A system that will accept a multipart form upload (say, containing an audio
file) while displaying a percentage progress.


Usage:

$> node server.js


Specification:

When the user picks a file from their computer and the form is submitted, the
upload begins. While uploading, the status text paragraph should be updating
with the current percentage complete at least once every 2 seconds. While
uploading, the user should be able to enter text into the title text field.

When the upload completes, the status text should display the path on the
server to the saved file, and the current value of the title text field should
be posted to the server. The response to the form post request should display
both the title and the path to the file.


Implementation notes:

The server is implemented using Node.js. Two modules (formidable and paperboy)
handle multipart form parsing and the serving of static files. The client
consists of a plain html form and a sprinkle of jquery.

The upload form is posted into an iframe so that the user does not move away
from the initial page.

Upload progress is polled regularly by the client. In order to keep track of
the progress of one than one concurrent upload, the client sends a random
identification string as a parameter to the initial file upload. This
identification string can then be used to query the server for progress via a
GET request to /progress/#{uuid}.

When the upload is complete, a load event is triggered on the iframe. The
response from the server ends up inside a text area in the iframe and is thus
invisible to the user.

Concurrent to reporting upload completion status to the user, the client POSTs
the contents of the title text field to the server. The /metadata/#{uuid}
endpoint is used for this transaction. This could be extended to allow the
user to update the title (and other meta data) at any time during the upload
process and have the data sent to the server in the background after each
update to the text fields.