// Hook: BeforeProcessing
// Halt the job if a required source file is missing.
//
// BeforeProcessing runs before any workbook is opened, so it's a great place
// to check that everything the job depends on is in place. AddError stops the
// job immediately with a clear message in the job history.

using System.IO;

var requiredFile = @"\\fileserver\reports\source_data.xlsx";

if (!File.Exists(requiredFile))
{
    AddError($"Required source file is missing: {requiredFile}. Please ensure the file is in place before running this job.");
}

Logger.LogInformation($"Pre-flight file check passed for '{JobName}'.");