Add post visibility and days_until_live helpers

blogex/lib/blogex/post.ex

@@ -44,6 +44,23 @@ defmodule Blogex.Post do
           published: boolean()
         }
 
+  @type visibility :: :draft | :scheduled | :live
+
+  @doc "Returns the visibility of a post: :draft, :scheduled, or :live."
+  def visibility(%__MODULE__{published: false}), do: :draft
+
+  def visibility(%__MODULE__{published: true, date: date}) do
+    if Date.after?(date, Date.utc_today()), do: :scheduled, else: :live
+  end
+
+  @doc "Returns days until a scheduled post goes live, or nil."
+  def days_until_live(%__MODULE__{} = post) do
+    case visibility(post) do
+      :scheduled -> Date.diff(post.date, Date.utc_today())
+      _ -> nil
+    end
+  end
+
   @doc """
   Build callback for NimblePublisher.