Add after_response callback (#22)

CHANGELOG.md

@@ -1,6 +1,7 @@
 ### next
 
 * Moved the development dependencies from the gemspec to the Gemfile (#19)
+* Introduce `after_response` callback (#22)
 
 ### 1.1.0
 

README.md

@@ -60,6 +60,11 @@ Billomat.configure do |config|
   # https://www.billomat.com/en/api/basics/rate-limiting/
   config.app_id = '12345'
   config.app_secret = 'c3df...'
+
+  config.after_response = lambda do |response|
+    # API response callback, e.g. for inspecting the rate limit
+    # header via response.headers[:x_rate_limit_remaining]
+  end
 end
 ```
 

lib/billomat/configuration.rb

@@ -4,5 +4,17 @@ module Billomat
   # The +billomat+ gem configuration.
   class Configuration
     attr_accessor :api_key, :subdomain, :timeout, :app_id, :app_secret
+    attr_reader :after_response
+
+    # Sets a callback to be called for each API response
+    #
+    # @param [Proc] callback The callback
+    def after_response=(callback)
+      unless callback.respond_to?(:call)
+        raise ArgumentError, "callback must respond to `call'"
+      end
+
+      @after_response = callback
+    end
   end
 end

lib/billomat/gateway.rb

@@ -68,7 +68,7 @@ def response
         timeout: timeout,
         headers: headers,
         payload: body.to_json
-      )
+      ).tap { |response| Billomat.configuration.after_response&.call(response) }
     end
 
     # @return [String] the complete URL for the request

spec/billomat/configuration_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Billomat::Configuration do
+  let(:configuration) { described_class.new }
+
+  describe '.after_response=' do
+    it 'sets after_response' do
+      callback = proc {}
+      configuration.after_response = callback
+      expect(configuration.after_response).to eq(callback)
+    end
+
+    it 'raises an error when assigned a non proc' do
+      expect { configuration.after_response = :foo }.to raise_error(ArgumentError)
+    end
+  end
+end

spec/billomat/gateway_spec.rb

@@ -32,6 +32,8 @@
   end
 
   describe '#run' do
+    let(:callback) { instance_double(Proc) }
+
     context 'when API Call is successful' do
       let(:execute_args) do
         {
@@ -52,6 +54,13 @@
 
         gateway.new(:get, '/clients', foo: 'bar').run
       end
+
+      it 'invokes after_response callback with response' do
+        expect(callback).to receive(:call).with(good_response)
+
+        Billomat.configuration.after_response = callback
+        gateway.new(:get, '/clients', foo: 'bar').run
+      end
     end
 
     context 'when API Call is not successful' do