using System;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using Newtonsoft.Json;
using System.Security.Cryptography;
using System.Text;
 
namespace BroadSky.WeChatAppDecrypt
{
 /// <summary>
 /// 處理微信小程序用戶數(shù)據(jù)的簽名驗證和解密
 /// </summary>
 public class WeChatAppDecrypt
 {
  private string appId;
  private string appSecret;
 
  /// <summary>
  /// 構(gòu)造函數(shù)
  /// </summary>
  /// <param name="appId">應(yīng)用程序的AppId</param>
  /// <param name="appSecret">應(yīng)用程序的AppSecret</param>
  public WeChatAppDecrypt(string appId, string appSecret)
  {
   this.appId = appId;
   this.appSecret = appSecret;
   return;
  }
 
  /// <summary>
  /// 獲取OpenId和SessionKey的Json數(shù)據(jù)包
  /// </summary>
  /// <param name="code">客戶端發(fā)來的code</param>
  /// <returns>Json數(shù)據(jù)包</returns>
  private string GetOpenIdAndSessionKeyString(string code)
  {
   string temp = "https://api.weixin.qq.com/sns/jscode2session?" + 
    "appid=" + appId
    + "&secret=" + appSecret
    + "&js_code=" + code 
    + "&grant_type=authorization_code";
 
   return GetResponse(temp);
 
  }
 
  /// <summary>
  /// 反序列化包含OpenId和SessionKey的Json數(shù)據(jù)包
  /// </summary>
  /// <param name="code">Json數(shù)據(jù)包</param>
  /// <returns>包含OpenId和SessionKey的類</returns>
  public OpenIdAndSessionKey DecodeOpenIdAndSessionKey(WechatLoginInfo loginInfo)
  {
   OpenIdAndSessionKey oiask = JsonConvert.DeserializeObject<OpenIdAndSessionKey>(GetOpenIdAndSessionKeyString(loginInfo.code));
   if (!String.IsNullOrEmpty(oiask.errcode))
    return null;
   return oiask;
  }
 
  /// <summary>
  /// 根據(jù)微信小程序平臺提供的簽名驗證算法驗證用戶發(fā)來的數(shù)據(jù)是否有效
  /// </summary>
  /// <param name="rawData">公開的用戶資料</param>
  /// <param name="signature">公開資料攜帶的簽名信息</param>
  /// <param name="sessionKey">從服務(wù)端獲取的SessionKey</param>
  /// <returns>True：資料有效，F(xiàn)alse：資料無效</returns>
  public bool VaildateUserInfo(string rawData, string signature, string sessionKey)
  {
   //創(chuàng)建SHA1簽名類
   SHA1 sha1 = new SHA1CryptoServiceProvider();
   //編碼用于SHA1驗證的源數(shù)據(jù)
   byte[] source = Encoding.UTF8.GetBytes(rawData + sessionKey);
   //生成簽名
   byte[] target = sha1.ComputeHash(source);
   //轉(zhuǎn)化為string類型，注意此處轉(zhuǎn)化后是中間帶短橫杠的大寫字母，需要剔除橫杠轉(zhuǎn)小寫字母
   string result = BitConverter.ToString(target).Replace("-","").ToLower();
   //比對，輸出驗證結(jié)果
   return signature == result;
  }
 
  /// <summary>
  /// 根據(jù)微信小程序平臺提供的簽名驗證算法驗證用戶發(fā)來的數(shù)據(jù)是否有效
  /// </summary>
  /// <param name="loginInfo">登陸信息</param>
  /// <param name="sessionKey">從服務(wù)端獲取的SessionKey</param>
  /// <returns>True：資料有效，F(xiàn)alse：資料無效</returns>
  public bool VaildateUserInfo(WechatLoginInfo loginInfo, string sessionKey)
  {
   return VaildateUserInfo(loginInfo.rawData, loginInfo.signature, sessionKey);
  }
 
  /// <summary>
  /// 根據(jù)微信小程序平臺提供的簽名驗證算法驗證用戶發(fā)來的數(shù)據(jù)是否有效
  /// </summary>
  /// <param name="loginInfo">登陸信息</param>
  /// <param name="idAndKey">包含OpenId和SessionKey的類</param>
  /// <returns>True：資料有效，F(xiàn)alse：資料無效</returns>
  public bool VaildateUserInfo(WechatLoginInfo loginInfo, OpenIdAndSessionKey idAndKey)
  {
   return VaildateUserInfo(loginInfo, idAndKey.session_key);
  }
 
