    """Utility class for keeping track of the context.

        A utility class that holds information about the file we are parsing
        and the environment we are doing it in.

        (c) Copyright by Jay Love, 2000 (mailto:jsliv@jslove.net)

        Permission to use, copy, modify, and distribute this software and its
        documentation for any purpose and without fee or royalty is hereby granted,
        provided that the above copyright notice appear in all copies and that
        both that copyright notice and this permission notice appear in
        supporting documentation or portions thereof, including modifications,
        that you make.

        THE AUTHORS DISCLAIM ALL WARRANTIES WITH REGARD TO
        THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
        FITNESS, IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL,
        INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
        FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
        NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
        WITH THE USE OR PERFORMANCE OF THIS SOFTWARE !

        This software is based in part on work done by the Jakarta group.

    """

    from ParseEventHandler import *
    import os

    class PSPContext:
        """PSPContext is an abstract base class for Context classes.

        Holds all the common stuff that various parts of the compilation
        will need access to. The items in this class will be used by both
        the compiler and the class generator.

        """

        def __init__(self):
            raise NotImplementedError

        def getClassPath(self):
            raise NotImplementedError

        def getReader(self):
            raise NotImplementedError

        def getWriter(self):
            raise NotImplementedError

        def getOutputDirectory(self):
            """Provide directory to dump PSP source file to."""
            raise NotImplementedError

        def getServletClassName(self):
            """Return the class name of the servlet being generated."""
            raise NotImplementedError

        def getFullClassName(self):
            """Return class name including package prefixes.

            Won't use this for now.
            """
            raise NotImplementedError

        def getPythonFileName(self):
            """the filename that we are generating to"""
            raise NotImplementedError

        def setPSPReader(self):
            """Set the PSPReader for this context."""
            raise NotImplementedError

        def setServletWriter(self):
            """Set the PSPWriter instance for this context."""
            raise NotImplementedError

        def setPythonFileName(self):
            """Set the name of the .py file to generate."""
            raise NotImplementedError

    #I'll implement this as I need it:
    class PSPCLContext(PSPContext):
        """A context for command line compilation.

        Currently used for both cammand line and PSPServletEngine compilation.
        This class provides all the information necessary during the parsing
        and page generation steps of the PSP compilation process.

        """

        def __init__(self, pspfile, trans=None):
            #self._transactrion = trans # I don't think I need this
            self._baseUri, self._pspfile = os.path.split(pspfile)
            self._fullpath = pspfile

        def getClassPath(self):
            raise NotImplementedError

        def getReader(self):
            """Return the PSPReader object assigned to this context."""
            return self._pspReader

        def getServletWriter(self):
            """Return the ServletWriter object assigned to this context"""
            return self._servletWriter

        def getOutputDirectory(self):
            """Provide directory to dump PSP source file to.

            I am probably doing this in reverse order at the moment.
            I should start with this and get the python filename from it.

            """
            return os.path.split(self._pyFileName)[0]

        def getServletClassName(self):
            """Return the class name of the servlet being generated.

            """
            return self._className

        def getFullClassName(self):
            """Return class name including package prefixes.

            Won't use this for now.
            """
            raise NotImplementedError

        def getPythonFileName(self):
            """The filename that we are generating to."""
            return self._pyFileName

        def getPspFileName(self):
            return self._pspfile

        def getFullPspFileName(self):
            return self._fullpath

        def setPSPReader(self, reader):
            """Set the PSPReader for this context."""
            self._pspReader = reader

        def setServletWriter(self, writer):
            """Set the ServletWriter instance for this context."""
            self._servletWriter = writer

        def setPythonFileName(self,name):
            """Sets the name of the .py file to generate."""
            self._pyFileName = name

        def setClassName(self , name):
            """Set the class name to create."""
            self._className = name

        def resolveRelativeURI(self, uri):
            """This is used mainly for including files.

            It simply returns the location relative to the base context
            directory, ie Examples/. If the filename has a leading /,
            it is assumed to be an absolute path.

            """
            if os.path.isabs(uri):
                return uri
            else:
                return os.path.join(self._baseUri, uri)

        def getBaseUri(self):
            return self._baseUri