Add hreflang alternate links for locales

app/helpers/better_together/application_helper.rb

@@ -160,6 +160,17 @@ def open_graph_meta_tags # rubocop:todo Metrics/AbcSize, Metrics/MethodLength, M
     # rubocop:enable Metrics/MethodLength
     # rubocop:enable Metrics/PerceivedComplexity
 
+    # Generates `<link rel="alternate" hreflang="..." href="...">` tags for
+    # each locale supported by the application. These tags help search engines
+    # understand language-specific versions of a page.
+    def hreflang_links
+      tags = I18n.available_locales.map do |locale|
+        tag.link(rel: 'alternate', hreflang: locale, href: url_for(locale:, only_path: false))
+      end
+
+      safe_join(tags, "\n")
+    end
+
     # Retrieves the setup wizard for hosts or raises an error if not found.
     # This is crucial for initial setup processes and should be pre-configured.
     def host_setup_wizard

app/views/layouts/better_together/application.html.erb

@@ -17,6 +17,8 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <%= csrf_meta_tags %>
     <%= csp_meta_tag %>
+    <%= tag.link rel: 'canonical', href: url_for(only_path: false) %>
+    <%= content_for?(:hreflang_links) ? yield(:hreflang_links) : hreflang_links %>
 
     <!-- Default Stylesheets -->
     <link rel="stylesheet" type="text/css" href="https://unpkg.com/[email protected]/dist/trix.css">

app/views/layouts/better_together/turbo_native.html.erb

@@ -15,8 +15,10 @@
     <%= robots_meta_tag %>
     <meta name="color-scheme" content="light dark">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <%= csrf_meta_tags %>
-    <%= csp_meta_tag %>
+   <%= csrf_meta_tags %>
+   <%= csp_meta_tag %>
+    <%= tag.link rel: 'canonical', href: url_for(only_path: false) %>
+    <%= content_for?(:hreflang_links) ? yield(:hreflang_links) : hreflang_links %>
 
     <!-- Default Stylesheets -->
     <link rel="stylesheet" type="text/css" href="https://unpkg.com/[email protected]/dist/trix.css">

spec/helpers/better_together/application_helper_spec.rb

@@ -3,7 +3,22 @@
 require 'rails_helper'
 
 module BetterTogether
-  RSpec.describe ApplicationHelper do
+  RSpec.describe ApplicationHelper, type: :helper do
+
+    describe '#hreflang_links' do
+      it 'returns alternate link tags for all locales' do
+        allow(I18n).to receive(:available_locales).and_return(%i[en fr])
+        allow(helper).to receive(:url_for) do |options|
+          "http://example.com/#{options[:locale]}"
+        end
+
+        html = helper.hreflang_links
+
+        expect(html).to include('rel="alternate" hreflang="en" href="http://example.com/en"')
+        expect(html).to include('rel="alternate" hreflang="fr" href="http://example.com/fr"')
+      end
+    end
+
     describe '#robots_meta_tag' do
       it 'renders default robots meta tag' do # rubocop:todo RSpec/MultipleExpectations
         tag = helper.robots_meta_tag

spec/views/layouts/better_together/application.html.erb_spec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'layouts/better_together/application', type: :view do
+  before do
+    view.extend BetterTogether::ApplicationHelper
+
+    allow(view).to receive(:host_platform).and_return(double(name: 'Platform', cache_key_with_version: '1', css_block: nil))
+    allow(view).to receive(:open_graph_meta_tags).and_return('')
+    allow(view).to receive(:seo_meta_tags).and_return('')
+    allow(view).to receive(:metrics_body_tag).and_yield
+    allow(view).to receive(:javascript_importmap_tags).and_return('')
+    allow(view).to receive(:stylesheet_link_tag).and_return('')
+    allow(view).to receive(:csrf_meta_tags).and_return('')
+    allow(view).to receive(:csp_meta_tag).and_return('')
+    allow(view).to receive(:javascript_i18n).and_return({ translations: {} })
+    allow(view).to receive(:render).and_call_original
+    allow(view).to receive(:render).with('layouts/better_together/custom_head_javascript').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/custom_stylesheets').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/header').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/flash_messages').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/extra_page_content_bottom').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/footer').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/mobile_bar').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/custom_body_javascript').and_return('')
+    allow(view).to receive(:hreflang_links).and_return('<link rel="alternate" hreflang="en" href="/en" />')
+    allow(view).to receive(:url_for).with(only_path: false).and_return('http://test.host/current')
+  end
+
+  it 'renders canonical and hreflang links by default' do
+    render template: 'layouts/better_together/application'
+
+    expect(rendered).to match(%r{<link[^>]+rel="canonical"[^>]+href="http://test.host/current"[^>]*>})
+    expect(rendered).to include('<link rel="alternate" hreflang="en" href="/en" />')
+  end
+
+  it 'renders custom hreflang links when content_for provided' do
+    view.content_for :hreflang_links, '<link rel="alternate" hreflang="fr" href="/fr" />'
+
+    render template: 'layouts/better_together/application'
+
+    expect(rendered).to include('<link rel="alternate" hreflang="fr" href="/fr" />')
+    expect(rendered).not_to include('<link rel="alternate" hreflang="en" href="/en" />')
+  end
+end
+

spec/views/layouts/better_together/turbo_native.html.erb_spec.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'layouts/better_together/turbo_native', type: :view do
+  before do
+    view.extend BetterTogether::ApplicationHelper
+
+    allow(view).to receive(:host_platform).and_return(double(name: 'Platform', cache_key_with_version: '1', css_block: nil))
+    allow(view).to receive(:open_graph_meta_tags).and_return('')
+    allow(view).to receive(:seo_meta_tags).and_return('')
+    allow(view).to receive(:metrics_body_tag).and_yield
+    allow(view).to receive(:javascript_importmap_tags).and_return('')
+    allow(view).to receive(:stylesheet_link_tag).and_return('')
+    allow(view).to receive(:csrf_meta_tags).and_return('')
+    allow(view).to receive(:csp_meta_tag).and_return('')
+    allow(view).to receive(:javascript_i18n).and_return({ translations: {} })
+    allow(view).to receive(:render).and_call_original
+    allow(view).to receive(:render).with('layouts/better_together/custom_head_javascript').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/custom_stylesheets').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/header').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/flash_messages').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/extra_page_content_bottom').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/footer').and_return('')
+    allow(view).to receive(:render).with('layouts/better_together/custom_body_javascript').and_return('')
+    allow(view).to receive(:hreflang_links).and_return('<link rel="alternate" hreflang="en" href="/en" />')
+    allow(view).to receive(:url_for).with(only_path: false).and_return('http://test.host/current')
+  end
+
+  it 'renders canonical and hreflang links by default' do
+    render template: 'layouts/better_together/turbo_native'
+
+    expect(rendered).to match(%r{<link[^>]+rel="canonical"[^>]+href="http://test.host/current"[^>]*>})
+    expect(rendered).to include('<link rel="alternate" hreflang="en" href="/en" />')
+  end
+
+  it 'renders custom hreflang links when content_for provided' do
+    view.content_for :hreflang_links, '<link rel="alternate" hreflang="fr" href="/fr" />'
+
+    render template: 'layouts/better_together/turbo_native'
+
+    expect(rendered).to include('<link rel="alternate" hreflang="fr" href="/fr" />')
+    expect(rendered).not_to include('<link rel="alternate" hreflang="en" href="/en" />')
+  end
+end
+