JWT Cache

JwtCache.cs

using System;
using System.IdentityModel.Tokens.Jwt;
using System.Threading.Tasks;
using Microsoft.Extensions.Caching.Memory;

namespace JwtUtils
{
    public interface IJwtCache
    {
        void Set(string key, JwtSecurityToken token);

        Task<string> GetOrCreateAsync(string key, Func<Task<JwtSecurityToken>> tokenFactory = null);
    }

    public class JwtCacheOptions
    {
        public TimeSpan ClockSkew { get; set; } = TimeSpan.FromSeconds(15);
    }

    internal class JwtCache : IJwtCache
    {
        private readonly IMemoryCache _cache;
        private readonly JwtCacheOptions _options;

        public JwtCache(IMemoryCache cache, JwtCacheOptions options = null)
        {
            _cache = cache;
            _options = options ?? new JwtCacheOptions();
        }

        public void Set(string key, JwtSecurityToken token)
        {
            if (token.ValidTo < DateTime.UtcNow)
            {
                throw new ArgumentException("Token has expired", nameof(token));
            }

            _cache.Set(key, token, token.ValidTo - _options.ClockSkew);
        }

        public Task<string> GetOrCreateAsync(string key, Func<Task<JwtSecurityToken>> tokenFactory = null)
        {
            if (tokenFactory == null)
            {
                return Task.FromResult(_cache.Get<string>(key));
            }

            return _cache.GetOrCreateAsync<string>(
                key,
                async entry =>
                {
                    var token = await tokenFactory();
                    entry.AbsoluteExpiration = token.ValidTo - _options.ClockSkew;
                    return new JwtSecurityTokenHandler().WriteToken(token);
                }
            );
        }
    }
}