IM/backend/IM_API/Services/JWTService.cs

using IM_API.Interface.Services;
using Microsoft.IdentityModel.Tokens;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;

namespace IM_API.Services
{
    public class JWTService : IJWTService
    {
        private readonly IConfiguration _config;
        private readonly string _key;
        private readonly string _issuer;
        private readonly string _audience;
        private readonly int _accessMinutes;

        public JWTService(IConfiguration config)
        {
            _config = config;
            _key = _config["Jwt:Key"]!;
            _issuer = _config["Jwt:Issuer"]!;
            _audience = _config["Jwt:Audience"]!;
            _accessMinutes = int.Parse(_config["Jwt:AccessTokenMinutes"] ?? "15");
        }

        public string GenerateAccessToken(IEnumerable<Claim> claims, DateTime expiresAt)
        {
            var keyBytes = Encoding.UTF8.GetBytes(_key);
            var creds = new SigningCredentials(new SymmetricSecurityKey(keyBytes), SecurityAlgorithms.HmacSha256);

            var token = new JwtSecurityToken(
                issuer: _issuer,
                audience: _audience,
                claims: claims,
                expires: expiresAt,
                signingCredentials: creds
            );

            return new JwtSecurityTokenHandler().WriteToken(token);
        }

        public (string token, DateTime expiresAt) CreateAccessTokenForUser(int userId, string username, string role)
        {
            var expiresAt = DateTime.Now.AddMinutes(_accessMinutes);
            var claims = new[]
            {
                new Claim(JwtRegisteredClaimNames.Sub, userId.ToString()),
                new Claim(ClaimTypes.Name, username),
                new Claim(ClaimTypes.Role, role)
            };
            var token = GenerateAccessToken(claims, expiresAt);
            return (token, expiresAt);
        }
    }
}