makes the census api try several variants before failing a verification

lib/census_api.rb

@@ -1,7 +1,54 @@
 class CensusApi
 
   def call(document_type, document_number)
-    Response.new(get_response_body(document_type, document_number))
+    response = nil
+    get_document_number_variants(document_type, document_number).each do |variant|
+      response = Response.new(get_response_body(document_type, variant))
+      return response if response.valid?
+    end
+    response
+  end
+
+  def get_document_number_variants(document_type, document_number)
+    # Delete all non-alphanumerics
+    document_number = document_number.to_s.gsub(/[^0-9A-Za-z]/i, '')
+    variants = []
+
+    if is_dni?(document_type)
+      # If a letter exists at the end, delete it and put it on the letter var
+      letter = document_number.last
+      if letter[/[A-Za-z]/] == letter
+        document_number = document_number[0..-2]
+      else
+        letter = nil
+      end
+
+      document_number = document_number.last(8) # Keep only the last 7 digits
+      document_number = document_number.gsub(/^0+/, '') # Removes leading zeros
+
+      # if the number has less than 7 digits, pad with zeros to the left and add each variant to the list
+      # For example, if the initial document_number is 1234, possible numbers should have
+      # [1234, 01234, 001234, 0001234]
+      possible_numbers = []
+      possible_numbers << document_number unless document_number.blank?
+      while document_number.size < 8
+        document_number = "0#{document_number}"
+        possible_numbers << document_number
+      end
+
+      variants += possible_numbers
+
+      # if a letter was given, try the numbers followed by the letter in upper and lowercase
+      if letter.present? then
+        possible_numbers.each do |number|
+          variants << number + letter.downcase << number + letter.upcase
+        end
+      end
+    else # not a DNI
+      variants << document_number
+    end
+
+    variants
   end
 
   class Response
@@ -60,4 +107,8 @@ class CensusApi
     def stubbed_response_body
       {:get_habita_datos_response=>{:get_habita_datos_return=>{:hay_errores=>false, :datos_habitante=>{:item=>{:fecha_nacimiento_string=>"31-12-1980", :identificador_documento=>"12345678Z", }}, :datos_vivienda=>{:item=>{:codigo_postal=>"28013"}}}}}
     end
+
+    def is_dni?(document_type)
+      document_type.to_s == "1"
+    end
 end