<?php

namespace SilverStripe\CMS\Model;

use Page;
use SilverStripe\Admin\AddToCampaignHandler_FormAction;
use SilverStripe\Admin\CMSPreviewable;
use SilverStripe\CMS\Controllers\CMSPageEditController;
use SilverStripe\CMS\Controllers\ContentController;
use SilverStripe\CMS\Controllers\ModelAsController;
use SilverStripe\CMS\Controllers\RootURLController;
use SilverStripe\CMS\Forms\SiteTreeURLSegmentField;
use SilverStripe\Control\Controller;
use SilverStripe\Control\Director;
use SilverStripe\Core\ClassInfo;
use SilverStripe\Core\Config\Config;
use SilverStripe\Core\Convert;
use SilverStripe\Dev\Deprecation;
use SilverStripe\Forms\CheckboxField;
use SilverStripe\Forms\CompositeField;
use SilverStripe\Forms\DropdownField;
use SilverStripe\Forms\FieldGroup;
use SilverStripe\Forms\FieldList;
use SilverStripe\Forms\FormAction;
use SilverStripe\Forms\FormField;
use SilverStripe\Forms\GridField\GridField;
use SilverStripe\Forms\GridField\GridFieldDataColumns;
use SilverStripe\Forms\HTMLEditor\HTMLEditorField;
use SilverStripe\Forms\ListboxField;
use SilverStripe\Forms\LiteralField;
use SilverStripe\Forms\OptionsetField;
use SilverStripe\Forms\Tab;
use SilverStripe\Forms\TabSet;
use SilverStripe\Forms\TextareaField;
use SilverStripe\Forms\TextField;
use SilverStripe\Forms\ToggleCompositeField;
use SilverStripe\Forms\TreeDropdownField;
use SilverStripe\i18n\i18n;
use SilverStripe\i18n\i18nEntityProvider;
use SilverStripe\ORM\ArrayList;
use SilverStripe\ORM\DataList;
use SilverStripe\ORM\DataObject;
use SilverStripe\ORM\DB;
use SilverStripe\ORM\HiddenClass;
use SilverStripe\ORM\Hierarchy\Hierarchy;
use SilverStripe\ORM\ManyManyList;
use SilverStripe\ORM\ValidationResult;
use SilverStripe\ORM\Versioning\Versioned;
use SilverStripe\Security\Group;
use SilverStripe\Security\Member;
use SilverStripe\Security\Permission;
use SilverStripe\Security\PermissionProvider;
use SilverStripe\SiteConfig\SiteConfig;
use SilverStripe\View\ArrayData;
use SilverStripe\View\Parsers\ShortcodeParser;
use SilverStripe\View\Parsers\URLSegmentFilter;
use SilverStripe\View\SSViewer;
use Subsite;

/**
 * Basic data-object representing all pages within the site tree. All page types that live within the hierarchy should
 * inherit from this. In addition, it contains a number of static methods for querying the site tree and working with
 * draft and published states.
 *
 * <h2>URLs</h2>
 * A page is identified during request handling via its "URLSegment" database column. As pages can be nested, the full
 * path of a URL might contain multiple segments. Each segment is stored in its filtered representation (through
 * {@link URLSegmentFilter}). The full path is constructed via {@link Link()}, {@link RelativeLink()} and
 * {@link AbsoluteLink()}. You can allow these segments to contain multibyte characters through
 * {@link URLSegmentFilter::$default_allow_multibyte}.
 *
 * @property string URLSegment
 * @property string Title
 * @property string MenuTitle
 * @property string Content HTML content of the page.
 * @property string MetaDescription
 * @property string ExtraMeta
 * @property string ShowInMenus
 * @property string ShowInSearch
 * @property string Sort Integer value denoting the sort order.
 * @property string ReportClass
 * @property string CanViewType Type of restriction for viewing this object.
 * @property string CanEditType Type of restriction for editing this object.
 *
 * @method ManyManyList ViewerGroups() List of groups that can view this object.
 * @method ManyManyList EditorGroups() List of groups that can edit this object.
 * @method SiteTree Parent()
 *
 * @mixin Hierarchy
 * @mixin Versioned
 * @mixin SiteTreeLinkTracking
 */
class SiteTree extends DataObject implements PermissionProvider,i18nEntityProvider,CMSPreviewable {

	/**
	 * Indicates what kind of children this page type can have.
	 * This can be an array of allowed child classes, or the string "none" -
	 * indicating that this page type can't have children.
	 * If a classname is prefixed by "*", such as "*Page", then only that
	 * class is allowed - no subclasses. Otherwise, the class and all its
	 * subclasses are allowed.
	 * To control allowed children on root level (no parent), use {@link $can_be_root}.
	 *
	 * Note that this setting is cached when used in the CMS, use the "flush" query parameter to clear it.
	 *
	 * @config
	 * @var array
	 */
	private static $allowed_children = array("SilverStripe\\CMS\\Model\\SiteTree");

	/**
	 * The default child class for this page.
	 * Note: Value might be cached, see {@link $allowed_chilren}.
	 *
	 * @config
	 * @var string
	 */
	private static $default_child = "Page";

	/**
	 * Default value for SiteTree.ClassName enum
	 * {@see DBClassName::getDefault}
	 *
	 * @config
	 * @var string
	 */
	private static $default_classname = "Page";

	/**
	 * The default parent class for this page.
	 * Note: Value might be cached, see {@link $allowed_chilren}.
	 *
	 * @config
	 * @var string
	 */
	private static $default_parent = null;

	/**
	 * Controls whether a page can be in the root of the site tree.
	 * Note: Value might be cached, see {@link $allowed_chilren}.
	 *
	 * @config
	 * @var bool
	 */
	private static $can_be_root = true;

	/**
	 * List of permission codes a user can have to allow a user to create a page of this type.
	 * Note: Value might be cached, see {@link $allowed_chilren}.
	 *
	 * @config
	 * @var array
	 */
	private static $need_permission = null;

	/**
	 * If you extend a class, and don't want to be able to select the old class
	 * in the cms, set this to the old class name. Eg, if you extended Product
	 * to make ImprovedProduct, then you would set $hide_ancestor to Product.
	 *
	 * @config
	 * @var string
	 */
	private static $hide_ancestor = null;

	private static $db = array(
		"URLSegment" => "Varchar(255)",
		"Title" => "Varchar(255)",
		"MenuTitle" => "Varchar(100)",
		"Content" => "HTMLText",
		"MetaDescription" => "Text",
		"ExtraMeta" => "HTMLFragment(['whitelist' => ['meta', 'link']])",
		"ShowInMenus" => "Boolean",
		"ShowInSearch" => "Boolean",
		"Sort" => "Int",
		"HasBrokenFile" => "Boolean",
		"HasBrokenLink" => "Boolean",
		"ReportClass" => "Varchar",
		"CanViewType" => "Enum('Anyone, LoggedInUsers, OnlyTheseUsers, Inherit', 'Inherit')",
		"CanEditType" => "Enum('LoggedInUsers, OnlyTheseUsers, Inherit', 'Inherit')",
	);

	private static $indexes = array(
		"URLSegment" => true,
	);

	private static $many_many = array(
		"ViewerGroups" => "SilverStripe\\Security\\Group",
		"EditorGroups" => "SilverStripe\\Security\\Group",
	);

	private static $has_many = array(
		"VirtualPages" => "SilverStripe\\CMS\\Model\\VirtualPage.CopyContentFrom"
	);

	private static $owned_by = array(
		"VirtualPages"
	);

	private static $casting = array(
		"Breadcrumbs" => "HTMLFragment",
		"LastEdited" => "Datetime",
		"Created" => "Datetime",
		'Link' => 'Text',
		'RelativeLink' => 'Text',
		'AbsoluteLink' => 'Text',
		'CMSEditLink' => 'Text',
		'TreeTitle' => 'HTMLFragment',
		'MetaTags' => 'HTMLFragment',
	);

	private static $defaults = array(
		"ShowInMenus" => 1,
		"ShowInSearch" => 1,
		"CanViewType" => "Inherit",
		"CanEditType" => "Inherit"
	);

	private static $table_name = 'SiteTree';

	private static $versioning = array(
		"Stage",  "Live"
	);

	private static $default_sort = "\"Sort\"";

	/**
	 * If this is false, the class cannot be created in the CMS by regular content authors, only by ADMINs.
	 * @var boolean
	 * @config
	 */
	private static $can_create = true;

	/**
	 * Icon to use in the CMS page tree. This should be the full filename, relative to the webroot.
	 * Also supports custom CSS rule contents (applied to the correct selector for the tree UI implementation).
	 *
	 * @see CMSMain::generateTreeStylingCSS()
	 * @config
	 * @var string
	 */
	private static $icon = null;

	/**
	 * @config
	 * @var string Description of the class functionality, typically shown to a user
	 * when selecting which page type to create. Translated through {@link provideI18nEntities()}.
	 */
	private static $description = 'Generic content page';

	private static $extensions = array(
		'SilverStripe\\ORM\\Hierarchy\\Hierarchy',
		'SilverStripe\\ORM\\Versioning\\Versioned',
		"SilverStripe\\CMS\\Model\\SiteTreeLinkTracking"
	);

	private static $searchable_fields = array(
		'Title',
		'Content',
	);

	private static $field_labels = array(
		'URLSegment' => 'URL'
	);

	/**
	 * @config
	 */
	private static $nested_urls = true;

	/**
	 * @config
	*/
	private static $create_default_pages = true;

	/**
	 * This controls whether of not extendCMSFields() is called by getCMSFields.
	 */
	private static $runCMSFieldsExtensions = true;

	/**
	 * Cache for canView/Edit/Publish/Delete permissions.
	 * Keyed by permission type (e.g. 'edit'), with an array
	 * of IDs mapped to their boolean permission ability (true=allow, false=deny).
	 * See {@link batch_permission_check()} for details.
	 */
	private static $cache_permissions = array();

	/**
	 * @config
	 * @var boolean
	 */
	private static $enforce_strict_hierarchy = true;

	/**
	 * The value used for the meta generator tag. Leave blank to omit the tag.
	 *
	 * @config
	 * @var string
	 */
	private static $meta_generator = 'SilverStripe - http://silverstripe.org';

	protected $_cache_statusFlags = null;

	/**
	 * Fetches the {@link SiteTree} object that maps to a link.
	 *
	 * If you have enabled {@link SiteTree::config()->nested_urls} on this site, then you can use a nested link such as
	 * "about-us/staff/", and this function will traverse down the URL chain and grab the appropriate link.
	 *
	 * Note that if no model can be found, this method will fall over to a extended alternateGetByLink method provided
	 * by a extension attached to {@link SiteTree}
	 *
	 * @param string $link  The link of the page to search for
	 * @param bool   $cache True (default) to use caching, false to force a fresh search from the database
	 * @return SiteTree
	 */
	static public function get_by_link($link, $cache = true) {
		if(trim($link, '/')) {
			$link = trim(Director::makeRelative($link), '/');
		} else {
			$link = RootURLController::get_homepage_link();
		}

		$parts = preg_split('|/+|', $link);

		// Grab the initial root level page to traverse down from.
		$URLSegment = array_shift($parts);
		$conditions = array('"SiteTree"."URLSegment"' => rawurlencode($URLSegment));
		if(self::config()->nested_urls) {
			$conditions[] = array('"SiteTree"."ParentID"' => 0);
		}
		/** @var SiteTree $sitetree */
		$sitetree = DataObject::get_one(self::class, $conditions, $cache);

		/// Fall back on a unique URLSegment for b/c.
		if(	!$sitetree
			&& self::config()->nested_urls
			&& $sitetree = DataObject::get_one(self::class, array(
				'"SiteTree"."URLSegment"' => $URLSegment
			), $cache)
		) {
			return $sitetree;
		}

		// Attempt to grab an alternative page from extensions.
		if(!$sitetree) {
			$parentID = self::config()->nested_urls ? 0 : null;

			if($alternatives = static::singleton()->extend('alternateGetByLink', $URLSegment, $parentID)) {
				foreach($alternatives as $alternative) {
					if($alternative) {
						$sitetree = $alternative;
			}
				}
			}

			if(!$sitetree) {
				return null;
		}
		}

		// Check if we have any more URL parts to parse.
		if(!self::config()->nested_urls || !count($parts)) {
			return $sitetree;
		}

