Add admin pages routes

This is meant to be used from the admin pages preview frame
and always returns elements from the draft version.

app/controllers/alchemy/json_api/admin/pages_controller.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+module Alchemy
+  module JsonApi
+    module Admin
+      class PagesController < JsonApi::PagesController
+        authorize_resource
+
+        def show
+          render jsonapi: Page.new(@page, page_version: :draft_version)
+        end
+
+        private
+
+        def load_page
+          @page = page_scope.find(params[:id])
+        end
+
+        def base_page_scope
+          ::Alchemy::Page.all
+        end
+      end
+    end
+  end
+end

config/routes.rb

@@ -4,4 +4,8 @@
   get "pages/*path" => "pages#show", as: :page
   resources :layout_pages, only: [:index]
   get "layout_pages/*path" => "layout_pages#show", as: :layout_page
+
+  namespace :admin do
+    resources :pages, only: [:show]
+  end
 end

spec/requests/alchemy/json_api/admin/pages_spec.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+require "rails_helper"
+require "alchemy/devise/test_support/factories"
+
+RSpec.describe "Alchemy::JsonApi::Admin::PagesController", type: :request do
+  let(:page) do
+    FactoryBot.create(:alchemy_page)
+  end
+
+  describe "GET /alchemy/json_api/admin/pages/:id" do
+    subject { get alchemy_json_api.admin_page_path(page) }
+
+    context "as anonymous user" do
+      it "returns 404" do
+        get alchemy_json_api.page_path(page.urlname)
+        expect(response).to have_http_status(404)
+      end
+    end
+
+    context "as author user" do
+      before do
+        allow_any_instance_of(ApplicationController).to receive(:current_user) do
+          FactoryBot.create(:alchemy_author_user)
+        end
+      end
+
+      let(:document) { JSON.parse(response.body) }
+
+      it "gets a valid JSON:API document" do
+        subject
+        expect(response).to have_http_status(200)
+        expect(document["data"]).to have_id(page.id.to_s)
+        expect(document["data"]).to have_type("page")
+      end
+
+      it "loads elements from draft version" do
+        element = FactoryBot.create(:alchemy_element, page_version: page.draft_version)
+        subject
+        document = JSON.parse(response.body)
+        expect(document["data"]["relationships"]["elements"]).to eq(
+          {
+            "data" => [{
+              "id" => element.id.to_s,
+              "type" => "element",
+            }],
+          }
+        )
+      end
+    end
+  end
+end