VITEC-website/public/collateral-fallback.php

<?php

declare(strict_types=1);

/**
 * Fallback resolver for deleted versioned files in fileadmin/downloads/Collateral.
 *
 * Expected requested filename format:
 *   [fileprefix]__[filetype]__[number]-[letter].ext
 *
 * If a matching file no longer exists, this resolver redirects to the newest
 * available version (highest number, then highest letter sequence).
 */

$requestedRaw = isset($_GET['requested']) ? (string)$_GET['requested'] : '';
$requestedRaw = str_replace('\\', '/', $requestedRaw);
$requestedFilename = basename(rawurldecode($requestedRaw));

if ($requestedFilename === '' || $requestedFilename === '.' || $requestedFilename === '..') {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

if (!preg_match('/^(?P<prefix>.+?)__(?P<type>.+?)__(?P<number>\\d+)-(?P<letters>[A-Za-z]+)\\.(?P<ext>[A-Za-z0-9]+)$/', $requestedFilename, $parts)) {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

$prefix = (string)$parts['prefix'];
$type = (string)$parts['type'];

$baseDir = __DIR__ . '/fileadmin/downloads/Collateral';
if (!is_dir($baseDir) || !is_readable($baseDir)) {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

$escapedPrefix = preg_quote($prefix, '/');
$escapedType = preg_quote($type, '/');
$pattern = '/^' . $escapedPrefix . '__' . $escapedType . '__(\\d+)-([A-Za-z]+)\\.([A-Za-z0-9]+)$/';

$bestFilename = null;
$bestNumber = -1;
$bestLetterRank = -1;

$entries = scandir($baseDir);
if ($entries === false) {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

foreach ($entries as $entry) {
    if (!is_string($entry) || $entry === '.' || $entry === '..') {
        continue;
    }

    if (!preg_match($pattern, $entry, $matches)) {
        continue;
    }

    $number = (int)$matches[1];
    $letterRank = letterSequenceToRank((string)$matches[2]);

    if ($number > $bestNumber || ($number === $bestNumber && $letterRank > $bestLetterRank)) {
        $bestNumber = $number;
        $bestLetterRank = $letterRank;
        $bestFilename = $entry;
    }
}

if ($bestFilename === null) {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

$bestPath = $baseDir . '/' . $bestFilename;
if (!is_file($bestPath) || !is_readable($bestPath)) {
    http_response_code(404);
    header('Content-Type: text/plain; charset=utf-8');
    echo 'Not found';
    exit;
}

$clientIp = isset($_SERVER['REMOTE_ADDR']) ? (string)$_SERVER['REMOTE_ADDR'] : '-';
$userAgent = isset($_SERVER['HTTP_USER_AGENT']) ? (string)$_SERVER['HTTP_USER_AGENT'] : '-';
logFallbackRecovery($requestedFilename, $bestFilename, $clientIp, $userAgent);

$target = '/fileadmin/downloads/Collateral/' . rawurlencode($bestFilename);
header('Cache-Control: no-store, no-cache, must-revalidate, max-age=0');
header('Pragma: no-cache');
header('Location: ' . $target, true, 302);
exit;

function letterSequenceToRank(string $letters): int
{
    $rank = 0;
    $letters = strtoupper($letters);
    $length = strlen($letters);

    for ($i = 0; $i < $length; $i++) {
        $char = ord($letters[$i]);
        if ($char < 65 || $char > 90) {
            continue;
        }

        $rank = ($rank * 26) + ($char - 64);
    }

    return $rank;
}

function logFallbackRecovery(string $requested, string $resolved, string $clientIp, string $userAgent): void
{
    $logDir = dirname(__DIR__) . '/var/log';
    if (!is_dir($logDir)) {
        return;
    }

    $timestamp = gmdate('c');
    $line = sprintf(
        "%s collateral-fallback requested=\"%s\" resolved=\"%s\" ip=%s ua=\"%s\"\n",
        $timestamp,
        str_replace('"', '\\"', $requested),
        str_replace('"', '\\"', $resolved),
        $clientIp,
        str_replace('"', '\\"', $userAgent)
    );

    @file_put_contents($logDir . '/collateral-fallback.log', $line, FILE_APPEND | LOCK_EX);
}