namespace ComplianceBLL.Common;

// Shared MMYYYY return-period parsing — was previously a private copy inside GSTOutwardBLL with no
// shape validation (int.Parse on a malformed string throws an unhandled FormatException/
// ArgumentOutOfRangeException that surfaces as a 500 with no useful message).
public static class ReturnPeriodHelper
{
    public static bool IsValidShape(string returnPeriod)
        => returnPeriod.Length == 6
           && int.TryParse(returnPeriod.AsSpan(0, 2), out var month) && month is >= 1 and <= 12
           && int.TryParse(returnPeriod.AsSpan(2, 4), out _);

    public static (DateTime fromDate, DateTime toDate) ParseReturnPeriod(string returnPeriod)
    {
        var month = int.Parse(returnPeriod[..2]);
        var year  = int.Parse(returnPeriod[2..]);
        var from  = new DateTime(year, month, 1);
        return (from, from.AddMonths(1).AddDays(-1));
    }

    public static (int year, int month) ParseReturnPeriodYearMonth(string returnPeriod)
    {
        var month = int.Parse(returnPeriod[..2]);
        var year  = int.Parse(returnPeriod[2..]);
        return (year, month);
    }
}