		// Traverse down the remaining URL segments and grab the relevant SiteTree objects.
		foreach($parts as $segment) {
			$next = DataObject::get_one(self::class, array(
					'"SiteTree"."URLSegment"' => $segment,
					'"SiteTree"."ParentID"' => $sitetree->ID
				),
				$cache
			);

			if(!$next) {
				$parentID = (int) $sitetree->ID;

				if($alternatives = static::singleton()->extend('alternateGetByLink', $segment, $parentID)) {
					foreach($alternatives as $alternative) if($alternative) $next = $alternative;
				}

				if(!$next) {
					return null;
				}
			}

			$sitetree->destroy();
			$sitetree = $next;
		}

		return $sitetree;
	}

	/**
	 * Return a subclass map of SiteTree that shouldn't be hidden through {@link SiteTree::$hide_ancestor}
	 *
	 * @return array
	 */
	public static function page_type_classes() {
		$classes = ClassInfo::getValidSubClasses();

		$baseClassIndex = array_search(self::class, $classes);
		if($baseClassIndex !== false) {
			unset($classes[$baseClassIndex]);
		}

		$kill_ancestors = array();

		// figure out if there are any classes we don't want to appear
		foreach($classes as $class) {
			$instance = singleton($class);

			// do any of the progeny want to hide an ancestor?
			if($ancestor_to_hide = $instance->stat('hide_ancestor')) {
				// note for killing later
				$kill_ancestors[] = $ancestor_to_hide;
			}
		}

		// If any of the descendents don't want any of the elders to show up, cruelly render the elders surplus to
		// requirements
		if($kill_ancestors) {
			$kill_ancestors = array_unique($kill_ancestors);
			foreach($kill_ancestors as $mark) {
				// unset from $classes
				$idx = array_search($mark, $classes, true);
				if ($idx !== false) {
					unset($classes[$idx]);
				}
			}
		}

		return $classes;
	}

	/**
	 * Replace a "[sitetree_link id=n]" shortcode with a link to the page with the corresponding ID.
	 *
	 * @param array      $arguments
	 * @param string     $content
	 * @param ShortcodeParser $parser
	 * @return string
	 */
	static public function link_shortcode_handler($arguments, $content = null, $parser = null) {
		if(!isset($arguments['id']) || !is_numeric($arguments['id'])) {
			return null;
		}

		/** @var SiteTree $page */
		if (
			   !($page = DataObject::get_by_id(self::class, $arguments['id']))         // Get the current page by ID.
			&& !($page = Versioned::get_latest_version(self::class, $arguments['id'])) // Attempt link to old version.
		) {
			 return null; // There were no suitable matches at all.
		}

		/** @var SiteTree $page */
		$link = Convert::raw2att($page->Link());

		if($content) {
			return sprintf('<a href="%s">%s</a>', $link, $parser->parse($content));
		} else {
			return $link;
		}
	}

	/**
	 * Return the link for this {@link SiteTree} object, with the {@link Director::baseURL()} included.
	 *
	 * @param string $action Optional controller action (method).
	 *                       Note: URI encoding of this parameter is applied automatically through template casting,
	 *                       don't encode the passed parameter. Please use {@link Controller::join_links()} instead to
	 *                       append GET parameters.
	 * @return string
	 */
	public function Link($action = null) {
		return Controller::join_links(Director::baseURL(), $this->RelativeLink($action));
	}

	/**
	 * Get the absolute URL for this page, including protocol and host.
	 *
	 * @param string $action See {@link Link()}
	 * @return string
	 */
	public function AbsoluteLink($action = null) {
		if($this->hasMethod('alternateAbsoluteLink')) {
			return $this->alternateAbsoluteLink($action);
		} else {
			return Director::absoluteURL($this->Link($action));
		}
	}

	/**
	 * Base link used for previewing. Defaults to absolute URL, in order to account for domain changes, e.g. on multi
	 * site setups. Does not contain hints about the stage, see {@link SilverStripeNavigator} for details.
	 *
	 * @param string $action See {@link Link()}
	 * @return string
	 */
	public function PreviewLink($action = null) {
		if($this->hasMethod('alternatePreviewLink')) {
			Deprecation::notice('5.0', 'Use updatePreviewLink or override PreviewLink method');
			return $this->alternatePreviewLink($action);
		}

		$link = $this->AbsoluteLink($action);
		$this->extend('updatePreviewLink', $link, $action);
		return $link;
	}

	public function getMimeType() {
		return 'text/html';
	}

	/**
	 * Return the link for this {@link SiteTree} object relative to the SilverStripe root.
	 *
	 * By default, if this page is the current home page, and there is no action specified then this will return a link
	 * to the root of the site. However, if you set the $action parameter to TRUE then the link will not be rewritten
	 * and returned in its full form.
	 *
	 * @uses RootURLController::get_homepage_link()
	 *
	 * @param string $action See {@link Link()}
	 * @return string
	 */
	public function RelativeLink($action = null) {
		if($this->ParentID && self::config()->nested_urls) {
			$parent = $this->Parent();
			// If page is removed select parent from version history (for archive page view)
			if((!$parent || !$parent->exists()) && !$this->isOnDraft()) {
				$parent = Versioned::get_latest_version(self::class, $this->ParentID);
			}
			$base = $parent->RelativeLink($this->URLSegment);
		} elseif(!$action && $this->URLSegment == RootURLController::get_homepage_link()) {
			// Unset base for root-level homepages.
			// Note: Homepages with action parameters (or $action === true)
			// need to retain their URLSegment.
			$base = null;
		} else {
			$base = $this->URLSegment;
		}

		$this->extend('updateRelativeLink', $base, $action);

		// Legacy support: If $action === true, retain URLSegment for homepages,
		// but don't append any action
		if($action === true) $action = null;

		return Controller::join_links($base, '/', $action);
	}

	/**
	 * Get the absolute URL for this page on the Live site.
	 *
	 * @param bool $includeStageEqualsLive Whether to append the URL with ?stage=Live to force Live mode
	 * @return string
	 */
	public function getAbsoluteLiveLink($includeStageEqualsLive = true) {
		$oldReadingMode = Versioned::get_reading_mode();
		Versioned::set_stage(Versioned::LIVE);
		/** @var SiteTree $live */
		$live = Versioned::get_one_by_stage(self::class, Versioned::LIVE, array(
			'"SiteTree"."ID"' => $this->ID
		));
		if($live) {
			$link = $live->AbsoluteLink();
			if($includeStageEqualsLive) {
				$link = Controller::join_links($link, '?stage=Live');
			}
		} else {
			$link = null;
		}

		Versioned::set_reading_mode($oldReadingMode);
		return $link;
	}

	/**
	 * Generates a link to edit this page in the CMS.
	 *
	 * @return string
	 */
	public function CMSEditLink() {
		$link = Controller::join_links(
			CMSPageEditController::singleton()->Link('show'),
			$this->ID
		);
		return Director::absoluteURL($link);
	}


	/**
	 * Return a CSS identifier generated from this page's link.
	 *
	 * @return string The URL segment
	 */
	public function ElementName() {
		return str_replace('/', '-', trim($this->RelativeLink(true), '/'));
	}

	/**
	 * Returns true if this is the currently active page being used to handle this request.
	 *
	 * @return bool
	 */
	public function isCurrent() {
		$currentPage = Director::get_current_page();
		if ($currentPage instanceof ContentController) {
			$currentPage = $currentPage->data();
	}
		if($currentPage instanceof SiteTree) {
			return $currentPage === $this || $currentPage->ID === $this->ID;
		}
		return false;
	}

	/**
	 * Check if this page is in the currently active section (e.g. it is either current or one of its children is
	 * currently being viewed).
	 *
	 * @return bool
	 */
	public function isSection() {
		return $this->isCurrent() || (
			Director::get_current_page() instanceof SiteTree && in_array($this->ID, Director::get_current_page()->getAncestors()->column())
		);
	}

	/**
	 * Check if the parent of this page has been removed (or made otherwise unavailable), and is still referenced by
	 * this child. Any such orphaned page may still require access via the CMS, but should not be shown as accessible
	 * to external users.
	 *
	 * @return bool
	 */
	public function isOrphaned() {
		// Always false for root pages
		if(empty($this->ParentID)) {
			return false;
		}

		// Parent must exist and not be an orphan itself
		$parent = $this->Parent();
		return !$parent || !$parent->exists() || $parent->isOrphaned();
	}

	/**
	 * Return "link" or "current" depending on if this is the {@link SiteTree::isCurrent()} current page.
	 *
	 * @return string
	 */
	public function LinkOrCurrent() {
		return $this->isCurrent() ? 'current' : 'link';
	}

	/**
	 * Return "link" or "section" depending on if this is the {@link SiteTree::isSeciton()} current section.
	 *
	 * @return string
	 */
	public function LinkOrSection() {
		return $this->isSection() ? 'section' : 'link';
	}

	/**
	 * Return "link", "current" or "section" depending on if this page is the current page, or not on the current page
	 * but in the current section.
	 *
	 * @return string
	 */
	public function LinkingMode() {
		if($this->isCurrent()) {
			return 'current';
		} elseif($this->isSection()) {
			return 'section';
		} else {
			return 'link';
		}
	}

	/**
	 * Check if this page is in the given current section.
	 *
	 * @param string $sectionName Name of the section to check
	 * @return bool True if we are in the given section
	 */
	public function InSection($sectionName) {
		$page = Director::get_current_page();
		while($page && $page->exists()) {
			if($sectionName == $page->URLSegment) {
				return true;
			}
			$page = $page->Parent();
		}
		return false;
	}

	/**
	 * Reset Sort on duped page
	 *
	 * @param SiteTree $original
	 * @param bool $doWrite
	 */
	public function onBeforeDuplicate($original, $doWrite) {
		$this->Sort = 0;
	}

	/**
	 * Duplicates each child of this node recursively and returns the top-level duplicate node.
	 *
	 * @return static The duplicated object
	 */
	public function duplicateWithChildren() {
		/** @var SiteTree $clone */
		$clone = $this->duplicate();
		$children = $this->AllChildren();

		if($children) {
			/** @var SiteTree $child */
			$sort = 0;
			foreach($children as $child) {
				$childClone = $child->duplicateWithChildren();
				$childClone->ParentID = $clone->ID;
				//retain sort order by manually setting sort values
				$childClone->Sort = ++$sort;
				$childClone->write();
			}
		}

		return $clone;
	}

	/**
	 * Duplicate this node and its children as a child of the node with the given ID
	 *
	 * @param int $id ID of the new node's new parent
	 */
	public function duplicateAsChild($id) {
		/** @var SiteTree $newSiteTree */
		$newSiteTree = $this->duplicate();
		$newSiteTree->ParentID = $id;
		$newSiteTree->Sort = 0;
		$newSiteTree->write();
	}

	/**
	 * Return a breadcrumb trail to this page. Excludes "hidden" pages (with ShowInMenus=0) by default.
	 *
	 * @param int $maxDepth The maximum depth to traverse.
	 * @param boolean $unlinked Whether to link page titles.
	 * @param boolean|string $stopAtPageType ClassName of a page to stop the upwards traversal.
	 * @param boolean $showHidden Include pages marked with the attribute ShowInMenus = 0
	 * @return string The breadcrumb trail.
	 */
	public function Breadcrumbs($maxDepth = 20, $unlinked = false, $stopAtPageType = false, $showHidden = false) {
		$pages = $this->getBreadcrumbItems($maxDepth, $stopAtPageType, $showHidden);
		$template = new SSViewer('BreadcrumbsTemplate');
		return $template->process($this->customise(new ArrayData(array(
			"Pages" => $pages,
			"Unlinked" => $unlinked
		))));
	}


	/**
	 * Returns a list of breadcrumbs for the current page.
	 *
	 * @param int $maxDepth The maximum depth to traverse.
	 * @param boolean|string $stopAtPageType ClassName of a page to stop the upwards traversal.
	 * @param boolean $showHidden Include pages marked with the attribute ShowInMenus = 0
	 *
	 * @return ArrayList
	*/
	public function getBreadcrumbItems($maxDepth = 20, $stopAtPageType = false, $showHidden = false) {
		$page = $this;
		$pages = array();

		while(
			$page
			&& $page->exists()
 			&& (!$maxDepth || count($pages) < $maxDepth)
 			&& (!$stopAtPageType || $page->ClassName != $stopAtPageType)
 		) {
			if($showHidden || $page->ShowInMenus || ($page->ID == $this->ID)) {
				$pages[] = $page;
			}

			$page = $page->Parent();
		}

		return new ArrayList(array_reverse($pages));
	}


	/**
	 * Make this page a child of another page.
	 *
	 * If the parent page does not exist, resolve it to a valid ID before updating this page's reference.
	 *
	 * @param SiteTree|int $item Either the parent object, or the parent ID
	 */
	public function setParent($item) {
		if(is_object($item)) {
			if (!$item->exists()) $item->write();
			$this->setField("ParentID", $item->ID);
		} else {
			$this->setField("ParentID", $item);
		}
	}

