StatelessAuthConfigurationFactory.cs

public class StatelessAuthConfigurationFactory : IStatelessAuthConfigurationFactory
{
    private readonly IJwtKeyProvider keyProvider;
    private readonly IUserStore userStore;

    public StatelessAuthConfigurationFactory(IJwtKeyProvider keyProvider, IUserStore userStore)
    {
        this.keyProvider = keyProvider;
        this.userStore = userStore;
    }

    public StatelessAuthenticationConfiguration Create()
    {
        return new StatelessAuthenticationConfiguration(VerifyToken);
    }

    private IUserIdentity VerifyToken(NancyContext context)
    {
        var encryptedToken = context.Request.Headers.Authorization;

        if (ThereIsNoToken(encryptedToken))
            return null;

        var jwt = JsonWebToken.DecodeToObject<Jwt>(encryptedToken, keyProvider.Key);

        if (TheTokenIsExpired(jwt))
            return null;

        if (TheAudienceDoesNotMatch(keyProvider, jwt))
            return null;

        if (TheIssuerDoesNotMatch(keyProvider, jwt))
            return null;

        if (TheUserIsNotValid(jwt))
            return null;

        return new ValidUser(jwt);
    }

    private bool TheUserIsNotValid(Jwt jwt)
    {
        return !userStore.IsUserValid(jwt.Name);
    }

    private static bool TheIssuerDoesNotMatch(IJwtKeyProvider provider, Jwt jwt)
    {
        return !provider.Issuer.Equals(jwt.Issuer);
    }

    private static bool TheAudienceDoesNotMatch(IJwtKeyProvider provider, Jwt jwt)
    {
        return !provider.Audience.Equals(jwt.Audience);
    }

    private static bool ThereIsNoToken(string encryptedToken)
    {
        return string.IsNullOrWhiteSpace(encryptedToken);
    }

    private static bool TheTokenIsExpired(Jwt jwt)
    {
        return jwt.Expiration < DateTime.UtcNow;
    }
}