Add service to access FDC API

The current implementation of the FDC is not adhering to the DFC
standard. The difference is added in this compatibility layer.

This should be temporary code. The FDC dev team should change their API
in their next development cycle.

engines/dfc_provider/app/services/fdc_request.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require "private_address_check"
+require "private_address_check/tcpsocket_ext"
+
+# Request a JSON document from the FDC API with authentication.
+#
+# Currently, the API doesn't quite comply with the DFC standard and we need
+# to authenticate a little bit differently.
+#
+# And then we get slightly different data as well.
+class FdcRequest < DfcRequest
+  # Override main method to POST authorization data.
+  def call(url, data = {})
+    response = request(url, auth_data.merge(data).to_json)
+
+    if response.status >= 400 && token_stale?
+      refresh_access_token!
+      response = request(url, auth_data.merge(data).to_json)
+    end
+
+    response.body
+  end
+
+  private
+
+  def auth_data
+    {
+      userId: @user.oidc_account.uid,
+      accessToken: @user.oidc_account.token,
+    }
+  end
+end

engines/dfc_provider/spec/services/fdc_request_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative "../spec_helper"
+
+RSpec.describe FdcRequest do
+  subject(:api) { FdcRequest.new(user) }
+
+  let(:user) { build(:oidc_user) }
+  let(:account) { user.oidc_account }
+  let(:url) {
+    "https://food-data-collaboration-produc-fe870152f634.herokuapp.com/fdc/products?shop=test-hodmedod.myshopify.com"
+  }
+
+  it "refreshes the access token and retrieves a catalog", vcr: true do
+    # A refresh is only attempted if the token is stale.
+    account.uid = "testdfc@protonmail.com"
+    account.refresh_token = ENV.fetch("OPENID_REFRESH_TOKEN")
+    account.updated_at = 1.day.ago
+
+    response = nil
+    expect {
+      response = api.call(url)
+    }.to change {
+      account.token
+    }.and change {
+      account.refresh_token
+    }
+
+    json = JSON.parse(response)
+    expect(json["message"]).to eq "Products retrieved successfully"
+
+    graph = DfcIo.import(json["products"])
+    products = graph.select { |s| s.semanticType == "dfc-b:SuppliedProduct" }
+    expect(products).to be_present
+  end
+end

spec/support/vcr_setup.rb

@@ -40,4 +40,9 @@ VCR.configure do |config|
   config.filter_sensitive_data('<HIDDEN-OPENID-TOKEN>') { |interaction|
     interaction.response.body.match(/"refresh_token":"([^"]+)"/)&.public_send(:[], 1)
   }
+
+  # FDC specific parameter:
+  config.filter_sensitive_data('<HIDDEN-OPENID-TOKEN>') { |interaction|
+    interaction.request.body.match(/"accessToken":"([^"]+)"/)&.public_send(:[], 1)
+  }
 end