	/**
	 * Get the parent of this page.
	 *
	 * @return SiteTree Parent of this page
	 */
	public function getParent() {
		if ($parentID = $this->getField("ParentID")) {
			return DataObject::get_by_id("SilverStripe\\CMS\\Model\\SiteTree", $parentID);
		}
		return null;
	}

	/**
	 * Return a string of the form "parent - page" or "grandparent - parent - page" using page titles
	 *
	 * @param int $level The maximum amount of levels to traverse.
	 * @param string $separator Seperating string
	 * @return string The resulting string
	 */
	public function NestedTitle($level = 2, $separator = " - ") {
		$item = $this;
		$parts = [];
		while($item && $level > 0) {
			$parts[] = $item->Title;
			$item = $item->getParent();
			$level--;
		}
		return implode($separator, array_reverse($parts));
	}

	/**
	 * This function should return true if the current user can execute this action. It can be overloaded to customise
	 * the security model for an application.
	 *
	 * Slightly altered from parent behaviour in {@link DataObject->can()}:
	 * - Checks for existence of a method named "can<$perm>()" on the object
	 * - Calls decorators and only returns for FALSE "vetoes"
	 * - Falls back to {@link Permission::check()}
	 * - Does NOT check for many-many relations named "Can<$perm>"
	 *
	 * @uses DataObjectDecorator->can()
	 *
	 * @param string $perm The permission to be checked, such as 'View'
	 * @param Member $member The member whose permissions need checking. Defaults to the currently logged in user.
	 * @param array $context Context argument for canCreate()
	 * @return bool True if the the member is allowed to do the given action
	 */
	public function can($perm, $member = null, $context = array()) {
		if(!$member || !($member instanceof Member) || is_numeric($member)) {
			$member = Member::currentUserID();
		}

		if($member && Permission::checkMember($member, "ADMIN")) return true;

		if(is_string($perm) && method_exists($this, 'can' . ucfirst($perm))) {
			$method = 'can' . ucfirst($perm);
			return $this->$method($member);
		}

		$results = $this->extend('can', $member);
		if($results && is_array($results)) if(!min($results)) return false;

		return ($member && Permission::checkMember($member, $perm));
	}

	/**
	 * This function should return true if the current user can add children to this page. It can be overloaded to
	 * customise the security model for an application.
	 *
	 * Denies permission if any of the following conditions is true:
	 * - alternateCanAddChildren() on a extension returns false
	 * - canEdit() is not granted
	 * - There are no classes defined in {@link $allowed_children}
	 *
	 * @uses SiteTreeExtension->canAddChildren()
	 * @uses canEdit()
	 * @uses $allowed_children
	 *
	 * @param Member|int $member
	 * @return bool True if the current user can add children
	 */
	public function canAddChildren($member = null) {
		// Disable adding children to archived pages
		if(!$this->isOnDraft()) {
			return false;
		}

		if(!$member || !($member instanceof Member) || is_numeric($member)) {
			$member = Member::currentUserID();
		}

		// Standard mechanism for accepting permission changes from extensions
		$extended = $this->extendedCan('canAddChildren', $member);
		if($extended !== null) {
			return $extended;
		}

		// Default permissions
		if($member && Permission::checkMember($member, "ADMIN")) {
			return true;
		}

		return $this->canEdit($member) && $this->stat('allowed_children') != 'none';
	}

	/**
	 * This function should return true if the current user can view this page. It can be overloaded to customise the
	 * security model for an application.
	 *
	 * Denies permission if any of the following conditions is true:
	 * - canView() on any extension returns false
	 * - "CanViewType" directive is set to "Inherit" and any parent page return false for canView()
	 * - "CanViewType" directive is set to "LoggedInUsers" and no user is logged in
	 * - "CanViewType" directive is set to "OnlyTheseUsers" and user is not in the given groups
	 *
	 * @uses DataExtension->canView()
	 * @uses ViewerGroups()
	 *
	 * @param Member|int $member
	 * @return bool True if the current user can view this page
	 */
	public function canView($member = null) {
		if(!$member || !($member instanceof Member) || is_numeric($member)) {
			$member = Member::currentUserID();
		}

		// Standard mechanism for accepting permission changes from extensions
		$extended = $this->extendedCan('canView', $member);
		if($extended !== null) {
			return $extended;
		}

		// admin override
		if($member && Permission::checkMember($member, array("ADMIN", "SITETREE_VIEW_ALL"))) {
			return true;
		}

		// Orphaned pages (in the current stage) are unavailable, except for admins via the CMS
		if($this->isOrphaned()) {
			return false;
		}

		// check for empty spec
		if(!$this->CanViewType || $this->CanViewType == 'Anyone') {
			return true;
		}

		// check for inherit
		if($this->CanViewType == 'Inherit') {
			if($this->ParentID) return $this->Parent()->canView($member);
			else return $this->getSiteConfig()->canViewPages($member);
		}

		// check for any logged-in users
		if($this->CanViewType == 'LoggedInUsers' && $member) {
			return true;
		}

		// check for specific groups
		if($member && is_numeric($member)) {
			$member = DataObject::get_by_id('SilverStripe\\Security\\Member', $member);
		}
		if(
			$this->CanViewType == 'OnlyTheseUsers'
			&& $member
			&& $member->inGroups($this->ViewerGroups())
		) return true;

		return false;
	}

	/**
	 * Check if this page can be published
	 *
	 * @param Member $member
	 * @return bool
	 */
	public function canPublish($member = null) {
		if(!$member) {
			$member = Member::currentUser();
		}

		// Check extension
		$extended = $this->extendedCan('canPublish', $member);
		if($extended !== null) {
			return $extended;
		}

		if(Permission::checkMember($member, "ADMIN")) {
			return true;
		}

		// Default to relying on edit permission
		return $this->canEdit($member);
	}

	/**
	 * This function should return true if the current user can delete this page. It can be overloaded to customise the
	 * security model for an application.
	 *
	 * Denies permission if any of the following conditions is true:
	 * - canDelete() returns false on any extension
	 * - canEdit() returns false
	 * - any descendant page returns false for canDelete()
	 *
	 * @uses canDelete()
	 * @uses SiteTreeExtension->canDelete()
	 * @uses canEdit()
	 *
	 * @param Member $member
	 * @return bool True if the current user can delete this page
	 */
	public function canDelete($member = null) {
		if($member instanceof Member) $memberID = $member->ID;
		else if(is_numeric($member)) $memberID = $member;
		else $memberID = Member::currentUserID();

		// Standard mechanism for accepting permission changes from extensions
		$extended = $this->extendedCan('canDelete', $memberID);
		if($extended !== null) {
			return $extended;
		}

		// Default permission check
		if($memberID && Permission::checkMember($memberID, array("ADMIN", "SITETREE_EDIT_ALL"))) {
			return true;
		}

		// Regular canEdit logic is handled by can_edit_multiple
		$results = self::can_delete_multiple(array($this->ID), $memberID);

		// If this page no longer exists in stage/live results won't contain the page.
		// Fail-over to false
		return isset($results[$this->ID]) ? $results[$this->ID] : false;
	}

	/**
	 * This function should return true if the current user can create new pages of this class, regardless of class. It
	 * can be overloaded to customise the security model for an application.
	 *
	 * By default, permission to create at the root level is based on the SiteConfig configuration, and permission to
	 * create beneath a parent is based on the ability to edit that parent page.
	 *
	 * Use {@link canAddChildren()} to control behaviour of creating children under this page.
	 *
	 * @uses $can_create
	 * @uses DataExtension->canCreate()
	 *
	 * @param Member $member
	 * @param array $context Optional array which may contain array('Parent' => $parentObj)
	 *                       If a parent page is known, it will be checked for validity.
	 *                       If omitted, it will be assumed this is to be created as a top level page.
	 * @return bool True if the current user can create pages on this class.
	 */
	public function canCreate($member = null, $context = array()) {
		if(!$member || !(is_a($member, 'SilverStripe\\Security\\Member')) || is_numeric($member)) {
			$member = Member::currentUserID();
		}

		// Check parent (custom canCreate option for SiteTree)
		// Block children not allowed for this parent type
		$parent = isset($context['Parent']) ? $context['Parent'] : null;
		if($parent && !in_array(static::class, $parent->allowedChildren())) {
			return false;
		}

		// Standard mechanism for accepting permission changes from extensions
		$extended = $this->extendedCan(__FUNCTION__, $member, $context);
		if($extended !== null) {
			return $extended;
		}

		// Check permission
		if($member && Permission::checkMember($member, "ADMIN")) {
			return true;
		}

		// Fall over to inherited permissions
		if($parent) {
			return $parent->canAddChildren($member);
		} else {
			// This doesn't necessarily mean we are creating a root page, but that
			// we don't know if there is a parent, so default to this permission
			return SiteConfig::current_site_config()->canCreateTopLevel($member);
		}
	}

	/**
	 * This function should return true if the current user can edit this page. It can be overloaded to customise the
	 * security model for an application.
	 *
	 * Denies permission if any of the following conditions is true:
	 * - canEdit() on any extension returns false
	 * - canView() return false
	 * - "CanEditType" directive is set to "Inherit" and any parent page return false for canEdit()
	 * - "CanEditType" directive is set to "LoggedInUsers" and no user is logged in or doesn't have the
	 *   CMS_Access_CMSMAIN permission code
	 * - "CanEditType" directive is set to "OnlyTheseUsers" and user is not in the given groups
	 *
	 * @uses canView()
	 * @uses EditorGroups()
	 * @uses DataExtension->canEdit()
	 *
	 * @param Member $member Set to false if you want to explicitly test permissions without a valid user (useful for
	 *                       unit tests)
	 * @return bool True if the current user can edit this page
	 */
	public function canEdit($member = null) {
		if($member instanceof Member) $memberID = $member->ID;
		else if(is_numeric($member)) $memberID = $member;
		else $memberID = Member::currentUserID();

		// Standard mechanism for accepting permission changes from extensions
		$extended = $this->extendedCan('canEdit', $memberID);
		if($extended !== null) {
			return $extended;
		}

		// Default permissions
		if($memberID && Permission::checkMember($memberID, array("ADMIN", "SITETREE_EDIT_ALL"))) {
			return true;
		}

		if($this->ID) {
			// Regular canEdit logic is handled by can_edit_multiple
			$results = self::can_edit_multiple(array($this->ID), $memberID);

			// If this page no longer exists in stage/live results won't contain the page.
			// Fail-over to false
			return isset($results[$this->ID]) ? $results[$this->ID] : false;

		// Default for unsaved pages
		} else {
			return $this->getSiteConfig()->canEditPages($member);
		}
	}

	/**
	 * Stub method to get the site config, unless the current class can provide an alternate.
	 *
	 * @return SiteConfig
	 */
	public function getSiteConfig() {
		$configs = $this->invokeWithExtensions('alternateSiteConfig');
		foreach(array_filter($configs) as $config) {
			return $config;
		}

		return SiteConfig::current_site_config();
	}

	/**
	 * Pre-populate the cache of canEdit, canView, canDelete, canPublish permissions. This method will use the static
	 * can_(perm)_multiple method for efficiency.
	 *
	 * @param string          $permission    The permission: edit, view, publish, approve, etc.
	 * @param array           $ids           An array of page IDs
	 * @param callable|string $batchCallback The function/static method to call to calculate permissions.  Defaults
	 *                                       to 'SiteTree::can_(permission)_multiple'
	 */
	static public function prepopulate_permission_cache($permission = 'CanEditType', $ids, $batchCallback = null) {
		if(!$batchCallback) {
			$batchCallback = self::class . "::can_{$permission}_multiple";
		}

		if(is_callable($batchCallback)) {
			call_user_func($batchCallback, $ids, Member::currentUserID(), false);
		} else {
			user_error("SiteTree::prepopulate_permission_cache can't calculate '$permission' "
				. "with callback '$batchCallback'", E_USER_WARNING);
		}
	}

	/**
	 * This method is NOT a full replacement for the individual can*() methods, e.g. {@link canEdit()}. Rather than
	 * checking (potentially slow) PHP logic, it relies on the database group associations, e.g. the "CanEditType" field
	 * plus the "SiteTree_EditorGroups" many-many table. By batch checking multiple records, we can combine the queries
	 * efficiently.
	 *
	 * Caches based on $typeField data. To invalidate the cache, use {@link SiteTree::reset()} or set the $useCached
	 * property to FALSE.
	 *
	 * @param array  $ids              Of {@link SiteTree} IDs
	 * @param int    $memberID         Member ID
	 * @param string $typeField        A property on the data record, e.g. "CanEditType".
	 * @param string $groupJoinTable   A many-many table name on this record, e.g. "SiteTree_EditorGroups"
	 * @param string $siteConfigMethod Method to call on {@link SiteConfig} for toplevel items, e.g. "canEdit"
	 * @param string $globalPermission If the member doesn't have this permission code, don't bother iterating deeper
	 * @param bool   $useCached
	 * @return array An map of {@link SiteTree} ID keys to boolean values
	 */
	public static function batch_permission_check($ids, $memberID, $typeField, $groupJoinTable, $siteConfigMethod,
												  $globalPermission = null, $useCached = true) {
		if($globalPermission === NULL) $globalPermission = array('CMS_ACCESS_LeftAndMain', 'CMS_ACCESS_CMSMain');

