isAdmin())
			throw new NotAllowedException();
		$id_tag = isset($_GET['id']) ? (int) $_GET['id'] : 0;
		if (empty($id_tag) && !isset($_GET['add']))
			throw new UnexpectedValueException('Requested tag not found or not requesting a new tag.');
		// Adding an tag?
		if (isset($_GET['add']))
		{
			parent::__construct('Add a new tag');
			$form_title = 'Add a new tag';
			$this->page->addClass('edittag');
		}
		// Deleting one?
		elseif (isset($_GET['delete']))
		{
			// So far so good?
			$tag = Tag::fromId($id_tag);
			if (Session::validateSession('get') && $tag->kind !== 'Album' && $tag->delete())
			{
				header('Location: ' . BASEURL . '/managetags/');
				exit;
			}
			else
				trigger_error('Cannot delete tag: an error occured while processing the request.', E_USER_ERROR);
		}
		// Editing one, then, surely.
		else
		{
			$tag = Tag::fromId($id_tag);
			if ($tag->kind === 'Album')
				trigger_error('Cannot edit tag: is actually an album.', E_USER_ERROR);
			parent::__construct('Edit tag \'' . $tag->tag . '\'');
			$form_title = 'Edit tag \'' . $tag->tag . '\'';
			$this->page->addClass('edittag');
		}
		// Session checking!
		if (empty($_POST))
			Session::resetSessionToken();
		else
			Session::validateSession();
		if ($id_tag)
			$after_form = 'Delete tag';
		elseif (!$id_tag)
			$after_form = '';
		$form = new Form([
			'request_url' => BASEURL . '/edittag/?' . ($id_tag ? 'id=' . $id_tag : 'add'),
			'content_below' => $after_form,
			'fields' => [
				'id_asset_thumb' => [
					'type' => 'numeric',
					'label' => 'Thumbnail asset ID',
					'is_optional' => true,
				],
				'kind' => [
					'type' => 'select',
					'label' => 'Kind of tag',
					'options' => [
						'Location' => 'Location',
						'Person' => 'Person',
					],
				],
				'tag' => [
					'type' => 'text',
					'label' => 'Tag title',
					'size' => 50,
					'maxlength' => 255,
				],
				'slug' => [
					'type' => 'text',
					'label' => 'URL slug',
					'size' => 50,
					'maxlength' => 255,
				],
				'description' => [
					'type' => 'textbox',
					'label' => 'Description',
					'size' => 50,
					'maxlength' => 255,
					'is_optional' => true,
				],
			],
		]);
		// Create the form, add in default values.
		$form->setData($id_tag ? get_object_vars($tag) : $_POST);
		$formview = new FormView($form, $form_title ?? '');
		$this->page->adopt($formview);
		if (!empty($_POST))
		{
			$form->verify($_POST);
			// Anything missing?
			if (!empty($form->getMissing()))
				return $formview->adopt(new Alert('Some data missing', 'Please fill out the following fields: ' . implode(', ', $form->getMissing()), 'danger'));
			$data = $form->getData();
			$data['id_parent'] = 0;
			// Quick stripping.
			$data['slug'] = strtr($data['slug'], [' ' => '-', '--' => '-', '&' => 'and', '=>' => '', "'" => "", ":"=> "", '/' => '-', '\\' => '-']);
			// Creating a new tag?
			if (!$id_tag)
			{
				$return = Tag::createNew($data);
				if ($return === false)
					return $formview->adopt(new Alert('Cannot create this tag', 'Something went wrong while creating the tag...', 'danger'));
				if (isset($_POST['submit_and_new']))
				{
					header('Location: ' . BASEURL . '/edittag/?add');
					exit;
				}
			}
			// Just updating?
			else
			{
				foreach ($data as $key => $value)
					$tag->$key = $value;
				$tag->save();
			}
			// Redirect to the tag management page.
			header('Location: ' . BASEURL . '/managetags/');
			exit;
		}
	}
}