<?php
header('Content-Type: application/json');

// JSON vom Client einlesen
$data = json_decode(file_get_contents('php://input'), true);
if (!isset($data['device_id'])) {
    echo json_encode(["status" => "error", "message" => "device_id fehlt"]);
    exit;
}

$device_id = $data['device_id'];
$timestamp = date("Y-m-d H:i:s");

// Status-Datei
$file = 'online_devices.json';
$devices = [];

// Existierende Datei laden
if (file_exists($file)) {
    $devices = json_decode(file_get_contents($file), true) ?: [];
}

// Gerät updaten oder hinzufügen
$devices[$device_id] = ["device_id" => $device_id, "last_seen" => $timestamp];

// Speichern
file_put_contents($file, json_encode($devices, JSON_PRETTY_PRINT));

echo json_encode(["status" => "ok", "device_id" => $device_id, "last_seen" => $timestamp]);
?>