    #!/usr/bin/env python

    """CGIWrapper.py

    Webware for Python

    See the CGIWrapper.html documentation for more information.

    """

    # We first record the starting time, in case we're being run as a CGI script.
    from time import time, localtime, asctime
    serverStartTime  = time()

    # Some imports
    import cgi, os, sys, traceback
    from types import DictType, FloatType
    from random import randint
    try:
        from cStringIO import StringIO
    except ImportError:
        from StringIO import StringIO

    if '' not in sys.path:
        sys.path.insert(0, '')

    from Properties import version

    try:
        import WebUtils
    except ImportError:
        sys.path.append(os.path.abspath('..'))
        import WebUtils
    from WebUtils.HTMLForException import HTMLForException

    from MiscUtils.NamedValueAccess import NamedValueAccess

    class CGIWrapper(NamedValueAccess):
        """The CGI Wrapper class.

        A CGI wrapper executes a target script and provides various services
        for both the script and website developer and the administrator.

        See the CGIWrapper.html documentation for full information.

        """

        ## Init ##

        def __init__(self):
            self._config = self.config()

        ## Configuration ##

        def defaultConfig(self):
            """Return a dictionary with the default configuration.

            Subclasses could override to customize the values
            or where they're taken from.

            """
            return {
                'ScriptsHomeDir': 'Examples',
                'ChangeDir': 1,
                'ExtraPaths': [],
                'ExtraPathsIndex': 1,
                'LogScripts': 1,
                'ScriptLogFilename': 'Scripts.csv',
                'ScriptLogColumns': [
                    'environ.REMOTE_ADDR',
                    'environ.REQUEST_METHOD', 'environ.REQUEST_URI',
                    'responseSize', 'scriptName',
                    'serverStartTimeStamp', 'serverDuration',
                    'scriptDuration', 'errorOccurred'
                ],
                'ClassNames': ['', 'Page'],
                'ShowDebugInfoOnErrors': 1,
                'UserErrorMessage': 'The site is having technical difficulties'
                    ' with this page. An error has been logged, and the problem'
                    ' will be fixed as soon as possible. Sorry!',
                'LogErrors': 1,
                'ErrorLogFilename': 'Errors.csv',
                'SaveErrorMessages': 1,
                'ErrorMessagesDir': 'ErrorMsgs',
                'EmailErrors': 0,
                'ErrorEmailServer': 'localhost',
                'ErrorEmailHeaders': {
                    'From': 'webware@mydomain',
                    'To': ['webware@mydomain'],
                    'Reply-to': 'webware@mydomain',
                    'Content-type': 'text/html',
                    'Subject': 'Error'
                },
                'AdminRemoteAddr': ['127.0.0.1']
            }

        def configFilename(self):
            """Return the filename of the optional configuration file."""
            return 'CGIWrapper.config'

        def userConfig(self):
            """Return a dictionary with the user configuration.

            This are overrides found in the optional configuration file,
            or {} if there is no such file. The config filename is taken
            from configFilename().

            """
            try:
                f = open(self.configFilename())
            except IOError:
                return {}
            else:
                config = f.read()
                try:
                    dict
                except NameError: # Python < 2.2
                    config = eval(config)
                else:
                    config = eval('dict(%s)' % config)
                f.close()
                assert isinstance(config, DictType)
                return config

        def config(self):
            """Return the configuration for the CGIWrapper.

            This is a combination of defaultConfig() and userConfig().
            This method does no caching.

            """
            config = self.defaultConfig()
            config.update(self.userConfig())
            return config

        def setting(self, name):
            """Return the value of a particular setting in the configuration."""
            return self._config[name]

        ## Utilities ##

        def docType(self):
            return docType()

        def makeHeaders(self):
            """Return a default header dictionary containing {'Content-type': 'text/html'}."""
            return {'Content-type': 'text/html'}

        def makeFieldStorage(self):
            """Return a default field storage object created from the cgi module."""
            return cgi.FieldStorage()

        def enhanceThePath(self):
            """Enhance sys.path according to our configuration."""
            extraPathsIndex = self.setting('ExtraPathsIndex')
            sys.path[extraPathsIndex:extraPathsIndex] = self.setting('ExtraPaths')

        def requireEnvs(self, names):
            """Check that given environment variable names exist.

