<?php
/**
 * Akella Featured Content
 *
 * This module allows you to define a subset of posts to be displayed
 * in the theme's Featured Content area.
 */
class Featured_Content {

	/**
	 * The maximum number of posts a Featured Content area can contain.
	 *
	 * We define a default value here but themes can override
	 * this by defining a "max_posts" entry in the second parameter
	 * passed in the call to add_theme_support( 'featured-content' ).
	 *
	 * @see Featured_Content::init()
	 *
	 * @static
	 * @access public
	 * @var int
	 */
	public static $max_posts = 15;

	/**
	 * Instantiate.
	 *
	 * All custom functionality will be hooked into the "init" action.
	 *
	 * @static
	 * @access public
	 */
	public static function setup() {
		add_action( 'init', array( __CLASS__, 'init' ), 30 );
	}

	/**
	 * Conditionally hook into WordPress.
	 *
	 * Theme must declare that they support this module by adding
	 * add_theme_support( 'featured-content' ); during after_setup_theme.
	 *
	 * If no theme support is found there is no need to hook into WordPress.
	 * We'll just return early instead.
	 *
	 * @static
	 * @access public
	 */
	public static function init() {
		$theme_support = get_theme_support( 'featured-content' );

		// Return early if theme does not support Featured Content.
		if ( ! $theme_support ) {
			return;
		}

		/*
		 * An array of named arguments must be passed as the second parameter
		 * of add_theme_support().
		 */
		if ( ! isset( $theme_support[0] ) ) {
			return;
		}

		// Return early if "featured_content_filter" has not been defined.
		if ( ! isset( $theme_support[0]['featured_content_filter'] ) ) {
			return;
		}

		$filter = $theme_support[0]['featured_content_filter'];

		// Theme can override the number of max posts.
		if ( isset( $theme_support[0]['max_posts'] ) ) {
			self::$max_posts = absint( $theme_support[0]['max_posts'] );
		}

		add_filter( $filter,         array( __CLASS__, 'get_featured_posts' ) );
		add_action( 'switch_theme',  array( __CLASS__, 'delete_transient'   ) );
		add_action( 'save_post',     array( __CLASS__, 'delete_transient'   ) );
		add_action( 'pre_get_posts', array( __CLASS__, 'pre_get_posts'      ) );
	}

	/**
	 * Get featured posts.
	 *
	 * @static
	 * @access public
	 *
	 * @return array Array of featured posts.
	 */
	public static function get_featured_posts() {
		$post_ids = self::get_featured_post_ids();

		// No need to query if there is are no featured posts.
		if ( empty( $post_ids ) ) {
			return array();
		}

		$featured_posts = get_posts( array(
			'include'        => $post_ids,
			'posts_per_page' => count( $post_ids ),
		) );

		return $featured_posts;
	}

	/**
	 * Get featured post IDs
	 *
	 * This function will return the an array containing the
	 * post IDs of all featured posts.
	 *
	 * Sets the "featured_content_ids" transient.
	 *
	 * @static
	 * @access public
	 *
	 * @return array Array of post IDs.
	 */
	public static function get_featured_post_ids() {
		// Get array of cached results if they exist.
		$featured_ids = get_transient( 'featured_content_ids' );

		if ( false === $featured_ids ) {
			// Query for featured posts.
			$featured_ids = get_posts( array(
				'fields'           => 'ids',
				'numberposts'      => self::$max_posts,
				'suppress_filters' => false,
				'meta_key'         => 'visibility_settings_select',
				'meta_value'       => 'featured'
			) );

			set_transient( 'featured_content_ids', $featured_ids );
		}

		// Ensure correct format before return.
		return array_map( 'absint', $featured_ids );
	}

	/**
	 * Delete featured content ids transient.
	 *
	 * Hooks in the "save_post" and "switch_theme" action.
	 *
	 * @static
	 * @access public
	 */
	public static function delete_transient() {
		delete_transient( 'featured_content_ids' );
	}

	/**
	 * Exclude featured posts from the home page blog query.
	 *
	 * Filter the home page posts, and remove any featured post ID's from it.
	 * Hooked onto the 'pre_get_posts' action, this changes the parameters of
	 * the query before it gets any posts.
	 *
	 * @static
	 * @access public
	 *
	 * @param WP_Query $query WP_Query object.
	 * @return WP_Query Possibly-modified WP_Query.
	 */
	public static function pre_get_posts( $query ) {

		// Bail if not home or not main query.
		if ( ! $query->is_home() || ! $query->is_main_query() ) {
			return;
		}

		// Bail if the blog page is not the front page.
		if ( 'posts' !== get_option( 'show_on_front' ) ) {
			return;
		}

		$featured = self::get_featured_post_ids();

		// Bail if no featured posts.
		if ( ! $featured ) {
			return;
		}

		// We need to respect post ids already in the blacklist.
		$post__not_in = $query->get( 'post__not_in' );

		if ( ! empty( $post__not_in ) ) {
			$featured = array_merge( (array) $post__not_in, $featured );
			$featured = array_unique( $featured );
		}

		$query->set( 'post__not_in', $featured );
	}
} // Featured_Content

Featured_Content::setup();