		// Sanitise the IDs
		$ids = array_filter($ids, 'is_numeric');

		// This is the name used on the permission cache
		// converts something like 'CanEditType' to 'edit'.
		$cacheKey = strtolower(substr($typeField, 3, -4)) . "-$memberID";

		// Default result: nothing editable
		$result = array_fill_keys($ids, false);
		if($ids) {

			// Look in the cache for values
			if($useCached && isset(self::$cache_permissions[$cacheKey])) {
				$cachedValues = array_intersect_key(self::$cache_permissions[$cacheKey], $result);

				// If we can't find everything in the cache, then look up the remainder separately
				$uncachedValues = array_diff_key($result, self::$cache_permissions[$cacheKey]);
				if($uncachedValues) {
					$cachedValues = self::batch_permission_check(array_keys($uncachedValues), $memberID, $typeField, $groupJoinTable, $siteConfigMethod, $globalPermission, false) + $cachedValues;
				}
				return $cachedValues;
			}

			// If a member doesn't have a certain permission then they can't edit anything
			if(!$memberID || ($globalPermission && !Permission::checkMember($memberID, $globalPermission))) {
				return $result;
			}

			// Placeholder for parameterised ID list
			$idPlaceholders = DB::placeholders($ids);

			// If page can't be viewed, don't grant edit permissions to do - implement can_view_multiple(), so this can
			// be enabled
			//$ids = array_keys(array_filter(self::can_view_multiple($ids, $memberID)));

			// Get the groups that the given member belongs to
			/** @var Member $member */
			$member = DataObject::get_by_id('SilverStripe\\Security\\Member', $memberID);
			$groupIDs = $member->Groups()->column("ID");
			$SQL_groupList = implode(", ", $groupIDs);
			if (!$SQL_groupList) {
				$SQL_groupList = '0';
			}

			$combinedStageResult = array();

			foreach(array(Versioned::DRAFT, Versioned::LIVE) as $stage) {
				// Start by filling the array with the pages that actually exist
				/** @skipUpgrade */
				$table = ($stage=='Stage') ? "SiteTree" : "SiteTree_$stage";

				if($ids) {
					$idQuery = "SELECT \"ID\" FROM \"$table\" WHERE \"ID\" IN ($idPlaceholders)";
					$stageIds = DB::prepared_query($idQuery, $ids)->column();
				} else {
					$stageIds = array();
				}
				$result = array_fill_keys($stageIds, false);

				// Get the uninherited permissions
				$uninheritedPermissions = Versioned::get_by_stage("SilverStripe\\CMS\\Model\\SiteTree", $stage)
					->where(array(
						"(\"$typeField\" = 'LoggedInUsers' OR
						(\"$typeField\" = 'OnlyTheseUsers' AND \"$groupJoinTable\".\"SiteTreeID\" IS NOT NULL))
						AND \"SiteTree\".\"ID\" IN ($idPlaceholders)"
						=> $ids
					))
					->leftJoin($groupJoinTable, "\"$groupJoinTable\".\"SiteTreeID\" = \"SiteTree\".\"ID\" AND \"$groupJoinTable\".\"GroupID\" IN ($SQL_groupList)");

				if($uninheritedPermissions) {
					// Set all the relevant items in $result to true
					$result = array_fill_keys($uninheritedPermissions->column('ID'), true) + $result;
				}

				// Get permissions that are inherited
				$potentiallyInherited = Versioned::get_by_stage(
					"SilverStripe\\CMS\\Model\\SiteTree",
					$stage,
					array("\"$typeField\" = 'Inherit' AND \"SiteTree\".\"ID\" IN ($idPlaceholders)" => $ids)
				);

				if($potentiallyInherited) {
					// Group $potentiallyInherited by ParentID; we'll look at the permission of all those parents and
					// then see which ones the user has permission on
					$groupedByParent = array();
					foreach($potentiallyInherited as $item) {
						/** @var SiteTree $item */
						if($item->ParentID) {
							if(!isset($groupedByParent[$item->ParentID])) $groupedByParent[$item->ParentID] = array();
							$groupedByParent[$item->ParentID][] = $item->ID;
						} else {
							// Might return different site config based on record context, e.g. when subsites module
							// is used
							$siteConfig = $item->getSiteConfig();
							$result[$item->ID] = $siteConfig->{$siteConfigMethod}($memberID);
						}
					}

					if($groupedByParent) {
						$actuallyInherited = self::batch_permission_check(array_keys($groupedByParent), $memberID, $typeField, $groupJoinTable, $siteConfigMethod);
						if($actuallyInherited) {
							$parentIDs = array_keys(array_filter($actuallyInherited));
							foreach($parentIDs as $parentID) {
								// Set all the relevant items in $result to true
								$result = array_fill_keys($groupedByParent[$parentID], true) + $result;
							}
						}
					}
				}

				$combinedStageResult = $combinedStageResult + $result;

			}
		}

		if(isset($combinedStageResult)) {
			// Cache the results
 			if(empty(self::$cache_permissions[$cacheKey])) self::$cache_permissions[$cacheKey] = array();
 			self::$cache_permissions[$cacheKey] = $combinedStageResult + self::$cache_permissions[$cacheKey];
			return $combinedStageResult;
		} else {
			return array();
		}
	}

	/**
	 * Get the 'can edit' information for a number of SiteTree pages.
	 *
	 * @param array $ids       An array of IDs of the SiteTree pages to look up
	 * @param int   $memberID  ID of member
	 * @param bool  $useCached Return values from the permission cache if they exist
	 * @return array A map where the IDs are keys and the values are booleans stating whether the given page can be
	 *                         edited
	 */
	static public function can_edit_multiple($ids, $memberID, $useCached = true) {
		return self::batch_permission_check($ids, $memberID, 'CanEditType', 'SiteTree_EditorGroups', 'canEditPages', null, $useCached);
	}

	/**
	 * Get the 'can edit' information for a number of SiteTree pages.
	 *
	 * @param array $ids       An array of IDs of the SiteTree pages to look up
	 * @param int   $memberID  ID of member
	 * @param bool  $useCached Return values from the permission cache if they exist
	 * @return array
	 */
	static public function can_delete_multiple($ids, $memberID, $useCached = true) {
		$deletable = array();
		$result = array_fill_keys($ids, false);
		$cacheKey = "delete-$memberID";

		// Look in the cache for values
		if($useCached && isset(self::$cache_permissions[$cacheKey])) {
			$cachedValues = array_intersect_key(self::$cache_permissions[$cacheKey], $result);

			// If we can't find everything in the cache, then look up the remainder separately
			$uncachedValues = array_diff_key($result, self::$cache_permissions[$cacheKey]);
			if($uncachedValues) {
				$cachedValues = self::can_delete_multiple(array_keys($uncachedValues), $memberID, false)
					+ $cachedValues;
			}
			return $cachedValues;
		}

		// You can only delete pages that you can edit
		$editableIDs = array_keys(array_filter(self::can_edit_multiple($ids, $memberID)));
		if($editableIDs) {

			// You can only delete pages whose children you can delete
			$editablePlaceholders = DB::placeholders($editableIDs);
			$childRecords = SiteTree::get()->where(array(
				"\"SiteTree\".\"ParentID\" IN ($editablePlaceholders)" => $editableIDs
			));
			if($childRecords) {
				$children = $childRecords->map("ID", "ParentID");

				// Find out the children that can be deleted
				$deletableChildren = self::can_delete_multiple($children->keys(), $memberID);

				// Get a list of all the parents that have no undeletable children
				$deletableParents = array_fill_keys($editableIDs, true);
				foreach($deletableChildren as $id => $canDelete) {
					if(!$canDelete) unset($deletableParents[$children[$id]]);
				}

				// Use that to filter the list of deletable parents that have children
				$deletableParents = array_keys($deletableParents);

				// Also get the $ids that don't have children
				$parents = array_unique($children->values());
				$deletableLeafNodes = array_diff($editableIDs, $parents);

				// Combine the two
				$deletable = array_merge($deletableParents, $deletableLeafNodes);

			} else {
				$deletable = $editableIDs;
			}
		}

		// Convert the array of deletable IDs into a map of the original IDs with true/false as the value
		return array_fill_keys($deletable, true) + array_fill_keys($ids, false);
	}

	/**
	 * Collate selected descendants of this page.
	 *
	 * {@link $condition} will be evaluated on each descendant, and if it is succeeds, that item will be added to the
	 * $collator array.
	 *
	 * @param string $condition The PHP condition to be evaluated. The page will be called $item
	 * @param array  $collator  An array, passed by reference, to collect all of the matching descendants.
	 * @return bool
	 */
	public function collateDescendants($condition, &$collator) {
		$children = $this->Children();
		if($children) {
			foreach($children as $item) {

				if(eval("return $condition;")) {
					$collator[] = $item;
				}
				/** @var SiteTree $item */
				$item->collateDescendants($condition, $collator);
			}
			return true;
		}
		return false;
	}

	/**
	 * Return the title, description, keywords and language metatags.
	 *
	 * @todo Move <title> tag in separate getter for easier customization and more obvious usage
	 *
	 * @param bool $includeTitle Show default <title>-tag, set to false for custom templating
	 * @return string The XHTML metatags
	 */
	public function MetaTags($includeTitle = true) {
		$tags = array();
		if($includeTitle && strtolower($includeTitle) != 'false') {
			$tags[] = FormField::create_tag('title', array(), $this->obj('Title')->forTemplate());
		}

		$generator = trim(Config::inst()->get(self::class, 'meta_generator'));
		if (!empty($generator)) {
			$tags[] = FormField::create_tag('meta', array(
				'name' => 'generator',
				'content' => $generator,
			));
		}

		$charset = Config::inst()->get('SilverStripe\\Control\\ContentNegotiator', 'encoding');
		$tags[] = FormField::create_tag('meta', array(
			'http-equiv' => 'Content-Type',
			'content' => 'text/html; charset=' . $charset,
		));
		if($this->MetaDescription) {
			$tags[] = FormField::create_tag('meta', array(
				'name' => 'description',
				'content' => $this->MetaDescription,
			));
		}

		if(Permission::check('CMS_ACCESS_CMSMain')
			&& !$this instanceof ErrorPage
			&& $this->ID > 0
		) {
			$tags[] = FormField::create_tag('meta', array(
				'name' => 'x-page-id',
				'content' => $this->obj('ID')->forTemplate(),
			));
			$tags[] = FormField::create_tag('meta', array(
				'name' => 'x-cms-edit-link',
				'content' => $this->obj('CMSEditLink')->forTemplate(),
			));
		}

		$tags = implode("\n", $tags);
		if($this->ExtraMeta) {
			$tags .= $this->obj('ExtraMeta')->forTemplate();
		}

		$this->extend('MetaTags', $tags);

		return $tags;
	}

	/**
	 * Returns the object that contains the content that a user would associate with this page.
	 *
	 * Ordinarily, this is just the page itself, but for example on RedirectorPages or VirtualPages ContentSource() will
	 * return the page that is linked to.
	 *
	 * @return $this
	 */
	public function ContentSource() {
		return $this;
	}

	/**
	 * Add default records to database.
	 *
	 * This function is called whenever the database is built, after the database tables have all been created. Overload
	 * this to add default records when the database is built, but make sure you call parent::requireDefaultRecords().
	 */
	public function requireDefaultRecords() {
		parent::requireDefaultRecords();

		// default pages
		if(static::class == self::class && $this->config()->create_default_pages) {
			if(!SiteTree::get_by_link(RootURLController::config()->default_homepage_link)) {
				$homepage = new Page();
				$homepage->Title = _t('SiteTree.DEFAULTHOMETITLE', 'Home');
				$homepage->Content = _t('SiteTree.DEFAULTHOMECONTENT', '<p>Welcome to SilverStripe! This is the default homepage. You can edit this page by opening <a href="admin/">the CMS</a>.</p><p>You can now access the <a href="http://docs.silverstripe.org">developer documentation</a>, or begin the <a href="http://www.silverstripe.org/learn/lessons">SilverStripe lessons</a>.</p>');
				$homepage->URLSegment = RootURLController::config()->default_homepage_link;
				$homepage->Sort = 1;
				$homepage->write();
				$homepage->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
				$homepage->flushCache();
				DB::alteration_message('Home page created', 'created');
			}

			if(DB::query("SELECT COUNT(*) FROM \"SiteTree\"")->value() == 1) {
				$aboutus = new Page();
				$aboutus->Title = _t('SiteTree.DEFAULTABOUTTITLE', 'About Us');
				$aboutus->Content = _t(
					'SiteTree.DEFAULTABOUTCONTENT',
					'<p>You can fill this page out with your own content, or delete it and create your own pages.</p>'
				);
				$aboutus->Sort = 2;
				$aboutus->write();
				$aboutus->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
				$aboutus->flushCache();
				DB::alteration_message('About Us page created', 'created');

