#!/usr/bin/env python

__author__ = "Abhinav Sarkar <abhinav@abhinavsarkar.net>"
__version__ = "0.2"
__license__ = "GNU Lesser General Public License"
__package__ = "lastfm.mixins"

try:
    from threading import Lock
except ImportError:
    from dummy_threading import Lock
from lastfm.objectcache import ObjectCache

_lock = Lock()

def cacheable(cls):
    @classmethod
    def __new__(cls, *args, **kwds):
        args = args[1:]
        subject = None
        if 'subject' in kwds and not cls.__name__.startswith('Weekly'):
            subject = kwds['subject']
            #del kwds['subject']

        if 'bypass_registry' in kwds:
            del kwds['bypass_registry']
            inst = object.__new__(cls)
            inst.init(*args, **kwds)
            return inst

        key = cls._hash_func(*args, **kwds)
        if subject is not None:
            key = (hash(subject), key)
            
        with _lock:
            inst, already_registered = ObjectCache.register(object.__new__(cls), key)
            if not already_registered:
                inst.init(*args, **kwds)
        return inst
        
    @staticmethod
    def _hash_func(*args, **kwds):
        raise NotImplementedError("The subclass must override this method")
    
    cls.__new__ = __new__
    if not hasattr(cls, '_hash_func'):
        cls._hash_func = _hash_func
        
    if not hasattr(cls, '_mixins'):
            cls._mixins = []
    cls._mixins.append('__new__')
        
    return cls