namespace QuestionsApi.Services;

public sealed class ExamSimulationScoringMigrationService : BackgroundService
{
    private readonly ExamSimulationStore _simulations;
    private readonly ILogger<ExamSimulationScoringMigrationService> _logger;

    public ExamSimulationScoringMigrationService(
        ExamSimulationStore simulations,
        ILogger<ExamSimulationScoringMigrationService> logger)
    {
        _simulations = simulations;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        try
        {
            var result = await _simulations.BackfillScoringModelAsync(stoppingToken);
            _logger.LogInformation(
                "Exam simulation scoring migration completed; recalculated {UpdatedCount} simulation(s)",
                result.UpdatedCount);
            foreach (var reference in result.MissingQuestionIds)
                _logger.LogWarning(
                    "Exam simulation scoring migration used neutral difficulty for missing question {Reference}",
                    reference);
        }
        catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
        {
        }
        catch (Exception exception)
        {
            _logger.LogError(exception, "Exam simulation scoring migration failed");
        }
    }
}