<?php
/**
 * Feed retrieval, parsing, and manipulation
 */
class Feed {

    /**
     * Parse a feed into an XML tree
     * @param string $content The feed's RSS content
     * @return array|SimpleXMLElement[]|string[] [ 'ok' => feed ] if successful, [ 'error' => message] if not
     */
    public static function parseFeed(string $content): array {
        try {
            return [ 'ok' => new SimpleXMLElement($content) ];
        } catch (Exception $ex) {
            return [ 'error' => $ex->getMessage() ];
        }
    }

    /**
     * Retrieve the feed
     * @param string $url
     * @return array|SimpleXMLElement[]|string[] [ 'ok' => feedXml, 'url' => actualUrl ] if successful, [ 'error' => message ] if not
     */
    public static function retrieveFeed(string $url): array {
        $feedReq = curl_init($url);
        curl_setopt($feedReq, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($feedReq, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($feedReq, CURLOPT_CONNECTTIMEOUT, 5);
        curl_setopt($feedReq, CURLOPT_TIMEOUT,        15);

        $feedContent = curl_exec($feedReq);

        $result = array();
        $error  = curl_error($feedReq);
        $code   = curl_getinfo($feedReq, CURLINFO_RESPONSE_CODE);
        if ($error) {
            $result['error'] = $error;
        } else if ($code == 200) {
            $parsed = self::parseFeed($feedContent);
            if (array_key_exists('error', $parsed)) {
                $result['error'] = $parsed['error'];
            } else {
                $result['ok']  = $parsed['ok'];
                $result['url'] = curl_getinfo($feedReq, CURLINFO_EFFECTIVE_URL);
            }
        } else {
            $result['error'] = "HTTP Code $code: $feedContent";
        }

        curl_close($feedReq);
        return $result;
    }

    /**
     * Add an RSS feed
     * @param string $url The URL of the RSS feed to add
     * @return array [ 'ok' => true ] if successful, [ 'error' => message ] if not
     */
    public static function add(string $url): array {
        $feed = self::retrieveFeed($url);
        if (array_key_exists('error', $feed)) return $feed;

        $channel = $feed['ok']->channel;
        $feedId = Data::addFeed($feed['url'], (string) $channel->title, (string) $channel->lastBuildDate);

        return [ 'ok' => true ];
    }
}