105 lines
3.7 KiB
Python
105 lines
3.7 KiB
Python
from django.dispatch import Signal
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from .collection import CollectionElement
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from .dispatch import SignalConnectMetaClass
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class ProjectorElement(object, metaclass=SignalConnectMetaClass):
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"""
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Base class for an element on the projector.
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Every app which wants to add projector elements has to create classes
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subclassing from this base class with different names. The name attribute
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has to be set. The metaclass (SignalConnectMetaClass) does the rest of the
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magic.
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"""
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signal = Signal()
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name = None
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def __init__(self, **kwargs):
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"""
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Initializes the projector element instance. This is done when the
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signal is sent.
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Because of Django's signal API, we have to take wildcard keyword
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arguments. But they are not used here.
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"""
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pass
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@classmethod
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def get_dispatch_uid(cls):
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"""
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Returns the classname as a unique string for each class. Returns None
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for the base class so it will not be connected to the signal.
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"""
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if not cls.__name__ == 'ProjectorElement':
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return cls.__name__
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def check_and_update_data(self, projector_object, config_entry):
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"""
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Checks projector element data via self.check_data() and updates
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them via self.update_data(). The projector object and the config
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entry have to be given.
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"""
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self.projector_object = projector_object
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self.config_entry = config_entry
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assert self.config_entry.get('name') == self.name, (
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'To get data of a projector element, the correct config entry has to be given.')
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self.check_data()
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return self.update_data() or {}
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def check_data(self):
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"""
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Method can be overridden to validate projector element data. This
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may raise ProjectorException in case of an error.
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Default: Does nothing.
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"""
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pass
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def update_data(self):
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"""
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Method can be overridden to update the projector element data
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output. This should return a dictonary. Use this for server
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calculated data which have to be forwared to the client.
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Default: Does nothing.
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"""
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pass
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def get_requirements(self, config_entry):
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"""
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Returns an iterable of instances that are required for this projector
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element. The config_entry has to be given.
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"""
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return ()
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def get_requirements_as_collection_elements(self, config_entry):
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"""
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Returns an iterable of collection elements that are required for this
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projector element. The config_entry has to be given.
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"""
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return (CollectionElement.from_instance(instance) for instance in self.get_requirements(config_entry))
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def get_collection_elements_required_for_this(self, collection_element, config_entry):
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"""
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Returns a list of CollectionElements that have to be sent to every
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projector that shows this projector element according to the given
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collection_element.
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Default: Returns only the collection_element if it belongs to the
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requirements but return all requirements if the projector changes.
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"""
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requirements_as_collection_elements = list(self.get_requirements_as_collection_elements(config_entry))
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for requirement in requirements_as_collection_elements:
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if collection_element == requirement:
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output = [collection_element]
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break
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else:
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if collection_element.information.get('this_projector'):
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output = [collection_element]
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output.extend(requirements_as_collection_elements)
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else:
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output = []
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return output
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