"""
download.cobra

Downloads a file specified by a URL to the local file system.

Windows:
> cd \path\to\directory\of\download.cobra
> cobra -c download.cobra
> download http://www.google.com/images/logo_sm.gif
Downloading http://www.google.com/images/logo_sm.gif to logo_sm.gif
Done.

Unix-like:
> cd /path/to/directory/of/download.cobra
> cobra -c Download.cobra
> mono download.exe http://www.google.com/images/logo_sm.gif
Downloading http://www.google.com/images/logo_sm.gif to logo_sm.gif
Done.

You can specify the local filename:
> download http://www.google.com/images/logo_sm.gif GoogleLogo.gif
Downloading http://www.google.com/images/logo_sm.gif to GoogleLogo.gif
Done.

"""

use System.Net

class DownloadFile

    def main
        args = CobraCore.commandLineArgs
        if args.count < 2
            print 'usage: download URL \[LOCALFILENAME]'
            return
        url = args[1]

        # localFileName is derived from the url if missing:
        if args.count > 2
            localFileName = args[2]
        else
            s = url
            if s.endsWith('/'), s = s[:-1]
            i = s.lastIndexOf('/')
            if i <> -1, localFileName = s[i+1:]
            else, print 'Invalid URL.'

        print 'Downloading [url] to [localFileName]'
        Console.out.flush

        try
            WebClient().downloadFile(url, localFileName)
        catch e as Exception
            print e

        print 'Done.'