From 7824edbec0bb61dd7a8b7d468553d8d75e42c66b Mon Sep 17 00:00:00 2001
From: Ro <ro@ro.social>
Date: Fri, 11 Oct 2024 02:44:55 +0000
Subject: [PATCH] feat: Accept follow requests

---
 README.md                                     | 17 +++++++-
 lib/activity_pub/headers.ex                   |  4 +-
 lib/postland/activities.ex                    |  1 -
 lib/postland/activity.ex                      |  4 +-
 lib/postland/follows.ex                       | 43 +++++++++++++++++++
 ...011023003_add_timestamps_to_activities.exs |  9 ++++
 6 files changed, 72 insertions(+), 6 deletions(-)
 create mode 100644 priv/repo/migrations/20241011023003_add_timestamps_to_activities.exs

diff --git a/README.md b/README.md
index aa6f0a0..b0fdf94 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,25 @@
 # Postland
 
+## Backend
+
 - [ ] Posting
 - [ ] Timeline
 - [ ] Deleting posts
 - [x] Following
 - [ ] Unfollowing
-- [ ] Being followed
+- [x] Being followed
+- [x] Accepting follows
+- [ ] Liking
+- [ ] Unliking
+
+## UX
+
+- [ ] Posting
+- [ ] Timeline
+- [ ] Deleting posts
+- [x] Following
+- [ ] Unfollowing
+- [x] Being followed
+- [ ] Accepting follows
 - [ ] Liking
 - [ ] Unliking
diff --git a/lib/activity_pub/headers.ex b/lib/activity_pub/headers.ex
index 5ab22d9..fd7ef0c 100644
--- a/lib/activity_pub/headers.ex
+++ b/lib/activity_pub/headers.ex
@@ -52,11 +52,9 @@ defmodule ActivityPub.Headers do
   end
 
   def verify(method, path, headers, actor_fetcher \\ &fetch_actor_key/1) do
-    dbg(headers)
-
     {_key, signature_header} = Enum.find(headers, fn {key, _} -> key == "signature" end)
 
-    signature_kv = SignatureSplitter.split(signature_header) |> dbg()
+    signature_kv = SignatureSplitter.split(signature_header)
     key_id = find_value(signature_kv, "keyId")
     signature = signature_kv |> find_value("signature") |> Base.decode64!()
     signing_text_headers = signature_kv |> find_value("headers") |> String.split(" ")
diff --git a/lib/postland/activities.ex b/lib/postland/activities.ex
index 2929a79..e97b4b3 100644
--- a/lib/postland/activities.ex
+++ b/lib/postland/activities.ex
@@ -28,7 +28,6 @@ defmodule Postland.Activities do
 
     actor_id = case Regex.run(pattern, follow_id) do
       [_, encoded_actor_id] ->
-        dbg(encoded_actor_id)
         Base.url_decode64!(encoded_actor_id, padding: false)
 
       _other ->
diff --git a/lib/postland/activity.ex b/lib/postland/activity.ex
index 2da246a..08fcbff 100644
--- a/lib/postland/activity.ex
+++ b/lib/postland/activity.ex
@@ -12,13 +12,15 @@ defmodule Postland.Activity do
 
   def changeset(attrs) do
     attrs = %{
+      "id" => Map.get(attrs, "id", Ecto.UUID.autogenerate()),
       "actor_id" => Map.get(attrs, "actor"),
       "type" => Map.get(attrs, "type"),
       "data" => attrs
     }
 
     %__MODULE__{}
-    |> cast(attrs, [:actor_id, :type, :data])
+    |> cast(attrs, [:id, :actor_id, :type, :data])
+    |> validate_required(:id)
     |> validate_required(:data)
     |> validate_required(:type)
   end
diff --git a/lib/postland/follows.ex b/lib/postland/follows.ex
index 8daa6d4..6903534 100644
--- a/lib/postland/follows.ex
+++ b/lib/postland/follows.ex
@@ -4,12 +4,55 @@ defmodule Postland.Follows do
   import Ecto.Query, warn: false
 
   alias Postland.Accounts
+  alias Postland.Activity
   alias Postland.Follow
   alias Postland.Repo
   alias ActivityPub.Headers
 
   alias Ecto.Multi
 
+  def record_and_send_acceptance(request) do
+    Multi.new()
+    |> Multi.run(:confirm_timestamp, fn _data, _repo -> confirm_request(request) end)
+    |> Multi.run(:send_acceptance, fn _data, _repo ->
+      send_acceptance(request)
+    end)
+    |> Repo.transaction()
+  end
+
+  def send_acceptance(request) do
+    {:ok, actor} = ActivityPub.fetch_actor(request.follower)
+    inbox = Map.get(actor, "inbox")
+
+    case get_follow_activity(request.follower) do
+      nil ->
+        {:error, "could not find Follow activity to Accept"}
+
+      follow_activity ->
+        body =
+          %{
+            "@context" => "https://www.w3.org/ns/activitystreams",
+            "type" => "Accept",
+            "actor" => Postland.my_actor_id(),
+            "object" => %{
+              "actor" => request.follower,
+              "id" => Map.get(follow_activity.data, "id"),
+              "object" => Postland.my_actor_id(),
+              "type" => "Follow"
+            }
+          }
+          |> Jason.encode!()
+
+        headers = Headers.signing_headers("POST", inbox, body, Postland.my_actor_id(), Accounts.solo_user().private_key)
+
+        Req.post(inbox, headers: headers, body: body)
+    end
+  end
+
+  def get_follow_activity(follower) do
+    from(a in Activity, where: a.type == "Follow", where: a.actor_id == ^follower, limit: 1, order_by: [desc: :inserted_at]) |> Repo.one()
+  end
+
   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)
diff --git a/priv/repo/migrations/20241011023003_add_timestamps_to_activities.exs b/priv/repo/migrations/20241011023003_add_timestamps_to_activities.exs
new file mode 100644
index 0000000..2b454d1
--- /dev/null
+++ b/priv/repo/migrations/20241011023003_add_timestamps_to_activities.exs
@@ -0,0 +1,9 @@
+defmodule Postland.Repo.Migrations.AddTimestampsToActivities do
+  use Ecto.Migration
+
+  def change do
+    alter table("activities") do
+      timestamps()
+    end
+  end
+end