root/gaphor/tags/gaphor-0.12.0/gaphor/services/properties.py

#!/usr/bin/env python
"""
"""

import sys
import types
import os
import pprint
from zope import interface
from gaphor.interfaces import IService

if os.name == 'nt':
    home = 'USERPROFILE'
else:
    home = 'HOME'

user_data_dir = os.path.join(os.getenv(home), '.gaphor')


_no_default = object()

class Properties(object):
    """
    The Properties class holds a collection of application wide properties.

    Properties are persisted
    """
    interface.implements(IService)

    def __init__(self, backend=None):
        self._resources = {}
        self._backend = backend or FileBackend()

    def init(self, app):
        self._backend.load(self)
    
    def shutdown(self):
        self._backend.save(self)

    def __call__(self, r, default=_no_default):
        return self.get(r, default)

    def save(self):
        self._backend.save(self)

    def _items(self):
        return self._resources.iteritems()

    def dump(self, stream=sys.stdout):
        """
        TODO: define resources that are persistent (have to be saved
        and loaded.
        """
        import pprint
        pprint.pprint(self._resources.items(), stream)

    def get(self, r, default=_no_default):
        """
        Locate a property.

        Resource should be the class of the resource to look for or a string. In
        case of a string the resource will be looked up in the GConf configuration.
        """
        _resources = self._resources

        # Return the existing resource
        try:
            return _resources[r]
        except KeyError:
            pass

        if default is not _no_default:
            self.set(r, default)
            return default
        raise KeyError, 'No resource with name "%s"' % r

    def set(self, r, value):
        """
        Set a property to a specific value.

        No smart things are done with classes and class names (like the
        resource() method does).
        """
        self._resources[r] = value

    def persist(self, r, value):
        """
        Save the property to a persistent storage.
        """
        self._backend.update(r, value)


class FileBackend(object):
    """
    Resource backend that stores data to a resource file
    ($HOME/.gaphor/resource).
    """
    RESOURCE_FILE='resources'
   
    def __init__(self):
        pass

    def get_filename(self, datadir, create=False):
        if create and not os.path.exists(datadir):
            os.mkdir(datadir)
        return os.path.join(datadir, self.RESOURCE_FILE)

    def load(self, resource):
        filename = self.get_filename(user_data_dir)
        if os.path.exists(filename) and os.path.isfile(filename):
            f = open(filename)
            d = f.read()
            f.close()
            for k, v in eval(d).iteritems():
                resource.set(k, v)

    def save(self, resource):
        """
        Save persist resources from the resources dictionary.
        @resource is the Resource instance
        @persistent is a list of persistent resource names.
        """
        filename = self.get_filename(user_data_dir, create=True)
        f = open(filename, 'w')
        pprint.pprint(resource._resources, f)

    def update(self, r, value):
        pass


# vim:sw=4:et