Add mentions to status reply textarea

lib/clacks_web/templates/frontend/status.html.eex

@@ -4,7 +4,7 @@
 
 <%= form_tag Routes.frontend_path(@conn, :post_status), method: :post, class: "compose-status" do %>
   <input type="hidden" name="in_reply_to" value="<%= @status.data["object"]["id"] %>">
-  <textarea id="content" name="content" rows="5" placeholder="Reply" required></textarea>
+  <textarea id="content" name="content" rows="5" placeholder="Reply" required><%= mentions_for_replying_to(@conn, @status) %></textarea>
   <%= submit "Post" %>
   <hr>
 <% end %>

lib/clacks_web/views/frontend_view.ex

@@ -1,6 +1,6 @@
 defmodule ClacksWeb.FrontendView do
   use ClacksWeb, :view
-  alias Clacks.{Actor, Activity}
+  alias Clacks.{Actor, Activity, Repo}
   alias ClacksWeb.Router.Helpers, as: Routes
   alias ClacksWeb.Endpoint
 
@@ -88,4 +88,36 @@ defmodule ClacksWeb.FrontendView do
 
   defp activity_id(%Activity{id: id}), do: id
   defp activity_id({%Activity{id: id}, _}), do: id
+
+  @spec mentions_for_replying_to(Activity.t()) :: String.t()
+  defp mentions_for_replying_to(conn, %Activity{
+         data: %{"object" => %{"actor" => actor, "tag" => tags}}
+       }) do
+    current_user = conn.assigns[:user] |> Repo.preload(:actor)
+
+    tag_actors =
+      tags
+      |> Enum.filter(fn
+        %{"type" => "Mention"} -> true
+        _ -> false
+      end)
+      |> Enum.map(fn %{"href" => ap_id} -> ap_id end)
+
+    actors =
+      [actor | tag_actors]
+      |> List.delete(current_user.actor.ap_id)
+      |> Enum.uniq()
+
+    mentions =
+      actors
+      |> Enum.map(fn ap_id ->
+        actor = Actor.get_cached_by_ap_id(ap_id)
+        "@#{actor.nickname}"
+      end)
+      |> Enum.join(" ")
+
+    "#{mentions} "
+  end
+
+  defp mentions_for_replying_to(_), do: ""
 end