Refactor patron aggregate into separate modules

src/lending/model/patron/__init__.py

@@ -0,0 +1,25 @@
+from .checkout import (
+    BookCheckedOut,
+    BookOverdue,
+    BookReturned,
+    Checkout,
+    CheckoutStatus,
+)
+from .hold import Hold, HoldCancelled, HoldExpired, HoldPlaced, HoldStatus, HoldType
+from .patron import Patron, PatronType
+
+__all__ = [
+    Patron,
+    PatronType,
+    Hold,
+    HoldStatus,
+    HoldType,
+    HoldExpired,
+    HoldPlaced,
+    HoldCancelled,
+    Checkout,
+    CheckoutStatus,
+    BookCheckedOut,
+    BookReturned,
+    BookOverdue,
+]

src/lending/model/patron/checkout.py

@@ -0,0 +1,90 @@
+from datetime import date, datetime, timedelta
+from enum import Enum
+
+from protean.fields import Date, DateTime, Identifier, String
+
+from lending.domain import lending
+from lending.utils import utc_now
+
+
+class CheckoutStatus(Enum):
+    ACTIVE = "ACTIVE"
+    RETURNED = "RETURNED"
+    OVERDUE = "OVERDUE"
+
+
+@lending.event(part_of="Patron", abstract=True)
+class CheckoutEvent:
+    checkout_id = Identifier(required=True)
+    patron_id = Identifier(required=True)
+    patron_type = String(required=True)
+    book_id = Identifier(required=True)
+    branch_id = Identifier(required=True)
+    checked_out_at = DateTime(required=True)
+    due_on = Date(required=True)
+
+
+@lending.event(part_of="Patron")
+class BookCheckedOut(CheckoutEvent):
+    """Event raised when a patron checks out a book"""
+
+
+@lending.event(part_of="Patron")
+class BookReturned(CheckoutEvent):
+    """Event raised when a patron returns a book"""
+
+    returned_at = DateTime(required=True)
+
+
+@lending.event(part_of="Patron")
+class BookOverdue(CheckoutEvent):
+    """Event raised when a book is marked overdue"""
+
+
+@lending.entity(part_of="Patron")
+class Checkout:
+    """The action of a patron borrowing a book from the library
+    for a period of up to 60 days."""
+
+    book_id = Identifier(required=True)
+    branch_id = Identifier(required=True)
+    checked_out_at = DateTime(required=True, default=utc_now)
+    status = String(max_length=11, default=CheckoutStatus.ACTIVE.value)
+    due_on = Date(
+        required=True,
+        default=lambda: date.today()
+        + timedelta(days=lending.config["custom"]["CHECKOUT_PERIOD"]),
+    )
+    returned_at = DateTime()
+
+    def return_(self):
+        self.status = CheckoutStatus.RETURNED.value
+        self.returned_at = datetime.now()
+
+        self.raise_(
+            BookReturned(
+                checkout_id=self.id,
+                patron_id=self._owner.id,
+                patron_type=self._owner.patron_type,
+                book_id=self.book_id,
+                branch_id=self.branch_id,
+                checked_out_at=self.checked_out_at,
+                due_on=self.due_on,
+                returned_at=self.returned_at,
+            )
+        )
+
+    def overdue(self):
+        self.status = CheckoutStatus.OVERDUE.value
+
+        self.raise_(
+            BookOverdue(
+                checkout_id=self.id,
+                patron_id=self._owner.id,
+                patron_type=self._owner.patron_type,
+                book_id=self.book_id,
+                branch_id=self.branch_id,
+                checked_out_at=self.checked_out_at,
+                due_on=self.due_on,
+            )
+        )