Add SolidusTaxJar::API#tax_rate_for

When calculating tax rates, the recommended endpoint from TaxJar
support for live calculations is `/v2/taxes`, the same used for
calculating order taxes, as it accounts for all factors like
sourcing or nexus, while the `/v2/rates` endpoint will return
the full combined rate for the queried location.

2 files changed, 28 insertions, 0 deletions

diff --git a/lib/super_good/solidus_taxjar/api.rb b/lib/super_good/solidus_taxjar/api.rb
index 0d182ce..601a2ae 100644
--- a/lib/super_good/solidus_taxjar/api.rb
+++ b/lib/super_good/solidus_taxjar/api.rb
@@ -22,6 +22,10 @@ module SuperGood
         end
       end
 
+      def tax_rate_for(address)
+        taxjar_client.tax_for_order(APIParams.tax_rate_address_params(address)).rate
+      end
+
       def tax_rates_for(address)
         taxjar_client.rates_for_location(*APIParams.address_params(address))
       end
diff --git a/spec/super_good/solidus_taxjar/api_spec.rb b/spec/super_good/solidus_taxjar/api_spec.rb
index 0f890ca..8b0a5db 100644
--- a/spec/super_good/solidus_taxjar/api_spec.rb
+++ b/spec/super_good/solidus_taxjar/api_spec.rb
@@ -23,6 +23,30 @@ RSpec.describe SuperGood::SolidusTaxJar::API do
     it { is_expected.to eq({ some_kind_of: "response" }) }
   end
 
+  describe "tax_rate_for" do
+    subject { api.tax_rate_for address }
+
+    let(:api) { described_class.new(taxjar_client: dummy_client) }
+    let(:dummy_client) { instance_double ::Taxjar::Client }
+    let(:address) { Spree::Address.new }
+    let(:tax_rate) { 0.04 }
+    let(:response) { double(rate: tax_rate) }
+
+    before do
+      allow(SuperGood::SolidusTaxJar::APIParams)
+        .to receive(:tax_rate_address_params)
+        .with(address)
+        .and_return({ address: "params" })
+
+      allow(dummy_client)
+        .to receive(:tax_for_order)
+        .with({ address: "params" })
+        .and_return(response)
+    end
+
+    it { is_expected.to eq(tax_rate) }
+  end
+
   describe "#tax_rates_for" do
     subject { api.tax_rates_for address }