Allow to use a custom domain per event (#1617)

* Drop support for maindomain_urls/subdomain_urls in plugins

* Allow to use a custom domain per event

* Fix bug when manually saving domains

* Fix custom domains in debugging

* Fix middleware

* Fix middleware again, update docs

src/pretix/control/forms/event.py

@@ -1,4 +1,4 @@
-from urllib.parse import urlencode
+from urllib.parse import urlencode, urlparse
 
 from django import forms
 from django.conf import settings
@@ -32,6 +32,7 @@ from pretix.control.forms import (
     SplitDateTimeField, SplitDateTimePickerWidget,
 )
 from pretix.control.forms.widgets import Select2
+from pretix.multidomain.models import KnownDomain
 from pretix.multidomain.urlreverse import build_absolute_uri
 from pretix.plugins.banktransfer.payment import BankTransfer
 from pretix.presale.style import get_fonts
@@ -291,6 +292,15 @@ class EventUpdateForm(I18nModelForm):
 
     def __init__(self, *args, **kwargs):
         self.change_slug = kwargs.pop('change_slug', False)
+        self.domain = kwargs.pop('domain', False)
+
+        kwargs.setdefault('initial', {})
+        self.instance = kwargs['instance']
+        if self.domain and self.instance:
+            initial_domain = self.instance.domains.first()
+            if initial_domain:
+                kwargs['initial'].setdefault('domain', initial_domain.domainname)
+
         super().__init__(*args, **kwargs)
         if not self.change_slug:
             self.fields['slug'].widget.attrs['readonly'] = 'readonly'
@@ -298,6 +308,47 @@ class EventUpdateForm(I18nModelForm):
         self.fields['location'].widget.attrs['placeholder'] = _(
             'Sample Conference Center\nHeidelberg, Germany'
         )
+        if self.domain:
+            self.fields['domain'] = forms.CharField(
+                max_length=255,
+                label=_('Custom domain'),
+                required=False,
+                help_text=_('You need to configure the custom domain in the webserver beforehand.')
+            )
+
+    def clean_domain(self):
+        d = self.cleaned_data['domain']
+        if d:
+            if d == urlparse(settings.SITE_URL).hostname:
+                raise ValidationError(
+                    _('You cannot choose the base domain of this installation.')
+                )
+            if KnownDomain.objects.filter(domainname=d).exclude(event=self.instance.pk).exists():
+                raise ValidationError(
+                    _('This domain is already in use for a different event or organizer.')
+                )
+        return d
+
+    def save(self, commit=True):
+        instance = super().save(commit)
+
+        if self.domain:
+            current_domain = instance.domains.first()
+            if self.cleaned_data['domain']:
+                if current_domain and current_domain.domainname != self.cleaned_data['domain']:
+                    current_domain.delete()
+                    KnownDomain.objects.create(
+                        organizer=instance.organizer, event=instance, domainname=self.cleaned_data['domain']
+                    )
+                elif not current_domain:
+                    KnownDomain.objects.create(
+                        organizer=instance.organizer, event=instance, domainname=self.cleaned_data['domain']
+                    )
+            elif current_domain:
+                current_domain.delete()
+            instance.cache.clear()
+
+        return instance
 
     def clean_slug(self):
         if self.change_slug: