prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Registration message in calendar wrong
  ### Describe the bug
  In the calendar, when you have to register for an event, it says in the block; You can register on .......
  However, this seems to be the date of when the event will take place (or the registration deadline, can't tell for sure).
  See screenshots for an example.
  
  ### How to reproduce
  Steps to reproduce the behaviour:
  1. Go to the calendar and look for an event with a registration.
  2. Look at the message in the calendar view
  3. Compare with the registration date in the event itself.
  
  ### Expected behaviour
  The message in the calendar view matches the date of when the registrations will open.
  
  ### Screenshots
  ![image](https://user-images.githubusercontent.com/12615607/139580635-4f56710d-23ae-4680-a45d-ace2376cfeb7.png)
  ![image](https://user-images.githubusercontent.com/12615607/139580729-88d92dcd-e60d-4d13-8505-107fc2b69b14.png)
  
  
  </issue>
  <code>
  [start of website/events/api/calendarjs/serializers.py]
  1 from datetime import timedelta
  2 
  3 from django.contrib.humanize.templatetags.humanize import naturaltime
  4 from django.template.defaultfilters import date
  5 from django.utils import timezone
  6 from django.utils.translation import gettext_lazy as _
  7 from rest_framework.reverse import reverse
  8 
  9 from events import services
  10 from events.models import Event
  11 from thaliawebsite.api.calendarjs.serializers import CalenderJSSerializer
  12 
  13 
  14 class EventsCalenderJSSerializer(CalenderJSSerializer):
  15     class Meta(CalenderJSSerializer.Meta):
  16         model = Event
  17 
  18     def _url(self, instance):
  19         return reverse("events:event", kwargs={"pk": instance.id})
  20 
  21     def _class_names(self, instance):
  22         if self.context["member"] and services.is_user_registered(
  23             self.context["member"], instance
  24         ):
  25             if services.user_registration_pending(self.context["member"], instance):
  26                 return ["regular-event-pending-registration"]
  27             else:
  28                 return ["regular-event-has-registration"]
  29         elif (not instance.registration_required) or instance.registration_allowed:
  30             return ["regular-event-registration-open"]
  31         else:
  32             # I think this handles the case that registration is needed, but not yet possible
  33             return ["regular-event-registration-closed"]
  34 
  35     def _registration_info(self, instance: Event):
  36         # If registered in some way
  37         if self.context["member"] and services.is_user_registered(
  38             self.context["member"], instance
  39         ):
  40             queue_pos = services.user_registration_pending(
  41                 self.context["member"], instance
  42             )
  43             # In waiting list
  44             if type(queue_pos) is int:
  45                 return _("In waiting list at position {queue_pos}").format(
  46                     queue_pos=queue_pos
  47                 )
  48             # Actually registered
  49             else:
  50                 return _("You are registered for this event")
  51         # Optional registration possible
  52         elif instance.optional_registration_allowed:
  53             return _("You can optionally register for this event")
  54         # No places left
  55         elif instance.reached_participants_limit():
  56             return _("You can put yourself on the waiting list for this event")
  57         # Registration still possible
  58         elif instance.registration_allowed:
  59             return _("You can register for this event")
  60         # Not registration time yet
  61         elif instance.registration_end:
  62             now = timezone.now()
  63             if instance.registration_end < now:
  64                 return _("Registrations have been closed")
  65             elif instance.registration_end <= now + timedelta(days=2):
  66                 return _("You can register {at_time}").format(
  67                     at_time=naturaltime(instance.registration_end)
  68                 )
  69             else:
  70                 return _("You can register on {date}").format(
  71                     date=date(instance.registration_end)
  72                 )
  73 
  74 
  75 class UnpublishedEventsCalenderJSSerializer(CalenderJSSerializer):
  76     """See CalenderJSSerializer, customised classes."""
  77 
  78     class Meta(CalenderJSSerializer.Meta):
  79         model = Event
  80 
  81     def _class_names(self, instance):
  82         return ["unpublished-event"]
  83 
  84     def _url(self, instance):
  85         return reverse("admin:events_event_details", kwargs={"pk": instance.id})
  86 
  87     def _registration_info(self, instance):
  88         return "Unpublished event"
  89
  [end of website/events/api/calendarjs/serializers.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/website/events/api/calendarjs/serializers.py b/website/events/api/calendarjs/serializers.py
  --- a/website/events/api/calendarjs/serializers.py
  +++ b/website/events/api/calendarjs/serializers.py
  @@ -50,7 +50,7 @@
                   return _("You are registered for this event")
           # Optional registration possible
           elif instance.optional_registration_allowed:
  -            return _("You can optionally register for this event")
  +            return _("Registering for this event is optional")
           # No places left
           elif instance.reached_participants_limit():
               return _("You can put yourself on the waiting list for this event")
  @@ -62,13 +62,13 @@
               now = timezone.now()
               if instance.registration_end < now:
                   return _("Registrations have been closed")
  -            elif instance.registration_end <= now + timedelta(days=2):
  -                return _("You can register {at_time}").format(
  -                    at_time=naturaltime(instance.registration_end)
  +            elif instance.registration_start <= now + timedelta(days=2):
  +                return _("Registrations open {at_time}").format(
  +                    at_time=naturaltime(instance.registration_start)
                   )
               else:
  -                return _("You can register on {date}").format(
  -                    date=date(instance.registration_end)
  +                return _("Registrations open {date}").format(
  +                    date=date(instance.registration_start)
                   )
  
