Add Vaccine#delivery_method_to_vaccine_method

This moves the method out of the `DraftVaccinationRecord` model so it
can be used in multiple places.

Author: thomasleese

app/models/draft_vaccination_record.rb

@@ -204,8 +204,9 @@ def delivery_method=(value)
     super
     return if delivery_method_was.nil? # Don't clear batch on first set
 
-    previous_value = delivery_method_to_vaccine_method(delivery_method_was)
-    new_value = delivery_method_to_vaccine_method(value)
+    previous_value =
+      Vaccine.delivery_method_to_vaccine_method(delivery_method_was)
+    new_value = Vaccine.delivery_method_to_vaccine_method(value)
 
     self.batch_id = nil unless previous_value == new_value
   end
@@ -245,23 +246,13 @@ def vaccine_method_matches_consent_and_triage?
     return true if delivery_method.blank? || !administered?
 
     approved_methods = patient.approved_vaccine_methods(programme:)
-    vaccine_method = delivery_method_to_vaccine_method(delivery_method)
+    vaccine_method = Vaccine.delivery_method_to_vaccine_method(delivery_method)
 
     approved_methods.include?(vaccine_method)
   end
 
   private
 
-  def delivery_method_to_vaccine_method(delivery_method)
-    return nil if delivery_method.nil?
-
-    if delivery_method.in?(Vaccine::INJECTION_DELIVERY_METHODS)
-      "injection"
-    else
-      "nasal"
-    end
-  end
-
   def readable_attribute_names
     writable_attribute_names - %w[vaccine_id]
   end

app/models/vaccine.rb

@@ -91,6 +91,17 @@ def available_delivery_methods
     AVAILABLE_DELIVERY_METHODS.fetch(method)
   end
 
+  def self.delivery_method_to_vaccine_method(delivery_method)
+    return nil if delivery_method.nil?
+
+    suitable_delivery_methods =
+      AVAILABLE_DELIVERY_METHODS.select do |_key, value|
+        delivery_method.in?(value)
+      end
+
+    suitable_delivery_methods.keys.first
+  end
+
   private
 
   def fhir_mapper = @fhir_mapper ||= FHIRMapper::Vaccine.new(self)