Add an API-first Provider model

This integrates with the Provider API in an API-first way – e.g. by
calling out to the API rather than relying on an overnight "ETL" sync
job to cache Provider records in a local Active Record model.

However, I'm putting this work on hold for now because it's become
increasingly clear that an overnight ETL would grant us more flexibility
in how we interact with Provider data. It currently seems to be the more
pragmatic approach, so I'm putting this API-first implementation on ice
for now.

app/lib/teacher_training_courses/api_client.rb

@@ -0,0 +1,40 @@
+require "net/http"
+
+module TeacherTrainingCourses
+  class ApiClient
+    BASE_URL =
+      "https://api.publish-teacher-training-courses.service.gov.uk/api/public/v1".freeze
+
+    class << self
+      def get(endpoint)
+        request(method: :get, endpoint:)
+      end
+
+      def get_all_pages(endpoint)
+        results = []
+        is_last_page = false
+
+        until is_last_page
+          response = request(method: :get, endpoint:)
+          results.concat response.fetch("data")
+
+          if (next_page = response.dig("links", "next"))
+            endpoint = next_page.delete_prefix(BASE_URL)
+          else
+            is_last_page = true
+          end
+        end
+
+        results
+      end
+
+      private
+
+      def request(method:, endpoint:)
+        url = URI("#{BASE_URL}#{endpoint}")
+        response = Net::HTTP.public_send(method, url)
+        JSON.parse(response)
+      end
+    end
+  end
+end

app/lib/teacher_training_courses/provider.rb

@@ -0,0 +1,51 @@
+module TeacherTrainingCourses
+  class Provider
+    ATTRIBUTES = %i[code name email website ukprn accredited_body].freeze
+
+    attr_reader(*ATTRIBUTES)
+
+    def initialize(_code, attributes)
+      ATTRIBUTES.each do |attribute|
+        attribute = attribute.to_s
+        instance_variable_set("@#{attribute}", attributes[attribute])
+      end
+    end
+
+    class << self
+      def all
+        providers_from_api.map { |code, attributes| new(code, attributes) }
+      end
+
+      def find(code)
+        if (attributes = providers_from_api[code])
+          new(code, attributes)
+        else
+          raise ProviderNotFound, code
+        end
+      end
+
+      private
+
+      def providers_from_api
+        @providers_from_api ||= Rails.cache.fetch("providers_from_api", expires_in: 1.hour) do
+          # Fetch all providers from the Teacher Training Courses API
+          providers = ApiClient.get_all_pages("/recruitment_cycles/2024/providers")
+
+          # Drop attributes we don't need
+          providers = providers.map do |provider|
+            provider["attributes"].select { |key, _value| ATTRIBUTES.include?(key.to_sym) }
+          end
+
+          # Transform to a Hash indexed by provider code
+          providers.index_by { |provider| provider["code"] }
+        end
+      end
+    end
+
+    class ProviderNotFound < StandardError
+      def initialize(code)
+        super("Couldn't find provider with code '#{code}'")
+      end
+    end
+  end
+end

spec/lib/teacher_training_courses/api_client_spec.rb

@@ -0,0 +1,11 @@
+require "rails_helper"
+
+RSpec.describe TeacherTrainingCourses::ApiClient do
+  describe ".get" do
+    it "makes a GET request to the API" do
+      stub_providers
+      debugger
+      expect(described_class.get("/recruitment_cycles/2024/providers")).to eq("Hello")
+    end
+  end
+end

spec/lib/teacher_training_courses/provider_spec.rb

@@ -0,0 +1,24 @@
+require "rails_helper"
+
+RSpec.describe TeacherTrainingCourses::Provider do
+  describe ".all" do
+    it "makes a GET request to the API" do
+      stub_providers
+      expect(described_class.all).to eq []
+    end
+  end
+
+  describe ".find" do
+    it "gets a specific provider by its code" do
+      stub_providers([
+        build(:teacher_training_courses_provider, code: "T92", name: "Example provider")
+      ])
+
+      provider = described_class.find("T92")
+
+      expect(provider).to be_a TeacherTrainingCourses::Provider
+      expect(provider.code).to eq "T92"
+      expect(provider.name).to eq "Example provider"
+    end
+  end
+end