display concurrent events on event#show

app/helpers/application_helper.rb

@@ -575,4 +575,21 @@ module ApplicationHelper
   def quantity_left_of(resource)
     "#{resource.quantity - resource.used}/#{resource.quantity}"
   end
+
+  def concurrent_events(event)
+    return nil unless event.scheduled? && event.program.selected_event_schedules
+    event_schedule = event.program.selected_event_schedules.find_by(event: event)
+    other_event_schedules = event.program.selected_event_schedules.reject { |other_event_schedule| other_event_schedule == event_schedule }
+    concurrent_events = []
+
+    event_time_range = (event_schedule.start_time.strftime '%Y-%m-%d %H:%M')...(event_schedule.end_time.strftime '%Y-%m-%d %H:%M')
+    other_event_schedules.each do |other_event_schedule|
+      next unless other_event_schedule.event.confirmed?
+      other_event_time_range = (other_event_schedule.start_time.strftime '%Y-%m-%d %H:%M')...(other_event_schedule.end_time.strftime '%Y-%m-%d %H:%M')
+      if (event_time_range.to_a & other_event_time_range.to_a).present?
+        concurrent_events << other_event_schedule.event
+      end
+    end
+    concurrent_events
+  end
 end

app/views/proposals/show.html.haml

@@ -97,3 +97,20 @@
               %dt Requires Registration:
               %dd
                 = link_to "Yes (#{registered_text(@event)})", new_conference_conference_registration_path(@conference.short_title), class: 'btn btn-xs btn-danger', disabled: !@event.registration_possible?
+          - if concurrent_events(@event).present?
+            .col-md-12
+              %hr
+              %h4 Happening at the same time:
+              %ol
+                - concurrent_events(@event).each do |event|
+                  %li
+                    = link_to conference_program_proposal_path(@conference.short_title, event.id) do
+                      = event.title
+                  %dl
+                    %dt Start Time:
+                    %dd
+                      = event.program.selected_event_schedules.find_by(event: event).start_time.strftime("%Y %B %e %H:%M")
+                    %br
+                      %dt Room:
+                      %dd
+                        = event.room.name