<?php
// ??? ????? ???? ????? ??? ???????
$filename = 'links.txt';

// ?????? ?? ???? ?????
if (!file_exists($filename )) {
    die("?????? ??? ??????? ??? ?????.");
}

// ??? ????? ??????? ??????? ????????
$fp = fopen($filename, 'c+');

if (!$fp) {
    die("?????? ?? ???? ??? ??? ???????. ???? ?? ?????? ????? (Permissions).");
}

// ??? ????? ?????? (???? ????? ??????? ??? ????? ?? ??? ??????)
if (flock($fp, LOCK_EX)) {
    
    // ????? ????? ?????
    $filesize = filesize($filename);
    $content = $filesize > 0 ? fread($fp, $filesize) : '';
    
    // ????? ??????? ??? ?????? (?? ??? ????)
    $lines = explode("\n", $content);
    
    $redirect_url = '';
    $remaining_lines = [];

    // ????? ?? ??? ???? ????
    foreach ($lines as $line) {
        $line = trim($line); // ????? ???????? ?????????
        
        if (empty($redirect_url) && !empty($line)) {
            // ????? ??? ????! ????? ???????
            $redirect_url = $line;
        } else {
            // ???? ??????? ????? ??? ????? ??????? ?? ?????
            $remaining_lines[] = $line;
        }
    }

    // ??? ????? ??????? ???? ?????? ????? (??? ?????? ???????)
    if (!empty($redirect_url)) {
        // ??? ????? ????? ???????
        ftruncate($fp, 0);
        rewind($fp);
        
        // ????? ????? ??????? ????????
        fwrite($fp, implode("\n", $remaining_lines));
    }

    // ?? ????? ?????? ?????
    flock($fp, LOCK_UN);
    fclose($fp);

    // ????? ??????? (Redirect) ??? ????? ??????
    if (!empty($redirect_url)) {
        header("Location: " . $redirect_url);
        exit();
    } else {
        // ??? ??? ????? ?????? ??? ???? ?????
        die("?????? ?? ???? ????? ??? ????? ??????. ???? ???????? ?????? ?? ??????? ?? ?????.");
    }

} else {
    // ?? ??? ??? ??? ?????
    fclose($fp);
    die("??? ??? ????? ?????? ?????. ???? ????? ??????.");
}
?>