Add region data and update list_cities method

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features
 
+* [#23](https://github.com/sarslanoglu/turkish_cities/pull/23): Add region data to cities.yaml and update ```list_cities``` method to support regions
 * [#21](https://github.com/sarslanoglu/turkish_cities/pull/21): Add city finding with phone code and vice versa. ```find_name_by_phone_code``` and ```find_phone_code_by_name``` methods are added
 
 ### Bug fixes

lib/turkish_cities/city.rb

@@ -33,24 +33,20 @@ def find_by_phone_code(phone_code)
 
   def find_by_name(city_name, return_type)
     CITY_LIST.each do |city|
-      if convert_chars(city['name'].downcase(:turkic)) == convert_chars(city_name.downcase(:turkic))
+      if convert_chars(city['name']) == convert_chars(city_name)
         return return_type == 'plate_number' ? city['plate_number'] : city['phone_code']
       end
     end
     "Couldn't find city name with '#{city_name}'"
   end
 
   def list_cities(options)
-    if options[:metropolitan_municipality]
-      city_list = CITY_LIST.map do |city|
-        city unless city['metropolitan_municipality_since'].nil?
-      end
-      city_list
-    else
-      city_list = CITY_LIST
-    end
+    city_list = CITY_LIST
 
-    final_city_list = prepare_city_list(city_list.compact)
+    city_list = filter_metropolitan_municipalities(city_list) if options[:metropolitan_municipality]
+    city_list = filter_regions(city_list, options[:region]) if options[:region]
+
+    final_city_list = prepare_city_list(city_list)
     options[:alphabetically_sorted] ? sort_cities(final_city_list) : final_city_list
   end
 
@@ -69,7 +65,16 @@ def check_phone_code(input)
   end
 
   def convert_chars(string)
-    I18n.transliterate(string)
+    I18n.transliterate(string.downcase(:turkic))
+  end
+
+  def filter_metropolitan_municipalities(city_list)
+    city_list.map { |city| city unless city['metropolitan_municipality_since'].nil? }.compact
+  end
+
+  def filter_regions(city_list, region)
+    region = convert_chars(region.to_s)
+    city_list.map { |city| city if convert_chars(city['region']) == region }.compact
   end
 
   def prepare_city_list(city_list)