clacks_web/controllers/inbox_controller.ex
@@ -1,4 +1,5 @@
 defmodule ClacksWeb.InboxController do
+  require Logger
   use ClacksWeb, :controller
   alias Clacks.Inbox
 
@@ -18,13 +19,22 @@ defmodule ClacksWeb.InboxController do
 
     conn
     |> put_status(200)
+    |> json(%{})
   end
 
   def handle(conn, %{"type" => "Follow", "object" => object} = activity) when is_binary(object) do
-    Inbox.handle_follow(activity)
+    case Inbox.handle_follow(activity) do
+      :ok ->
+        conn
+        |> put_status(200)
 
-    conn
-    |> put_status(200)
+      {:error, reason} ->
+        Logger.error("Could not handle incoming follow: #{inspect(reason)}")
+
+        conn
+        |> put_status(500)
+    end
+    |> json(%{})
   end
 
   # def handle(conn, _) do