"""Parse a page and add a Link header to the request, which CloudFlare can use to push static media to an HTTP/2 client."""
from django.conf import settings
from django.contrib.staticfiles import storage
from django.contrib.staticfiles.templatetags import staticfiles
from django.core.files.storage import get_storage_class
from django.utils.functional import LazyObject
EXTENSION_AS = {
'js': 'script',
'css': 'style',
'png': 'image',
'jpg': 'image',
'jpeg': 'image',
'svg': 'image',
'gif': 'image',
'ttf': 'font',
'woff': 'font',
'woff2': 'font'
}
FILE_FILTER = getattr(settings, 'CLOUDFLARE_PUSH_FILTER', lambda x: True)
class FileCollector(object):
def __init__(self):
self.collection = []
def collect(self, path):
if not path.endswith('/') and FILE_FILTER(path.lower()):
self.collection.append(path)
def storage_factory(collector):
class DebugConfiguredStorage(LazyObject):
def _setup(self):
configured_storage_cls = get_storage_class(settings.STATICFILES_STORAGE)
class DebugStaticFilesStorage(configured_storage_cls):
def __init__(self, collector, *args, **kwargs):
super(DebugStaticFilesStorage, self).__init__(*args, **kwargs)
self.collector = collector
def url(self, path):
self.collector.collect(path)
return super(DebugStaticFilesStorage, self).url(path)
self._wrapped = DebugStaticFilesStorage(collector)
return DebugConfiguredStorage
def sort_urls(urls):
"""
Order URLs by extension.
This function accepts a list of URLs and orders them by their extension.
CSS files are sorted to the start of the list, then JS, then everything
else.
"""
order = {"css": 0, "js": 1}
urls.sort(key=lambda x: order.get(x.rsplit(".")[-1].lower(), 2))
return urls
def create_header_content(urls):
"""
Creates the content for the Link header.
"""
links = []
for url in urls[:10]:
ext = url.rsplit(".")[-1].lower()
if ext in EXTENSION_AS:
link = "<%s>; rel=preload; as=%s" % (url, EXTENSION_AS[ext])
else:
link = "<%s>; rel=preload" % (url,)
links.append(link)
return ", ".join(links)
def push_middleware(get_response):
def middleware(request):
collector = FileCollector()
storage.staticfiles_storage = staticfiles.staticfiles_storage = storage_factory(collector)()
response = get_response(request)
collection_copy = list(collector.collection) # For compatibility with 2.7.
urls = list(set(storage.staticfiles_storage.url(f) for f in collection_copy))
urls = sort_urls(urls)
response["Link"] = create_header_content(urls)
return response
return middleware