  /// <summary>
  /// 根據(jù)微信小程序平臺提供的解密算法解密數(shù)據(jù)
  /// </summary>
  /// <param name="encryptedData">加密數(shù)據(jù)</param>
  /// <param name="iv">初始向量</param>
  /// <param name="sessionKey">從服務(wù)端獲取的SessionKey</param>
  /// <returns></returns>
  public WechatUserInfo Decrypt(string encryptedData, string iv, string sessionKey)
  {
   WechatUserInfo userInfo;
   //創(chuàng)建解密器生成工具實例
   AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
   //設(shè)置解密器參數(shù)
   aes.Mode = CipherMode.CBC;
   aes.BlockSize = 128;
   aes.Padding = PaddingMode.PKCS7;
   //格式化待處理字符串
   byte[] byte_encryptedData = Convert.FromBase64String(encryptedData);
   byte[] byte_iv = Convert.FromBase64String(iv);
   byte[] byte_sessionKey = Convert.FromBase64String(sessionKey);
 
   aes.IV = byte_iv;
   aes.Key = byte_sessionKey;
   //根據(jù)設(shè)置好的數(shù)據(jù)生成解密器實例
   ICryptoTransform transform = aes.CreateDecryptor();
   
   //解密
   byte [] final = transform.TransformFinalBlock(byte_encryptedData, 0, byte_encryptedData.Length);
 
   //生成結(jié)果
   string result = Encoding.UTF8.GetString(final);
 
   //反序列化結(jié)果，生成用戶信息實例
   userInfo = JsonConvert.DeserializeObject<WechatUserInfo>(result);
 
   return userInfo;
 
  }
 
  /// <summary>
  /// 根據(jù)微信小程序平臺提供的解密算法解密數(shù)據(jù)，推薦直接使用此方法
  /// </summary>
  /// <param name="loginInfo">登陸信息</param>
  /// <returns>用戶信息</returns>
  public WechatUserInfo Decrypt(WechatLoginInfo loginInfo)
  {
   if (loginInfo == null)
    return null;
 
   if (String.IsNullOrEmpty(loginInfo.code))
    return null;
 
   OpenIdAndSessionKey oiask = DecodeOpenIdAndSessionKey(loginInfo);
 
   if (oiask == null)
    return null;
 
   if (!VaildateUserInfo(loginInfo, oiask))
    return null;
 
   WechatUserInfo userInfo = Decrypt(loginInfo.encryptedData, loginInfo.iv, oiask.session_key);
 
   return userInfo;
  }
 
  /// <summary>
  /// GET請求
  /// </summary>
  /// <param name="url"></param>
  /// <returns></returns>
  private string GetResponse(string url)
  {
   if (url.StartsWith("https"))
    System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
 
   HttpClient httpClient = new HttpClient();
   httpClient.DefaultRequestHeaders.Accept.Add(
   new MediaTypeWithQualityHeaderValue("application/json"));
   HttpResponseMessage response = httpClient.GetAsync(url).Result;
 
   if (response.IsSuccessStatusCode)
   {
    string result = response.Content.ReadAsStringAsync().Result;
    return result;
   }
   return null;
  }
 
  
 }
 /// <summary>
 /// 微信小程序登錄信息結(jié)構(gòu)
 /// </summary>
 public class WechatLoginInfo
 {
  public string code { get; set; }
  public string encryptedData { get; set; }
  public string iv { get; set; }
  public string rawData { get; set; }
  public string signature { get; set; }
 }
 /// <summary>
 /// 微信小程序用戶信息結(jié)構(gòu)
 /// </summary>
 public class WechatUserInfo
 {
  public string openId { get; set; }
  public string nickName { get; set; }
  public string gender { get; set; }
  public string city { get; set; }
  public string province { get; set; }
  public string country { get; set; }
  public string avatarUrl { get; set; }
  public string unionId { get; set; }
  public Watermark watermark { get; set; }
 
  public class Watermark
  {
   public string appid { get; set; }
   public string timestamp { get; set; }
  }
 }
 /// <summary>
 /// 微信小程序從服務(wù)端獲取的OpenId和SessionKey信息結(jié)構(gòu)
 /// </summary>
 public class OpenIdAndSessionKey
 {
  public string openid { get; set; }
  public string session_key { get; set; }
  public string errcode { get; set; }
  public string errmsg { get; set; }
 }
}