feat: Send follow requests

lib/activity_pub.ex

@@ -1,2 +1,15 @@
 defmodule ActivityPub do
+  def fetch_actor(actor_id) do
+      request =
+        Req.new(url: actor_id)
+        |> Req.Request.put_header("accept", "application/json")
+
+      case Req.get(request) do
+        {:ok, result} ->
+          {:ok, result.body}
+
+        error ->
+          error
+      end
+  end
 end

lib/activity_pub/headers.ex

@@ -85,13 +85,9 @@ defmodule ActivityPub.Headers do
   end
 
   def fetch_actor_key(key_id) do
-    request =
-      Req.new(url: key_id)
-      |> Req.Request.put_header("accept", "application/json")
-
-    case Req.get(request) do
-      {:ok, result} ->
-        key_map = result.body["publicKey"]
+    case ActivityPub.fetch_actor(key_id) do
+      {:ok, body} ->
+        key_map = body["publicKey"]
 
         if key_map["id"] == key_id do
           [public_key | _] =

lib/postland/activities.ex

@@ -1,8 +1,11 @@
 defmodule Postland.Activities do
   use Phoenix.VerifiedRoutes, endpoint: PostlandWeb.Endpoint, router: PostlandWeb.Router
 
+  require Logger
+
   alias Postland.Activity
   alias Postland.Repo
+  alias Postland.Follows
 
   def process_activity(params) do
     case record_activity(params) do
@@ -20,6 +23,20 @@ defmodule Postland.Activities do
     |> Repo.insert()
   end
 
+  def cause_effects(%Activity{actor_id: actor_id, type: "Accept", data: %{"object" => %{"type" => "Follow"}}} = activity) do
+    case Follows.get(Postland.my_actor_id(), actor_id) do
+      nil ->
+        Logger.warning("Got accept for a follow we don't have in the db: #{actor_id}")
+
+        {:ok, activity}
+
+      request ->
+        Follows.confirm_request(request)
+    end
+
+      {:ok, activity}
+  end
+
   def cause_effects(%Activity{actor_id: actor_id, type: "Follow", data: %{"object" => object}} = activity) do
     if object == Postland.my_actor_id() do
       case Postland.Follows.record_inbound_request(actor_id) do

lib/postland/follow.ex

@@ -3,6 +3,7 @@ defmodule Postland.Follow do
 
   import Ecto.Changeset
 
+  @primary_key false
   schema "follows" do
     field :follower, :string, primary_key: true
     field :followee, :string, primary_key: true

lib/postland/follows.ex

@@ -1,8 +1,47 @@
 defmodule Postland.Follows do
+  use Phoenix.VerifiedRoutes, endpoint: PostlandWeb.Endpoint, router: PostlandWeb.Router
+
   import Ecto.Query, warn: false
 
+  alias Postland.Accounts
   alias Postland.Follow
   alias Postland.Repo
+  alias ActivityPub.Headers
+
+  alias Ecto.Multi
+
+  def record_and_send_follow_request(to_actor_id) do
+    Multi.new()
+    |> Multi.run(:follow_record, fn _data, _repo -> record_outbound_request(to_actor_id) end)
+    |> Multi.run(:send_request, fn _data, _repo ->
+      send_follow_request(to_actor_id)
+    end)
+    |> Repo.transaction()
+  end
+
+  def send_follow_request(to_actor_id) do
+    encoded_followee = Base.url_encode64(to_actor_id)
+    encoded_follower = Base.url_encode64(Postland.my_actor_id())
+
+    actor = ActivityPub.fetch_actor(to_actor_id)
+    inbox = Map.get(actor, "inbox")
+    follow_request = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "id" => url(~p"/follows/#{encoded_followee}/#{encoded_follower}"),
+        "type" => "Follow",
+        "actor" => Postland.my_actor_id(),
+        "object" => to_actor_id
+    }
+    |> Jason.encode!()
+
+    headers = Headers.signing_headers("POST", inbox, follow_request, Postland.my_actor_id(), Accounts.solo_user().private_key)
+
+    Req.post(inbox, headers: headers, body: follow_request)
+  end
+
+  def get(follower, followee) do
+    from(f in Follow, where: f.followee == ^followee, where: f.follower == ^follower) |> Repo.one()
+  end
 
   def pending_inbound_requests() do
     my_actor_id = Postland.my_actor_id()