On demand versions

filebrowser/base.py

@@ -430,11 +430,20 @@ def is_empty(self):
         return False
 
     # VERSION ATTRIBUTES/PROPERTIES
+    # version
     # is_version
     # versions_basedir
     # original
     # original_filename
 
+    @property
+    def version(self):
+        "Returns version name"
+        tmp = self.filename_root.split("_")
+        if tmp[-1] in VERSIONS:
+            return tmp[-1]
+        return None
+
     @property
     def is_version(self):
         "True if file is a version, false otherwise"

filebrowser/middleware.py

@@ -0,0 +1,32 @@
+from django.conf import settings
+from django.http.response import Http404
+from django.shortcuts import redirect
+from filebrowser.base import FileObject
+
+
+class OnDemandMiddleware(object):
+    """
+    Middleware that handles 404 errors of images and generates missing image versions.
+
+    If the new version is successfully generated, redirects to generated version url.
+    This make sure new request is made by browser, and  file serving will be done
+    in ordinary way (probably by web-server).
+
+    Just make sure the web-server request is handled by django if the requested file does not exist.
+    """
+
+    def process_exception(self, request, exception):
+        # Check that exception is 404 error for file in media folder
+        if isinstance(exception, Http404) and request.path.startswith(settings.MEDIA_URL):
+            # Strip MEDIA_URL from path and test if requested path is image version
+            # with existing original image
+            relative_path = request.path[len(settings.MEDIA_URL):]
+            file_obj = FileObject(relative_path)
+            if file_obj.is_version:
+                original_obj = file_obj.original
+                if original_obj.exists:
+                    # Generate requested image version
+                    new_file_obj = original_obj.version_generate(file_obj.version)
+
+                    # Redirects to generated image URL
+                    return redirect(new_file_obj.url)