<?php
declare(strict_types=1);

header('Content-Type: application/json');
header('Cache-Control: no-store, no-cache, must-revalidate, max-age=0');

$layoutPath = __DIR__ . '/layout.json';
$method = $_SERVER['REQUEST_METHOD'] ?? 'GET';

if ($method === 'GET') {
    if (is_file($layoutPath)) {
        readfile($layoutPath);
    } else {
        echo json_encode(['nodes' => new stdClass()], JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
    }
    exit;
}

if ($method === 'POST') {
    $raw = file_get_contents('php://input');
    if ($raw === false || trim($raw) === '') {
        http_response_code(400);
        echo json_encode(['error' => 'Empty request body']);
        exit;
    }

    $decoded = json_decode($raw, true);
    if (!is_array($decoded)) {
        http_response_code(400);
        echo json_encode(['error' => 'Invalid JSON payload']);
        exit;
    }

    $encoded = json_encode($decoded, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
    if ($encoded === false) {
        http_response_code(500);
        echo json_encode(['error' => 'Failed to encode layout']);
        exit;
    }

    $result = @file_put_contents($layoutPath, $encoded . PHP_EOL, LOCK_EX);
    if ($result === false) {
        http_response_code(500);
        echo json_encode(['error' => 'Failed to write layout file']);
        exit;
    }

    echo json_encode(['status' => 'ok']);
    exit;
}

http_response_code(405);
header('Allow: GET, POST');
echo json_encode(['error' => 'Method not allowed']);