<%@ WebHandler Language="C#" Class="validGoogleLogin" %>

using System;
using System.Web;
using Google.Apis.Auth;
using System.Runtime.Serialization.Json;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System.Web.Services.Protocols;
using System.Security.Cryptography;
using System.Text;
using System.Web.SessionState;
using System.Data;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Generic;

public class validGoogleLogin : System.Web.HttpTaskAsyncHandler {
    
    public override async System.Threading.Tasks.Task ProcessRequestAsync(HttpContext context) {
        result objRet = new result();
		DataContractJsonSerializer json = new DataContractJsonSerializer(objRet.GetType());
		context.Response.ContentType = "application/json;charset=utf-8";

		string jwt = (context.Request["jwt"] == null) ? "" : context.Request["jwt"].ToString();//回傳憑證
		string remember = (context.Request["rem"] == null) ? "N" : context.Request["rem"].ToString();

		if (jwt == "") {

			objRet.ret = "no";
			objRet.err_code = "0001";
			objRet.message = "無JWT資料可以登入!";
			json.WriteObject(context.Response.OutputStream, objRet);
			return;
		}

		//validate it using Google.Apis.Auth (null if invalid)
		//var validPayload = await GoogleJsonWebSignature.ValidateAsync(jwt);
		GoogleJsonWebSignature.Payload payload = await ValidateGoogleTokenAsync(jwt);

		if (payload == null) {
			objRet.ret = "no";
			objRet.err_code = "0002";
			objRet.message = "JWT驗證失敗!";
			json.WriteObject(context.Response.OutputStream, objRet);
			return;
		}
		string googleID = System.Web.Configuration.WebConfigurationManager.AppSettings["googleOAuthID"].ToString();
		string audience = payload.Audience.ToString();

		if (audience != googleID) {
			objRet.ret = "no";
			objRet.err_code = "0003";
			objRet.message = "JWT驗證失敗!";
			json.WriteObject(context.Response.OutputStream, objRet);
			return;
		}

		string userId = payload.Subject;
		string email = payload.Email;
		string name = payload.Name;

		string user_sql = string.Format("select * from users where user_email = '{0}' and user_onjob = 'Y'", email);
		autoBindDataTable objUser = new autoBindDataTable(user_sql);

		if (objUser.dataRows.Count == 0) {
			objRet.ret = "no";
			objRet.err_code = "0004";
			objRet.message = "無此Email帳號於PRM系統中，請直屬主管加入!";
			json.WriteObject(context.Response.OutputStream, objRet);
			return;
		}

		string token_key = CreateRandomCode(36);
		string user_uid = objUser.dataRows[0]["user_uid"].ToString();
		string id = objUser.dataRows[0]["user_id"].ToString();

		autoBindDataTable dataToken = new autoBindDataTable("select * from token where token_sn = -1");
		DataRow rowToken = dataToken.newRow;
		dataToken.dataRows.Add(rowToken);
		rowToken["token_key"] = token_key;
		rowToken["user_uid"] = user_uid;
		rowToken["token_isremember"] = remember;
		rowToken["token_expireddate"] = DateTime.Now.AddMinutes(60);


		HttpCookie tokenCookie = new HttpCookie("token");
		HttpCookie idCookie = new HttpCookie("id");
		tokenCookie["token"] = token_key;
		tokenCookie["uid"] = user_uid;
		idCookie["id"] = id;

		idCookie.Expires = DateTime.Now.AddDays(31);

		if (remember == "Y") {
			tokenCookie.Expires = DateTime.Now.AddDays(10);
			rowToken["token_expireddate"] = DateTime.Now.AddDays(10);
		}

		dataToken.updateDataTable();
		context.Response.Cookies.Add(tokenCookie);
		context.Response.Cookies.Add(idCookie);

		objRet.ret = "yes";
		json.WriteObject(context.Response.OutputStream, objRet);
    }

    private static async Task<GoogleJsonWebSignature.Payload> ValidateGoogleTokenAsync(string idToken)
	{
		try
		{
			var payload = await GoogleJsonWebSignature.ValidateAsync(idToken);

			if (payload == null || string.IsNullOrEmpty(payload.Email))
				throw new UnauthorizedAccessException("Invalid Google Token");

			return payload;
		}
		catch (Exception ex){
			string exM = ex.Message;
			throw new UnauthorizedAccessException("Invalid Google Token");
			return null;
		}
	}

	public string CreateRandomCode(int Number)
	{
		string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
		string[] allCharArray = allChar.Split(',');
		string randomCode = "";

		Random rand = new Random(Guid.NewGuid().GetHashCode());
		for (int i = 0; i <= Number - 1; i++)
		{
			int t = rand.Next(allCharArray.Length);
			randomCode += allCharArray[t];
		}
		return randomCode;
	}

	public class result {
		public string ret = "no";
		public string err_code = "0000";
		public string message = "";
	}
 
    public bool IsReusable {
        get {
            return false;
        }
    }

}