				$contactus = new Page();
				$contactus->Title = _t('SiteTree.DEFAULTCONTACTTITLE', 'Contact Us');
				$contactus->Content = _t(
					'SiteTree.DEFAULTCONTACTCONTENT',
					'<p>You can fill this page out with your own content, or delete it and create your own pages.</p>'
				);
				$contactus->Sort = 3;
				$contactus->write();
				$contactus->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
				$contactus->flushCache();
				DB::alteration_message('Contact Us page created', 'created');
			}
		}
	}

	protected function onBeforeWrite() {
		parent::onBeforeWrite();

		// If Sort hasn't been set, make this page come after it's siblings
		if(!$this->Sort) {
			$parentID = ($this->ParentID) ? $this->ParentID : 0;
			$this->Sort = DB::prepared_query(
				"SELECT MAX(\"Sort\") + 1 FROM \"SiteTree\" WHERE \"ParentID\" = ?",
				array($parentID)
			)->value();
		}

		// If there is no URLSegment set, generate one from Title
		$defaultSegment = $this->generateURLSegment(_t(
			'CMSMain.NEWPAGE',
			array('pagetype' => $this->i18n_singular_name())
		));
		if((!$this->URLSegment || $this->URLSegment == $defaultSegment) && $this->Title) {
			$this->URLSegment = $this->generateURLSegment($this->Title);
		} else if($this->isChanged('URLSegment', 2)) {
			// Do a strict check on change level, to avoid double encoding caused by
			// bogus changes through forceChange()
			$filter = URLSegmentFilter::create();
			$this->URLSegment = $filter->filter($this->URLSegment);
			// If after sanitising there is no URLSegment, give it a reasonable default
			if(!$this->URLSegment) $this->URLSegment = "page-$this->ID";
		}

		// Ensure that this object has a non-conflicting URLSegment value.
		$count = 2;
		while(!$this->validURLSegment()) {
			$this->URLSegment = preg_replace('/-[0-9]+$/', null, $this->URLSegment) . '-' . $count;
			$count++;
		}

		$this->syncLinkTracking();

		// Check to see if we've only altered fields that shouldn't affect versioning
		$fieldsIgnoredByVersioning = array('HasBrokenLink', 'Status', 'HasBrokenFile', 'ToDo', 'VersionID', 'SaveCount');
		$changedFields = array_keys($this->getChangedFields(true, 2));

		// This more rigorous check is inline with the test that write() does to decide whether or not to write to the
		// DB. We use that to avoid cluttering the system with a migrateVersion() call that doesn't get used
		$oneChangedFields = array_keys($this->getChangedFields(true, 1));

		if($oneChangedFields && !array_diff($changedFields, $fieldsIgnoredByVersioning)) {
			// This will have the affect of preserving the versioning
			$this->migrateVersion($this->Version);
		}
	}

	/**
	 * Trigger synchronisation of link tracking
	 *
	 * {@see SiteTreeLinkTracking::augmentSyncLinkTracking}
	 */
	public function syncLinkTracking() {
		$this->extend('augmentSyncLinkTracking');
	}

	public function onBeforeDelete() {
		parent::onBeforeDelete();

		// If deleting this page, delete all its children.
		if(SiteTree::config()->enforce_strict_hierarchy && $children = $this->AllChildren()) {
			foreach($children as $child) {
				/** @var SiteTree $child */
				$child->delete();
			}
		}
	}

	public function onAfterDelete() {
		// Need to flush cache to avoid outdated versionnumber references
		$this->flushCache();

		// Need to mark pages depending to this one as broken
		$dependentPages = $this->DependentPages();
		if($dependentPages) foreach($dependentPages as $page) {
			// $page->write() calls syncLinkTracking, which does all the hard work for us.
			$page->write();
		}

		parent::onAfterDelete();
	}

	public function flushCache($persistent = true) {
		parent::flushCache($persistent);
		$this->_cache_statusFlags = null;
	}

	public function validate() {
		$result = parent::validate();

		// Allowed children validation
		$parent = $this->getParent();
		if($parent && $parent->exists()) {
			// No need to check for subclasses or instanceof, as allowedChildren() already
			// deconstructs any inheritance trees already.
			$allowed = $parent->allowedChildren();
			$subject = ($this instanceof VirtualPage && $this->CopyContentFromID)
				? $this->CopyContentFrom()
				: $this;
			if(!in_array($subject->ClassName, $allowed)) {
				$result->addError(
					_t(
						'SiteTree.PageTypeNotAllowed',
						'Page type "{type}" not allowed as child of this parent page',
						array('type' => $subject->i18n_singular_name())
					),
					ValidationResult::TYPE_ERROR,
					'ALLOWED_CHILDREN'
				);
			}
		}

		// "Can be root" validation
		if(!$this->stat('can_be_root') && !$this->ParentID) {
			$result->addError(
				_t(
					'SiteTree.PageTypNotAllowedOnRoot',
					'Page type "{type}" is not allowed on the root level',
					array('type' => $this->i18n_singular_name())
				),
				ValidationResult::TYPE_ERROR,
				'CAN_BE_ROOT'
			);
		}

		return $result;
	}

	/**
	 * Returns true if this object has a URLSegment value that does not conflict with any other objects. This method
	 * checks for:
	 *  - A page with the same URLSegment that has a conflict
	 *  - Conflicts with actions on the parent page
	 *  - A conflict caused by a root page having the same URLSegment as a class name
	 *
	 * @return bool
	 */
	public function validURLSegment() {
		if(self::config()->nested_urls && $parent = $this->Parent()) {
			if($controller = ModelAsController::controller_for($parent)) {
				if($controller instanceof Controller && $controller->hasAction($this->URLSegment)) return false;
			}
		}

		if(!self::config()->nested_urls || !$this->ParentID) {
			if(class_exists($this->URLSegment) && is_subclass_of($this->URLSegment, 'SilverStripe\\Control\\RequestHandler')) return false;
		}

		// Filters by url, id, and parent
		$filter = array('"SiteTree"."URLSegment"' => $this->URLSegment);
		if($this->ID) {
			$filter['"SiteTree"."ID" <> ?'] = $this->ID;
		}
		if(self::config()->nested_urls) {
			$filter['"SiteTree"."ParentID"'] = $this->ParentID ? $this->ParentID : 0;
		}

		$votes = array_filter(
			(array)$this->extend('augmentValidURLSegment'),
			function($v) {return !is_null($v);}
		);
		if($votes) {
			return min($votes);
		}

		// Check existence
		$existingPage = DataObject::get_one(self::class, $filter);
		if ($existingPage) return false;

		return !($existingPage);
		}

	/**
	 * Generate a URL segment based on the title provided.
	 *
	 * If {@link Extension}s wish to alter URL segment generation, they can do so by defining
	 * updateURLSegment(&$url, $title).  $url will be passed by reference and should be modified. $title will contain
	 * the title that was originally used as the source of this generated URL. This lets extensions either start from
	 * scratch, or incrementally modify the generated URL.
	 *
	 * @param string $title Page title
	 * @return string Generated url segment
	 */
	public function generateURLSegment($title){
		$filter = URLSegmentFilter::create();
		$t = $filter->filter($title);

		// Fallback to generic page name if path is empty (= no valid, convertable characters)
		if(!$t || $t == '-' || $t == '-1') $t = "page-$this->ID";

		// Hook for extensions
		$this->extend('updateURLSegment', $t, $title);

		return $t;
	}

	/**
	 * Gets the URL segment for the latest draft version of this page.
	 *
	 * @return string
	 */
	public function getStageURLSegment() {
		$stageRecord = Versioned::get_one_by_stage(self::class, Versioned::DRAFT, array(
			'"SiteTree"."ID"' => $this->ID
		));
		return ($stageRecord) ? $stageRecord->URLSegment : null;
	}

	/**
	 * Gets the URL segment for the currently published version of this page.
	 *
	 * @return string
	 */
	public function getLiveURLSegment() {
		$liveRecord = Versioned::get_one_by_stage(self::class, Versioned::LIVE, array(
			'"SiteTree"."ID"' => $this->ID
		));
		return ($liveRecord) ? $liveRecord->URLSegment : null;
	}

	/**
	 * Returns the pages that depend on this page. This includes virtual pages, pages that link to it, etc.
	 *
	 * @param bool $includeVirtuals Set to false to exlcude virtual pages.
	 * @return ArrayList
	 */
	public function DependentPages($includeVirtuals = true) {
		if(class_exists('Subsite')) {
			$origDisableSubsiteFilter = Subsite::$disable_subsite_filter;
			Subsite::disable_subsite_filter(true);
		}

		// Content links
		$items = new ArrayList();

		// We merge all into a regular SS_List, because DataList doesn't support merge
		if($contentLinks = $this->BackLinkTracking()) {
			$linkList = new ArrayList();
			foreach($contentLinks as $item) {
				$item->DependentLinkType = 'Content link';
				$linkList->push($item);
			}
			$items->merge($linkList);
		}

		// Virtual pages
		if($includeVirtuals) {
			$virtuals = $this->VirtualPages();
			if($virtuals) {
				$virtualList = new ArrayList();
				foreach($virtuals as $item) {
					$item->DependentLinkType = 'Virtual page';
					$virtualList->push($item);
				}
				$items->merge($virtualList);
			}
		}

		// Redirector pages
		$redirectors = RedirectorPage::get()->where(array(
			'"RedirectorPage"."RedirectionType"' => 'Internal',
			'"RedirectorPage"."LinkToID"' => $this->ID
		));
		if($redirectors) {
			$redirectorList = new ArrayList();
			foreach($redirectors as $item) {
				$item->DependentLinkType = 'Redirector page';
				$redirectorList->push($item);
			}
			$items->merge($redirectorList);
		}

		if(class_exists('Subsite')) {
			Subsite::disable_subsite_filter($origDisableSubsiteFilter);
		}

		return $items;
	}

	/**
	 * Return all virtual pages that link to this page.
	 *
	 * @return DataList
	 */
	public function VirtualPages() {
		$pages = parent::VirtualPages();

		// Disable subsite filter for these pages
		if($pages instanceof DataList) {
			return $pages->setDataQueryParam('Subsite.filter', false);
		} else {
			return $pages;
		}
	}

	/**
	 * Returns a FieldList with which to create the main editing form.
	 *
	 * You can override this in your child classes to add extra fields - first get the parent fields using
	 * parent::getCMSFields(), then use addFieldToTab() on the FieldList.
	 *
	 * See {@link getSettingsFields()} for a different set of fields concerned with configuration aspects on the record,
	 * e.g. access control.
	 *
	 * @return FieldList The fields to be displayed in the CMS
	 */
	public function getCMSFields() {
		// Status / message
		// Create a status message for multiple parents
		if($this->ID && is_numeric($this->ID)) {
			$linkedPages = $this->VirtualPages();

			$parentPageLinks = array();

			if($linkedPages->count() > 0) {
				/** @var VirtualPage $linkedPage */
				foreach($linkedPages as $linkedPage) {
					$parentPage = $linkedPage->Parent();
					if($parentPage && $parentPage->exists()) {
						$link = Convert::raw2att($parentPage->CMSEditLink());
						$title = Convert::raw2xml($parentPage->Title);
						} else {
						$link = CMSPageEditController::singleton()->Link('show');
						$title = _t('SiteTree.TOPLEVEL', 'Site Content (Top Level)');
						}
					$parentPageLinks[] = "<a class=\"cmsEditlink\" href=\"{$link}\">{$title}</a>";
				}

				$lastParent = array_pop($parentPageLinks);
				$parentList = "'$lastParent'";

				if(count($parentPageLinks)) {
					$parentList = "'" . implode("', '", $parentPageLinks) . "' and "
						. $parentList;
				}

				$statusMessage[] = _t(
					'SiteTree.APPEARSVIRTUALPAGES',
					"This content also appears on the virtual pages in the {title} sections.",
					array('title' => $parentList)
				);
			}
		}

		if($this->HasBrokenLink || $this->HasBrokenFile) {
			$statusMessage[] = _t('SiteTree.HASBROKENLINKS', "This page has broken links.");
		}

		$dependentNote = '';
		$dependentTable = new LiteralField('DependentNote', '<p></p>');

