<?php

declare(strict_types=1);

final class FeedParser
{
    private static string $nitterAuthToken;

    /** @return Post[] */
    public static function run(array $feedUrls): array
    {
        $multiHandle = curl_multi_init();

        $curlHandles = [];

        foreach ($feedUrls as $feedUrl) {
            $curlHandle = curl_init();

            curl_setopt_array($curlHandle, [
                CURLOPT_URL => $feedUrl,
                CURLOPT_RETURNTRANSFER => true,
                CURLOPT_USERAGENT => 'RSS Feed Reader/1.0',
                CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_2_0,
                CURLOPT_TIMEOUT => 10,
                CURLOPT_CONNECTTIMEOUT => 5,
                CURLOPT_ENCODING => 'gzip',
            ]);

            if (parse_url($feedUrl, PHP_URL_HOST) === 'nitter.poast.org') {
                curl_setopt($curlHandle, CURLOPT_COOKIE, 'res=' . self::getNitterAuthToken());
            }

            curl_multi_add_handle($multiHandle, $curlHandle);

            $curlHandles[] = $curlHandle;
        }

        do {
            $status = curl_multi_exec($multiHandle, $pendingRequests);

            if (curl_multi_select($multiHandle, 0.1) === -1) {
                usleep(5_000);
            }
        } while ($pendingRequests > 0 && $status === CURLM_OK);

        $posts = [];

        foreach ($curlHandles as $handle) {
            $url = curl_getinfo($handle, CURLINFO_EFFECTIVE_URL);
            $httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
            $content = curl_multi_getcontent($handle);

            if ($httpCode === 200) {
                try {
                    $feed = self::getFeed($url, $content);

                    $posts = [...$posts, ...$feed->posts];
                } catch (Exception $e) {
                    user_error($e->getMessage());
                }
            }

            curl_multi_remove_handle($multiHandle, $handle);
        }

        curl_multi_close($multiHandle);

        return $posts;
    }

    private static function getNitterAuthToken(): string
    {
        if (isset(self::$nitterAuthToken)) {
            return self::$nitterAuthToken;
        }

        $curlHandle = curl_init();

        curl_setopt_array($curlHandle, [
            CURLOPT_URL => 'https://nitter.poast.org',
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_USERAGENT => 'Feed Reader/1.0',
            CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_2_0,
            CURLOPT_TIMEOUT => 10,
            CURLOPT_CONNECTTIMEOUT => 5,
            CURLOPT_ENCODING => 'gzip',
        ]);

        $body = curl_exec($curlHandle);

        if (preg_match('/[A-Z0-9]{40}/', $body, $matches) !== 1) {
            throw new Exception('Unable to find Nitter challenge');
        }

        return self::$nitterAuthToken = self::solveNitterChallenge($matches[0]);
    }
    
    private static function solveNitterChallenge(string $challenge): string
    {
        $i = 0;
        $byteOffset = hexdec($challenge[0]); // Get position from first character of the challenge

        while (true) {
            $solution = $challenge . $i;
            $solutionHash = sha1($solution, true);

            if (ord($solutionHash[$byteOffset]) === 0xB0 && ord($solutionHash[$byteOffset + 1]) === 0x0B) {
                return $solution;
            }

            $i++;
        }
    }

    private static function getFeed(string $url, string $xmlString): Feed
    {
        libxml_use_internal_errors(true);
        $xml = simplexml_load_string($xmlString);

        if ($xml === false) {
            $errors = libxml_get_errors();
            libxml_clear_errors();

            throw new Exception('Failed to parse XML: ' . $errors[0]->message);
        }

        return match(true) {
            parse_url($url, PHP_URL_HOST) === 'nitter.poast.org' => new NitterParser($xml)->parse(),
            $xml->getName() === 'feed' => new AtomParser($xml)->parse(),
            $xml->getName() === 'rss' => new RssParser($xml)->parse(),
        };
    }
}