untested implementation

lib/vonbraun/activity_pub/handler/accept.ex

@@ -1,10 +1,67 @@
 defmodule Vonbraun.ActivityPub.Handler.Accept do
   @behaviour Vonbraun.ActivityPub.HandlerBehaviour
 
+  require Logger
+  alias Vonbraun.Ecto.Schema.Actor
+  alias Vonbraun.ActivityPub.Object
+
   def type, do: "Accept"
 
-  # Lots of kinds of things can be accepted.
-  def handle(_activity = %{"type" => "Accept"}) do
-    :ok
+  def extract_follow_object_actor(%{"type" => "Follow", "actor" => actor_id})
+      when is_binary(actor_id) do
+    {:ok, actor_id}
   end
+
+  def extract_follow_object_actor(%{"type" => "Follow", "id" => provided_follow_activity_id})
+      when is_binary(provided_follow_activity_id) do
+    domain = Application.fetch_env!(:vonbraun, :domain)
+    actual_activity_id_prefix = "https://#{domain}/id/follow:"
+
+    with ^actual_activity_id_prefix <> actor_id <- provided_follow_activity_id do
+      {:ok, actor_id}
+    else
+      _ ->
+        {:error, :notfound}
+    end
+  end
+
+  def extract_follow_object_actor(_) do
+    {:error, :notfound}
+  end
+
+  # Lots of kinds of things can be accepted but for right now only follows.
+  def handle(%{
+        "type" => "Accept",
+        "actor" => actor_id,
+        "object" => object = %{"type" => "Follow"}
+      }) do
+    with {:actor, {:ok, follow_actor_id}} <- {:actor, extract_follow_object_actor(object)},
+         {:match, true} <- {:match, follow_actor_id == Object.my_id()},
+         {:asked, {:ok, %Actor{:blocked => nil, :following_state => "accepted"}}} <-
+           {:asked, Actor.mark_pending_follow(actor_id, "accepted", force: true)} do
+      Logger.info("Now following: #{actor_id}")
+      {:ok, :following}
+    else
+      {:asked, {:error, :blocked}} ->
+        {:ok, :blocked_user}
+
+      {:asked, {:error, error}} ->
+        {:error, error}
+
+      {:asked, {:ok, %Actor{:blocked => nil, :following_state => following_state}}} ->
+        Logger.error(
+          "Weird following state after received Accept: #{following_state} from actor: #{actor_id} this should not happen."
+        )
+
+        {:error, :following_state}
+
+      {:actor, {:error, _error}} ->
+        {:ok, :unauthorized}
+
+      {:match, false} ->
+        {:ok, :unauthorized}
+    end
+  end
+
+  def handle(%{}), do: {:error, :match}
 end

lib/vonbraun/activity_pub/handler/follow.ex

@@ -1,9 +1,76 @@
 defmodule Vonbraun.ActivityPub.Handler.Follow do
   @behaviour Vonbraun.ActivityPub.HandlerBehaviour
 
+  require Logger
+  alias Vonbraun.ActivityPubReq
+  alias Vonbraun.Ecto.Schema.Actor
+  alias Vonbraun.ActivityPub.Object
+
   def type, do: "Follow"
 
