API/src/HeartTrackAPI/Services/TokenService.cs

using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;
using Entities;
using Microsoft.IdentityModel.Tokens;

namespace HeartTrackAPI.Services;
public interface ITokenService
{
    string CreateToken(AthleteEntity user);
}

public class TokenService : ITokenService
{
    private readonly IConfiguration _config;
    private readonly SymmetricSecurityKey _key;

    public TokenService(IConfiguration config)
    {
        _config = config;
        _key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_config["JWT:SigningKey"]));
    }
    public string CreateToken(AthleteEntity user)
    {
        var claims = new List<Claim>
        {
            new (JwtRegisteredClaimNames.Email, user.Email),
            new (JwtRegisteredClaimNames.NameId, user.Id.ToString()),
            new (JwtRegisteredClaimNames.GivenName, user.UserName)
        };

        var creds = new SigningCredentials(_key, SecurityAlgorithms.HmacSha512Signature);

        var tokenDescriptor = new SecurityTokenDescriptor
        {
            Subject = new ClaimsIdentity(claims),
            Expires = DateTime.Now.AddDays(7),
            SigningCredentials = creds,
            Issuer = _config["JWT:Issuer"],
            Audience = _config["JWT:Audience"]
        };

        var tokenHandler = new JwtSecurityTokenHandler();

        var token = tokenHandler.CreateToken(tokenDescriptor);

        return tokenHandler.WriteToken(token);
    }
}