api/file.php

<?php
header('Content-Type: application/json');
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type');

if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(204);
    exit;
}

if ($_SERVER['REQUEST_METHOD'] !== 'GET') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit;
}

$username = trim($_GET['username'] ?? '');
$filepath = trim($_GET['filepath'] ?? '');

// Validate username
if (!preg_match('/^[a-z0-9]{3,32}$/', $username)) {
    http_response_code(400);
    echo json_encode(['error' => 'Invalid username']);
    exit;
}

// Sanitise filepath — no directory traversal
$filepath = basename($filepath);
if (empty($filepath)) {
    http_response_code(400);
    echo json_encode(['error' => 'Invalid filepath']);
    exit;
}

// Check user exists
$db = new PDO('sqlite:/data/db/platform.sqlite');
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $db->prepare('SELECT id FROM users WHERE username = ?');
$stmt->execute([$username]);
if (!$stmt->fetch()) {
    http_response_code(404);
    echo json_encode(['error' => 'User not found']);
    exit;
}

$dest = "/data/sites/{$username}/htdocs/{$filepath}";

if (!file_exists($dest)) {
    http_response_code(404);
    echo json_encode(['error' => 'File not found']);
    exit;
}

$content = file_get_contents($dest);

echo json_encode([
    'success'  => true,
    'username' => $username,
    'filepath' => $filepath,
    'content'  => $content
]);