Add show method to return local authority json

- This is much simpler, at this point we're just doing slug lookups and returning
  a 404 or the local authority hash (including the parent hash if there is one).

Author: KludgeKML

app/controllers/api/local_authority_controller.rb

@@ -17,6 +17,14 @@ def index
       render json: { errors: { "postcode": [e.message] } }, status:
     end
 
+    def show
+      @local_authority = LocalAuthority.from_slug(params[:authority_slug])
+
+      render json: { local_authority: @local_authority.to_h }
+    rescue GdsApi::HTTPNotFound
+      render json: {}, status: :not_found
+    end
+
   private
 
     def check_postcode_param

config/routes.rb

@@ -25,6 +25,7 @@
   scope "/api" do
     scope "/local-authority" do
       get "/" => "api/local_authority#index"
+      get "/:authority_slug" => "api/local_authority#show"
     end
   end
 

spec/requests/local_authority_api_spec.rb

@@ -72,4 +72,57 @@
       end
     end
   end
+
+  describe "local authority slugs" do
+    context "when the slug is not found"
+    before { stub_local_links_manager_does_not_have_an_authority("foo") }
+
+    it "returns a 404 if the slug is not found" do
+      get "/api/local-authority/foo"
+
+      expect(response).to have_http_status(:not_found)
+    end
+
+    context "when the slug points to a unitary authority" do
+      before { stub_local_links_manager_has_a_local_authority("westminster") }
+
+      it "returns the authority with no parent and tier set to unitary" do
+        get "/api/local-authority/westminster"
+
+        expect(response).to have_http_status(:ok)
+        expect(response.parsed_body).to eq({
+          "local_authority" => {
+            "name" => "Westminster",
+            "homepage_url" => "http://westminster.example.com",
+            "tier" => "unitary",
+            "slug" => "westminster",
+          },
+        })
+      end
+    end
+
+    context "when the slug points to a district authority" do
+      before { stub_local_links_manager_has_a_district_and_county_local_authority("aylesbury", "buckinghamshire") }
+
+      it "returns the authority with the parent and tier set to district" do
+        get "/api/local-authority/aylesbury"
+
+        expect(response).to have_http_status(:ok)
+        expect(response.parsed_body).to eq({
+          "local_authority" => {
+            "name" => "Aylesbury",
+            "homepage_url" => "http://aylesbury.example.com",
+            "tier" => "district",
+            "slug" => "aylesbury",
+            "parent" => {
+              "name" => "Buckinghamshire",
+              "homepage_url" => "http://buckinghamshire.example.com",
+              "tier" => "county",
+              "slug" => "buckinghamshire",
+            },
+          },
+        })
+      end
+    end
+  end
 end