[conf] Intruduce the skeleton of zdict.conf

ref #86

zdict/conf.py

@@ -0,0 +1,167 @@
+'''
+The zdict config module
+
+This module create a conf daemon thread for us via ``start_conf_thread``.
+The thread hold all the configs. We just access it via ``conf`` object
+simply.
+
+Usage:
+
+>>> from zdict.conf import conf, start_conf_thread
+>>> start_conf_thread()
+>>> conf.foo
+'bar'
+>>> conf.truth = 42
+'''
+
+import logging
+
+from copy import deepcopy
+from queue import Queue
+from threading import Event, Thread
+
+
+__all__ = (
+    'start_conf_thread',
+    'conf',
+)
+
+logger = logging.getLogger(__name__)
+
+
+class _ConfWorker:
+    mq = Queue()
+
+    @classmethod
+    def conf_thread(cls):
+        '''
+        The config IO deamon thread
+        '''
+        conf = cls.load_ini()
+        conf.update(cls.load_py())
+
+        while True:
+            msg = cls.mq.get(block=True)
+
+            logger.debug(msg)
+
+            if msg.method == 'get':
+                # msg.value is a _Future object
+                if msg.name not in conf:
+                    msg.value.set_error()
+                    continue
+                msg.value.set(deepcopy(conf[msg.name]))
+            elif msg.method == 'set':
+                conf[msg.name] = msg.value
+
+    @classmethod
+    def start_thread(cls):
+        '''
+        :return: the ``threading.Thread`` object
+        '''
+        if hasattr(cls, '_conf_thread') and cls._conf_thread.is_alive():
+            raise RuntimeError('Config thread already started')
+
+        cls._conf_thread = Thread(target=cls.conf_thread, daemon=True)
+        cls._conf_thread.start()
+
+        return cls._conf_thread
+
+    @classmethod
+    def get(cls, name):
+        msg = _Message('get', name)
+        cls.mq.put(msg)
+
+        ret = msg.value.result  # msg.value is a _Future object
+        if msg.value.error:
+            raise AttributeError(msg.name)
+        return ret
+
+    @classmethod
+    def set(cls, name, value):
+        msg = _Message('set', name, value)
+        cls.mq.put(msg)
+
+    @staticmethod
+    def load_ini():
+        '''
+        Load from ``CONF_INI`` (``BASE_DIR/config.ini``)
+
+        :return: dict
+        '''
+        logger.warn('method "load_ini" not implemented, return dummy')
+        return {'foo': 'bar'}
+
+    @staticmethod
+    def load_py():
+        '''
+        Load from ``CONF_PY`` (``BASE_DIR/config.py``)
+
+        :return: dict
+        '''
+        logger.warn('method "load_py" not implemented, return dummy')
+        return {}
+
+
+class _Conf:
+    __worker = _ConfWorker
+
+    def __getattr__(self, name):
+        return self.__worker.get(name)
+
+    def __setattr__(self, name, value):
+        self.__worker.set(name, value)
+
+    def __iter__(self):
+        raise NotImplemented()
+
+
+class _Future(Event):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.error = False
+
+    def set(self, value):
+        super().set()
+        self._value = value
+
+    @property
+    def result(self):
+        if not hasattr(self, '_value'):
+            self.wait()
+        return self._value
+
+    def set_error(self):
+        super().set()
+        self.error = True
+        self._value = None
+
+
+class _Message:
+    '''
+    The message object to communicate with config thread via ``Queue``
+
+    We have two format for message:
+    - ('get', name, _Future)
+    - ('set', name, value)
+
+    :param method: the action ``get`` or ``set``
+    :param str name: the config property name
+    :param value: required arg for ``set``
+    '''
+    def __init__(self, method: 'get' or 'set', name, value=None):
+        if method not in ('get', 'set'):
+            raise TypeError('Invalide method {}'.format(method))
+
+        self.method = method
+        self.name = name
+        self.value = _Future() if self.method == 'get' else value
+
+    def __repr__(self):
+        return '_Message: ({}, {}, {})'.format(
+            self.method, self.name, self.value)
+
+
+start_conf_thread = _ConfWorker.start_thread
+
+conf = _Conf()

zdict/constants.py

@@ -8,3 +8,6 @@
 
 DB_NAME = 'zdict.db'
 DB_FILE = os.path.join(BASE_DIR, DB_NAME)
+
+CONF_INI = 'config.ini'
+CONF_PY = 'config.py'