Add a file upload type to questions (#534)

* Initial stuff

* More features

src/pretix/base/exporters/__init__.py

@@ -1,3 +1,4 @@
+from .answers import *  # noqa
 from .invoices import *  # noqa
 from .json import *  # noqa
 from .mail import *  # noqa

src/pretix/base/exporters/answers.py

@@ -0,0 +1,61 @@
+import os
+import tempfile
+from collections import OrderedDict
+from zipfile import ZipFile
+
+from django import forms
+from django.dispatch import receiver
+from django.utils.translation import ugettext_lazy as _
+
+from pretix.base.models import QuestionAnswer
+
+from ..exporter import BaseExporter
+from ..signals import register_data_exporters
+
+
+class AnswerFilesExporter(BaseExporter):
+    identifier = 'answerfiles'
+    verbose_name = _('Answers to file upload questions')
+
+    @property
+    def export_form_fields(self):
+        return OrderedDict(
+            [
+                ('questions',
+                 forms.ModelMultipleChoiceField(
+                     queryset=self.event.questions.filter(type='F'),
+                     label=_('Questions'),
+                     widget=forms.CheckboxSelectMultiple,
+                     required=False
+                 )),
+            ]
+        )
+
+    def render(self, form_data: dict):
+        qs = QuestionAnswer.objects.filter(
+            orderposition__order__event=self.event,
+        ).select_related('orderposition', 'orderposition__order', 'question')
+        if form_data.get('questions'):
+            qs = qs.filter(question__in=form_data['questions'])
+        with tempfile.TemporaryDirectory() as d:
+            with ZipFile(os.path.join(d, 'tmp.zip'), 'w') as zipf:
+                for i in qs:
+                    if i.file:
+                        i.file.open('r')
+                        fname = '{}-{}-{}-q{}-{}'.format(
+                            self.event.slug.upper(),
+                            i.orderposition.order.code,
+                            i.orderposition.positionid,
+                            i.question.pk,
+                            os.path.basename(i.file.name).split('.', 1)[1]
+                        )
+                        zipf.writestr(fname, i.file.read())
+                        i.file.close()
+
+            with open(os.path.join(d, 'tmp.zip'), 'rb') as zipf:
+                return 'answers.zip', 'application/zip', zipf.read()
+
+
+@receiver(register_data_exporters, dispatch_uid="exporter_answers")
+def register_anwers_export(sender, **kwargs):
+    return AnswerFilesExporter