I DECLARE BANKRUPTCY

app/mailers/hackathons/digest_mailer.rb

@@ -7,6 +7,16 @@ def digest
       .includes(:subscription, hackathon: {logo_attachment: :blob})
       .group_by(&:subscription)
 
+    @new_listings_by_subscription = @digest.listings
+      .includes(:subscription, hackathon: {logo_attachment: :blob})
+      .select { |listing| listing.previously_listed_for_recipient? }
+      .group_by(&:subscription)
+
+    @previous_listings_by_subscription = @digest.listings
+      .includes(:subscription, hackathon: {logo_attachment: :blob})
+      .reject { |listing| listing.previously_listed_for_recipient? }
+      .group_by(&:subscription)
+
     set_unsubscribe_urls_for @recipient
     mail to: @recipient.email_address, subject: "Hackathons near you"
   end

app/models/hackathon/digest/listing.rb

@@ -2,4 +2,8 @@ class Hackathon::Digest::Listing < ApplicationRecord
   belongs_to :digest, class_name: "Hackathon::Digest"
   belongs_to :hackathon
   belongs_to :subscription
+
+  def previously_listed_for_recipient?(recipient: digest.recipient)
+    self.class.where(hackathon:, recipient:) > 1
+  end
 end

app/models/hackathon/digest/listings.rb

@@ -7,24 +7,32 @@ module Hackathon::Digest::Listings
     has_many :listed_subscriptions, through: :listings, source: :subscription
 
     before_validation :build_candidate_listings, on: :create, if: -> { listings.empty? }
+
     validates_length_of :listings, minimum: 1, on: :create, message: "must not be empty"
+    validate :minimum_one_unseen_listing, on: :create, if: -> { errors.none? }
   end
 
   private
 
   LISTING_CRITERIA = [Criterion::Location]
   MAX_LISTINGS = 8
 
+  def build_candidate_listings
+    applicable_listings.each do |result|
+      listings.build hackathon: result[:hackathon], subscription: result[:subscription]
+    end
+  end
+
   def applicable_listings(listing_criteria: LISTING_CRITERIA, max_listings: MAX_LISTINGS)
     listing_criteria
       .flat_map { |criterion| criterion.new(recipient:).candidate_listings }
       .sort_by { |candidate| candidate[:hackathon].starts_at }
       .first(max_listings)
   end
 
-  def build_candidate_listings
-    applicable_listings.each do |result|
-      listings.build hackathon: result[:hackathon], subscription: result[:subscription]
+  def minimum_one_unseen_listing
+    if listed_hackathons.all? ->(hackathon) { Hackathon::Digest::Listing.exists?(recipient:, hackathon:) }
+      errors.add :listings, "must include at least one unseen hackathon"
     end
   end
 end

app/views/hackathons/digest_mailer/digest.html.erb

@@ -1,13 +1,29 @@
 <p>
   Check out
-  <% if (count = @digest.listings.count) > 1 %>
-    these <%= count %> hackathons
+  <% if (count = @digest.listings.count { |listing| listing.previously_listed_for_recipient? }) > 1 %>
+    these <%= count %> new hackathons
   <% else %>
-    this hackathon
+    this newly listed hackathon
   <% end %>
   coming up near you.
 </p>
 
-<% @listings_by_subscription.each do |subscription, listings| %>
+<% @new_listings_by_subscription.each do |subscription, listings| %>
   <%= render "subscription", subscription:, listings: %>
 <% end %>
+
+<% if @previous_listings_by_subscription.any? %>
+  <p>
+    Here
+    <% if (count = @digest.listings.count - @digest.listings.count { |listing| listing.previously_listed_for_recipient? }) > 1 %>
+      are <%= count %> more hackathons
+    <% else %>
+      is one more hackathon
+    <% end %>
+    coming up near you.
+  </p>
+
+  <% @previous_listings_by_subscription.each do |subscription, listings| %>
+    <%= render "subscription", subscription:, listings: %>
+  <% end %>
+<% end %>

app/views/hackathons/digest_mailer/digest.text.erb

@@ -1,7 +1,25 @@
 Check out
-<%= (count = @digest.listings.count) > 1 ? "these #{count} hackathons" : "this hackathon" %>
+<% if (count = @digest.listings.count { |listing| listing.previously_listed_for_recipient? }) > 1 %>
+  these <%= count %> newly listed hackathons
+<% else %>
+  this newly listed hackathon
+<% end %>
 coming up near you.
 
 <% @listings_by_subscription.each do |subscription, listings| %>
-  <%= render "subscription", subscription:, listings: %>
+  <%= render "subscription", subscription:, listings: listings.select { |listing| listing.previously_listed_for_recipient? }) %>
 <% end %>
+
+<% if listings.reject { |listing| listing.previously_listed_for_recipient? }.count > 0 %>
+  Here
+  <% if (count = @digest.listings.count - @digest.listings.count { |listing| listing.previously_listed_for_recipient? }) > 1 %>
+    are <%= count %> more hackathons
+  <% else %>
+    is one more hackathon
+  <% end %>
+  coming up near you.
+
+  <% @listings_by_subscription.each do |subscription, listings| %>
+    <%= render "subscription", subscription:, listings: listings.reject { |listing| listing.previously_listed_for_recipient? }) %>
+  <% end %>
+<% end %>