<?php
/**
 * Webhook receiver: accepts POST with JSON body and appends to data/einsaetze.json.
 * Payload is stored under webhook_events[] with a received timestamp; einsaetze is unchanged.
 */

declare(strict_types=1);

header('Content-Type: application/json; charset=utf-8');

const DEFAULT_DATA_PATH = 'data/einsaetze.json';
const MAX_BODY_SIZE = 1024 * 1024 * 10; // 10 MB

$dataPath = getenv('EINSATZ_JSON_PATH') ?: DEFAULT_DATA_PATH;

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method Not Allowed']);
    exit;
}

$raw = file_get_contents('php://input');
if ($raw === false || $raw === '') {
    http_response_code(400);
    echo json_encode(['error' => 'Invalid or empty JSON']);
    exit;
}

if (strlen($raw) > MAX_BODY_SIZE) {
    http_response_code(400);
    echo json_encode(['error' => 'Request body too large']);
    exit;
}

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

$received = (new DateTimeImmutable('now', new DateTimeZone('UTC')))->format('Y-m-d\TH:i:s.uP');

$dir = dirname($dataPath);
if (!is_dir($dir)) {
    if (!@mkdir($dir, 0755, true)) {
        http_response_code(500);
        echo json_encode(['error' => 'Could not create data directory']);
        exit;
    }
}

$fp = fopen($dataPath, 'c+');
if ($fp === false) {
    http_response_code(500);
    echo json_encode(['error' => 'Could not open data file']);
    exit;
}

if (!flock($fp, LOCK_EX)) {
    fclose($fp);
    http_response_code(500);
    echo json_encode(['error' => 'Could not lock data file']);
    exit;
}

$content = stream_get_contents($fp);
$data = [];
if ($content !== false && $content !== '') {
    $data = json_decode($content, true);
    if (!is_array($data)) {
        $data = [];
    }
}

if (!isset($data['einsaetze'])) {
    $data['einsaetze'] = [];
}
if (!isset($data['webhook_events'])) {
    $data['webhook_events'] = [];
}

$data['webhook_events'][] = [
    'received' => $received,
    'data' => $payload,
];
$data['updated'] = $received;

$json = json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
if ($json === false) {
    flock($fp, LOCK_UN);
    fclose($fp);
    http_response_code(500);
    echo json_encode(['error' => 'Could not encode JSON']);
    exit;
}

ftruncate($fp, 0);
rewind($fp);
$written = fwrite($fp, $json);
flock($fp, LOCK_UN);
fclose($fp);

if ($written === false || $written !== strlen($json)) {
    http_response_code(500);
    echo json_encode(['error' => 'Could not write data file']);
    exit;
}

http_response_code(200);
echo json_encode(['ok' => true, 'received' => $received]);