<?php
/**
 * Superfice – Distance API
 *
 * GET /api/distance.php?plz=XXXXX
 *
 * Returns JSON: { "distance": <km>, "plz": "XXXXX" }
 * or            { "error": "<message>" }
 *
 * Uses OpenStreetMap Nominatim for geocoding (free, no API key needed).
 * For production traffic, replace with Google Maps or a local PLZ dataset.
 */

require_once __DIR__ . '/config.php';
require_once __DIR__ . '/helpers.php';

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

// -------------------------------------------------------
// Input validation
// -------------------------------------------------------
$plz = isset($_GET['plz']) ? preg_replace('/[^0-9]/', '', trim($_GET['plz'])) : '';

if (strlen($plz) !== 5) {
    json_error('Ungültige PLZ. Bitte geben Sie eine 5-stellige Postleitzahl ein.');
}

// -------------------------------------------------------
// Rate limiting
// -------------------------------------------------------
rate_limit('dist_' . client_ip(), RATE_LIMIT_DISTANCE, RATE_LIMIT_WINDOW);

// -------------------------------------------------------
// Geocode PLZ via Nominatim
// -------------------------------------------------------
$url = sprintf(
    'https://nominatim.openstreetmap.org/search?postalcode=%s&country=de&format=json&limit=1&addressdetails=0',
    urlencode($plz)
);

$ctx = stream_context_create([
    'http' => [
        'header'          => "User-Agent: SuperficeWebsite/1.0 (info@superfice.de)\r\n",
        'timeout'         => 5,
        'ignore_errors'   => true,
    ],
    'ssl' => [
        'verify_peer'     => true,
        'verify_peer_name'=> true,
    ],
]);

$raw = @file_get_contents($url, false, $ctx);

if ($raw === false) {
    json_error('PLZ-Suche momentan nicht verfügbar. Bitte versuchen Sie es später erneut.');
}

$data = json_decode($raw, true);

if (empty($data) || !isset($data[0]['lat'], $data[0]['lon'])) {
    json_error('PLZ nicht gefunden. Bitte prüfen Sie Ihre Eingabe.');
}

$lat = (float) $data[0]['lat'];
$lon = (float) $data[0]['lon'];

// -------------------------------------------------------
// Haversine distance to HQ
// -------------------------------------------------------
$distance = haversine(HQ_LAT, HQ_LON, $lat, $lon);

echo json_encode([
    'distance' => $distance,
    'plz'      => $plz,
]);