using DevExpress.Spreadsheet;
using Microsoft.AspNetCore.Mvc;

async Task<Stream> ImportList(IList<UserModel> users, string[] selectedFields, DocumentFormat outputFormat) {

    using Workbook workbook = new Workbook();

    // Prepare first worksheet
    var firstWorksheet = workbook.Worksheets.First();
    firstWorksheet.Name = "Users";
    firstWorksheet["A1"].Value = "Import data from a list of users:";

    // Set headers
    if(selectedFields == null || !selectedFields.Any()) {
        selectedFields = new string[3];
        selectedFields[0] = nameof(UserModel.FirstName);
        selectedFields[1] = nameof(UserModel.LastName);
        selectedFields[2] = nameof(UserModel.BirthDate);
    }
    for(int i = 0; i < selectedFields.Length; i++) {
        firstWorksheet[0, i + 1].Value = selectedFields[i];
    }
    // Make header text bold
    var formatting = firstWorksheet["B1:D1"].BeginUpdateFormatting();
    formatting.Font.Bold = true;
    firstWorksheet["B1:D1"].EndUpdateFormatting(formatting);

    // Import values from specific data source fields
    // Data starts with the B1 cell.
    var importOptions = new DataSourceImportOptions() {
        PropertyNames = selectedFields
    };
    firstWorksheet.Import(users, 1, 1, importOptions);

    // AutoFit columns
    firstWorksheet.Columns.AutoFit(0, 4);

    // Prepare output stream
    var outputStream = new MemoryStream();

    // Save the document
    workbook.SaveDocument(outputStream, outputFormat);
    outputStream.Seek(0, SeekOrigin.Begin);

    return outputStream;
}