using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Akari.Prototype.Server.Services
{
    public class AuthLifetimeService : IHostedService
    {
        public static TimeSpan CleanupInterval => TimeSpan.FromSeconds(5);
        public static TimeSpan AuthLifetime => TimeSpan.FromSeconds(30);

        private readonly ILogger<AuthLifetimeService> _logger;
        private readonly IAuthManager _authManager;
        private CancellationTokenSource _cleanupCancellationTokenSource;
        private Timer _timer;

        public AuthLifetimeService(ILogger<AuthLifetimeService> logger, IAuthManager authManager)
        {
            _logger = logger;
            _authManager = authManager;
        }

        public Task StartAsync(CancellationToken cancellationToken)
        {
            _cleanupCancellationTokenSource = new CancellationTokenSource();

            _timer = new Timer(AuthCleanup, _cleanupCancellationTokenSource.Token, CleanupInterval, CleanupInterval);

            _logger.LogDebug("Cleanup timer is running");

            return Task.CompletedTask;
        }

        public Task StopAsync(CancellationToken cancellationToken)
        {
            _logger.LogDebug("Stopping");

            _timer?.Change(Timeout.Infinite, Timeout.Infinite);

            _cleanupCancellationTokenSource?.Cancel();

            return Task.CompletedTask;
        }

        private void AuthCleanup(object state)
        {
            var cancellationToken = (CancellationToken)state;
            var date = DateTime.Now;

            if (cancellationToken.IsCancellationRequested)
            {
                _logger.LogDebug("Cancellation requested, aborted cleanup");

                return;
            }

            _logger.LogDebug($"Running cleanup at: {date}");

            foreach (var (key, value) in _authManager.Pairs)
            {
                if (cancellationToken.IsCancellationRequested)
                {
                    _logger.LogDebug("Cancellation requested, aborted cleanup");

                    return;
                }

                if (date - value.CreationDate >= AuthLifetime)
                {
                    _logger.LogDebug($"'{key}' auth expired");

                    _authManager.Remove(key);
                }
            }
        }

        public void Dispose()
        {
            _timer?.Dispose();
        }
    }
}