Add UPRN Client

app/services/uprn_client.rb

@@ -0,0 +1,50 @@
+require "net/http"
+
+class UprnClient
+  attr_reader :uprn
+  attr_accessor :error
+
+  ADDRESS = "api.os.uk".freeze
+  PATH = "/search/places/v1/uprn".freeze
+
+  def initialize(uprn)
+    @uprn = uprn
+  end
+
+  def call
+    unless response.is_a?(Net::HTTPSuccess) && result.present?
+      @error = "UPRN is not recognised. Check the number, or enter the address"
+    end
+  rescue JSON::ParserError
+    @error = "UPRN is not recognised. Check the number, or enter the address"
+  end
+
+  def result
+    @result ||= JSON.parse(response.body).dig("results", 0, "DPA")
+  end
+
+private
+
+  def http_client
+    client = Net::HTTP.new(ADDRESS, 443)
+    client.use_ssl = true
+    client.verify_mode = OpenSSL::SSL::VERIFY_PEER
+    client.max_retries = 3
+    client.read_timeout = 10 # seconds
+    client
+  end
+
+  def endpoint_uri
+    uri = URI(PATH)
+    params = {
+      uprn:,
+      key: ENV["OS_DATA_KEY"],
+    }
+    uri.query = URI.encode_www_form(params)
+    uri.to_s
+  end
+
+  def response
+    @response ||= http_client.request_get(endpoint_uri)
+  end
+end

spec/services/uprn_client_spec.rb

@@ -0,0 +1,68 @@
+require "rails_helper"
+
+describe UprnClient do
+  let(:client) { described_class.new("123") }
+
+  let(:valid_response) do
+    { results: [{ DPA: { postcode: "12345" } }] }.to_json
+  end
+
+  def stub_api_request(body:, status: 200)
+    stub_request(:get, "https://api.os.uk/search/places/v1/uprn?key=OS_DATA_KEY&uprn=123")
+    .to_return(status:, body:, headers: {})
+  end
+
+  describe "call" do
+    context "when json parse error" do
+      before do
+        stub_api_request(body: "{", status: 200)
+
+        client.call
+      end
+
+      it "returns error" do
+        expect(client.error).to eq("UPRN is not recognised. Check the number, or enter the address")
+      end
+    end
+
+    context "when http error" do
+      before do
+        stub_api_request(body: valid_response, status: 500)
+
+        client.call
+      end
+
+      it "returns error" do
+        expect(client.error).to eq("UPRN is not recognised. Check the number, or enter the address")
+      end
+    end
+
+    context "when results empty" do
+      before do
+        stub_api_request(body: {}.to_json)
+
+        client.call
+      end
+
+      it "returns error" do
+        expect(client.error).to eq("UPRN is not recognised. Check the number, or enter the address")
+      end
+    end
+
+    context "with results" do
+      before do
+        stub_api_request(body: valid_response)
+
+        client.call
+      end
+
+      it "returns result" do
+        expect(client.result).to eq({ "postcode" => "12345" })
+      end
+
+      it "returns no error" do
+        expect(client.error).to be_nil
+      end
+    end
+  end
+end