<?php

/**
 * RSS feed importer.
 *
 * @author     Time.ly Network Inc.
 * @since      2.1
 *
 * @package    AI1EC
 * @subpackage AI1EC.News
 */
class Ai1ec_News_Feed {

    /**
     * Import RSS feed.
     *
     * @param int    $limit Number of entries to fetch.
     * @param string $feed  URI of RSS feed to import.
     *
     * @return array RSS feed entries.
     */
    public function import_feed( $limit = 5, $feed = AI1EC_RSS_FEED ) {
        include_once(
            ABSPATH . WPINC . DIRECTORY_SEPARATOR . 'class-simplepie.php'
        );
        $cache  = $this->get_transient_name( $feed );
        $result = get_site_transient( $cache );
        if ( false === $result || AI1EC_DEBUG ) {
            $result     = $this->fetch_feed( $limit, $feed );
            $expiration = $this->get_expiration( $feed );
            set_site_transient( $cache, $result, $expiration );
        }
        return $result;
    }

    /**
     * Fetch feed w/o caching.
     *
     * @param int    $limit Number of entries to fetch.
     * @param string $feed  URI of RSS feed to import.
     *
     * @return array List of feed entries.
     */
    public function fetch_feed( $limit, $feed ) {
        if ( ! class_exists( 'SimplePie_File' ) ) {
            include_once(
                ABSPATH . WPINC . DIRECTORY_SEPARATOR .'SimplePie'
                . DIRECTORY_SEPARATOR .'File.php'
            );
        }
        $result = array();
        try {
            $file = new SimplePie_File( $feed );
            $feed = new SimplePie();
            $feed->set_raw_data( $file->body );
            $feed->init();
            if ( ! is_wp_error( $feed ) ) {
                $result = $feed->get_items( 0, $limit );
            }
        } catch ( Exception $exception ) {} // discard
        return $result;
    }

    /**
     * Get name to be used for transient.
     *
     * @param string $feed URI of feed to get transien name for.
     *
     * @return string Transient name to use.
     */
    public function get_transient_name( $feed ) {
        return ( AI1EC_RSS_FEED === $feed )
            ? 'ai1ec_rss_feed' :
            'ai1ec_rss_' . substr( md5( $feed ), 5, 8 );
    }

    /**
     * Get expiration time (in seconds) for feed.
     *
     * @param string $feed URI of feed to get transien name for.
     *
     * @return int Number of seconds to keep cached feed output.
     */
    public function get_expiration( $feed ) {
        $expiration = apply_filters(
            'wp_feed_cache_transient_lifetime',
            12 * HOUR_IN_SECONDS,
            $feed
        );
        return $expiration;
    }

}