Map country names to ISO codes

Apple doesn't guarantee that the ISO code will be present and
recommended to match country names against common spellings instead.
This will use the country code if it's provided, but otherwise attempt
to map the country name to the corresponding ISO code.

app/assets/javascripts/spree/frontend/solidus_paypal_braintree.js

@@ -161,6 +161,7 @@ window.SolidusPaypalBraintree = {
 
   buildAddress: function(shippingContact) {
     var addressHash = {
+      country_name:   shippingContact.country,
       country_code:   shippingContact.countryCode,
       first_name:     shippingContact.givenName,
       last_name:      shippingContact.familyName,

app/models/solidus_paypal_braintree/transaction_address.rb

@@ -4,6 +4,7 @@ module SolidusPaypalBraintree
   class TransactionAddress
     include ActiveModel::Model
     include ActiveModel::Validations::Callbacks
+    include SolidusPaypalBraintree::CountryMapper
 
     attr_accessor :country_code, :last_name, :first_name,
       :city, :zip, :state_code, :address_line_1, :address_line_2
@@ -18,6 +19,15 @@ class TransactionAddress
     validates :spree_country, presence: true
     validates :spree_state, presence: true, if: :should_match_state_model?
 
+    def initialize(attributes = {})
+      country_name = attributes.delete(:country_name) || ""
+      if attributes[:country_code].blank?
+        attributes[:country_code] = iso_from_name(country_name)
+      end
+
+      super(attributes)
+    end
+
     def spree_country
       country_code && (@country ||= Spree::Country.find_by(iso: country_code.upcase))
     end

lib/solidus_paypal_braintree.rb

@@ -1,5 +1,6 @@
 require 'solidus_core'
 require 'solidus_paypal_braintree/engine'
+require 'solidus_paypal_braintree/country_mapper'
 
 module SolidusPaypalBraintree
   def self.table_name_prefix

lib/solidus_paypal_braintree/country_mapper.rb

@@ -0,0 +1,35 @@
+module SolidusPaypalBraintree
+  module CountryMapper
+    extend ActiveSupport::Concern
+
+    USA_VARIANTS = [
+      "the united states of america",
+      "united states of america",
+      "the united states",
+      "united states",
+      "us of a",
+      "u.s.a.",
+      "usa",
+      "u.s.",
+      "us",
+    ]
+
+    CANADA_VARIANTS = [
+      "canada",
+      "ca",
+    ]
+
+    # Generates a hash mapping each variant of the country name to the same ISO
+    # ie: { "usa" => "US", "united states" => "US", "canada" => "CA", ... }
+    COUNTRY_MAP = {
+      USA_VARIANTS => "US",
+      CANADA_VARIANTS => "CA"
+    }.flat_map { |variants, iso| variants.map { |v| [v, iso] } }.to_h
+
+    included do
+      def iso_from_name country_name
+        COUNTRY_MAP[country_name.downcase.strip]
+      end
+    end
+  end
+end

spec/models/solidus_paypal_braintree/transaction_address_spec.rb

@@ -72,6 +72,37 @@
     end
   end
 
+  describe "#attributes=" do
+    subject { described_class.new(attrs) }
+
+    context "when an ISO code is provided" do
+      let(:attrs) { { country_code: "US" } }
+
+      it "uses the ISO code provided" do
+        expect(subject.country_code).to eq "US"
+      end
+    end
+
+    context "when the ISO code is blank" do
+      context "and a valid country name is provided" do
+        let!(:canada) { create :country, name: "Canada", iso: "CA" }
+        let(:attrs) { { country_name: "Canada" } }
+
+        it "looks up the ISO code by the country name" do
+          expect(subject.country_code).to eq "CA"
+        end
+      end
+
+      context "and no valid country name is provided" do
+        let(:attrs) { { country_name: "Neverland" } }
+
+        it "leaves the country code blank" do
+          expect(subject.country_code).to be_nil
+        end
+      end
+    end
+  end
+
   describe '#spree_country' do
     subject { described_class.new(country_code: country_code).spree_country }