Source code for everest.resources.service

"""
Service.

This file is part of the everest project. 
See LICENSE.txt for licensing, CONTRIBUTORS.txt for contributor information.

Created on Jul 27, 2011.
"""
from everest.repository import as_repository
from everest.resources.base import Resource
from everest.resources.interfaces import IService
from zope.interface import implements # pylint: disable=E0611,F0401

__docformat__ = 'reStructuredText en'
__all__ = ['Service',
           ]


class Service(Resource):
    """
    The service resource class.

    The service resource is placed at the root of the resource tree and 
    provides traversal (=URL) access to all exposed collection resources. 
    """
    implements(IService)

    relation = 'service'

    def __init__(self):
        Resource.__init__(self)
        # Setting the __name__ to None ensures a leading slash in model paths.
        self.__name__ = None
        # Collects all interfaces managed by the service.
        self.__registered_interfaces = set()
        # Maps collection names to resource interfaces.
        self.__collections = {}
        self.__started = False

    def register(self, irc):
        """
        Registers the given resource interface with this service.
        """
        if self.__started:
            raise RuntimeError("Can not register new resource interfaces when "
                               "the service has been started.")
        self.__registered_interfaces.add(irc)

    def start(self):
        """
        Starts the service.
        
        This adds all registered resource interfaces to the service. Multiple
        calls to this method will only perform the startup once.
        """
        if not self.__started:
            self.__started = True
            for irc in self.__registered_interfaces:
                self.add(irc)

    def __getitem__(self, key):
        """
        Overrides __getitem__ to return a clone of the requested collection.

        :param key: collection name.
        :type key: str
        :returns: object implementing
          :class:`everest.resources.interfaces.ICollectionResource`.
        """
        irc = self.__collections[key]
        repo = as_repository(irc)
        return repo.get(irc)

    def __len__(self):
        return len(self.__collections)

    def __iter__(self):
        for key in self.__collections.iterkeys():
            yield self.__getitem__(key)

    def __str__(self):
        return "%s(%s)" % (self.__class__.__name__,
                           'started' if self.__started else 'not started')

    def add(self, irc):
        repo = as_repository(irc)
        coll = repo.get(irc)
        if coll.__name__ in self.__collections:
            raise ValueError('Root collection for collection name %s '
                             ' already exists.' % coll.__name__)
        # We replace the repository collection with a clone that has the
        # service as the parent so that URL generation works.
        coll.__parent__ = self
        repo.set(irc, coll)
        # 
        self.__collections[coll.__name__] = irc

    def remove(self, irc):
        repo = as_repository(irc)
        coll = repo.get(irc)
        del self.__collections[coll.__name__]

    def get(self, name, default=None):
        try:
            coll = self.__getitem__(name)
        except KeyError:
            coll = default
        return coll