using OpenIddict.Abstractions;

namespace PrivaPub.Api.Mastodon.Auth
{
	public class OAuthPruner : BackgroundService
	{
		static readonly TimeSpan Interval = TimeSpan.FromHours(6);
		static readonly TimeSpan Threshold = TimeSpan.FromDays(14);

		readonly IServiceProvider _services;
		readonly ILogger<OAuthPruner> _logger;

		public OAuthPruner(IServiceProvider services, ILogger<OAuthPruner> logger)
		{
			_services = services;
			_logger = logger;
		}

		protected override async Task ExecuteAsync(CancellationToken stoppingToken)
		{
			while (!stoppingToken.IsCancellationRequested)
			{
				try
				{
					await Task.Delay(Interval, stoppingToken);
					var (tokens, authorizations) = await Prune(DateTimeOffset.UtcNow - Threshold, stoppingToken);
					if (tokens + authorizations > 0)
						_logger.LogInformation("{Service} removed {Tokens} tokens and {Authorizations} authorizations", nameof(OAuthPruner), tokens, authorizations);
				}
				catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
				{
					return;
				}
				catch (Exception ex)
				{
					_logger.LogWarning(ex, "{Service} pass failed", nameof(OAuthPruner));
				}
			}
		}

		//one pass: tokens and authorizations created before the threshold that are no longer valid
		public async Task<(long Tokens, long Authorizations)> Prune(DateTimeOffset threshold, CancellationToken token)
		{
			using var scope = _services.CreateScope();
			var tokens = await scope.ServiceProvider.GetRequiredService<IOpenIddictTokenManager>().PruneAsync(threshold, token);
			var authorizations = await scope.ServiceProvider.GetRequiredService<IOpenIddictAuthorizationManager>().PruneAsync(threshold, token);
			return (tokens, authorizations);
		}
	}
}