fill categories panel

site/collections/categories.php

@@ -0,0 +1,27 @@
+<?php
+
+return function ($site) {
+    $textsPage = $site->find('texts');
+    $years = $textsPage->children();
+    $texts = $years->children()->index();
+
+    $categories = array();
+
+    foreach ($textsPage->categories()->split() as $category) {
+        $categories[$category] = array(
+          'title' => $category,
+          'texts' => array()
+        );
+    }
+
+    foreach ($texts as $text) {
+        try {
+            $categories[$text->category()->value()]['texts'][] = $text;
+        } catch (\Throwable $th) {
+            throw new Exception(json_encode($th->getFile() . ' : ' . $th->getMessage()));
+        }
+    }
+
+    return $categories;
+
+};