		// Create a table for showing pages linked to this one
		$dependentPages = $this->DependentPages();
		$dependentPagesCount = $dependentPages->count();
		if($dependentPagesCount) {
			$dependentColumns = array(
				'Title' => $this->fieldLabel('Title'),
				'AbsoluteLink' => _t('SiteTree.DependtPageColumnURL', 'URL'),
				'DependentLinkType' => _t('SiteTree.DependtPageColumnLinkType', 'Link type'),
			);
			if(class_exists('Subsite')) $dependentColumns['Subsite.Title'] = singleton('Subsite')->i18n_singular_name();

			$dependentNote = new LiteralField('DependentNote', '<p>' . _t('SiteTree.DEPENDENT_NOTE', 'The following pages depend on this page. This includes virtual pages, redirector pages, and pages with content links.') . '</p>');
			$dependentTable = GridField::create(
				'DependentPages',
				false,
				$dependentPages
			);
			/** @var GridFieldDataColumns $dataColumns */
			$dataColumns = $dependentTable->getConfig()->getComponentByType('SilverStripe\\Forms\\GridField\\GridFieldDataColumns');
			$dataColumns
				->setDisplayFields($dependentColumns)
				->setFieldFormatting(array(
					'Title' => function($value, &$item) {
						return sprintf(
							'<a href="admin/pages/edit/show/%d">%s</a>',
							(int)$item->ID,
							Convert::raw2xml($item->Title)
						);
					},
					'AbsoluteLink' => function($value, &$item) {
						return sprintf(
							'<a href="%s" target="_blank">%s</a>',
							Convert::raw2xml($value),
							Convert::raw2xml($value)
						);
					}
				));
		}

		$baseLink = Controller::join_links (
			Director::absoluteBaseURL(),
			(self::config()->nested_urls && $this->ParentID ? $this->Parent()->RelativeLink(true) : null)
		);

		$urlsegment = SiteTreeURLSegmentField::create("URLSegment", $this->fieldLabel('URLSegment'))
			->setURLPrefix($baseLink)
			->setDefaultURL($this->generateURLSegment(_t(
				'CMSMain.NEWPAGE',
				array('pagetype' => $this->i18n_singular_name())
			)));
		$helpText = (self::config()->nested_urls && $this->Children()->count())
			? $this->fieldLabel('LinkChangeNote')
			: '';
		if(!Config::inst()->get('SilverStripe\\View\\Parsers\\URLSegmentFilter', 'default_allow_multibyte')) {
			$helpText .= _t('SiteTreeURLSegmentField.HelpChars', ' Special characters are automatically converted or removed.');
		}
		$urlsegment->setHelpText($helpText);

		$fields = new FieldList(
			$rootTab = new TabSet("Root",
				$tabMain = new Tab('Main',
					new TextField("Title", $this->fieldLabel('Title')),
					$urlsegment,
					new TextField("MenuTitle", $this->fieldLabel('MenuTitle')),
					$htmlField = new HTMLEditorField("Content", _t('SiteTree.HTMLEDITORTITLE', "Content", 'HTML editor title')),
					ToggleCompositeField::create('Metadata', _t('SiteTree.MetadataToggle', 'Metadata'),
						array(
							$metaFieldDesc = new TextareaField("MetaDescription", $this->fieldLabel('MetaDescription')),
							$metaFieldExtra = new TextareaField("ExtraMeta",$this->fieldLabel('ExtraMeta'))
						)
					)->setHeadingLevel(4)
				),
				$tabDependent = new Tab('Dependent',
					$dependentNote,
					$dependentTable
				)
			)
		);
		$htmlField->addExtraClass('stacked');

		// Help text for MetaData on page content editor
		$metaFieldDesc
			->setRightTitle(
				_t(
					'SiteTree.METADESCHELP',
					"Search engines use this content for displaying search results (although it will not influence their ranking)."
				)
			)
			->addExtraClass('help');
		$metaFieldExtra
			->setRightTitle(
				_t(
					'SiteTree.METAEXTRAHELP',
					"HTML tags for additional meta information. For example &lt;meta name=\"customName\" content=\"your custom content here\" /&gt;"
				)
			)
			->addExtraClass('help');

		// Conditional dependent pages tab
		if($dependentPagesCount) $tabDependent->setTitle(_t('SiteTree.TABDEPENDENT', "Dependent pages") . " ($dependentPagesCount)");
		else $fields->removeFieldFromTab('Root', 'Dependent');

		$tabMain->setTitle(_t('SiteTree.TABCONTENT', "Main Content"));

		if($this->ObsoleteClassName) {
			$obsoleteWarning = _t(
				'SiteTree.OBSOLETECLASS',
				"This page is of obsolete type {type}. Saving will reset its type and you may lose data",
				array('type' => $this->ObsoleteClassName)
			);

			$fields->addFieldToTab(
				"Root.Main",
				new LiteralField("ObsoleteWarningHeader", "<p class=\"message warning\">$obsoleteWarning</p>"),
				"Title"
			);
		}

		if(file_exists(BASE_PATH . '/install.php')) {
			$fields->addFieldToTab("Root.Main", new LiteralField("InstallWarningHeader",
				"<p class=\"message warning\">" . _t("SiteTree.REMOVE_INSTALL_WARNING",
				"Warning: You should remove install.php from this SilverStripe install for security reasons.")
				. "</p>"), "Title");
		}

		if(self::$runCMSFieldsExtensions) {
			$this->extend('updateCMSFields', $fields);
		}

		return $fields;
	}


	/**
	 * Returns fields related to configuration aspects on this record, e.g. access control. See {@link getCMSFields()}
	 * for content-related fields.
	 *
	 * @return FieldList
	 */
	public function getSettingsFields() {
		$groupsMap = array();
		foreach(Group::get() as $group) {
			// Listboxfield values are escaped, use ASCII char instead of &raquo;
			$groupsMap[$group->ID] = $group->getBreadcrumbs(' > ');
		}
		asort($groupsMap);

		$fields = new FieldList(
			$rootTab = new TabSet("Root",
				$tabBehaviour = new Tab('Settings',
					new DropdownField(
						"ClassName",
						$this->fieldLabel('ClassName'),
						$this->getClassDropdown()
					),
					$parentTypeSelector = new CompositeField(
						$parentType = new OptionsetField("ParentType", _t("SiteTree.PAGELOCATION", "Page location"), array(
							"root" => _t("SiteTree.PARENTTYPE_ROOT", "Top-level page"),
							"subpage" => _t("SiteTree.PARENTTYPE_SUBPAGE", "Sub-page underneath a parent page"),
						)),
						$parentIDField = new TreeDropdownField("ParentID", $this->fieldLabel('ParentID'), self::class, 'ID', 'MenuTitle')
					),
					$visibility = new FieldGroup(
						new CheckboxField("ShowInMenus", $this->fieldLabel('ShowInMenus')),
						new CheckboxField("ShowInSearch", $this->fieldLabel('ShowInSearch'))
					),
					$viewersOptionsField = new OptionsetField(
						"CanViewType",
						_t('SiteTree.ACCESSHEADER', "Who can view this page?")
					),
					$viewerGroupsField = ListboxField::create("ViewerGroups", _t('SiteTree.VIEWERGROUPS', "Viewer Groups"))
						->setSource($groupsMap)
						->setAttribute(
							'data-placeholder',
							_t('SiteTree.GroupPlaceholder', 'Click to select group')
						),
					$editorsOptionsField = new OptionsetField(
						"CanEditType",
						_t('SiteTree.EDITHEADER', "Who can edit this page?")
					),
					$editorGroupsField = ListboxField::create("EditorGroups", _t('SiteTree.EDITORGROUPS', "Editor Groups"))
						->setSource($groupsMap)
						->setAttribute(
							'data-placeholder',
							_t('SiteTree.GroupPlaceholder', 'Click to select group')
						)
				)
			)
		);

		$parentType->addExtraClass('noborder');
		$visibility->setTitle($this->fieldLabel('Visibility'));


		// This filter ensures that the ParentID dropdown selection does not show this node,
		// or its descendents, as this causes vanishing bugs
		$parentIDField->setFilterFunction(create_function('$node', "return \$node->ID != {$this->ID};"));
		$parentTypeSelector->addExtraClass('parentTypeSelector');

		$tabBehaviour->setTitle(_t('SiteTree.TABBEHAVIOUR', "Behavior"));

		// Make page location fields read-only if the user doesn't have the appropriate permission
		if(!Permission::check("SITETREE_REORGANISE")) {
			$fields->makeFieldReadonly('ParentType');
			if($this->getParentType() === 'root') {
				$fields->removeByName('ParentID');
			} else {
				$fields->makeFieldReadonly('ParentID');
			}
		}

		$viewersOptionsSource = array();
		$viewersOptionsSource["Inherit"] = _t('SiteTree.INHERIT', "Inherit from parent page");
		$viewersOptionsSource["Anyone"] = _t('SiteTree.ACCESSANYONE', "Anyone");
		$viewersOptionsSource["LoggedInUsers"] = _t('SiteTree.ACCESSLOGGEDIN', "Logged-in users");
		$viewersOptionsSource["OnlyTheseUsers"] = _t('SiteTree.ACCESSONLYTHESE', "Only these people (choose from list)");
		$viewersOptionsField->setSource($viewersOptionsSource);

		$editorsOptionsSource = array();
		$editorsOptionsSource["Inherit"] = _t('SiteTree.INHERIT', "Inherit from parent page");
		$editorsOptionsSource["LoggedInUsers"] = _t('SiteTree.EDITANYONE', "Anyone who can log-in to the CMS");
		$editorsOptionsSource["OnlyTheseUsers"] = _t('SiteTree.EDITONLYTHESE', "Only these people (choose from list)");
		$editorsOptionsField->setSource($editorsOptionsSource);

		if(!Permission::check('SITETREE_GRANT_ACCESS')) {
			$fields->makeFieldReadonly($viewersOptionsField);
			if($this->CanViewType == 'OnlyTheseUsers') {
				$fields->makeFieldReadonly($viewerGroupsField);
			} else {
				$fields->removeByName('ViewerGroups');
			}

			$fields->makeFieldReadonly($editorsOptionsField);
			if($this->CanEditType == 'OnlyTheseUsers') {
				$fields->makeFieldReadonly($editorGroupsField);
			} else {
				$fields->removeByName('EditorGroups');
			}
		}

		if(self::$runCMSFieldsExtensions) {
			$this->extend('updateSettingsFields', $fields);
		}

		return $fields;
	}

	/**
	 * @param bool $includerelations A boolean value to indicate if the labels returned should include relation fields
	 * @return array
	 */
	public function fieldLabels($includerelations = true) {
		$cacheKey = static::class . '_' . $includerelations;
		if(!isset(self::$_cache_field_labels[$cacheKey])) {
			$labels = parent::fieldLabels($includerelations);
			$labels['Title'] = _t('SiteTree.PAGETITLE', "Page name");
			$labels['MenuTitle'] = _t('SiteTree.MENUTITLE', "Navigation label");
			$labels['MetaDescription'] = _t('SiteTree.METADESC', "Meta Description");
			$labels['ExtraMeta'] = _t('SiteTree.METAEXTRA', "Custom Meta Tags");
			$labels['ClassName'] = _t('SiteTree.PAGETYPE', "Page type", 'Classname of a page object');
			$labels['ParentType'] = _t('SiteTree.PARENTTYPE', "Page location");
			$labels['ParentID'] = _t('SiteTree.PARENTID', "Parent page");
			$labels['ShowInMenus'] =_t('SiteTree.SHOWINMENUS', "Show in menus?");
			$labels['ShowInSearch'] = _t('SiteTree.SHOWINSEARCH', "Show in search?");
			$labels['ProvideComments'] = _t('SiteTree.ALLOWCOMMENTS', "Allow comments on this page?");
			$labels['ViewerGroups'] = _t('SiteTree.VIEWERGROUPS', "Viewer Groups");
			$labels['EditorGroups'] = _t('SiteTree.EDITORGROUPS', "Editor Groups");
			$labels['URLSegment'] = _t('SiteTree.URLSegment', 'URL Segment', 'URL for this page');
			$labels['Content'] = _t('SiteTree.Content', 'Content', 'Main HTML Content for a page');
			$labels['CanViewType'] = _t('SiteTree.Viewers', 'Viewers Groups');
			$labels['CanEditType'] = _t('SiteTree.Editors', 'Editors Groups');
			$labels['Comments'] = _t('SiteTree.Comments', 'Comments');
			$labels['Visibility'] = _t('SiteTree.Visibility', 'Visibility');
			$labels['LinkChangeNote'] = _t (
				'SiteTree.LINKCHANGENOTE', 'Changing this page\'s link will also affect the links of all child pages.'
			);

			if($includerelations){
				$labels['Parent'] = _t('SiteTree.has_one_Parent', 'Parent Page', 'The parent page in the site hierarchy');
				$labels['LinkTracking'] = _t('SiteTree.many_many_LinkTracking', 'Link Tracking');
				$labels['ImageTracking'] = _t('SiteTree.many_many_ImageTracking', 'Image Tracking');
				$labels['BackLinkTracking'] = _t('SiteTree.many_many_BackLinkTracking', 'Backlink Tracking');
			}

			self::$_cache_field_labels[$cacheKey] = $labels;
		}

		return self::$_cache_field_labels[$cacheKey];
	}

	/**
	 * Get the actions available in the CMS for this page - eg Save, Publish.
	 *
	 * Frontend scripts and styles know how to handle the following FormFields:
	 * - top-level FormActions appear as standalone buttons
	 * - top-level CompositeField with FormActions within appear as grouped buttons
	 * - TabSet & Tabs appear as a drop ups
	 * - FormActions within the Tab are restyled as links
	 * - major actions can provide alternate states for richer presentation (see ssui.button widget extension)
	 *
	 * @return FieldList The available actions for this page.
	 */
	public function getCMSActions() {
		// Get status of page
		$isOnDraft = $this->isOnDraft();
		$isPublished = $this->isPublished();
		$stagesDiffer = $this->stagesDiffer(Versioned::DRAFT, Versioned::LIVE);

