Add posts from archive to weekly posts

app/views/posts/show.rb

@@ -1,3 +1,5 @@
+require "time_math"
+
 module Adamantium
   module Views
     module Posts
@@ -7,6 +9,13 @@ module Adamantium
         expose :post do |slug:|
           Decorators::Posts::Decorator.new(post_repo.fetch!(slug))
         end
+
+        expose :past_posts do |post|
+          start_date = TimeMath.week.floor(post.published_at)
+          end_date = TimeMath.week.ceil(post.published_at)
+          posts = post_repo.from_the_archives(start_date: start_date, end_date: end_date)
+          posts.map { |p| Decorators::Posts::Decorator.new(p) }
+        end
       end
     end
   end