silverstripe-blog/code/widgets/BlogArchiveWidget.php

<?php

if(!class_exists('Widget')) {
	return;
}

/**
 * @method Blog Blog()
 *
 * @property string $ArchiveType
 * @property int $NumberToDisplay
 */
class BlogArchiveWidget extends Widget {
	/**
	 * @var string
	 */
	private static $title = 'Archive';

	/**
	 * @var string
	 */
	private static $cmsTitle = 'Archive';

	/**
	 * @var string
	 */
	private static $description = 'Displays an archive list of posts.';

	/**
	 * @var array
	 */
	private static $db = array(
		'NumberToDisplay' => 'Int',
		'ArchiveType' => 'Enum("Monthly,Yearly", "Monthly")',
	);

	/**
	 * @var array
	 */
	private static $defaults = array(
		'NumberOfMonths' => 12,
	);

	/**
	 * @var array
	 */
	private static $has_one = array(
		'Blog' => 'Blog',
	);

	/**
	 * {@inheritdoc}
	 */
	public function getCMSFields() {
		$self = &$this;

		$this->beforeUpdateCMSFields(function ($fields) use ($self) {
			$type = $self->dbObject('ArchiveType')->enumValues();

			foreach($type as $k => $v) {
				$type[$k] = _t('BlogArchiveWidget.' . ucfirst(strtolower($v)), $v);
			}

			$fields->merge(array(
				DropdownField::create('BlogID', _t('BlogArchiveWidget.Blog', 'Blog'), Blog::get()->map()),
				DropdownField::create('ArchiveType', _t('BlogArchiveWidget.ArchiveType', 'ArchiveType'), $type),
				NumericField::create('NumberToDisplay', _t('BlogArchiveWidget.NumberToDisplay', 'No. to Display'))
			));
		});

		return parent::getCMSFields();
	}

	/**
	 * Returns a list of months where blog posts are present.
	 *
	 * @return DataList
	 */
	public function getArchive() {
		$query = $this->Blog()->getBlogPosts()->dataQuery();

		if($this->ArchiveType == 'Yearly') {
			$query->groupBy('DATE_FORMAT(PublishDate, "%Y")');
		} else {
			$query->groupBy('DATE_FORMAT(PublishDate, "%Y-%M")');
		}

		$posts = $this->Blog()->getBlogPosts()->setDataQuery($query);

		if($this->NumberToDisplay > 0) {
			$posts = $posts->limit($this->NumberToDisplay);
		}

		$archive = new ArrayList();

		if($posts->count() > 0) {
			foreach($posts as $post) {
				/**
				 * @var BlogPost $post
				 */

				if($this->ArchiveType == 'Yearly') {
					$year = date('Y', strtotime($post->PublishDate));
					$month = null;
					$title = $year;
				} else {
					$year = date('Y', strtotime($post->PublishDate));
					$month = date('m', strtotime($post->PublishDate));
					$title = date('F Y', strtotime($post->PublishDate));
				}

				$archive->push(new ArrayData(array(
					'Title' => $title,
					'Link' => Controller::join_links($this->Blog()->Link('archive'), $year, $month)
				)));
			}
		}

		return $archive;
	}
}

class BlogArchiveWidget_Controller extends Widget_Controller {

}