<?php declare(strict_types=1);

function getParam(string $name, string $default = ""): string {
  if (isset($_GET[$name]) && !empty($_GET[$name])) {
    return (string)$_GET[$name];
  }

  return $default;
}

function getParamInt(string $name, int $default = 0): int {
  if (isset($_GET[$name]) && !empty($_GET[$name])) {
    return (int)$_GET[$name];
  }

  return $default;
}

$zip = getParamInt("zip", 0);
$city = getParam("city", "");
$time = time();

$url = "https://service.post.ch/zopa/app/api/addresschecker/v1/zips?limit=9999&noCache={$time}";

if (strlen($city) > 0) {
  $url .= "&city={$city}";
}

if ($zip >= 1000 && $zip <= 9999) {
  $url .= "&zip={$zip}";
}

$response = file_get_contents($url);
$json = json_decode($response);

$zips = [];
if (isset($json->zips) && !empty($json->zips)) {
  foreach ($json->zips as $zip) {
    if (!isset($zip->zip) || empty($zip->zip)) {
      continue;
    }

    if (!isset($zip->city27) || empty($zip->city27)) {
      continue;
    }

    $zips[] = [
      "zip" => (int)$zip->zip,
      "city" => $zip->city27
    ];
  }
}

header("Content-Type: application/json");
echo json_encode([
  "zips" => $zips
], JSON_PRETTY_PRINT);