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"""Defines the DatapointsManager type (class); a centralized facility where all |
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datapoints objects should arrived and be retrieved from.""" |
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from typing import Iterable, Optional |
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import logging |
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import attr |
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from so_magic.utils import Observer, Subject |
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logger = logging.getLogger(__name__) |
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@attr.s |
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class DatapointsManager(Observer): |
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"""Manage operations revolved around datapoints collection objects. |
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Instances of this class are able to monitor (listener/observer pattern) the creation of |
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datapoints collection objects and store them in a dictionary structure. |
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They also provide retrieval methods to the client to "pick up" a datapoints object. |
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Args: |
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datapoints_objects (dict, optional): the initial structure that stores datapoints objects |
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""" |
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datapoints_objects = attr.ib(init=True, default={}) |
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_last_key = attr.ib(init=False, default='') |
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def update(self, subject: Subject): |
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"""Update our state based on the event/observation captured/made. |
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Stores the datapoints object observed in a dictionary using a the Subject |
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name attribute as key. |
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Args: |
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subject (Subject): the subject object observed; it acts as an event |
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Raises: |
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RuntimeError: in case there is no 'name' attribute on the subject or if it is an empty string '' |
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RuntimeError: in case the 'name' attribute on the subject has already been used to store a datapoints object |
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""" |
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datapoints_object = subject.state |
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key = getattr(subject, 'name', '') |
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if key == '': |
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raise RuntimeError(f'Subject {subject} with state {str(subject.state)} resulted in an empty string as key.' |
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f'We reject the key, since it is going to "query" a in dict/hash).') |
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if key in self.datapoints_objects: |
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raise RuntimeError(f"Attempted to register a new Datapoints object at the existing key '{key}'.") |
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self.datapoints_objects[key] = datapoints_object |
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self._last_key = key |
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@property |
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def state(self): |
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"""The latest (most recent) key used to store a datapoints object. |
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Returns: |
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str: the key under which we stored a datapoints object last time |
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""" |
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return self._last_key |
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@property |
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def datapoints(self) -> Optional[Iterable]: # indicates that the method can return an Iterable or None types |
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"""The most recently stored datapoints object. |
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Returns: |
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Optional[Iterable]: the reference to the datapoints object |
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""" |
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try: |
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return self.datapoints_objects[self._last_key] |
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except KeyError as exception: |
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logger.error("%s . Requested datapoints with id '%s', but was not found in registered [%s]", |
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exception, self._last_key, {', '.join(_ for _ in self.datapoints_objects.keys())}) |
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boromir674 /
so-magic