verification_info: {"golden_diff": "diff --git a/website/events/api/calendarjs/serializers.py b/website/events/api/calendarjs/serializers.py\n--- a/website/events/api/calendarjs/serializers.py\n+++ b/website/events/api/calendarjs/serializers.py\n@@ -50,7 +50,7 @@\n                 return _(\"You are registered for this event\")\n         # Optional registration possible\n         elif instance.optional_registration_allowed:\n-            return _(\"You can optionally register for this event\")\n+            return _(\"Registering for this event is optional\")\n         # No places left\n         elif instance.reached_participants_limit():\n             return _(\"You can put yourself on the waiting list for this event\")\n@@ -62,13 +62,13 @@\n             now = timezone.now()\n             if instance.registration_end < now:\n                 return _(\"Registrations have been closed\")\n-            elif instance.registration_end <= now + timedelta(days=2):\n-                return _(\"You can register {at_time}\").format(\n-                    at_time=naturaltime(instance.registration_end)\n+            elif instance.registration_start <= now + timedelta(days=2):\n+                return _(\"Registrations open {at_time}\").format(\n+                    at_time=naturaltime(instance.registration_start)\n                 )\n             else:\n-                return _(\"You can register on {date}\").format(\n-                    date=date(instance.registration_end)\n+                return _(\"Registrations open {date}\").format(\n+                    date=date(instance.registration_start)\n                 )\n", "issue": "Registration message in calendar wrong\n### Describe the bug\r\nIn the calendar, when you have to register for an event, it says in the block; You can register on .......\r\nHowever, this seems to be the date of when the event will take place (or the registration deadline, can't tell for sure).\r\nSee screenshots for an example.\r\n\r\n### How to reproduce\r\nSteps to reproduce the behaviour:\r\n1. Go to the calendar and look for an event with a registration.\r\n2. Look at the message in the calendar view\r\n3. Compare with the registration date in the event itself.\r\n\r\n### Expected behaviour\r\nThe message in the calendar view matches the date of when the registrations will open.\r\n\r\n### Screenshots\r\n![image](https://user-images.githubusercontent.com/12615607/139580635-4f56710d-23ae-4680-a45d-ace2376cfeb7.png)\r\n![image](https://user-images.githubusercontent.com/12615607/139580729-88d92dcd-e60d-4d13-8505-107fc2b69b14.png)\r\n\n", "before_files": [{"content": "from datetime import timedelta\n\nfrom django.contrib.humanize.templatetags.humanize import naturaltime\nfrom django.template.defaultfilters import date\nfrom django.utils import timezone\nfrom django.utils.translation import gettext_lazy as _\nfrom rest_framework.reverse import reverse\n\nfrom events import services\nfrom events.models import Event\nfrom thaliawebsite.api.calendarjs.serializers import CalenderJSSerializer\n\n\nclass EventsCalenderJSSerializer(CalenderJSSerializer):\n    class Meta(CalenderJSSerializer.Meta):\n        model = Event\n\n    def _url(self, instance):\n        return reverse(\"events:event\", kwargs={\"pk\": instance.id})\n\n    def _class_names(self, instance):\n        if self.context[\"member\"] and services.is_user_registered(\n            self.context[\"member\"], instance\n        ):\n            if services.user_registration_pending(self.context[\"member\"], instance):\n                return [\"regular-event-pending-registration\"]\n            else:\n                return [\"regular-event-has-registration\"]\n        elif (not instance.registration_required) or instance.registration_allowed:\n            return [\"regular-event-registration-open\"]\n        else:\n            # I think this handles the case that registration is needed, but not yet possible\n            return [\"regular-event-registration-closed\"]\n\n    def _registration_info(self, instance: Event):\n        # If registered in some way\n        if self.context[\"member\"] and services.is_user_registered(\n            self.context[\"member\"], instance\n        ):\n            queue_pos = services.user_registration_pending(\n                self.context[\"member\"], instance\n            )\n            # In waiting list\n            if type(queue_pos) is int:\n                return _(\"In waiting list at position {queue_pos}\").format(\n                    queue_pos=queue_pos\n                )\n            # Actually registered\n            else:\n                return _(\"You are registered for this event\")\n        # Optional registration possible\n        elif instance.optional_registration_allowed:\n            return _(\"You can optionally register for this event\")\n        # No places left\n        elif instance.reached_participants_limit():\n            return _(\"You can put yourself on the waiting list for this event\")\n        # Registration still possible\n        elif instance.registration_allowed:\n            return _(\"You can register for this event\")\n        # Not registration time yet\n        elif instance.registration_end:\n            now = timezone.now()\n            if instance.registration_end < now:\n                return _(\"Registrations have been closed\")\n            elif instance.registration_end <= now + timedelta(days=2):\n                return _(\"You can register {at_time}\").format(\n                    at_time=naturaltime(instance.registration_end)\n                )\n            else:\n                return _(\"You can register on {date}\").format(\n                    date=date(instance.registration_end)\n                )\n\n\nclass UnpublishedEventsCalenderJSSerializer(CalenderJSSerializer):\n    \"\"\"See CalenderJSSerializer, customised classes.\"\"\"\n\n    class Meta(CalenderJSSerializer.Meta):\n        model = Event\n\n    def _class_names(self, instance):\n        return [\"unpublished-event\"]\n\n    def _url(self, instance):\n        return reverse(\"admin:events_event_details\", kwargs={\"pk\": instance.id})\n\n    def _registration_info(self, instance):\n        return \"Unpublished event\"\n", "path": "website/events/api/calendarjs/serializers.py"}]}