From ef14cc7b64c1ce02c2955018759005854e2ffc2f Mon Sep 17 00:00:00 2001
From: Edem Topuzov <keltikan@gmail.com>
Date: Tue, 14 May 2024 04:47:22 +0300
Subject: [PATCH] Add conversion methods for country codes

---
 README.md                                   |  8 +++++
 lib/countries/country.rb                    |  1 +
 lib/countries/country/conversion_methods.rb | 17 +++++++++++
 lib/countries/iso3166.rb                    |  1 +
 spec/country_spec.rb                        | 34 +++++++++++++++++++++
 5 files changed, 61 insertions(+)
 create mode 100644 lib/countries/country/conversion_methods.rb

diff --git a/README.md b/README.md
index 4ca54005..6a8f56c0 100644
--- a/README.md
+++ b/README.md
@@ -264,6 +264,14 @@ ISO3166::Country.collect_likely_countries_by_subdivision_name("San José",:commo
  => ["Costa Rica", "Uruguay"]
 ```
 
+### Conversions
+
+```ruby
+ISO3166::Country.from_alpha3_to_alpha2('USA') # => "US"
+ISO3166::Country.from_alpha2_to_alpha3('US') # => "USA"
+
+ISO3166::Country.from_alpha2_to_alpha3('--') # => nil
+```
 
 ## Currencies
 
diff --git a/lib/countries/country.rb b/lib/countries/country.rb
index 9f0afa22..7ed411b1 100644
--- a/lib/countries/country.rb
+++ b/lib/countries/country.rb
@@ -3,6 +3,7 @@
 module ISO3166
   class Country
     extend CountryClassMethods
+    extend ConversionMethods
     extend CountryFinderMethods
     include Emoji
     include CountrySubdivisionMethods
diff --git a/lib/countries/country/conversion_methods.rb b/lib/countries/country/conversion_methods.rb
new file mode 100644
index 00000000..f29569d8
--- /dev/null
+++ b/lib/countries/country/conversion_methods.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ISO3166
+  module ConversionMethods
+    # @param alpha2 [String] ISO 3166 alpha-2 country code.
+    # @return [String] ISO 3166 alpha-3 country code.
+    def from_alpha2_to_alpha3(alpha2)
+      find_country_by_alpha2(alpha2)&.alpha3
+    end
+
+    # @param alpha3 [String] ISO 3166 alpha-3 country code.
+    # @return [String] ISO 3166 alpha-2 country code.
+    def from_alpha3_to_alpha2(alpha3)
+      find_country_by_alpha3(alpha3)&.alpha2
+    end
+  end
+end
diff --git a/lib/countries/iso3166.rb b/lib/countries/iso3166.rb
index 925501f3..8b538fee 100644
--- a/lib/countries/iso3166.rb
+++ b/lib/countries/iso3166.rb
@@ -11,6 +11,7 @@
 require 'countries/translations'
 require 'countries/country/country_subdivision_methods'
 require 'countries/country/class_methods'
+require 'countries/country/conversion_methods'
 require 'countries/country/finder_methods'
 require 'countries/country/emoji'
 require 'countries/country'
diff --git a/spec/country_spec.rb b/spec/country_spec.rb
index 2b81837a..7cb7c7ff 100644
--- a/spec/country_spec.rb
+++ b/spec/country_spec.rb
@@ -664,6 +664,40 @@
     end
   end
 
+  describe 'conversion methods' do
+    describe 'from_alpha2_to_alpha3' do
+      subject { ISO3166::Country.from_alpha2_to_alpha3(alpha2) }
+
+      context 'when country exists' do
+        let(:alpha2) { 'US' }
+
+        it { is_expected.to eq('USA') }
+      end
+
+      context 'when country does not exist' do
+        let(:alpha2) { '..' }
+
+        it { is_expected.to be_nil }
+      end
+    end
+
+    describe 'from_alpha3_to_alpha2' do
+      subject { ISO3166::Country.from_alpha3_to_alpha2(alpha3) }
+
+      context 'when country exists' do
+        let(:alpha3) { 'USA' }
+
+        it { is_expected.to eq('US') }
+      end
+
+      context 'when country does not exist' do
+        let(:alpha3) { '...' }
+
+        it { is_expected.to be_nil }
+      end
+    end
+  end
+
   describe 'hash finder methods' do
     context "when search name in 'iso_short_name'" do
       subject { ISO3166::Country.find_by_iso_short_name('Poland') }