-  def handle(_activity = %{"type" => "Follow"}) do
-    :ok
+  def handle(%{"type" => "Follow", "actor" => follow_requester_id, "object" => follow_target}) when is_binary(follow_requester_id) and is_binary(follow_target) do
+    with {:valid_target, true} <- {:valid_target, Object.my_id() == follow_target},
+         {:actor, {:ok, actor}} <- {:actor, ActivityPubReq.get_actor(follow_requester_id)},
+         {:add, {:ok, %Actor{:blocked => nil, :follows_me_state => follows_me_state}}}
+         when not is_nil(follows_me_state) <-
+           {:add, Actor.maybe_add_follower(follow_requester_id)} do
+      activity_type =
+        case follows_me_state do
+          "accepted" ->
+            :accept
+
+          "rejected" ->
+            :reject
+
+          "pending" ->
+            nil
         end
+
+      if activity_type do
+        payload =
+          Object.accept_follow_activity(follow_requester_id, activity_type) |> Jason.encode!()
+
+        Logger.debug("Replying to follow request with: #{activity_type}")
+        Logger.debug("And payload: `#{payload}`")
+
+        with {:inbox, {:ok, inbox}} <- {:inbox, ActivityPubReq.extract_actor_inbox(actor)},
+             {:inbox_uri, inbox = %URI{}} <- {:inbox_uri, URI.parse(inbox)} do
+          Task.start(fn ->
+            case ActivityPubReq.post(inbox, payload) do
+              {:ok, %{:status => status, :body => body}} ->
+                Logger.debug("Accept response status: #{status} body: #{inspect(body)}")
+
+              {:error, error} ->
+                Logger.error("Failed to Accept: #{inspect(error)}")
+            end
+          end)
+
+          {:ok, String.to_atom(follows_me_state)}
+        else
+          {:inbox, {:error, _}} ->
+            {:error, :inbox}
+        end
+      else
+        {:ok, :ignored}
+      end
+    else
+      {:valid_target, false} ->
+        {:ok, :unauthorized}
+
+      {:actor, {:error, error}} ->
+        {:error, {:actor, error}}
+
+      {:add, {:ok, %Actor{:blocked => blocked_ts}}} when not is_nil(blocked_ts) ->
+        {:ok, :unauthorized}
+
+      {:add, {:ok, %Actor{:follows_me_state => nil}}} ->
+        Logger.error("follows-me state was nil, this should never happen")
+        {:error, :impossible}
+
+      {:add, {:error, error}} ->
+        {:error, error}
+    end
+  end
+
+  def handle(%{}), do: {:error, :match}
 end

lib/vonbraun/activity_pub/handler/reject.ex

@@ -1,10 +1,48 @@
 defmodule Vonbraun.ActivityPub.Handler.Reject do
   @behaviour Vonbraun.ActivityPub.HandlerBehaviour
 
+  require Logger
+  alias Vonbraun.Ecto.Schema.Actor
+  alias Vonbraun.ActivityPub.Object
+  import Vonbraun.ActivityPub.Handler.Accept, only: [extract_follow_object_actor: 1]
+
   def type, do: "Reject"
 
-  # Lots of kinds of things can be accepted.
-  def handle(_activity = %{"type" => "Reject"}) do
-    :ok
+  # Lots of kinds of things can be rejected but for right now only follows.
+  def handle(
+        %{
+          "type" => "Reject",
+          "actor" => actor_id,
+          "object" => object = %{"type" => "Follow"}
+        }
+      ) do
+    with {:actor, {:ok, follow_actor_id}} <- {:actor, extract_follow_object_actor(object)},
+         {:match, true} <- {:match, follow_actor_id == Object.my_id()},
+         {:asked, {:ok, %Actor{:blocked => nil, :following_state => "accepted"}}} <-
+          {:asked, Actor.mark_pending_follow(actor_id, "rejected", force: true)} do
+      Logger.info("Now following: #{actor_id}")
+      {:ok, :following}
+    else
+      {:asked, {:error, :blocked}} ->
+        {:ok, :blocked_user}
+
+      {:asked, {:error, error}} ->
+        {:error, error}
+
+      {:asked, {:ok, %Actor{:blocked => nil, :following_state => following_state}}} ->
+        Logger.error(
+          "Weird following state after received Accept: #{following_state} from actor: #{actor_id} this should not happen."
+        )
+
+        {:error, :following_state}
+
+      {:actor, {:error, _error}} ->
+        {:ok, :unauthorized}
+
+      {:match, false} ->
+        {:ok, :unauthorized}
     end
+  end
+
+  def handle(%{}), do: {:error, :match}
 end

lib/vonbraun/activity_pub/handler/undo.ex

@@ -5,6 +5,6 @@ defmodule Vonbraun.ActivityPub.Handler.Undo do
 
   # Lots of different kinds of things can be undone.
   def handle(_activity = %{"type" => "Undo"}) do
-    :ok
+    {:ok, :unknown}
   end
 end