feat: add the translations menu on lessons pages

user/plugins/m3-p2/m3-p2.php

@@ -355,6 +355,7 @@ class M3P2Plugin extends Plugin
             return;
         }
 
+        $current_lesson_lang = $target_pages[0]->language();
         $current_lesson_name = "";
         $other_lessons = [];  // of slug => ['name' => …, 'slug' => …]
         foreach ($target_pages as $target_page) {
@@ -378,15 +379,53 @@ class M3P2Plugin extends Plugin
             }
         }
 
-        //dd($other_lessons);
+        $translated_lessons = [];  // lang => slug
+        $translated_lessons_contenders = [];  // lang => [ slug => likelihood ]
+
+        foreach ($target_pages as $target_page) {
+
+            $translated_target_pages = $this->getTranslationsOfPage($target_page);
+            foreach ($translated_target_pages as $translated_target_page) {
+                /** @var Page $translated_target_page */
+                $lang = $translated_target_page->language();
+                if ($lang == $current_lesson_lang) { continue; }
+
+                $page_config = $translated_target_page->header();
+                if ( ! isset($page_config->lessons) || empty($page_config->lessons)) {
+                    return false;
+                }
+
+                foreach ($page_config->lessons as $lesson) {
+                    if ( ! isset($lesson['slug'])) { continue; }
+
+                    if ( ! isset($translated_lessons_contenders[$lang])) {
+                        $translated_lessons_contenders[$lang] = [];
+                    }
+
+                    if ( ! isset($translated_lessons_contenders[$lang][$lesson['slug']])) {
+                        $translated_lessons_contenders[$lang][$lesson['slug']] = 0;
+                    }
+
+                    $translated_lessons_contenders[$lang][$lesson['slug']] += 1;
+                }
+            }
+        }
+
+        foreach ($translated_lessons_contenders as $lang => $slug_to_likelihood) {
+            $best_likelihood = 0;
+            foreach ($slug_to_likelihood as $slug => $likelihood) {
+                if ($likelihood > $best_likelihood) {
+                    $best_likelihood = $likelihood;
+                    $translated_lessons[$lang] = $slug;
+                }
+            }
+        }
+
+//        dd($translated_lessons);
 
         $this->grav['twig']->twig()->addGlobal('target_pages', $target_pages);
         $this->grav['twig']->twig()->addGlobal('related_lessons', $other_lessons);
-        $this->grav['twig']->twig()->addGlobal('disable_multilingual', true);
-
-        // hotfix until we know how to fetch the appropriate translation
-        // disabled in template lesson-columns.html.twig
-        //$this->grav['twig']->twig()->addGlobal('disable_language_selector', true);
+        $this->grav['twig']->twig()->addGlobal('translated_lessons', $translated_lessons);
 
         $page = new Page();
         $page->init(new \SplFileInfo(__DIR__ . '/pages/lesson-columns.md'));

user/themes/textbook/templates/lesson-columns.html.twig

@@ -30,6 +30,11 @@
 {# Disable the language selector. #}
 {# We also do this procedurally in user/plugins/m3-p2/m3-p2.php #}
 {% block header_language_selection %}
+
+{% embed 'partials/language-selector.html.twig' %}
+    {% block polyglot_language_selector %}{% endblock %}
+{% endembed %}
+
 {% if related_lessons %}
 
 <div id="lesson-selector" class="dropdown-selector">

user/themes/textbook/templates/partials/language-selector.html.twig

@@ -14,9 +14,12 @@
 
     {% set show_language = true %}
 
-    {% if uri.paths and uri.paths(0) == "lesson" %}
+    {% if uri.paths and uri.paths(0) == "lessons" %}
         {% set base_lang_url = base_url_simple ~ grav.language.getLanguageURLPrefix(language) %}
-        {% set lang_url = base_lang_url ~ uri.path %}
+        {% set lang_url = base_lang_url ~ "/lessons/" ~ translated_lessons[language] %}
+        {% if language == language_selector.current %}
+            {% set show_language = false %}
+        {% endif %}
     {% else %}
         {% if language == language_selector.current %}
             {% set lang_url = page.url %}