<?php
/**
 * Media file serving controller
 *
 * Serves uploaded files that are stored outside the webroot (STORAGE_ROOT).
 * This is the sole access point for thesis files, covers, and annexes — they
 * are never exposed as direct filesystem paths from the web server.
 *
 * Security:
 *   - Strict character whitelist on the path parameter (no path traversal)
 *   - realpath() jail: resolved path must stay inside STORAGE_ROOT
 *   - MIME type verified against an allow-list before serving
 */
require_once __DIR__ . '/../config/bootstrap.php';

// --- 1. Extract and validate the requested path -------------------------------

$requestedPath = $_GET['path'] ?? '';

// Only allow safe characters: letters, digits, forward slashes, dots, hyphens, underscores.
// This explicitly rejects null bytes, backslashes, and sequences like "../".
if (!preg_match('#^[a-zA-Z0-9/_\-.]+$#', $requestedPath) || $requestedPath === '') {
    http_response_code(400);
    exit;
}

// --- 2. Resolve full filesystem path and enforce storage jail -----------------

$storageRoot = defined('STORAGE_ROOT') ? STORAGE_ROOT : '/var/www/posterg/storage';
$fullPath    = $storageRoot . '/' . $requestedPath;

$realStorage = realpath($storageRoot);
$realFull    = realpath($fullPath);

if (
    $realFull === false
    || $realStorage === false
    || strpos($realFull, $realStorage . '/') !== 0
) {
    http_response_code(404);
    exit;
}

if (!is_file($realFull)) {
    http_response_code(404);
    exit;
}

// --- 3. Verify MIME type from file content (not extension) --------------------

$finfo    = new finfo(FILEINFO_MIME_TYPE);
$mimeType = $finfo->file($realFull);

$allowedMimes = [
    'image/jpeg',
    'image/png',
    'image/gif',
    'application/pdf',
    'video/mp4',
    'application/zip',
];

if (!in_array($mimeType, $allowedMimes, true)) {
    http_response_code(403);
    exit;
}

// --- 4. Send response headers -------------------------------------------------

header('Content-Type: ' . $mimeType);
header('Content-Length: ' . filesize($realFull));
header('X-Content-Type-Options: nosniff');

$ext = strtolower(pathinfo($realFull, PATHINFO_EXTENSION));

if (in_array($ext, ['jpg', 'jpeg', 'png', 'gif'], true)) {
    // Images: cache publicly for 7 days
    header('Cache-Control: public, max-age=604800');
} elseif ($ext === 'pdf') {
    // PDFs: cache for 1 day, display inline
    header('Cache-Control: public, max-age=86400');
    header('Content-Disposition: inline');
} else {
    // Everything else: no public caching
    header('Cache-Control: private, no-store');
}

// --- 5. Stream file -----------------------------------------------------------

readfile($realFull);