<?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 一定要动态获取，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();

    // 这里参数的顺序要按照 key 值 ASCII 码升序排序

    $string = "jsapi_ticket=$jsapiTicket&noncestr=$nonceStr&timestamp=$timestamp&url=$url";

    $signature = sha1($string);

    $signPackage = array(

      "appId"     => $this->appId,

      "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 应该全局存储与更新，以下代码以写入到文件中做示例

    $data = json_decode($this->get_php_file("jsapi_ticket.php"));

    if ($data->expire_time < time() || !$data) {

      $accessToken = $this->getAccessToken();

      // 如果是企业号用以下 URL 获取 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";

      $res = json_decode(dcurl($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 应该全局存储与更新，以下代码以写入到文件中做示例

    $data = json_decode($this->get_php_file("access_token.php"));

    if ($data->expire_time < time() || !$data) {

      // 如果是企业号用以下URL获取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";

      $res = json_decode(dcurl($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 get_php_file($filename) {

    return trim(substr(file_get('/jssdk_'.$filename), 15));

  }

  private function set_php_file($filename, $content) {

      file_put('/jssdk_'.$filename, "<?php exit();?>".$content);

  }

}