Support predefined locations

The service that looks up the locations changes sometimes. Therefore it
is useful to have some "predefined" locations, which we can change in
one place; the format is "$NAME". Since the metadata is yaml, this
exclude the nice "#NAME" or even ":NAME".

Rules

@@ -36,6 +36,7 @@ preprocess do
 
   add_report_metadata
   add_project_metadata
+  convert_locations
 end
 
 #

lib/helpers/preprocess.rb

@@ -12,6 +12,14 @@ module PreprocessHelper
     }
   end
 
+  def predefined_locations
+    {
+      '$kelder' => 'Zeus WPI, Gent',
+      '$s9' => 'S9, Gent',
+      '$therminal' => 'De Therminal, Gent'
+    }
+  end
+
   def allowed_privacy_status
     %w(additional general processor development)
   end
@@ -87,6 +95,16 @@ module PreprocessHelper
     end
   end
 
+  def convert_locations
+    @items.find_all('/events/*/*.md').each do |event|
+      location_link = event[:locationlink]&.downcase&.strip
+      if location_link&.start_with?('$') && !predefined_locations.key?(location_link)
+        raise "unknown location variable #{location_link}, must be one of #{predefined_locations.keys}"
+      end
+      event[:locationlink] = predefined_locations.fetch(location_link, event[:locationlink])
+    end
+  end
+
   def add_report_metadata
     @items.find_all('/about/verslagen/*/*').each do |report|
       report[:academic_year] = report.identifier.to_s.split('/')[-2]