Add postcode validation functionality

lib/postcodes_io.rb

@@ -3,11 +3,13 @@
 require "postcodes_io/autocomplete"
 require "postcodes_io/postcode"
 require "postcodes_io/reverse_geocode"
+require "postcodes_io/validate"
 
 module Postcodes
   class IO
     include Lookup
     include Autocomplete
     include ReverseGeocode
+    include Validate
   end
 end

lib/postcodes_io/validate.rb

@@ -0,0 +1,28 @@
+require 'excon'
+require 'json'
+require 'postcodes_io/postcode'
+
+module Postcodes
+  module Validate
+    def validate(postcode)
+      validate_postcode(postcode)
+    end
+
+    private
+
+    def validate_postcode(postcode)
+      postcode = remove_whitespace postcode
+      response = Excon.get("https://api.postcodes.io/postcodes/#{postcode}/validate")
+
+      unless response.status == 404
+        parsed_response = JSON.parse(response.body)
+        return parsed_response['result'] == true
+      end
+      return nil
+    end
+
+    def remove_whitespace(string)
+      string.gsub(/\s+/, '') # remove any whitespace. m1 1ab => m11ab
+    end
+  end
+end

spec/fixtures/validation_invalid_response.json

@@ -0,0 +1,4 @@
+{
+    "status": 200,
+    "result": false
+}

spec/fixtures/validation_valid_response.json

@@ -0,0 +1,4 @@
+{
+    "status": 200,
+    "result": true
+}

spec/validate_spec.rb

@@ -0,0 +1,42 @@
+require 'spec_helper'
+
+describe Postcodes::IO do
+  let(:base_url) {'https://api.postcodes.io'}
+  let(:stub_valid_response) { File.read('spec/fixtures/validation_valid_response.json') }
+  let(:stub_invalid_response) { File.read('spec/fixtures/validation_invalid_response.json') }
+
+  describe '#validate' do
+    before :each do
+      stub_request(:get, "#{base_url}/postcodes/CM129TR/validate")
+          .to_return(status: 200, body: stub_valid_response)
+
+      stub_request(:get, "#{base_url}/postcodes/TR49BW/validate")
+          .to_return(status: 200, body: stub_valid_response)
+
+      stub_request(:get, "#{base_url}/postcodes/helloooooo/validate")
+          .to_return(status: 200, body: stub_invalid_response)
+    end
+
+    def validate(postcode)
+      subject.validate(postcode)
+    end
+
+    it 'removes whitespace from postcodes' do
+      validate('CM12     9TR')
+      WebMock.should have_requested(:get, "#{base_url}/postcodes/CM129TR/validate")
+    end
+
+    it 'validates a postcode' do
+      validate('CM129TR')
+      WebMock.should have_requested(:get, "#{base_url}/postcodes/CM129TR/validate")
+    end
+
+    it 'returns true for valid postcodes' do
+      expect(validate('TR49BW')).to be_truthy
+    end
+
+    it 'returns false for valid postcodes' do
+      expect(validate('helloooooo')).to be_falsy
+    end
+  end
+end