Add MultiSheetListExporter base class

src/pretix/base/exporter.py

@@ -5,7 +5,7 @@ from typing import Tuple
 
 from defusedcsv import csv
 from django import forms
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import ugettext, ugettext_lazy as _
 from openpyxl import Workbook
 from openpyxl.cell.cell import KNOWN_TYPES
 
@@ -143,3 +143,73 @@ class ListExporter(BaseExporter):
             return self._render_csv(form_data, dialect='excel')
         elif form_data.get('_format') == 'semicolon':
             return self._render_csv(form_data, dialect='excel', delimiter=';')
+
+
+class MultiSheetListExporter(ListExporter):
+
+    @property
+    def sheets(self):
+        raise NotImplementedError()
+
+    @property
+    def export_form_fields(self) -> dict:
+        choices = [
+            ('xlsx', _('Excel (.xlsx)')),
+        ]
+        for s, l in self.sheets:
+            choices += [
+                (s + ':default', str(l) + ' – ' + ugettext('CSV (with commas)')),
+                (s + ':excel', str(l) + ' – ' + ugettext('CSV (Excel-style)')),
+                (s + ':semicolon', str(l) + ' – ' + ugettext('CSV (with semicolons)')),
+            ]
+        ff = OrderedDict(
+            [
+                ('_format',
+                 forms.ChoiceField(
+                     label=_('Export format'),
+                     choices=choices,
+                 )),
+            ]
+        )
+        ff.update(self.additional_form_fields)
+        return ff
+
+    def iterate_list(self, form_data):
+        pass
+
+    def iterate_sheet(self, form_data, sheet):
+        raise NotImplementedError()  # noqa
+
+    def _render_sheet_csv(self, form_data, sheet, **kwargs):
+        output = io.StringIO()
+        writer = csv.writer(output, **kwargs)
+        for line in self.iterate_sheet(form_data, sheet):
+            writer.writerow(line)
+        return self.get_filename() + '.csv', 'text/csv', output.getvalue().encode("utf-8")
+
+    def _render_xlsx(self, form_data):
+        wb = Workbook()
+        ws = wb.get_active_sheet()
+        wb.remove(ws)
+        for s, l in self.sheets:
+            ws = wb.create_sheet(str(l))
+            for i, line in enumerate(self.iterate_sheet(form_data, sheet=s)):
+                for j, val in enumerate(line):
+                    ws.cell(row=i + 1, column=j + 1).value = str(val) if not isinstance(val, KNOWN_TYPES) else val
+
+        with tempfile.NamedTemporaryFile(suffix='.xlsx') as f:
+            wb.save(f.name)
+            f.seek(0)
+            return self.get_filename() + '.xlsx', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', f.read()
+
+    def render(self, form_data: dict) -> Tuple[str, str, bytes]:
+        if form_data.get('_format') == 'xlsx':
+            return self._render_xlsx(form_data)
+        elif ':' in form_data.get('_format'):
+            sheet, f = form_data.get('_format').split(':')
+            if f == 'default':
+                return self._render_sheet_csv(form_data, sheet, quoting=csv.QUOTE_NONNUMERIC, delimiter=',')
+            elif f == 'csv-excel':
+                return self._render_sheet_csv(form_data, sheet, dialect='excel')
+            elif f == 'semicolon':
+                return self._render_sheet_csv(form_data, sheet, dialect='excel', delimiter=';')