import datetime
import json
import urllib
from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from django.core.signing import TimestampSigner
from django.db import models
from django.shortcuts import render
class PagePreview(models.Model):
token = models.CharField(max_length=255, unique=True)
content_type = models.ForeignKey(
"contenttypes.ContentType", on_delete=models.CASCADE
)
content_json = models.TextField()
created_at = models.DateField(auto_now_add=True)
def as_page(self):
content = json.loads(self.content_json)
page_model = ContentType.objects.get_for_id(
content["content_type"]
).model_class()
page = page_model.from_json(self.content_json)
page.pk = content["pk"]
return page
@classmethod
def garbage_collect(cls):
yesterday = datetime.datetime.now() - datetime.timedelta(hours=24)
cls.objects.filter(created_at__lt=yesterday).delete()
class HeadlessPreviewMixin:
@classmethod
def get_preview_signer(cls):
return TimestampSigner(salt="headlesspreview.token")
def create_page_preview(self):
if self.pk is None:
identifier = "parent_id=%d;page_type=%s" % (
self.get_parent().pk,
self._meta.label,
)
else:
identifier = "id=%d" % self.pk
# Note: Using get_or_create() instead of just create() to avoid unique constraint failures if
# preview is clicked multiple times
preview, _ = PagePreview.objects.get_or_create(
token=self.get_preview_signer().sign(identifier),
content_type=self.content_type,
content_json=self.to_json(),
)
return preview
def update_page_preview(self, token):
return PagePreview.objects.update_or_create(
token=token,
defaults={
"content_type": self.content_type,
"content_json": self.to_json(),
},
)
def get_client_root_url(self):
try:
return settings.HEADLESS_PREVIEW_CLIENT_URLS[self.get_site().hostname]
except (AttributeError, KeyError):
return settings.HEADLESS_PREVIEW_CLIENT_URLS["default"]
@classmethod
def get_content_type_str(cls):
return cls._meta.app_label + "." + cls.__name__.lower()
def get_preview_url(self, token):
return (
self.get_client_root_url()
+ "?"
+ urllib.parse.urlencode(
{"content_type": self.get_content_type_str(), "token": token}
)
)
def dummy_request(self, original_request=None, **meta):
request = super(HeadlessPreviewMixin, self).dummy_request(
original_request=original_request, **meta
)
request.GET = request.GET.copy()
request.GET["live_preview"] = original_request.GET.get("live_preview")
return request
def serve_preview(self, request, mode_name):
use_live_preview = request.GET.get("live_preview")
token = request.COOKIES.get("used-token")
if use_live_preview and token:
page_preview, existed = self.update_page_preview(token)
PagePreview.garbage_collect()
from wagtail_headless_preview.signals import (
preview_update,
) # Imported locally as live preview is optional
preview_update.send(sender=HeadlessPreviewMixin, token=token)
else:
PagePreview.garbage_collect()
page_preview = self.create_page_preview()
page_preview.save()
response_token = token or page_preview.token
response = render(
request,
"wagtail_headless_preview/preview.html",
{"preview_url": self.get_preview_url(response_token)},
)
if use_live_preview:
# Set cookie that auto-expires after 5mins
response.set_cookie(key="used-token", value=response_token, max_age=300)
return response
@classmethod
def get_page_from_preview_token(cls, token):
content_type = ContentType.objects.get_for_model(cls)
# Check token is valid
cls.get_preview_signer().unsign(token)
try:
return PagePreview.objects.get(
content_type=content_type, token=token
).as_page()
except PagePreview.DoesNotExist:
return
