AtlassianOAuthCredentialsManager.cs

using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.IdentityModel.JsonWebTokens;
using Nito.AsyncEx;


namespace YourProject
{
	public interface IAtlassianOAuthCredentialsManager
	{
		Task<string> GetJwtAsync();
		Task RefreshJwtAsync();
	}
	
	private readonly IAtlassianOAuthenticator _authenticator;
		private readonly AsyncReaderWriterLock _jwtLock = new AsyncReaderWriterLock();
		private AtlassianOAuthTokenResponse _tokenResponse = null;
		private DateTime? _validTo = null;

		public AtlassianOAuthCredentialsManager(
			IAtlassianOAuthenticator authenticator
		)
		{
			_authenticator = authenticator;
		}

		public async Task<string> GetJwtAsync()
		{
			if (await ShouldRefreshJwtAsync())
			{
				await RefreshJwtAsync();
			}

			string result;
			using (await _jwtLock.ReaderLockAsync())
			{
				result = _tokenResponse.access_token;   // should make an immutable copy
			}

			return result;
		}

		public async Task<AtlassianOAuthTokenResponse> GetCurrentTokenResponse()
		{
			using (await _jwtLock.ReaderLockAsync())
			{
				var result = new AtlassianOAuthTokenResponse()
				{
					access_token = _tokenResponse.access_token,
					scope = _tokenResponse.scope,
					expires_in = _tokenResponse.expires_in,
					token_type = _tokenResponse.token_type
				};
				return result;
			}
		}

		private async Task<bool> ShouldRefreshJwtAsync()
		{
			using(await _jwtLock.ReaderLockAsync()) {
				if (_tokenResponse == null) return true;
				if (_validTo == null) return true;
				if (DateTime.Now >= _validTo.Value) return true;

				return false;
			}
		}

		public async Task RefreshJwtAsync()
		{
			using(await _jwtLock.WriterLockAsync()) {
				var response = await _authenticator.AuthenticateAsync();
				SetJwt(response);
			}
		}

		private void SetJwt(AtlassianOAuthTokenResponse tokenResponse)
		{
			_tokenResponse = tokenResponse;

			var jwtHandler = new JsonWebTokenHandler();
			var token = jwtHandler.ReadJsonWebToken(_tokenResponse.access_token);

			//	https://developer.atlassian.com/cloud/jira/software/integrate-jsw-cloud-with-onpremises-tools/
			//	Write your code to anticipate that a granted token might no longer work. For example,
			//	track the expiration time and request a new token before the existing one expires
			//	(at least 30-60 seconds prior).
			_validTo = token.ValidTo.AddMinutes(-1);
		}
	}
}