silverstripe-blog/code/extensions/BlogFilter.php

<?php

/**
 * This class is responsible for filtering the SiteTree when necessary and also overlaps into
 * filtering only published posts.
 *
 * @package silverstripe
 * @subpackage blog
 */
class BlogFilter extends Lumberjack {
	/**
	 * {@inheritdoc}
	 */
	public function stageChildren($showAll = false) {
		$staged = parent::stageChildren($showAll);

		if(!$this->shouldFilter() && $this->subclassForBlog() && !Permission::check('VIEW_DRAFT_CONTENT')) {
			$stage = Versioned::current_stage();

			if($stage == 'Stage') {
				$stage = '';
			} elseif($stage) {
				$stage = '_' . $stage;
			}

			$dataQuery = $staged->dataQuery()
				->innerJoin('BlogPost', sprintf('BlogPost%s.ID = SiteTree%s.ID', $stage, $stage))
				->where(sprintf('PublishDate < \'%s\'', Convert::raw2sql(SS_Datetime::now())));

			$staged = $staged->setDataQuery($dataQuery);
		}

		return $staged;
	}

	/**
	 * @return bool
	 */
	protected function subclassForBlog() {
		return in_array(get_class($this->owner), ClassInfo::subClassesFor('Blog'));
	}

	/**
	 * {@inheritdoc}
	 */
	public function liveChildren($showAll = false, $onlyDeletedFromStage = false) {
		$staged = parent::liveChildren($showAll, $onlyDeletedFromStage);

		if(!$this->shouldFilter() && $this->isBlog() && !Permission::check('VIEW_DRAFT_CONTENT')) {
			$dataQuery = $staged->dataQuery()
				->innerJoin('BlogPost', 'BlogPost_Live.ID = SiteTree_Live.ID')
				->where(sprintf('PublishDate < \'%s\'', Convert::raw2sql(SS_Datetime::now())));

			$staged = $staged->setDataQuery($dataQuery);
		}

		return $staged;
	}

	/**
	 * @return bool
	 */
	protected function isBlog() {
		return $this->owner instanceof Blog;
	}

	/**
	 * {@inheritdoc}
	 */
	public function updateCMSFields(FieldList $fields) {
		$excluded = $this->owner->getExcludedSiteTreeClassNames();

		if(!empty($excluded)) {
			$pages = SiteTree::get()->filter(array(
				'ParentID' => $this->owner->ID,
				'ClassName' => $excluded
			))->sort('SiteTree.Created DESC');

			$gridField = new BlogFilter_GridField(
				'ChildPages',
				$this->getLumberjackTitle(),
				$pages,
				$this->getLumberjackGridFieldConfig()
			);

			$tab = new Tab('ChildPages', $this->getLumberjackTitle(), $gridField);

			$fields->insertBefore($tab, 'Main');
		}
	}
}


/**
 * Enables children of non-editable pages to be edited.
 */
class BlogFilter_GridField extends GridField {
	/**
	 * @param FormTransformation $transformation
	 *
	 * @return $this
	 */
	public function transform(FormTransformation $transformation) {
		return $this;
	}
}