Make iCalendar feed routes return calendar data

Both iCalendar routes were unusable:

* `/conferences/.../schedule.ics` raised
  `NoMethodError: undefined method 'icalendar_proposals'` because the
  `ConferenceHelper#icalendar_proposals` helper isn't auto-included in
  controllers; the action crashed before rendering.

* `/calendar.ics` silently redirected to `/`. The controller goes
  through `load_and_authorize_resource`, which authorises `:calendar`
  on `Conference` and is rejected for anonymous visitors because no
  ability grants it — CanCan's `AccessDenied` rescue redirects to
  root.

The helper is invoked through the controller `helpers` proxy so it
works in both contexts, and the calendar action is opted out of
resource loading and explicitly marked as not requiring authorization
since it serves a public feed across conferences. The helper is also
hardened so that proposals missing a room, difficulty level, track,
event type or scheduled time produce a valid event instead of
crashing the whole feed.

app/controllers/conferences_controller.rb

@@ -3,7 +3,8 @@
 class ConferencesController < ApplicationController
   protect_from_forgery with: :null_session
   before_action :respond_to_options
-  load_and_authorize_resource find_by: :short_title, except: :show
+  load_and_authorize_resource find_by: :short_title, except: %i[show calendar]
+  skip_authorization_check only: :calendar
 
   def index
     @current    = Conference.upcoming.reorder(start_date: :asc)
@@ -76,7 +77,7 @@ class ConferencesController < ApplicationController
             event_schedules = conf.program.selected_event_schedules(
               includes: [{ event: %i[event_type speakers submitter] }]
             )
-            calendar = icalendar_proposals(calendar, event_schedules.map(&:event), conf)
+            calendar = helpers.icalendar_proposals(calendar, event_schedules.map(&:event), conf)
           else
             calendar.event do |e|
               e.dtstart = conf.start_date

app/controllers/schedules_controller.rb

@@ -23,7 +23,7 @@ class SchedulesController < ApplicationController
       end
       format.ics do
         cal = Icalendar::Calendar.new
-        cal = icalendar_proposals(cal, event_schedules.map(&:event), @conference)
+        cal = helpers.icalendar_proposals(cal, event_schedules.map(&:event), @conference)
         cal.publish
         render inline: cal.to_ical
       end

app/helpers/conference_helper.rb

@@ -25,29 +25,45 @@ module ConferenceHelper
   # adds events to icalendar for proposals in a conference
   def icalendar_proposals(calendar, proposals, conference)
     proposals.each do |proposal|
-      calendar.event do |e|
-        e.dtstart = proposal.time
-        e.dtend = proposal.time + proposal.event_type.length * 60
-        e.duration = "PT#{proposal.event_type.length}M"
-        e.created = proposal.created_at
-        e.last_modified = proposal.updated_at
-        e.summary = proposal.title
-        e.description = proposal.abstract
-        e.uid = proposal.guid
-        e.url = conference_program_proposal_url(conference.short_title, proposal.id)
-        v = conference.venue
-        if v
-          e.geo = v.latitude, v.longitude if v.latitude && v.longitude
-          location = ''
-          location += "#{proposal.room.name} - " if proposal.room.name
-          location += " - #{v.street}, " if v.street
-          location += "#{v.postalcode} #{v.city}, " if v.postalcode && v.city
-          location += "#{v.country_name}, " if v.country_name
-          e.location = location
-        end
-        e.categories = conference.title, "Difficulty: #{proposal.difficulty_level.title}", "Track: #{proposal.track.name}"
-      end
+      calendar.event { |e| populate_icalendar_event(e, proposal, conference) }
     end
     calendar
   end
+
+  private
+
+  def populate_icalendar_event(event, proposal, conference)
+    length = proposal.event_type&.length
+    event.dtstart = proposal.time
+    event.dtend = proposal.time + (length * 60) if proposal.time && length
+    event.duration = "PT#{length}M" if length
+    event.created = proposal.created_at
+    event.last_modified = proposal.updated_at
+    event.summary = proposal.title
+    event.description = proposal.abstract
+    event.uid = proposal.guid
+    event.url = conference_program_proposal_url(conference.short_title, proposal.id)
+    venue = conference.venue
+    if venue
+      event.geo = venue.latitude, venue.longitude if venue.latitude && venue.longitude
+      event.location = icalendar_event_location(proposal, venue)
+    end
+    event.categories = icalendar_event_categories(proposal, conference)
+  end
+
+  def icalendar_event_location(proposal, venue)
+    location = ''
+    location += "#{proposal.room.name} - " if proposal.room&.name
+    location += " - #{venue.street}, " if venue.street
+    location += "#{venue.postalcode} #{venue.city}, " if venue.postalcode && venue.city
+    location += "#{venue.country_name}, " if venue.country_name
+    location
+  end
+
+  def icalendar_event_categories(proposal, conference)
+    categories = [conference.title]
+    categories << "Difficulty: #{proposal.difficulty_level.title}" if proposal.difficulty_level
+    categories << "Track: #{proposal.track.name}" if proposal.track
+    categories
+  end
 end

spec/controllers/conferences_controller_spec.rb

@@ -49,4 +49,25 @@ describe ConferencesController do
     end
   end
 
+  describe 'GET #calendar' do
+    it 'returns iCalendar data for all conferences' do
+      get :calendar, params: { format: :ics }
+
+      expect(response).to be_successful
+      expect(response.content_type).to start_with('text/calendar')
+      expect(response.body).to start_with('BEGIN:VCALENDAR')
+    end
+
+    it 'returns iCalendar data with full schedule when full=true' do
+      conference.program.update!(schedule_public: true)
+      create(:event_scheduled, program: conference.program)
+
+      get :calendar, params: { full: true, format: :ics }
+
+      expect(response).to be_successful
+      expect(response.content_type).to start_with('text/calendar')
+      expect(response.body).to start_with('BEGIN:VCALENDAR')
+    end
+  end
+
 end

spec/controllers/schedules_controller_spec.rb

@@ -6,13 +6,13 @@ describe SchedulesController do
   let(:conference) { create(:conference, splashpage: create(:splashpage, public: true), venue: create(:venue)) }
 
   describe 'GET #show' do
+    before :each do
+      conference.program.update!(schedule_public: true)
+      create_pair(:event_scheduled, program: conference.program)
+    end
+
     context 'XML' do
       before :each do
-        conference.program.schedule_public = true
-        conference.program.save!
-        create(:event_scheduled, program: conference.program)
-        create(:event_scheduled, program: conference.program)
-
         get :show, params: { conference_id: conference.short_title, format: :xml }
       end
 
@@ -26,5 +26,20 @@ describe SchedulesController do
         expect(response).to be_successful
       end
     end
+
+    context 'iCalendar' do
+      before :each do
+        get :show, params: { conference_id: conference.short_title, format: :ics }
+      end
+
+      it 'has 200 status code' do
+        expect(response).to be_successful
+      end
+
+      it 'returns iCalendar data' do
+        expect(response.content_type).to start_with('text/calendar')
+        expect(response.body).to start_with('BEGIN:VCALENDAR')
+      end
+    end
   end
 end