chore: Add functions for recursively fetching reply threads

lib/postland/replies.ex

@@ -0,0 +1,59 @@
+defmodule Postland.Replies do
+  def recurse_note(url, actor_id, private_key) when is_binary(url) do
+    {:ok, note} = ActivityPub.get(url, actor_id, private_key)
+    dbg(note)
+
+    reply_collection =
+      fetch_whole_collection(note["replies"], actor_id, private_key)
+
+    {note, reply_collection}
+  end
+
+  def recurse_note(map, _actor_id, _private_key) when is_map(map), do: map
+
+  def fetch_whole_collection(%{"first" => first}, actor_id, private_key) do
+    fetch_whole_collection(first, actor_id, private_key)
+  end
+
+  def fetch_whole_collection(map, actor_id, private_key) when is_map(map) do
+    next_url =
+      dbg(map)
+
+    items =
+      case Map.get(map, "items") do
+        [] ->
+          []
+
+        list when is_list(list) ->
+          Enum.map(list, &recurse_note(&1, actor_id, private_key))
+      end
+
+    next =
+      case Map.get(map, "next") do
+        nil ->
+          []
+
+        next_url ->
+          fetch_whole_collection(next_url, actor_id, private_key)
+      end
+
+    items ++ next
+  end
+
+  def fetch_whole_collection(url, actor_id, private_key) when is_binary(url) do
+    url
+    |> ActivityPub.get(actor_id, private_key)
+    |> case do
+      {:ok, collection_page} ->
+        fetch_whole_collection(collection_page, actor_id, private_key)
+
+      other ->
+        other
+    end
+  end
+
+  def _debug({note, replies}, level \\ 0) do
+    IO.puts("#{String.pad_leading("", level * 2)}#{Map.get(note, "content")}")
+    Enum.each(replies, &_debug(&1, level + 1))
+  end
+end