Filtering on dates for existing diffs to show

app/controllers/diffs_controller.rb

@@ -4,13 +4,15 @@ class DiffsController < ApplicationController
 		return redirect_to action: :show, id: last.created_at.to_date if last
 	end
 
+	DATE_DELTA = 3
+
 	def show
-		@dates = Diff.select(:created_at).distinct
-		@all_dates = []
-		@dates.each do |d|
-			@all_dates.push(d.created_at.to_date)
-		end
 		@date = Date.parse params[:id]
+		dates = Diff.dates
+		current = dates.index @date
+		min = [0, current - DATE_DELTA].max
+		max = current + DATE_DELTA
+		@dates = dates[min..max]
 		@diffs = Diff.where created_at: @date..@date+1
 	end
 end

app/models/diff.rb

@@ -1,3 +1,13 @@
 class Diff < ApplicationRecord
 	belongs_to :site
+
+	def self.dates
+		sql = <<-SQL
+			SELECT DISTINCT date_trunc('day', created_at) AS date
+			FROM #{self.table_name}
+			ORDER BY date ASC
+		SQL
+		ActiveRecord::Base.connection.execute(sql)
+			.collect { |r| Date.parse r['date'] }
+	end
 end

app/views/diffs/show.html.erb

@@ -1,15 +1,8 @@
 <div class="autogrid txtcenter">
-	<% (-3..3).each do |n|
-		date = @date + n %>
-		<% if @all_dates.include?(date) %>
-			<%= content_tag :div, class: (:current if @date == date) do %>
-				<%= link_to l(date), diff_path(date) %>
-			<% end %>
-		<% else %>
-			<%= content_tag :div, class: (:nodata) do %>
-				<%= link_to l(date), diff_path(date) %>
-			<%end %>
-		<% end %>
+	<% @dates.each do |date| %>
+		<%= content_tag :div, class: (:current if @date == date) do
+			link_to l(date), diff_path(date)
+		end %>
 	<% end %>
 </div>