[Bug 2888] New: last-modified information not sent, not even with images

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=2888

Summary: last-modified information not sent, not even with images
           Product: WineHQ Apps Database
           Version: unspecified
          Platform: Other
               URL: http://appdb.winehq.com
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: website-bugs
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

In the app database,  there are a number of objects for which we have a
historical modification time and which shouldn't get changed very often,  but
the PHP scripts always set the "no-cache" header and otherwise make sure that
they aren cached.  In particular,  /appimage.php (the screenshot viewer) sets
the following headers on a positive lookup:

Set-Cookie: whq_appdb=91649fe42c6dbd10991df9899e4cfa7b; expires=Thu, 21-Jul-05
14:47:31 GMT; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache

Note the absence of a Last-Modified: header, the cookie, and the Cache-Control:
line.  Since the URL includes "id" (which is the primary key of the appData
table) and a parameter for "thumbnail",  there is no reason for these headers in
the response.  Instead,  the Last-Modified: header ought to be the modification
time (i.e., upload time) of the underlying image file,  and it would be best to
also send:

Cache-Control: public

along with the response.

Furthermore,  it should be OK to optimize the response to "HEAD" requests by
checking the REQUEST_METHOD CGI variable.  At present,  the script would not
need to do any image-processing, just:

1.  Check whether the URL is valid
2.  Check that the image is in the database
3.  Get the file's access-time,  and look for a JPEG or PNG header
4.  Make sure it is public, or that the user (verified by the login cookie) is
an administrator.  (This will prevent spam.)