            If they don't, a basic HTML error message is printed and we exit.

            """
            badNames = []
            for name in names:
                if not self._environ.has_key(name):
                    badNames.append(name)
            if badNames:
                print 'Content-type: text/html'
                print
                print docType()
                print '<html><head><title>Error</title></head><body>'
                print '<p>', 'ERROR: Missing', ', '.join(badNames), '</p>'
                print '</body></html>'
                sys.exit(0)

        def scriptPathname(self):
            """Return the full pathname of the target script.

            Scripts that start with an underscore are special -- they run
            out of the same directory as the CGI Wrapper and are typically
            CGI Wrapper support scripts.

            """
            # remove the CGI Wrapper's filename part
            pathname = os.path.split(self._environ['SCRIPT_FILENAME'])[0]
            filename = self._environ['PATH_INFO'][1:]
            ext = os.path.splitext(filename)[1]
            if ext == '':
                # No extension - we assume a Python CGI script.
                if filename[0] == '_':
                    # Underscores denote private scripts packaged with CGI Wrapper, such as '_admin.py'.
                    if self.setting('AdminRemoteAddr'):
                        # Users with the wrong remote address are redirected to the access denied script.
                        self.requireEnvs(['REMOTE_ADDR'])
                        remoteAddr = self._environ['REMOTE_ADDR'] + '.'
                        for addr in self.setting('AdminRemoteAddr'):
                            if remoteAddr.startswith(addr + '.'):
                                break
                        else:
                            filename = '_accessDenied'
                    filename = os.path.join(pathname, filename + '.py')
                else:
                    # All other scripts are based in the directory named by the 'ScriptsHomeDir' setting.
                    filename = os.path.join(pathname, self.setting('ScriptsHomeDir'), filename + '.py')
                self._servingScript = 1
            else:
                # Hmmm, some kind of extension like maybe '.html'.
                # Leave out the 'ScriptsHomeDir' and leave the extension alone.
                filename = os.path.join(pathname, filename)
                self._servingScript = 0
            return filename

        def writeScriptLog(self):
            """Write an entry to the script log file.

            Uses settings ScriptLogFilename and ScriptLogColumns.

            """
            filename = self.setting('ScriptLogFilename')
            if os.path.exists(filename):
                f = open(filename, 'a')
            else:
                f = open(filename, 'w')
                f.write(','.join(self.setting('ScriptLogColumns')) + '\n')
            values = []
            for column in self.setting('ScriptLogColumns'):
                value = self.valueForName(column)
                if isinstance(value, FloatType):
                    value = '%0.4f' % value # might need more flexibility in the future
                else:
                    value = str(value)
                values.append(value)
            f.write(','.join(values) + '\n')
            f.close()

        def version(self):
            return '.'.join(map(str, version))

        ## Exception handling ##

        def handleException(self, excInfo):
            """Handle an exception in the target script.

            Invoked by self when an exception occurs in the target script.
            <code>excInfo</code> is a sys.exc_info()-style tuple of information
            about the exception.

            """
            # Note the duration of the script and time of the exception
            self._scriptEndTime = time()
            self.logExceptionToConsole()
            self.reset()
            print self.htmlErrorPage(showDebugInfo=self.setting('ShowDebugInfoOnErrors'))
            fullErrorMsg = None
            if self.setting('SaveErrorMessages'):
                fullErrorMsg = self.htmlErrorPage(showDebugInfo=1)
                filename = self.saveHTMLErrorPage(fullErrorMsg)
            else:
                filename = ''
            self.logExceptionToDisk(filename)
            if self.setting('EmailErrors'):
                if fullErrorMsg is None:
                    fullErrorMsg = self.htmlErrorPage(showDebugInfo=1)
                self.emailException(fullErrorMsg)

        def logExceptionToConsole(self, stderr=sys.stderr):
            """Log an exception in the target script.

            Logs the time, script name and traceback to the console
            (typically stderr). This usually results in the information
            appearing in the web server's error log. Used by handleException().

            """
            # stderr logging
            stderr.write('[%s] [error] CGI Wrapper: Error while executing script %s\n' % (
                asctime(localtime(self._scriptEndTime)), self._scriptPathname))
            traceback.print_exc(file=stderr)

        def reset(self):
            """Reset CGI output.

