Add a GeneratePreviewHtml service

We will use this service in the next commit, splitting up the responsibility for generating the HTML from fetching content/metadata and generating the HTML.
alphagov · Jan 10, 2025 · 0e09a2f · 0e09a2f
1 parent 49eb6b0
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diff --git a/...engines/content_block_manager/app/services/content_block_manager/generate_preview_html.rb b/...engines/content_block_manager/app/services/content_block_manager/generate_preview_html.rb
@@ -0,0 +1,89 @@
+require "net/http"
+require "json"
+require "uri"
+
+module ContentBlockManager
+  class GeneratePreviewHtml
+    include ContentBlockManager::Engine.routes.url_helpers
+
+    def initialize(content_id:, content_block_edition:, base_path:)
+      @content_id = content_id
+      @content_block_edition = content_block_edition
+      @base_path = base_path
+    end
+
+    def call
+      uri = URI(frontend_path)
+      nokogiri_html = html_snapshot_from_frontend(uri)
+      update_local_link_paths(nokogiri_html)
+      add_draft_style(nokogiri_html)
+      replace_existing_content_blocks(nokogiri_html).to_s
+    end
+
+  private
+
+    BLOCK_STYLE = "background-color: yellow;".freeze
+    ERROR_HTML = "<html><body><p>Preview not found</p></body></html>".freeze
+
+    attr_reader :content_block_edition, :content_id, :base_path
+
+    def frontend_path
+      frontend_base_path + base_path
+    end
+
+    def frontend_base_path
+      Rails.env.development? ? Plek.external_url_for("government-frontend") : Plek.website_root
+    end
+
+    def html_snapshot_from_frontend(uri)
+      begin
+        raw_html = Net::HTTP.get(uri)
+      rescue StandardError
+        raw_html = ERROR_HTML
+      end
+      Nokogiri::HTML.parse(raw_html)
+    end
+
+    def update_local_link_paths(nokogiri_html)
+      url = content_block_manager_content_block_host_content_preview_path(id: content_block_edition.id, host_content_id: content_id)
+      nokogiri_html.css("a").each do |link|
+        next if link[:href].start_with?("//") || link[:href].start_with?("http")
+
+        link[:href] = "#{url}?base_path=#{link[:href]}"
+        link[:target] = "_parent"
+      end
+
+      nokogiri_html
+    end
+
+    def add_draft_style(nokogiri_html)
+      nokogiri_html.css("body").each do |body|
+        body["class"] ||= ""
+        body["class"] += " draft"
+      end
+      nokogiri_html
+    end
+
+    def replace_existing_content_blocks(nokogiri_html)
+      replace_blocks(nokogiri_html)
+      style_blocks(nokogiri_html)
+      nokogiri_html
+    end
+
+    def replace_blocks(nokogiri_html)
+      content_block_spans(nokogiri_html).each do |span|
+        span.replace content_block_edition.render
+      end
+    end
+
+    def style_blocks(nokogiri_html)
+      content_block_spans(nokogiri_html).each do |span|
+        span["style"] = BLOCK_STYLE
+      end
+    end
+
+    def content_block_spans(nokogiri_html)
+      nokogiri_html.css("span[data-content-id=\"#{@content_block_edition.document.content_id}\"]")
+    end
+  end
+end
diff --git a/lib/engines/content_block_manager/test/unit/app/services/generate_preview_html_test.rb b/lib/engines/content_block_manager/test/unit/app/services/generate_preview_html_test.rb
@@ -0,0 +1,92 @@
+require "test_helper"
+
+class ContentBlockManager::GeneratePreviewHtmlTest < ActiveSupport::TestCase
+  extend Minitest::Spec::DSL
+  include ContentBlockManager::Engine.routes.url_helpers
+  include TextAssertions
+
+  let(:host_content_id) { SecureRandom.uuid }
+  let(:preview_content_id) { SecureRandom.uuid }
+  let(:host_title) { "Test" }
+  let(:host_base_path) { "/test" }
+  let(:uri_mock) { mock }
+  let(:fake_frontend_response) do
+    "<body class=\"govuk-body\"><p>test</p><span class=\"content-embed content-embed__content_block_email_address\" data-content-block=\"\" data-document-type=\"content_block_email_address\" data-content-id=\"#{preview_content_id}\">[email protected]</span></body>"
+  end
+  let(:block_render) do
+    "<span class=\"content-embed content-embed__content_block_email_address\" data-content-block=\"\" data-document-type=\"content_block_email_address\" data-content-id=\"#{preview_content_id}\">[email protected]</span>"
+  end
+  let(:block_render_with_style) do
+    "<span class=\"content-embed content-embed__content_block_email_address\" data-content-block=\"\" data-document-type=\"content_block_email_address\" data-content-id=\"#{preview_content_id}\" style=\"background-color: yellow;\">[email protected]</span>"
+  end
+  let(:expected_html) do
+    "<body class=\"govuk-body draft\"><p>test</p>#{block_render_with_style}</body>"
+  end
+  let(:error_html) do
+    "<html><body class=\" draft\"><p>Preview not found</p></body></html>"
+  end
+  let(:document) do
+    build(:content_block_document, :email_address, content_id: preview_content_id)
+  end
+  let(:block_to_preview) do
+    build(:content_block_edition, :email_address, document:, details: { "email_address" => "[email protected]" }, id: 1)
+  end
+
+  it "returns the preview html" do
+    Net::HTTP.expects(:get).with(URI(Plek.website_root + host_base_path)).returns(fake_frontend_response)
+
+    expected_content = Nokogiri::HTML.parse(expected_html).to_s
+
+    actual_content = ContentBlockManager::GeneratePreviewHtml.new(
+      content_id: host_content_id,
+      content_block_edition: block_to_preview,
+      base_path: host_base_path,
+    ).call
+
+    assert_equal expected_content, actual_content
+  end
+
+  it "shows an error template when the request to the frontend throws an error" do
+    exception = StandardError.new("Something went wrong")
+    Net::HTTP.expects(:get).with(URI(Plek.website_root + host_base_path)).raises(exception)
+
+    expected_content = Nokogiri::HTML.parse(error_html).to_s
+
+    actual_content = ContentBlockManager::GeneratePreviewHtml.new(
+      content_id: host_content_id,
+      content_block_edition: block_to_preview,
+      base_path: host_base_path,
+    ).call
+
+    assert_equal expected_content, actual_content
+  end
+
+  it "updates any link paths" do
+    fake_frontend_response = "
+        <a href='/foo'>Internal link</a>
+        <a href='https://example.com'>External link</a>
+        <a href='//example.com'>Protocol relative link</a>
+      "
+    Net::HTTP.expects(:get).with(URI(Plek.website_root + host_base_path)).returns(fake_frontend_response)
+
+    actual_content = ContentBlockManager::GeneratePreviewHtml.new(
+      content_id: host_content_id,
+      content_block_edition: block_to_preview,
+      base_path: host_base_path,
+    ).call
+
+    url = content_block_manager_content_block_host_content_preview_path(id: block_to_preview.id, host_content_id:)
+
+    expected_content = Nokogiri::HTML.parse("
+        <html>
+          <body class=' draft'>
+            <a href='#{url}?base_path=/foo' target='_parent'>Internal link</a>
+            <a href='https://example.com'>External link</a>
+            <a href='//example.com'>Protocol relative link</a>
+          </body>
+        </html>
+      ").to_s
+
+    assert_equal_ignoring_whitespace actual_content.to_s, expected_content
+  end
+end