carparkvalidation/CarParkValidationAPI/Authorization/JwtUtils.cs

using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using System;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Security.Claims;
using System.Text;
using CarParkValidationAPI.Entities;
using CarParkValidationAPI.Interface;
using CarParkValidationAPI.Models;

namespace CarParkValidationAPI.Authorization
{
   

    public class JwtUtils : IJwtUtils
    {
        private readonly AppSettings _appSettings;

        public JwtUtils(IOptions<AppSettings> appSettings)
        {
            _appSettings = appSettings.Value;
        }

        public string GenerateJwtToken(User user)
        {
            // generate token that is valid for 2 days
            var tokenHandler = new JwtSecurityTokenHandler();
            var key = Encoding.ASCII.GetBytes(_appSettings.Secret);
            var tokenDescriptor = new SecurityTokenDescriptor
            {
                Subject = new ClaimsIdentity(new[] { 
                  new Claim("id", user.Id.ToString()) 
                  //add more if we need it
                }
                ),
                Expires = DateTime.UtcNow.AddDays(2),
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature)
            };
            var token = tokenHandler.CreateToken(tokenDescriptor);
            return tokenHandler.WriteToken(token);
        }

        public int? ValidateJwtToken(string token)
        {
            if (token == null)
                return null;

            var tokenHandler = new JwtSecurityTokenHandler();
            var key = Encoding.ASCII.GetBytes(_appSettings.Secret);
            try
            {
                tokenHandler.ValidateToken(token, new TokenValidationParameters
                {
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ValidateIssuer = false,
                    ValidateAudience = false,
                    // set clockskew to zero so tokens expire exactly at token expiration time (instead of 5 minutes later)
                    ClockSkew = TimeSpan.Zero
                }, out SecurityToken validatedToken);

                var jwtToken = (JwtSecurityToken)validatedToken;
                var userId = int.Parse(jwtToken.Claims.First(x => x.Type == "id").Value);

                // return user id from JWT token if validation successful
                return userId;
            }
            catch
            {
                // return null if validation fails
                return null;
            }
        }
    }
}