Voting: import of voters from CSV/Excel

[uatisdeproblem]

The placeholder button is already in place. More or less, this is the expected result:

Everything must happen front-end.

If possible, let's also add the export of the same list.

Note: the maximum amount of voters is 1000.

The import substitute the previous values (i.e., remove all → import).

[uatisdeproblem]

On a branch of the branch voting (coming soon).

[uatisdeproblem]

If possible, let's use Sheet.js (aka XLSX): https://docs.sheetjs.com/docs/getting-started/installation/nodejs. 🙂

Example export:

  private downloadDataAsExcel(flatData: any[], title: string): any {
    // prepare the Excel's workbook
    const wb: WorkBook = { SheetNames: [], Sheets: {}, Props: { Title: title, Author: env.idea.app.title } };
    // add the spreadsheet with users data to the workbook
    utils.book_append_sheet(wb, utils.json_to_sheet(flatData), '1');
    // generate a buffer of the Excel file
    return writeFile(wb, title.concat('.xlsx'));
  }

Example import

private parseRecordsFromExcel(excelContent: File): any[] {
    try {
      const workbook = read(excelContent, { type: 'binary' });
      // acquire the header in a preliminar step,
      // to avoid a bug that occurs when the last column of the first not-header row is empty
      const header = utils.sheet_to_json(workbook.Sheets[workbook.SheetNames[0]], { raw: true, header: 1 })[0];
      // acquire the rows, forcing the header read in the first row
      const rows = utils.sheet_to_json(workbook.Sheets[workbook.SheetNames[0]], {
        raw: true,
        header: header as any,
        defval: '',
        range: 1 // skip header row
      });
      return rows;
    } catch (err) {
      return [];
    }
  }