using System.Threading;
using Microsoft.Extensions.DependencyInjection;
using NCrontab;
using LCU.Api.Internal.DispatcherSharedLib.Utilities;
using LCU.Api.Internal.Dispatcher.Configurations;
using LCU.Api.Internal.Dispatcher.Services.DispatcherOperationServices;
using LCU.Library.Internal.LCUHostedService.LCUBackgroundService;
namespace LCU.Api.Internal.Dispatcher.HostedServices;

public class BatchErroredJobsHostedService : LCUBackgroundService, IBatchErroredJobsHostedService
{
    private readonly ApiConfiguration _apiConfiguration;
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly CrontabSchedule _batchErroredJobsSchedule;
    private DateTime _nextScheduleRun;
    public const string DefaultBatchErroredJobsCronPattern = "*/15 * * * *";
    private CancellationToken _cancellationToken;

    public BatchErroredJobsHostedService(IServiceScopeFactory scopeFactory,
                                  ApiConfiguration apiConfiguration)
    {
        _scopeFactory = scopeFactory;
        _apiConfiguration = apiConfiguration;
        _batchErroredJobsSchedule = CronHelpers.SetCronSchedule(_apiConfiguration.BatchErroredJobsCronSchedule,
                                                                DefaultBatchErroredJobsCronPattern);
        _nextScheduleRun = _batchErroredJobsSchedule.GetNextOccurrence(DateTime.Now);
        _cancellationToken = new CancellationToken();
    }

    protected override async Task ExecuteAsync(CancellationToken cancellationToken)
    {
        if (!_apiConfiguration.FeatureFlags.RunBatchErroredJobsHostedService)
        {
			Log.Error("Batch Errored Jobs Hosted Service is disabled by feature flag. Service not started.");
			return;
		}

        Log.Debug("Dispatcher's Batch Errored Jobs Hosted Service is starting.");
        try
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                await Task.Delay(UntilNextExecution(), cancellationToken); // wait until next time

                using (var scope = _scopeFactory.CreateAsyncScope())
                {
                    Log.Debug("Running Batch Errored Jobs Service");
                    await scope.ServiceProvider.GetRequiredService<IBatchErroredJobsService>().PerformBatchErroredJobs(_cancellationToken);
                }

                _nextScheduleRun = _batchErroredJobsSchedule.GetNextOccurrence(DateTime.Now);
            }
        }
        catch(OperationCanceledException taskCanceledEx)
        {
            Log.Error(taskCanceledEx, $"Manual start/stop of Dispatcher's Batch Errored Jobs Hosted Service was initiated.");
        }
        catch (Exception exception)
        {
            Log.Error(exception,
                "Error trying to startup main thread for Dispatcher's Batch Errored Jobs Hosted Service");
        }

        Log.Debug("Dispatcher's Batch Errored Jobs Hosted Service is stopping.");
    }

    private int UntilNextExecution() => Math.Max(0, (int)_nextScheduleRun.Subtract(DateTime.Now).TotalMilliseconds);
}