		// Check permissions
		$canPublish = $this->canPublish();
		$canUnpublish = $this->canUnpublish();
		$canEdit = $this->canEdit();

		// Major actions appear as buttons immediately visible as page actions.
		$majorActions = CompositeField::create()->setName('MajorActions');
		$majorActions->setFieldHolderTemplate(get_class($majorActions) . '_holder_buttongroup');

		// Minor options are hidden behind a drop-up and appear as links (although they are still FormActions).
		$rootTabSet = new TabSet('ActionMenus');
		$moreOptions = new Tab(
			'MoreOptions',
			_t('SiteTree.MoreOptions', 'More options', 'Expands a view for more buttons')
		);
		$rootTabSet->push($moreOptions);
		$rootTabSet->addExtraClass('ss-ui-action-tabset action-menus noborder');

		// Render page information into the "more-options" drop-up, on the top.
		$liveRecord = Versioned::get_by_stage(self::class, Versioned::LIVE)->byID($this->ID);
		$infoTemplate = SSViewer::get_templates_by_class(static::class, '_Information', self::class);
		$moreOptions->push(
			new LiteralField('Information',
				$this->customise(array(
					'Live' => $liveRecord,
					'ExistsOnLive' => $isPublished
				))->renderWith($infoTemplate)
			)
		);

		// Add to campaign option if not-archived and has publish permission
		if (($isPublished || $isOnDraft) && $canPublish) {
			$moreOptions->push(AddToCampaignHandler_FormAction::create());
		}

		// "readonly"/viewing version that isn't the current version of the record
		$stageRecord = Versioned::get_by_stage(static::class, Versioned::DRAFT)->byID($this->ID);
		/** @skipUpgrade */
		if($stageRecord && $stageRecord->Version != $this->Version) {
			$moreOptions->push(FormAction::create('email', _t('CMSMain.EMAIL', 'Email')));
			$moreOptions->push(FormAction::create('rollback', _t('CMSMain.ROLLBACK', 'Roll back to this version')));
			$actions = new FieldList(array($majorActions, $rootTabSet));

			// getCMSActions() can be extended with updateCMSActions() on a extension
			$this->extend('updateCMSActions', $actions);
			return $actions;
		}

		// "unpublish"
		if($isPublished && $canPublish && $isOnDraft && $canUnpublish) {
			$moreOptions->push(
				FormAction::create('unpublish', _t('SiteTree.BUTTONUNPUBLISH', 'Unpublish'), 'delete')
					->setDescription(_t('SiteTree.BUTTONUNPUBLISHDESC', 'Remove this page from the published site'))
					->addExtraClass('ss-ui-action-destructive')
			);
		}

		// "rollback"
		if($isOnDraft && $isPublished && $canEdit && $stagesDiffer) {
			$moreOptions->push(
				FormAction::create('rollback', _t('SiteTree.BUTTONCANCELDRAFT', 'Cancel draft changes'))
					->setDescription(_t(
						'SiteTree.BUTTONCANCELDRAFTDESC',
						'Delete your draft and revert to the currently published page'
					))
			);
		}

		// "restore"
		if($canEdit && !$isOnDraft && $isPublished) {
			$majorActions->push(FormAction::create('revert',_t('CMSMain.RESTORE','Restore')));
		}

		// Check if we can restore a deleted page
		// Note: It would be nice to have a canRestore() permission at some point
		if($canEdit && !$isOnDraft && !$isPublished) {
			// Determine if we should force a restore to root (where once it was a subpage)
			$restoreToRoot = $this->isParentArchived();

			// "restore"
			$title = $restoreToRoot
				? _t('CMSMain.RESTORE_TO_ROOT','Restore draft at top level')
				: _t('CMSMain.RESTORE','Restore draft');
			$description = $restoreToRoot
				? _t('CMSMain.RESTORE_TO_ROOT_DESC','Restore the archived version to draft as a top level page')
				: _t('CMSMain.RESTORE_DESC', 'Restore the archived version to draft');
			$majorActions->push(
				FormAction::create('restore', $title)
					->setDescription($description)
					->setAttribute('data-to-root', $restoreToRoot)
					->setAttribute('data-icon', 'decline')
			);
		}

		// If a page is on any stage it can be archived
		if (($isOnDraft || $isPublished) && $this->canArchive()) {
			$title = $isPublished
				? _t('CMSMain.UNPUBLISH_AND_ARCHIVE', 'Unpublish and archive')
				: _t('CMSMain.ARCHIVE', 'Archive');
			$moreOptions->push(
				FormAction::create('archive', $title)
					->addExtraClass('delete ss-ui-action-destructive')
					->setDescription(_t(
						'SiteTree.BUTTONDELETEDESC',
						'Remove from draft/live and send to archive'
					))
			);
		}

		// "save", supports an alternate state that is still clickable, but notifies the user that the action is not needed.
		if ($canEdit && $isOnDraft) {
			$majorActions->push(
				FormAction::create('save', _t('SiteTree.BUTTONSAVED', 'Saved'))
					->setAttribute('data-icon', 'accept')
					->setAttribute('data-icon-alternate', 'addpage')
					->setAttribute('data-text-alternate', _t('CMSMain.SAVEDRAFT','Save draft'))
			);
		}

		if($canPublish && $isOnDraft) {
			// "publish", as with "save", it supports an alternate state to show when action is needed.
			$majorActions->push(
				$publish = FormAction::create('publish', _t('SiteTree.BUTTONPUBLISHED', 'Published'))
					->setAttribute('data-icon', 'accept')
					->setAttribute('data-icon-alternate', 'disk')
					->setAttribute('data-text-alternate', _t('SiteTree.BUTTONSAVEPUBLISH', 'Save & publish'))
			);

			// Set up the initial state of the button to reflect the state of the underlying SiteTree object.
			if($stagesDiffer) {
				$publish->addExtraClass('ss-ui-alternate');
			}
		}

		$actions = new FieldList(array($majorActions, $rootTabSet));

		// Hook for extensions to add/remove actions.
		$this->extend('updateCMSActions', $actions);

		return $actions;
	}

	public function onAfterPublish() {
		// Force live sort order to match stage sort order
		DB::prepared_query('UPDATE "SiteTree_Live"
			SET "Sort" = (SELECT "SiteTree"."Sort" FROM "SiteTree" WHERE "SiteTree_Live"."ID" = "SiteTree"."ID")
			WHERE EXISTS (SELECT "SiteTree"."Sort" FROM "SiteTree" WHERE "SiteTree_Live"."ID" = "SiteTree"."ID") AND "ParentID" = ?',
			array($this->ParentID)
		);
		}

	/**
	 * Update draft dependant pages
	 */
	public function onAfterRevertToLive() {
		// Use an alias to get the updates made by $this->publish
		/** @var SiteTree $stageSelf */
		$stageSelf = Versioned::get_by_stage(self::class, Versioned::DRAFT)->byID($this->ID);
		$stageSelf->writeWithoutVersion();

		// Need to update pages linking to this one as no longer broken
		foreach($stageSelf->DependentPages() as $page) {
			/** @var SiteTree $page */
			$page->writeWithoutVersion();
		}
	}

	/**
	 * Determine if this page references a parent which is archived, and not available in stage
	 *
	 * @return bool True if there is an archived parent
	 */
	protected function isParentArchived() {
		if($parentID = $this->ParentID) {
			/** @var SiteTree $parentPage */
			$parentPage = Versioned::get_latest_version(self::class, $parentID);
			if(!$parentPage || !$parentPage->isOnDraft()) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Restore the content in the active copy of this SiteTree page to the stage site.
	 *
	 * @return self
	 */
	public function doRestoreToStage() {
		$this->invokeWithExtensions('onBeforeRestoreToStage', $this);

		// Ensure that the parent page is restored, otherwise restore to root
		if($this->isParentArchived()) {
			$this->ParentID = 0;
		}

		// if no record can be found on draft stage (meaning it has been "deleted from draft" before),
		// create an empty record
		if(!DB::prepared_query("SELECT \"ID\" FROM \"SiteTree\" WHERE \"ID\" = ?", array($this->ID))->value()) {
			$conn = DB::get_conn();
			if(method_exists($conn, 'allowPrimaryKeyEditing')) $conn->allowPrimaryKeyEditing(self::class, true);
			DB::prepared_query("INSERT INTO \"SiteTree\" (\"ID\") VALUES (?)", array($this->ID));
			if(method_exists($conn, 'allowPrimaryKeyEditing')) $conn->allowPrimaryKeyEditing(self::class, false);
		}

		$oldReadingMode = Versioned::get_reading_mode();
		Versioned::set_stage(Versioned::DRAFT);
		$this->forceChange();
		$this->write();

		/** @var SiteTree $result */
		$result = DataObject::get_by_id(self::class, $this->ID);

		// Need to update pages linking to this one as no longer broken
		foreach($result->DependentPages(false) as $page) {
			// $page->write() calls syncLinkTracking, which does all the hard work for us.
			$page->write();
		}

		Versioned::set_reading_mode($oldReadingMode);

		$this->invokeWithExtensions('onAfterRestoreToStage', $this);

		return $result;
	}

	/**
	 * Check if this page is new - that is, if it has yet to have been written to the database.
	 *
	 * @return bool
	 */
	public function isNew() {
		/**
		 * This check was a problem for a self-hosted site, and may indicate a bug in the interpreter on their server,
		 * or a bug here. Changing the condition from empty($this->ID) to !$this->ID && !$this->record['ID'] fixed this.
		 */
		if(empty($this->ID)) return true;

		if(is_numeric($this->ID)) return false;

		return stripos($this->ID, 'new') === 0;
	}

	/**
	 * Get the class dropdown used in the CMS to change the class of a page. This returns the list of options in the
	 * dropdown as a Map from class name to singular name. Filters by {@link SiteTree->canCreate()}, as well as
	 * {@link SiteTree::$needs_permission}.
	 *
	 * @return array
	 */
	protected function getClassDropdown() {
		$classes = self::page_type_classes();
		$currentClass = null;

		$result = array();
		foreach($classes as $class) {
			$instance = singleton($class);

			// if the current page type is this the same as the class type always show the page type in the list
			if ($this->ClassName != $instance->ClassName) {
				if($instance instanceof HiddenClass) continue;
				if(!$instance->canCreate(null, array('Parent' => $this->ParentID ? $this->Parent() : null))) continue;
			}

			if($perms = $instance->stat('need_permission')) {
				if(!$this->can($perms)) continue;
			}

			$pageTypeName = $instance->i18n_singular_name();

			$currentClass = $class;
			$result[$class] = $pageTypeName;

			// If we're in translation mode, the link between the translated pagetype title and the actual classname
			// might not be obvious, so we add it in parantheses. Example: class "RedirectorPage" has the title
			// "Weiterleitung" in German, so it shows up as "Weiterleitung (RedirectorPage)"
			if(i18n::get_lang_from_locale(i18n::get_locale()) != 'en') {
				$result[$class] = $result[$class] .  " ({$class})";
			}
		}

