diff -r 12e8b65146d9 -r aff5d3498f68 cubicweb/web/test/data/cubicweb_file/hooks.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/web/test/data/cubicweb_file/hooks.py	Tue Mar 19 13:17:47 2019 +0100
@@ -0,0 +1,69 @@
+import os
+
+from cubicweb.server import hook
+from cubicweb.predicates import is_instance
+from cubicweb.entities import adapters
+
+from cubicweb_file.entities import UnResizeable
+
+
+class UpdateFileHook(hook.Hook):
+    """a file has been updated, check data_format/data_encoding consistency
+    """
+    __regid__ = 'updatefilehook'
+    __select__ = hook.Hook.__select__ & is_instance('File')
+    events = ('before_add_entity', 'before_update_entity',)
+    order = -1  # should be run before other hooks
+    category = 'hash'
+
+    def __call__(self):
+        edited = self.entity.cw_edited
+        if 'data' in edited:
+            self.entity.set_format_and_encoding()
+            maxsize = None
+            if maxsize and self.entity.data_format.startswith('image/'):
+                iimage = self.entity.cw_adapt_to('IImage')
+                try:
+                    edited['data'] = iimage.resize(maxsize)
+                except UnResizeable:
+                    # if the resize fails for some reason, do nothing
+                    # (original image will be stored)
+                    pass
+
+            # thumbnail cache invalidation
+            if 'update' in self.event and 'data' in edited:
+                thumb = self.entity.cw_adapt_to('IThumbnail')
+                if not thumb:
+                    return
+                thumbpath = thumb.thumbnail_path()
+                if thumbpath:
+                    try:
+                        os.unlink(thumbpath)
+                    except Exception as exc:
+                        self.warning(
+                            'could not invalidate thumbnail file `%s` '
+                            '(cause: %s)',
+                            thumbpath, exc)
+
+
+class FileIDownloadableAdapter(adapters.IDownloadableAdapter):
+    __select__ = is_instance('File')
+
+    # IDownloadable
+    def download_url(self, **kwargs):
+        # include filename in download url for nicer url
+        name = self._cw.url_quote(self.download_file_name())
+        path = '%s/raw/%s' % (self.entity.rest_path(), name)
+        return self._cw.build_url(path, **kwargs)
+
+    def download_content_type(self):
+        return self.entity.data_format
+
+    def download_encoding(self):
+        return self.entity.data_encoding
+
+    def download_file_name(self):
+        return self.entity.data_name
+
+    def download_data(self):
+        return self.entity.data.getvalue()