using Google.Authenticator;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for GoogleAuth
/// </summary>
public class GoogleAuth
{
    public string User { get; set; }
    public string Password { get; set; }
    public string WebTitle { get; set; }
    public string WebKey { get; set; }
    public string SecretKey { get; set; }
    public SetupCode setupCode { get; set; }
    public GoogleAuth()
    {
        //
        // TODO: Add constructor logic here
        //
        WebKey = ConfigurationManager.AppSettings["SC"].ToString();
        WebTitle = WebKey;//可為中文?
    }
    public Image CreateSecretKeyAndQrCode()
    {
        Image ret;
        TwoFactorAuthenticator tfA = new TwoFactorAuthenticator();
        string issuer = WebKey + ":" + User;//發行者:用戶+網站
        string accountTitle = WebKey + "::" + User;//標題(可為中文字?)
        string accountSecKey = Password + SecretKey;//密鑰:密碼+隨機
        setupCode = tfA.GenerateSetupCode(
            issuer, accountTitle, accountSecKey, false, 3);

        //1. QRCode圖片從記憶體轉到畫面上
        using (MemoryStream ms = new MemoryStream(Convert.FromBase64String(
            setupCode.QrCodeSetupImageUrl.Replace("data:image/png;base64,", ""))))
        {
            ret = Image.FromStream(ms);
        }

        //2. 產生的金鑰與資訊
        //this.textBox_Message.Text =
        //   "結合密鑰的文字 Account: " + textBox_account.Text + System.Environment.NewLine +
        //   "自已加密的密鑰 Secret Key: " + textBox_SecretKey.Text + System.Environment.NewLine +
        //   "手動輸入的密鑰 Encoded Key: " + setupCode.ManualEntryKey;

        return ret;
    }
    public string ImageToBase64(Image image)
    {
        System.Drawing.Imaging.ImageFormat format = ImageFormat.Png;
        string mime = "data:image/png;base64,";
        using (MemoryStream ms = new MemoryStream())
        {
            // Convert Image to byte[]
            image.Save(ms, format);
            byte[] imageBytes = ms.ToArray();

            // Convert byte[] to base 64 string
            string base64String = mime+Convert.ToBase64String(imageBytes);
            return base64String;
        }
    }

    /// <summary>
    /// 驗證碼是否正確
    /// </summary>
    /// <returns></returns>
    public bool ValidateGoogleAuthCode(string ValidateCode)
    {
        string k = Password + SecretKey; //要存到資料庫, 才能重用
        var r = false;
        TwoFactorAuthenticator tfA = new TwoFactorAuthenticator();
        r = tfA.ValidateTwoFactorPIN(k, ValidateCode);
        return r;
    }
    /// <summary>
    /// 產生Secret當前的驗證碼
    /// </summary>
    public List<string> GeneratorCurrentCode()
    {
        var resultArray = new TwoFactorAuthenticator().GetCurrentPINs(SecretKey);
        var resultList = new List<string>(resultArray);
        return resultList;
    }
}
/*
# 例:

綁定資訊:
使用者帳號: user1
網站代號: erp17168
使用者密碼: G0t0r5hPel4EJnAfFkmhAI=
動態密鑰: aJn7TSc3Nl2UPUTWtiBE
setupCode: I4YHIMDSGVUFAZLMGRCUU3SBMZDGW3LIIFET2YKKNY3VIU3DGNHGYMSVKBKVIV3UNFBEK

---
# 傳回QRCODE
otpauth://totp/erp17168%3Auser1:erp17168:user1?secret=I4YHIMDSGVUFAZLMGRCUU3SBMZDGW3LIIFET2YKKNY3VIU3DGNHGYMSVKBKVIV3UNFBEK&issuer=erp17168%3Auser1

otpauth://totp/
erp17168:user1:erp17168:user1
?
secret=I4YHIMDSGVUFAZLMGRCUU3SBMZDGW3LIIFET2YKKNY3VIU3DGNHGYMSVKBKVIV3UNFBEK
&
issuer=erp17168%3Auser1                


# 建立:
動態=亂數()
U="網站:用戶"
K="密碼+動態"

QRCODE= "otpauth://" + U + SecretKey(回傳的)
SecretKey:不用存
用戶拍QRCODE, 記在Google Anth. App中
每30秒自動更新一次

# 驗證:
(先檢查帳密:通過)
再傳出:
K="密碼+動態" (從資料庫抓:用戶)
V=(用戶即時輸入的驗證碼, 來自APP)
傳回:true / false

---
參考
https://dotblogs.com.tw/milkgreenteaprograme_c_sharp/2020/10/28/135725
https://github.com/gotoa1234/GoogleAuthenticatorExample

---
# 未實作功能
# button : 取得當前SecretKey的密碼
        private void button_GeneratorCode_Click(object sender, EventArgs e)
        {
            DataGridViewRow row = (DataGridViewRow)dataGridView_KeyCode.RowTemplate.Clone();
            var currentCodeList = GeneratorCurrentCode().Take(1);
            var takeSingle = currentCodeList.Take(1).First();//取一筆做為比較
            if (_lastCurrentCode != takeSingle)
            {
                _lastCurrentCode = takeSingle;
                var currentDateTimeNow = DateTime.Now;
                foreach (var code in currentCodeList)
                {
                    dataGridView_KeyCode.Rows.Add(
                        currentDateTimeNow.ToString("yyyy/MM/d HH:mm:ss"),
                        textBox_account.Text,
                        textBox_SecretKey.Text,
                        code);
                }
                //排序
                dataGridView_KeyCode.Sort(dataGridView_KeyCode.Columns["GeneratorDateTime"], System.ComponentModel.ListSortDirection.Descending);
            }
        }
 # grid
產生時間:GeneratorDateTime
手產字串:Account
手產金鑰:SecretKey
當前驗證金鑰:CurrentCode
 */