Looking for CGI program to browse/manage/process files thru the web

[vbfoobar at gmail.com]

Hello,

I am looking for Python code no other language wanted) that I couls
use/reuse/adapt to implement (via CGI, no specific app server wanted)
a web-based app that would offer the following functionality:

- browse a file hierarchy perhaps dealing with access rights check

- classical file management operations like viewing downloading
  and perhaps renaming or deleting or copying...

- but above all I want to esaily add custom operations that can be
  applied to browsable files
  for example, easily add a button that would apply a filter (perhaps
  user-parametrable) against  the file and would display the output,
  adding another button to run such or such other file processing
  treatment...

- security/coherency checks, as e.g. asserting that a processed file
has
  such or such characteristics before even attempting to process it

It would be nice for me to start with existing code that would
constitute a clean and simple base that I could customize.
I'd like to avoid coding another HTML+forms+etc generator...

+ this should be open source.

Any advice?