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label_manager.py
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label_manager.py
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# This file will include filtration functionalities based on resource labels
from lockable_resource.models import LockableResource
from lockable_resource.exceptions import (
FreeResourceNotAvailableException,
InvalidLabelException,
)
class LabelManager:
def __init__(self, label):
"""
constructor
:param label: for the filtration, we receive one param as the
wanted label
all_free_resources - gather all the Lockable resource objects that
could be locked (Not filtered by a label)
We should raise an exception if the given label does NOT MATCH ALL the
existing labels in the entire platform
"""
self.label = label
self.validate_label()
self.all_free_resources = LockableResource.get_all_free_resources()
self.all_resources = LockableResource.objects.all()
@property
def resources(self):
return self.get_resources()
def get_resources(self):
matching_resources = []
for resource in self.all_resources:
if resource.has_label(self.label):
matching_resources.append(resource)
return matching_resources
@property
def free_resources(self):
return self.get_free_resources()
def get_free_resources(self):
"""
Instance Method
Filtration to receive all free resources that are matching the
given label when the class is instantiated
:return: List of all free resources that matches the label
"""
matching_resources = []
for resource in self.all_free_resources:
if resource.has_label(self.label):
matching_resources.append(resource)
return matching_resources
def prioritize_resources(self):
"""
Instance Method
Sorting to have the free resources sorted by the amount of labels
We know that the more labels a resource has, the more rare the cases
that we'd like to lock it.
Hence, we sort by the length of the labels list
:return: List (Sorted)
"""
lambda_prioritize = lambda x: len(x.labels)
resources_prioritized = self.get_free_resources()
resources_prioritized.sort(key=lambda_prioritize)
return resources_prioritized
def retrieve_free_resource(self, not_exist_ok=True):
"""
Attempts to retrieve free resource with the instantiated label
:param: not_exist_ok(default: True) - Not always we'd like to throw exception,
If no free resource could be retrieved
Tries:
To catch the first index of prioritized resources.
Since we prioritize from low to high, then it is Ok to attempt
indexing zero.
:return: LockableResource object
Raises:
FreeResourceNotAvailableException - If there is an IndexError
when we attempt to index zero, it means the prioritize was
empty from the beginning.
Therefore, we raise this exception
"""
try:
retrieved_resource = self.prioritize_resources()[0]
return retrieved_resource
except IndexError:
if not_exist_ok:
return None
else:
raise FreeResourceNotAvailableException(self.label)
def validate_label(self):
"""
Instance Method
We check here if the given label is a label that exists in the entire platform
:return:
"""
if self.label not in LockableResource.get_all_labels():
raise InvalidLabelException(self.label)