    """Servlet factory for Kid templates.

    This allows you to run Kid template files directly from within Webware.
    Compiled templates are cached either along with the templates or in the
    KidKit subdirectory of the WebKit Cache directory.

    Note that the Kid package itself is not part of Webware; you need to install
    it separately (see http://www.kid-templating.org for more information).

    CREDITS:

    * Kid has been developed by Ryan Tomayko (rtomayko<at>gmail.com).
    * KidKit was contributed by Winston Wolff (winstonw<at>stratolab.com).
      Based on the Cheetah servlet factory. No caching, fixed servlet hook.
    * Improved version contributed by Christoph Zwerschke (cito<at>online.de).
      Based on the PSP servlet factory. Supports caching and servlet hooks.

    """

    import os
    from glob import glob
    from WebKit.ServletFactory import ServletFactory
    from WebKit.Servlet import Servlet
    from WebKit.Page import Page

    defaultHook = Page.respond # the default hook for Kid servlets
    defaultOutput = 'html' # the default Kid output method
    defaultFormat = 'default' # the default Kid output format
    defaultExtensions = ['.kid'] # the default extensions for Kid templates

    from kid import load_template, output_methods
    try: # output formatting exists in newer Kid versions only
        from kid.format import output_formats
    except ImportError:
        output_formats = None
    from kid.compiler import KidFile

    def kidClass(module):
        """Return a WebKit servlet class for a Kid template module."""

        try:
            hook = module.hook
        except AttributeError:
            hook = defaultHook
        assert type(hook) == type(defaultHook)
        ServletClass = hook.im_class
        assert issubclass(ServletClass, Servlet)
        writeMethod = hook.__name__
        try:
            output = module.output
        except AttributeError:
            output = defaultOutput
        assert output in output_methods
        if output_formats is None:
            format = None
        else:
            try:
                format = module.format
            except AttributeError:
                format = defaultFormat
            assert format in output_formats

        class KidServlet(ServletClass):
            """The base class for a Kid servlet."""

            _module = module
            _template = module.Template()
            _output = output
            _format = format

            def writeTemplate(self, *args, **kwargs):
                self._template.servlet = self
                response = self._response
                fragment = response.size() > 0
                if format is None:
                    self._template.write(self._response,
                        fragment=fragment, output=output)
                else:
                    self._template.write(self._response,
                        fragment=fragment, output=output, format=format)

        setattr(KidServlet, writeMethod, KidServlet.writeTemplate)
        return KidServlet

    class KidServletFactory(ServletFactory):
        """Servlet factory for Kid templates."""

        def __init__(self, application):
            ServletFactory.__init__(self, application)
            setting = application.setting
            global defaultOutput # the default Kid output method
            defaultOutput = setting('KidOutputMethod', defaultOutput)
            global defaultFormat # the default Kid output format
            defaultFormat = setting('KidOutputFormat', defaultFormat)
            global defaultExtensions # the default Kid template extensions
            self._extensions = setting('ExtensionsForKid', defaultExtensions)
            defaultExtensions = self._extensions
            self._cacheTemplates = setting('CacheKidTemplates', True)
            self._useCache = setting('UseKidKitCache', False)
            if self._useCache:
                self._cacheSource = setting('CacheKidSource', True)
                self._clearCache = setting('ClearKidCacheOnStart', False)
                self._cacheDir = os.path.join(application._cacheDir, 'KidKit')
                if self._clearCache:
                    self.clearFileCache()
            else:
                self._cacheSource = self._clearCache = False
                self._cacheDir = None
            t = ['_'] * 256
            from string import digits, letters
            for c in digits + letters:
                t[ord(c)] = c
            self._classNameTrans = ''.join(t)

        def uniqueness(self):
            return 'file'

        def extensions(self):
            return self._extensions

        def flushCache(self):
            """Clean out the cache of classes in memory and on disk."""
            ServletFactory.flushCache(self)
            if self._clearCache:
                self.clearFileCache()

        def clearFileCache(self):
            """Clear class files stored on disk."""
            files = glob(os.path.join(self._cacheDir, '*.*'))
            map(os.remove, files)

        def computeClassName(self, pagename):
            """Generate a (hopefully) unique class/file name for each Kid file.

            Argument: pagename: the path to the Kid template file
            Returns: a unique name for the class generated fom this Kid file

            """
            # Compute class name by taking the path and substituting
            # underscores for all non-alphanumeric characters:
            return os.path.splitdrive(pagename)[1].translate(self._classNameTrans)

        def loadClass(self, transaction, path):
            """Load servlet class for the given Kid template."""
            classname = self.computeClassName(path)
            if self._cacheTemplates and self._useCache:
                # Cache the compiled templates separately:
                mtime = os.path.getmtime(path)
                classfile = os.path.join(self._cacheDir, classname + ".py")
                if not self._cacheSource:
                    classfile += __debug__ and 'c' or 'o'
                if not os.path.exists(classfile) \
                        or os.path.getmtime(classfile) != mtime:
                    kidFile = KidFile(path)
                    if self._cacheSource:
                        kidFile.dump_source(classfile)
                    else:
                        kidFile.dump_code(classfile)
                    # Set the modification time of the compiled file
                    # to be the same as the source file;
                    # that's how we'll know if it needs to be recompiled:
                    os.utime(classfile, (os.path.getatime(classfile), mtime))
                module = self.importAsPackage(transaction, classfile)
            else:
                # Let Kid care about the caching:
                module = load_template(path, cache=self._cacheTemplates)
            # Setting __orig_file__ here is already too late,
            module.__orig_file__ = path
            # so we need to tell ImportSpy explicitely about the file:
            self._imp.watchFile(path)
            theClass = kidClass(module)
            theClass._orig_file = path
            theClass.__name__ = self.computeClassName(path)
            return theClass