            Used by handleException() to clear out the current CGI output results
            in preparation of delivering an HTML error message page.
            Currently resets headers and deletes cookies, if present.
            """
            # Set headers to basic text/html. We don't want stray headers from a script that failed.
            self._headers = self.makeHeaders()
            # Get rid of cookies, too
            if self._namespace.has_key('cookies'):
                del self._namespace['cookies']

        def htmlErrorPage(self, showDebugInfo=1):
            """Return an HTML page explaining that there is an error.

            There could be more options in the future so using named arguments
            (e.g., 'showDebugInfo=1') is recommended. Invoked by handleException().

            """
            html = ['''%s
    <html>
        <title>Error</title>
        <body text="black" bgcolor="white">
    %s<p>%s</p>
    ''' % (docType(), htTitle('Error'), self.setting('UserErrorMessage'))]

            if self.setting('ShowDebugInfoOnErrors'):
                html.append(self.htmlDebugInfo())

            html.append('</body></html>')
            return ''.join(html)

        def htmlDebugInfo(self):
            """Return an HTML page with debugging info on the current exception.

            Used by handleException().

            """
            html = ['''
    %s<p><i>%s</i></p>
    ''' % (htTitle('Traceback'), self._scriptPathname)]
            html.append(HTMLForException())
            html.extend([
                htTitle('Misc Info'),
                htDictionary({
                    'time':        asctime(localtime(self._scriptEndTime)),
                    'filename':    self._scriptPathname,
                    'os.getcwd()': os.getcwd(),
                    'sys.path':    sys.path
                }),
                htTitle('Fields'),      htDictionary(self._fields),
                htTitle('Headers'),     htDictionary(self._headers),
                htTitle('Environment'), htDictionary(self._environ, {'PATH': ';'}),
                htTitle('Ids'),         htTable(osIdTable(), ['name', 'value'])])
            return ''.join(html)

        def saveHTMLErrorPage(self, html):
            """Save the given HTML error page for later viewing by the developer.

            Returns the filename used. Invoked by handleException().

            """
            dir = self.setting('ErrorMessagesDir')
            if not os.path.exists(dir):
                os.makedirs(dir)
            filename = os.path.join(dir, self.htmlErrorPageFilename())
            try:
                f = open(filename, 'w')
                try:
                    f.write(html)
                finally:
                    f.close()
            except IOError:
                sys.stderr.write('[%s] [error] CGI Wrapper: Cannot save error page (%s)\n'
                    % (asctime(localtime(time())), filename))
            else:
                return filename

        def htmlErrorPageFilename(self):
            """Construct a filename for an HTML error page.

            This filename does not include the 'ErrorMessagesDir' setting.

            """
            # Note: Using the timestamp and a random number is a poor technique
            # for filename uniqueness, but it is fast and good enough in practice.
            return 'Error-%s-%s-%06d.html' % (os.path.split(self._scriptPathname)[1],
                '-'.join(map(lambda x: '%02d' % x, localtime(self._scriptEndTime)[:6])),
                randint(0, 999999))

        def logExceptionToDisk(self, errorMsgFilename=None, excInfo=None):
            """Write exception info to the log file.

            Writes a tuple containing (date-time, filename, pathname,
            exception-name, exception-data, error report filename)
            to the errors file (typically 'Errors.csv') in CSV format.
            Invoked by handleException().

            """
            if not excInfo:
                excInfo = sys.exc_info()
            logline = (asctime(localtime(self._scriptEndTime)),
                os.path.split(self._scriptPathname)[1], self._scriptPathname,
                excInfo[0].__name__, str(excInfo[1]), errorMsgFilename or '')
            def fixElement(element):
                element = str(element)
                if element.find(',') >= 0 or element.find('"') >= 0:
                    element = element.replace('"', '""')
                    element = '"%s"' % element
                return element
            logline = map(fixElement, logline)
            filename = self.setting('ErrorLogFilename')
            if os.path.exists(filename):
                f = open(filename, 'a')
            else:
                f = open(filename, 'w')
                f.write('time,filename,pathname,exception name,'
                    'exception data,error report filename\n')
            f.write(','.join(logline) + '\n')
            f.close()