		// sort alphabetically, and put current on top
		asort($result);
		if($currentClass) {
			$currentPageTypeName = $result[$currentClass];
			unset($result[$currentClass]);
			$result = array_reverse($result);
			$result[$currentClass] = $currentPageTypeName;
			$result = array_reverse($result);
		}

		return $result;
	}

	/**
	 * Returns an array of the class names of classes that are allowed to be children of this class.
	 *
	 * @return string[]
	 */
	public function allowedChildren() {
		$allowedChildren = array();
		$candidates = $this->stat('allowed_children');
		if($candidates && $candidates != "none" && $candidates != "SiteTree_root") {
			foreach($candidates as $candidate) {
				// If a classname is prefixed by "*", such as "*Page", then only that class is allowed - no subclasses.
				// Otherwise, the class and all its subclasses are allowed.
				if(substr($candidate,0,1) == '*') {
					$allowedChildren[] = substr($candidate,1);
				} else {
					$subclasses = ClassInfo::subclassesFor($candidate);
					foreach($subclasses as $subclass) {
						if ($subclass == 'SiteTree_root' || singleton($subclass) instanceof HiddenClass) {
							continue;
						}
						$allowedChildren[] = $subclass;
					}
				}
			}
		}

		return $allowedChildren;
	}

	/**
	 * Returns the class name of the default class for children of this page.
	 *
	 * @return string
	 */
	public function defaultChild() {
		$default = $this->stat('default_child');
		$allowed = $this->allowedChildren();
		if($allowed) {
			if(!$default || !in_array($default, $allowed)) {
				$default = reset($allowed);
			}
			return $default;
		}
		return null;
	}

	/**
	 * Returns the class name of the default class for the parent of this page.
	 *
	 * @return string
	 */
	public function defaultParent() {
		return $this->stat('default_parent');
	}

	/**
	 * Get the title for use in menus for this page. If the MenuTitle field is set it returns that, else it returns the
	 * Title field.
	 *
	 * @return string
	 */
	public function getMenuTitle(){
		if($value = $this->getField("MenuTitle")) {
			return $value;
		} else {
			return $this->getField("Title");
		}
	}


	/**
	 * Set the menu title for this page.
	 *
	 * @param string $value
	 */
	public function setMenuTitle($value) {
		if($value == $this->getField("Title")) {
			$this->setField("MenuTitle", null);
		} else {
			$this->setField("MenuTitle", $value);
		}
	}

	/**
	 * A flag provides the user with additional data about the current page status, for example a "removed from draft"
	 * status. Each page can have more than one status flag. Returns a map of a unique key to a (localized) title for
	 * the flag. The unique key can be reused as a CSS class. Use the 'updateStatusFlags' extension point to customize
	 * the flags.
	 *
	 * Example (simple):
	 *   "deletedonlive" => "Deleted"
	 *
	 * Example (with optional title attribute):
	 *   "deletedonlive" => array('text' => "Deleted", 'title' => 'This page has been deleted')
	 *
	 * @param bool $cached Whether to serve the fields from cache; false regenerate them
	 * @return array
	 */
	public function getStatusFlags($cached = true) {
		if(!$this->_cache_statusFlags || !$cached) {
			$flags = array();
			if($this->isOnLiveOnly()) {
				$flags['removedfromdraft'] = array(
					'text' => _t('SiteTree.ONLIVEONLYSHORT', 'On live only'),
					'title' => _t('SiteTree.ONLIVEONLYSHORTHELP', 'Page is published, but has been deleted from draft'),
				);
			} elseif ($this->isArchived()) {
				$flags['archived'] = array(
					'text' => _t('SiteTree.ARCHIVEDPAGESHORT', 'Archived'),
					'title' => _t('SiteTree.ARCHIVEDPAGEHELP', 'Page is removed from draft and live'),
				);
			} else if($this->isOnDraftOnly()) {
				$flags['addedtodraft'] = array(
					'text' => _t('SiteTree.ADDEDTODRAFTSHORT', 'Draft'),
					'title' => _t('SiteTree.ADDEDTODRAFTHELP', "Page has not been published yet")
				);
			} else if($this->isModifiedOnDraft()) {
				$flags['modified'] = array(
					'text' => _t('SiteTree.MODIFIEDONDRAFTSHORT', 'Modified'),
					'title' => _t('SiteTree.MODIFIEDONDRAFTHELP', 'Page has unpublished changes'),
				);
			}

			$this->extend('updateStatusFlags', $flags);

			$this->_cache_statusFlags = $flags;
		}

		return $this->_cache_statusFlags;
	}

	/**
	 * getTreeTitle will return three <span> html DOM elements, an empty <span> with the class 'jstree-pageicon' in
	 * front, following by a <span> wrapping around its MenutTitle, then following by a <span> indicating its
	 * publication status.
	 *
	 * @return string An HTML string ready to be directly used in a template
	 */
	public function getTreeTitle() {
		// Build the list of candidate children
		$children = array();
		$candidates = static::page_type_classes();
		foreach($this->allowedChildren() as $childClass) {
			if(!in_array($childClass, $candidates)) continue;
			$child = singleton($childClass);
			if($child->canCreate(null, array('Parent' => $this))) {
				$children[$childClass] = $child->i18n_singular_name();
			}
		}
		$flags = $this->getStatusFlags();
		$treeTitle = sprintf(
			"<span class=\"jstree-pageicon\"></span><span class=\"item\" data-allowedchildren=\"%s\">%s</span>",
			Convert::raw2att(Convert::raw2json($children)),
			Convert::raw2xml(str_replace(array("\n","\r"),"",$this->MenuTitle))
		);
		foreach($flags as $class => $data) {
			if(is_string($data)) $data = array('text' => $data);
			$treeTitle .= sprintf(
				"<span class=\"badge %s\"%s>%s</span>",
				'status-' . Convert::raw2xml($class),
				(isset($data['title'])) ? sprintf(' title="%s"', Convert::raw2xml($data['title'])) : '',
				Convert::raw2xml($data['text'])
			);
		}

		return $treeTitle;
	}

	/**
	 * Returns the page in the current page stack of the given level. Level(1) will return the main menu item that
	 * we're currently inside, etc.
	 *
	 * @param int $level
	 * @return SiteTree
	 */
	public function Level($level) {
		$parent = $this;
		$stack = array($parent);
		while(($parent = $parent->Parent()) && $parent->exists()) {
			array_unshift($stack, $parent);
		}

		return isset($stack[$level-1]) ? $stack[$level-1] : null;
	}

	/**
	 * Gets the depth of this page in the sitetree, where 1 is the root level
	 *
	 * @return int
	 */
	public function getPageLevel() {
		if($this->ParentID) {
			return 1 + $this->Parent()->getPageLevel();
		}
		return 1;
	}

	/**
	 * Find the controller name by our convention of {$ModelClass}_Controller
	 *
	 * @return string
	 */
	public function getControllerName() {
		//default controller for SiteTree objects
		$controller = ContentController::class;

		//go through the ancestry for this class looking for
		$ancestry = ClassInfo::ancestry(static::class);
		// loop over the array going from the deepest descendant (ie: the current class) to SiteTree
		while ($class = array_pop($ancestry)) {
			//we don't need to go any deeper than the SiteTree class
			if ($class == SiteTree::class) {
				break;
			}
			//if we have a class of "{$ClassName}_Controller" then we found our controller
			if (class_exists($candidate = sprintf('%s_Controller', $class))) {
				$controller = $candidate;
				break;
			}
		}

		return $controller;
	}

	/**
	 * Return the CSS classes to apply to this node in the CMS tree.
	 *
	 * @param string $numChildrenMethod
	 * @return string
	 */
	public function CMSTreeClasses($numChildrenMethod="numChildren") {
		$classes = sprintf('class-%s', static::class);
		if($this->HasBrokenFile || $this->HasBrokenLink) {
			$classes .= " BrokenLink";
		}

		if(!$this->canAddChildren()) {
			$classes .= " nochildren";
		}

		if(!$this->canEdit() && !$this->canAddChildren()) {
			if (!$this->canView()) {
				$classes .= " disabled";
			} else {
				$classes .= " edit-disabled";
			}
		}

		if(!$this->ShowInMenus) {
			$classes .= " notinmenu";
		}

		//TODO: Add integration
		/*
		if($this->hasExtension('Translatable') && $controller->Locale != Translatable::default_locale() && !$this->isTranslation())
			$classes .= " untranslated ";
		*/
		$classes .= $this->markingClasses($numChildrenMethod);

		return $classes;
	}

	/**
	 * Stops extendCMSFields() being called on getCMSFields(). This is useful when you need access to fields added by
	 * subclasses of SiteTree in a extension. Call before calling parent::getCMSFields(), and reenable afterwards.
	 */
	static public function disableCMSFieldsExtensions() {
		self::$runCMSFieldsExtensions = false;
	}

	/**
	 * Reenables extendCMSFields() being called on getCMSFields() after it has been disabled by
	 * disableCMSFieldsExtensions().
	 */
	static public function enableCMSFieldsExtensions() {
		self::$runCMSFieldsExtensions = true;
	}

	public function providePermissions() {
		return array(
			'SITETREE_GRANT_ACCESS' => array(
				'name' => _t('SiteTree.PERMISSION_GRANTACCESS_DESCRIPTION', 'Manage access rights for content'),
				'help' => _t('SiteTree.PERMISSION_GRANTACCESS_HELP',  'Allow setting of page-specific access restrictions in the "Pages" section.'),
				'category' => _t('Permissions.PERMISSIONS_CATEGORY', 'Roles and access permissions'),
				'sort' => 100
			),
			'SITETREE_VIEW_ALL' => array(
				'name' => _t('SiteTree.VIEW_ALL_DESCRIPTION', 'View any page'),
				'category' => _t('Permissions.CONTENT_CATEGORY', 'Content permissions'),
				'sort' => -100,
				'help' => _t('SiteTree.VIEW_ALL_HELP', 'Ability to view any page on the site, regardless of the settings on the Access tab.  Requires the "Access to \'Pages\' section" permission')
			),
			'SITETREE_EDIT_ALL' => array(
				'name' => _t('SiteTree.EDIT_ALL_DESCRIPTION', 'Edit any page'),
				'category' => _t('Permissions.CONTENT_CATEGORY', 'Content permissions'),
				'sort' => -50,
				'help' => _t('SiteTree.EDIT_ALL_HELP', 'Ability to edit any page on the site, regardless of the settings on the Access tab.  Requires the "Access to \'Pages\' section" permission')
			),
			'SITETREE_REORGANISE' => array(
				'name' => _t('SiteTree.REORGANISE_DESCRIPTION', 'Change site structure'),
				'category' => _t('Permissions.CONTENT_CATEGORY', 'Content permissions'),
				'help' => _t('SiteTree.REORGANISE_HELP', 'Rearrange pages in the site tree through drag&drop.'),
				'sort' => 100
			),
			'VIEW_DRAFT_CONTENT' => array(
				'name' => _t('SiteTree.VIEW_DRAFT_CONTENT', 'View draft content'),
				'category' => _t('Permissions.CONTENT_CATEGORY', 'Content permissions'),
				'help' => _t('SiteTree.VIEW_DRAFT_CONTENT_HELP', 'Applies to viewing pages outside of the CMS in draft mode. Useful for external collaborators without CMS access.'),
				'sort' => 100
			)
		);
	}

	/**
	 * Return the translated Singular name.
	 *
	 * @return string
	 */
	public function i18n_singular_name() {
		// Convert 'Page' to 'SiteTree' for correct localization lookups
		/** @skipUpgrade */
		// @todo When we namespace translations, change 'SiteTree' to FQN of the class
		$class = (static::class == 'Page' || static::class === self::class)
			? 'SiteTree'
			: static::class;
		return _t($class.'.SINGULARNAME', $this->singular_name());
	}

	/**
	 * Overloaded to also provide entities for 'Page' class which is usually located in custom code, hence textcollector
	 * picks it up for the wrong folder.
	 *
	 * @return array
	 */
	public function provideI18nEntities() {
		$entities = parent::provideI18nEntities();

		if(isset($entities['Page.SINGULARNAME'])) $entities['Page.SINGULARNAME'][3] = CMS_DIR;
		if(isset($entities['Page.PLURALNAME'])) $entities['Page.PLURALNAME'][3] = CMS_DIR;

		$entities[static::class . '.DESCRIPTION'] = array(
			$this->stat('description'),
			'Description of the page type (shown in the "add page" dialog)'
		);

		$entities['SiteTree.SINGULARNAME'][0] = 'Page';
		$entities['SiteTree.PLURALNAME'][0] = 'Pages';

		return $entities;
	}

	/**
	 * Returns 'root' if the current page has no parent, or 'subpage' otherwise
	 *
	 * @return string
	 */
	public function getParentType() {
		return $this->ParentID == 0 ? 'root' : 'subpage';
	}

	/**
	 * Clear the permissions cache for SiteTree
	 */
	public static function reset() {
		self::$cache_permissions = array();
	}

	static public function on_db_reset() {
		self::$cache_permissions = array();
	}

}