174 lines
5.3 KiB
Python
174 lines
5.3 KiB
Python
from dataclasses import asdict, dataclass
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from typing import Self, TypedDict
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from layercake.dateutils import now, ttl
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from layercake.dynamodb import DynamoDBPersistenceLayer, KeyPair
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from layercake.strutils import md5_hash
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from schemas import Enrollment
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Tenant = TypedDict('Tenant', {'id': str, 'name': str})
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Author = TypedDict('Author', {'id': str, 'name': str})
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DeduplicationWindow = TypedDict('DeduplicationWindow', {'offset_days': int})
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class LinkedEntity(str):
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def __new__(cls, id: str, type: str) -> Self:
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return super().__new__(cls, '#'.join([type.lower(), id]))
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def __init__(self, id: str, type: str) -> None:
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# __init__ is used to store the parameters for later reference.
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# For immutable types like str, __init__ cannot change the instance's value.
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self.id = id
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self.type = type
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@dataclass(frozen=True)
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class Slot:
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id: str
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sk: str
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@property
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def order_id(self) -> LinkedEntity:
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idx, _ = self.sk.split('#')
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return LinkedEntity(idx, 'ORDER')
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class DeduplicationConflictError(Exception):
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def __init__(self, *args):
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super().__init__('Enrollment already exists')
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class SlotDoesNotExistError(Exception):
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def __init__(self, *args):
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super().__init__('Slot does not exist')
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def enroll(
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enrollment: Enrollment,
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*,
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slot: Slot | None = None,
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author: Author | None = None,
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linked_entities: frozenset[LinkedEntity] = frozenset(),
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deduplication_window: DeduplicationWindow | None = None,
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persistence_layer: DynamoDBPersistenceLayer,
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) -> bool:
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"""Enrolls a user into a course and schedules lifecycle events."""
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now_ = now()
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user = enrollment.user
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course = enrollment.course
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lock_hash = md5_hash('%s%s' % (user.id, course.id))
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with persistence_layer.transact_writer() as transact:
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if slot:
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linked_entities = frozenset({slot.order_id}) | linked_entities
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transact.put(
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item={
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'sk': '0',
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'created_at': now_,
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**enrollment.model_dump(),
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},
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)
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transact.put(
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item={
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'id': enrollment.id,
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'sk': 'METADATA#COURSE',
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'created_at': now_,
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**course.model_dump(include={'cert', 'access_period'}),
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}
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)
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for entity in linked_entities:
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keyprefix = entity.type.lower()
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transact.put(
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item={
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'id': enrollment.id,
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'sk': f'LINKED_ENTITIES#{entity.type}',
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'created_at': now_,
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f'{keyprefix}_id': entity.id,
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}
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)
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if slot:
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transact.put(
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item={
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'id': enrollment.id,
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# Post-migration: uncomment the following line
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# 'sk': 'METADATA#SOURCE_SLOT',
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'sk': 'parent_vacancy',
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'vacancy': asdict(slot),
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'created_at': now_,
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}
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)
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transact.delete(
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key=KeyPair(slot.id, slot.sk),
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cond_expr='attribute_exists(sk)',
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exc_cls=SlotDoesNotExistError,
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)
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transact.put(
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item={
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'id': enrollment.id,
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'sk': 'CANCEL_POLICY',
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'created_at': now_,
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}
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)
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if author:
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transact.put(
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item={
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'id': enrollment.id,
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'sk': 'author',
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'user_id': author['id'],
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'name': author['name'],
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'created_at': now_,
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},
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)
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# Prevents the user from enrolling in the same course again until
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# the deduplication window expires or is removed.
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if deduplication_window:
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offset_days = deduplication_window['offset_days']
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ttl_ = ttl(
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start_dt=now_,
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days=course.access_period - offset_days,
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)
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transact.put(
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item={
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'id': 'LOCK',
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'sk': lock_hash,
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'enrollment_id': enrollment.id,
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'created_at': now_,
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'ttl': ttl_,
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},
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cond_expr='attribute_not_exists(sk)',
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exc_cls=DeduplicationConflictError,
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)
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transact.put(
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item={
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'id': enrollment.id,
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'sk': 'LOCK',
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'hash': lock_hash,
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'created_at': now_,
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'ttl': ttl_,
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},
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)
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# Deduplication window can be recalculated if needed
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transact.put(
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item={
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'id': enrollment.id,
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'sk': 'METADATA#DEDUPLICATION_WINDOW',
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'offset_days': offset_days,
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'created_at': now_,
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},
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)
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else:
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transact.condition(
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key=KeyPair('LOCK', lock_hash),
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cond_expr='attribute_not_exists(sk)',
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exc_cls=DeduplicationConflictError,
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)
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return True
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