Add category system to categorize posts (readme)

This commit implements a new category system to categorize posts. Each
category can have an unlimited number of nested children categories. A
single post don't necessarily need to be in a category, but it can.

Each category can have a full content body like posts or pages, so you
have enough space to describe the content of your categories.

Please note that you need to have at least the following MySQL/MariaDB
versions to use the category system, because it uses "WITH RECURSIVE"
database queries, the so-called "Common-Table-Expressions (CTE)".

MariaDB: 10.2.2
MySQL: 8.0

See: https://mariadb.com/kb/en/with/
See: https://dev.mysql.com/doc/refman/8.0/en/with.html

3 files changed, 220 insertions, 0 deletions

diff --git a/core/include/category/list.php b/core/include/category/list.php
new file mode 100644
index 0000000..9bd2a68
--- /dev/null
+++ b/core/include/category/list.php
@@ -0,0 +1,69 @@
+<?php
+#===============================================================================
+# Get instances
+#===============================================================================
+$Language = Application::getLanguage();
+
+#===============================================================================
+# Get repositories
+#===============================================================================
+$CategoryRepository = Application::getRepository('Category');
+$PostRepository = Application::getRepository('Post');
+
+#===============================================================================
+# Pagination
+#===============================================================================
+$site_size = Application::get('CATEGORY.LIST_SIZE');
+$site_sort = Application::get('CATEGORY.LIST_SORT');
+
+#$count = $CategoryRepository->getCount(['parent' => NULL]);
+$count = $CategoryRepository->getCount();
+$lastSite = ceil($count / $site_size);
+
+$currentSite = HTTP::GET('site') ?? 1;
+$currentSite = intval($currentSite);
+
+if($currentSite < 1 OR ($currentSite > $lastSite AND $lastSite > 0)) {
+	Application::error404();
+}
+
+#===============================================================================
+# Single redirect
+#===============================================================================
+if(Application::get('CATEGORY.SINGLE_REDIRECT') === TRUE AND $count === 1) {
+	$Category = $CategoryRepository->getLast();
+	HTTP::redirect(Application::getEntityURL($Category));
+}
+
+#===============================================================================
+# Get paginated category list
+#===============================================================================
+$categories = $CategoryRepository->getPaginatedTree(
+	$site_size,
+	($currentSite-1) * $site_size
+);
+
+foreach($categories as $Category) {
+	$templates[] = generateCategoryItemTemplate($Category, TRUE);
+}
+
+#===============================================================================
+# Build document
+#===============================================================================
+$ListTemplate = Template\Factory::build('category/list');
+$ListTemplate->set('PAGINATION', [
+	'THIS' => $currentSite,
+	'LAST' => $lastSite,
+	'HTML' => generateCategoryNaviTemplate($currentSite)
+]);
+$ListTemplate->set('LIST', [
+	'CATEGORIES' => $templates ?? []
+]);
+
+$MainTemplate = Template\Factory::build('main');
+$MainTemplate->set('HTML', $ListTemplate);
+$MainTemplate->set('HEAD', [
+	'NAME' => $Language->text('title_category_overview', $currentSite)
+]);
+
+echo $MainTemplate;
diff --git a/core/include/category/main.php b/core/include/category/main.php
new file mode 100644
index 0000000..57f8625
--- /dev/null
+++ b/core/include/category/main.php
@@ -0,0 +1,134 @@
+<?php
+#===============================================================================
+# Get repositories
+#===============================================================================
+$CategoryRepository = Application::getRepository('Category');
+$PostRepository = Application::getRepository('Post');
+$UserRepository = Application::getRepository('User');
+
+#===============================================================================
+# Try to find category (with parents) by slug URL or unique ID
+#===============================================================================
+if(Application::get('CATEGORY.SLUG_URLS')) {
+	if(!$categories = $CategoryRepository->findWithParentsBy('slug', $param)) {
+		if($categories = $CategoryRepository->findWithParents($param)) {
+			$redirect_scheduled = TRUE;
+		}
+	}
+}
+
+else {
+	if(!$categories = $CategoryRepository->findWithParents($param)) {
+		if($categories = $CategoryRepository->findWithParentsBy('slug', $param)) {
+			$redirect_scheduled = TRUE;
+		}
+	}
+}
+
+#===============================================================================
+# Throw 404 error if category (with parents) could not be found
+#===============================================================================
+if(!isset($categories)) {
+	Application::error404();
+}
+
+#===============================================================================
+# The last element represents the current category
+#===============================================================================
+$Category = $categories[array_key_last($categories)];
+
+#===============================================================================
+# If category with parents was found by alternative, redirect to correct URL