        def emailException(self, html, excInfo=None):
            """Email an exception."""
            # Construct the message
            if not excInfo:
                excInfo = sys.exc_info()
            headers = self.setting('ErrorEmailHeaders')
            msg = []
            for key in headers.keys():
                if key != 'From' and key != 'To':
                    msg.append('%s: %s\n' % (key, headers[key]))
            msg.append('\n')
            msg.append(html)
            msg = ''.join(msg)
            # Send the message
            import smtplib
            server = smtplib.SMTP(self.setting('ErrorEmailServer'))
            server.set_debuglevel(0)
            server.sendmail(headers['From'], headers['To'], msg)
            server.quit()

        ## Serve ##

        def serve(self, environ=os.environ):
            """Serve a request."""
            # Record the time
            if globals().has_key('isMain'):
                self._serverStartTime = serverStartTime
            else:
                self._serverStartTime = time()
            self._serverStartTimeStamp = asctime(localtime(self._serverStartTime))

            # Set up environment
            self._environ = environ

            # Ensure that filenames and paths have been provided
            self.requireEnvs(['SCRIPT_FILENAME', 'PATH_INFO'])

            # Set up the namespace
            self._headers = self.makeHeaders()
            self._fields = self.makeFieldStorage()
            self._scriptPathname = self.scriptPathname()
            self._scriptName = os.path.split(self._scriptPathname)[1]

            self._namespace = {
                'headers': self._headers,
                'fields': self._fields,
                'environ': self._environ,
                'wrapper': self,
            }
            info = self._namespace.copy()

            # Set up sys.stdout to be captured as a string. This allows scripts
            # to set CGI headers at any time, which we then print prior to
            # printing the main output. This also allows us to skip on writing
            # any of the script's output if there was an error.
            #
            # This technique was taken from Andrew M. Kuchling's Feb 1998
            # WebTechniques article.
            #
            self._realStdout = sys.stdout
            sys.stdout = StringIO()

            # Change directories if needed
            if self.setting('ChangeDir'):
                origDir = os.getcwd()
                os.chdir(os.path.split(self._scriptPathname)[0])
            else:
                origDir = None

            # A little more setup
            self._errorOccurred = 0
            self._scriptStartTime = time()

            # Run the target script
            try:
                if self._servingScript:
                    execfile(self._scriptPathname, self._namespace)
                    for name in self.setting('ClassNames'):
                        if name == '':
                            name = os.path.splitext(self._scriptName)[0]
                        if self._namespace.has_key(name):
                            # our hook for class-oriented scripts
                            print self._namespace[name](info).html()
                            break
                else:
                    self._headers = {'Location':
                        os.path.split(self._environ['SCRIPT_NAME'])[0]
                        + self._environ['PATH_INFO']}

                # Note the end time of the script
                self._scriptEndTime = time()
                self._scriptDuration = self._scriptEndTime - self._scriptStartTime
            except:
                # Note the end time of the script
                self._scriptEndTime = time()
                self._scriptDuration = self._scriptEndTime - self._scriptStartTime

                self._errorOccurred = 1

                # Not really an error, if it was sys.exit(0)
                excInfo = sys.exc_info()
                if excInfo[0] == SystemExit:
                    code = excInfo[1].code
                    if not code:
                        self._errorOccurred = 0

                # Clean up
                if self._errorOccurred:
                    if origDir:
                        os.chdir(origDir)
                        origDir = None

                    # Handle exception
                    self.handleException(sys.exc_info())

            self.deliver()

            # Restore original directory
            if origDir:
                os.chdir(origDir)

            # Note the duration of server processing (as late as we possibly can)
            self._serverDuration = time() - self._serverStartTime

            # Log it
            if self.setting('LogScripts'):
                self.writeScriptLog()

        def deliver(self):
            """Deliver the HTML.

            This is used for the output that came from the script being served,
            or from our own error reporting.

