<?php
class JSSDK {
  private $appId;
  private $appSecret;

  public function __construct($appId, $appSecret) {
    $this->appId = $appId;
    $this->appSecret = $appSecret;
  }

  public function getSignPackage() {
    $jsapiTicket = $this->getJsApiTicket();

    // 注意 URL 一定要動態獲取，不能 hardcode.
    $protocol = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443) ? "https://" : "http://";
    $url = "$protocol$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";

    $timestamp = time();
    $nonceStr = $this->createNonceStr();

    // 這裡引數的順序要按照 key 值 ASCII 碼升序排序
    $string = "jsapi_ticket=$jsapiTicket&noncestr=$nonceStr×tamp=$timestamp&url=$url";

    $signature = sha1($string);

    $signPackage = array(
        "appId"     => $this->appId,
        "jsapiTicket" => $jsapiTicket,
        "nonceStr"  => $nonceStr,
        "timestamp" => $timestamp,
        "url"       => $url,
        "signature" => $signature,
        "rawString" => $string
    );
    return $signPackage;
  }

  private function createNonceStr($length = 16) {
    $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    $str = "";
    for ($i = 0; $i < $length; $i++) {
      $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
    }
    return $str;
  }

  private function getJsApiTicket() {
    // jsapi_ticket 應該全域性儲存與更新，以下程式碼以寫入到檔案中做示例
    $data = json_decode($this->get_php_file("jsapi_ticket.php"));
    if ($data->expire_time < time()) {
      $accessToken = $this->getAccessToken();
      // 如果是企業號用以下 URL 獲取 ticket
      // $url = "https://qyapi.weixin.qq.com/cgi-bin/get_jsapi_ticket?access_token=$accessToken";
      $url = "https://api.weixin.qq.com/cgi-bin/ticket/getticket?type=jsapi&access_token=$accessToken";
      $res = json_decode($this->httpGet($url));
      $ticket = $res->ticket;
      if ($ticket) {
        $data->expire_time = time() + 7000;
        $data->jsapi_ticket = $ticket;
        $this->set_php_file("jsapi_ticket.php", json_encode($data));
      }
    } else {
      $ticket = $data->jsapi_ticket;
    }

    return $ticket;
  }

  private function getAccessToken() {
    // access_token 應該全域性儲存與更新，以下程式碼以寫入到檔案中做示例
    $data = json_decode($this->get_php_file("access_token.php"));
    if ($data->expire_time < time()) {
      // 如果是企業號用以下URL獲取access_token
      // $url = "https://qyapi.weixin.qq.com/cgi-bin/gettoken?corpid=$this->appId&corpsecret=$this->appSecret";
      $url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=$this->appId&secret=$this->appSecret";
      $res = json_decode($this->httpGet($url));
      $access_token = $res->access_token;
      if ($access_token) {
        $data->expire_time = time() + 7000;
        $data->access_token = $access_token;
        $this->set_php_file("access_token.php", json_encode($data));
      }
    } else {
      $access_token = $data->access_token;
    }
    return $access_token;
  }

  private function httpGet($url) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 500);
    // 為保證第三方伺服器與微信伺服器之間資料傳輸的安全性，所有微信介面採用https方式呼叫，必須使用下面2行程式碼開啟ssl安全校驗。
    // 如果在部署過程中程式碼在此處驗證失敗，請到 http://curl.haxx.se/ca/cacert.pem 下載新的證書判別檔案。
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, true);
    //curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, true);
    curl_setopt($curl, CURLOPT_URL, $url);

    $res = curl_exec($curl);
    curl_close($curl);

    return $res;
  }

  private function get_php_file($filename) {
    return trim(substr(file_get_contents($filename), 15));
  }
  private function set_php_file($filename, $content) {
    $fp = fopen($filename, "w");
    fwrite($fp, "<?php exit();?>" . $content);
    fclose($fp);
  }
}