+#===============================================================================
+if(isset($redirect_scheduled)) {
+	HTTP::redirect(Application::getEntityURL($Category));
+}
+
+#===============================================================================
+# Generate category template data (including parents)
+#===============================================================================
+foreach($categories as $_Category) {
+	$category_list[] = generateItemTemplateData($_Category);
+}
+
+#===============================================================================
+# Define data variable for current category
+#===============================================================================
+$category_data = $category_list[array_key_last($category_list)];
+
+#===============================================================================
+# Generate category children list
+#===============================================================================
+$child_categories = $CategoryRepository->getAll(
+	['parent' => $Category->getID()],
+	Application::get('CATEGORY.LIST_SORT')
+);
+
+foreach($child_categories as $ChildCategory) {
+	$child_templates[] = generateCategoryItemTemplate($ChildCategory);
+}
+
+#===============================================================================
+# Pagination (for posts in this category)
+#===============================================================================
+$site_size = Application::get('POST.LIST_SIZE');
+$site_sort = Application::get('POST.LIST_SORT');
+
+$count = $PostRepository->getCountByCategory($Category);
+$lastSite = ceil($count / $site_size);
+
+$currentSite = HTTP::GET('site') ?? 1;
+$currentSite = intval($currentSite);
+
+if($currentSite < 1 OR ($currentSite > $lastSite AND $lastSite > 0)) {
+	Application::error404();
+}
+
+#===============================================================================
+# Get paginated post list for this category
+#===============================================================================
+$posts = $PostRepository->getAll(
+	['category' => $Category->getID()],
+	$site_sort,
+	($currentSite-1) * $site_size.','.$site_size
+);
+
+foreach($posts as $Post) {
+	$User = $UserRepository->find($Post->get('user'));
+	$post_templates[] = generatePostItemTemplate($Post, $User);
+}
+
+#===============================================================================
+# Build document
+#===============================================================================
+$CategoryTemplate = Template\Factory::build('category/main');
+$CategoryTemplate->set('CATEGORY', $category_data);
+$CategoryTemplate->set('CATEGORIES', $category_list ?? []);
+$CategoryTemplate->set('COUNT', [
+	'POST' => $PostRepository->getCountByCategory($Category),
+	'CHILDREN' => $CategoryRepository->getChildrenCount($Category)
+]);
+$CategoryTemplate->set('PAGINATION', [
+	'THIS' => $currentSite,
+	'LAST' => $lastSite,
+	'HTML' => generatePostNaviTemplate($currentSite)
+]);
+$CategoryTemplate->set('LIST', [
+	'POSTS' => $post_templates ?? [],
+	'CATEGORIES' => $child_templates ?? []
+]);
+
+$MainTemplate = Template\Factory::build('main');
+$MainTemplate->set('TYPE', 'CATEGORY');
+$MainTemplate->set('CATEGORY', $category_data);
+$MainTemplate->set('CATEGORIES', $category_list ?? []);
+$MainTemplate->set('HTML', $CategoryTemplate);
+$MainTemplate->set('HEAD', [
+	'NAME' => $category_data['ATTR']['NAME'],
+	'DESC' => description($category_data['BODY']['HTML'](),
+		Application::get('CATEGORY.DESCRIPTION_SIZE')),
+	'PERM' => $category_data['URL'],
+	'OG_IMAGES' => $category_data['FILE']['LIST']
+]);
+
+echo $MainTemplate;
diff --git a/core/include/post/main.php b/core/include/post/main.php
index 86008f6..bfccc7b 100644
--- a/core/include/post/main.php
+++ b/core/include/post/main.php
@@ -2,6 +2,7 @@
 #===============================================================================
 # Get repositories
 #===============================================================================
+$CategoryRepository = Application::getRepository('Category');
 $PostRepository = Application::getRepository('Post');
 $UserRepository = Application::getRepository('User');
 
@@ -50,11 +51,27 @@ if($NextPost = $PostRepository->findNext($Post)) {
 }
 
 #===============================================================================
+# Generate category template data (including parents)
+#===============================================================================
+foreach($CategoryRepository->findWithParents($Post->get('category')) as $Category) {
+	$category_list[] = generateItemTemplateData($Category);
+}
+
+#===============================================================================
+# Define data variable for current category
+#===============================================================================
+if(isset($category_list)) {
+	$category_data = $category_list[array_key_last($category_list)];
+}
+
+#===============================================================================
 # Build document
 #===============================================================================
 $PostTemplate = Template\Factory::build('post/main');
 $PostTemplate->set('POST', $post_data);
 $PostTemplate->set('USER', $user_data);
+$PostTemplate->set('CATEGORY', $category_data ?? []);
+$PostTemplate->set('CATEGORIES', $category_list ?? []);
 
 $MainTemplate = Template\Factory::build('main');
 $MainTemplate->set('TYPE', 'POST');