            """
            # Compile the headers & cookies
            headers = StringIO()
            for header, value in self._headers.items():
                headers.write("%s: %s\n" % (header, value))
            if self._namespace.has_key('cookies'):
                headers.write(str(self._namespace['cookies']))
            headers.write('\n')

            # Get the string buffer values
            headersOut = headers.getvalue()
            stdoutOut  = sys.stdout.getvalue()

            # Compute size
            self._responseSize = len(headersOut) + len(stdoutOut)

            # Send to the real stdout
            self._realStdout.write(headersOut)
            self._realStdout.write(stdoutOut)

    ## Misc functions ##

    def docType():
        """Return a standard HTML document type"""
        return ('<!DOCTYPE HTML PUBLIC'
            ' "-//W3C//DTD HTML 4.01 Transitional//EN"'
            ' "http://www.w3.org/TR/html4/loose.dtd">')

    def htTitle(name):
        """Return an HTML section title."""
        return ('<h2 style="color:white;background-color:#993333;'
            'font-size:12pt;padding:1pt;font-weight:bold;'
            'font-family:Tahoma,Verdana,Arial,Helvetica,sans-serif"'
            ' align="center">%s</h2>\n' % name)

    def htDictionary(dict, addSpace=None):
        """Returns an HTML table where each row is a key-value pair."""
        if not dict:
            return '\n'
        keys = dict.keys()
        keys.sort()
        html = ['<table border="0" cellpadding="2" cellspacing="2">']
        for key in keys:
            value = dict[key]
            if addSpace is not None and addSpace.has_key(key):
                target = addSpace[key]
                value = (target + ' ').join(value.split(target))
            html.append('<tr><td bgcolor="#BBBBBB">%s</td>'
                '<td bgcolor="#EEEEEE">%s&nbsp;</td></tr>\n' % (key, value))
        html.append('</table>')
        return '\n'.join(html)

    def htTable(listOfDicts, keys=None):
        """Return an HTML table for a list of dictionaries.

        The listOfDicts parameter is expected to be a list of
        dictionaries whose keys are always the same. This function
        returns an HTML string with the contents of the table.
        If keys is None, the headings are taken from the first row in
        alphabetical order.

        Returns an empty string if listOfDicts is none or empty.

        Deficiencies: There's no way to influence the formatting or to
        use column titles that are different from the keys.

        """
        if not listOfDicts:
            return ''
        if keys is None:
            keys = listOfDicts[0].keys()
            keys.sort()
        html = ['<table border="0" cellpadding="2" cellspacing="2">']
        html.append('<tr>')
        for key in keys:
            html.append('<th bgcolor="#BBBBBB">%s</th>' % key)
        html.append('</tr>')
        for row in listOfDicts:
            html.append('<tr>')
            for key in keys:
                html.append('<td bgcolor="#EEEEEE">%s</td>' % row[key])
            html.append('</tr>')
        html.append('</table>')
        return '\n'.join(html)

    def osIdTable():
        """Get all OS id information.

        Returns a list of dictionaries containing id information such
        as uid, gid, etc., all obtained from the os module.

        Dictionary keys are 'name' and 'value'.

        """
        funcs = ['getegid', 'geteuid', 'getgid', 'getpgrp',
            'getpid', 'getppid', 'getuid']
        table = []
        for funcName in funcs:
            if hasattr(os, funcName):
                value = getattr(os, funcName)()
                table.append({'name': funcName, 'value': value})
        return table

    def main():
        stdout = sys.stdout
        try:
            wrapper = CGIWrapper()
            wrapper.serve()
        except:
            # There is already a fancy exception handler in the CGIWrapper for
            # uncaught exceptions from target scripts. However, we should also
            # catch exceptions here that might come from the wrapper, including
            # ones generated while it's handling exceptions.
            sys.stderr.write('[%s] [error] CGI Wrapper: Error while executing script (unknown)\n'
                % asctime(localtime(time())))
            traceback.print_exc(file=sys.stderr)
            if sys.exc_info()[0] != SystemExit:
                output = traceback.format_exception(*sys.exc_info())
                output = ''.join(output)
                output = output.replace('&', '&amp;').replace('<', '&lt;').replace('>', '&gt;')
                stdout.write('''Content-type: text/html

    %s
    <html>
    <head><title>Error</title>
    <body><h2>ERROR</h2>
    <pre>%s</pre>
    </body>
    </html>
    ''' % (docType(), output))

    if __name__ == '__main__':
        isMain = 1
        main()