class InventoryItem(Entity):
"""
An inventory item is responsible for tracking items of a specific SKU in the following states:
- on hand: location of each unsold item
- committed: location of each item which has been committed to a order/sale
- backorders: item quantity on backorder due to a specific order
- purchase orders: item quantity awaiting delivery from a purchase order issues to a supplied
- fulfillments: items which have been sold
Actions which can be performed on an inventory item:
- Enter new stock
- Commit stock for sale
- Fulfill sale commitment
- Fulfill backorders -> commit for sale
- Create purchase order for expected delivery of stock
- Track lost & found stock
"""
def __init__(self, sku, on_hand_buffer=None):
self.sku = sku
# Minimum on hand quantity before we need to physically verify stock levels, off by default
self.on_hand_buffer = on_hand_buffer if on_hand_buffer else 0
self.tracker = TrackingStateMachine()
self.tracker.add_state(OnHandState("OnHand"))
self.tracker.add_state(CommittedState("Committed"))
self.tracker.add_state(BackorderState("Backorder"))
self.tracker.add_state(FulfilledState("Fulfilled"))
self.tracker.add_state(PurchaseOrderState("PurchaseOrder"))
self.tracker.add_state(LostAndFoundState("Lost"))
self.tracker.add_state(LostAndFoundState("Found"))
self.tracker.add_transition("commit", "OnHand", "Committed")
self.tracker.add_transition("allocate", "OnHand", "Backorder")
self.tracker.add_transition("fulfill_backorder", "Backorder",
"Committed")
self.tracker.add_transition("cancel_backorder", "Backorder", "OnHand")
self.tracker.add_action("verify", "Committed")
self.tracker.add_transition("verify_out_of_stock", "Committed",
"Backorder")
self.tracker.add_transition("backorder_commitment", "Committed",
"Backorder")
self.tracker.add_transition("revert", "Committed", "OnHand")
self.tracker.add_transition("fulfill", "Committed", "Fulfilled")
self.tracker.add_transition("delivery", "PurchaseOrder", "OnHand")
self.tracker.add_action("cancel_purchase_order", "PurchaseOrder")
self.tracker.add_transition("lost", "OnHand", "Lost")
self.tracker.add_transition("found", "Found", "OnHand")
# Some shortcut attributes
self.on_hand = self.tracker.state("OnHand")
self.committed = self.tracker.state("Committed")
self.verification = self.tracker.state("Verify")
self.backorders = self.tracker.state("Backorder")
self.fulfilled = self.tracker.state("Fulfilled")
self.purchase_orders = self.tracker.state("PurchaseOrder")
self.lost = self.tracker.state("Lost")
self.found = self.tracker.state("Found")
def transition(self, *args, **kwargs):
self.tracker.transition(*args, **kwargs)
# On Hand methods
def enter_stock_on_hand(self, quantity):
try:
self.on_hand.track({"quantity": quantity})
except TransitionValidationError:
return False
return True
def effective_quantity_on_hand(self):
return self.on_hand.quantity()
def physical_quantity_on_hand(self):
physical_quantity = self.on_hand.quantity()
committed_quantity = self.committed.quantity()
return physical_quantity + committed_quantity
# Commited Items methods
def find_committed_for_order(self, order_id):
return self.committed.get(key=order_id)
def quantity_committed(self):
return self.committed.quantity()
def commit(self, quantity, order_id, dry_run=None):
result = True
effective_quantity = self.effective_quantity_on_hand()
backordered_quantity = max(0, quantity - effective_quantity)
if backordered_quantity > 0:
try:
# Create a backorder for quantity we know is impossible to commit
self.backorders.track(
{
"quantity": backordered_quantity,
"date": datetime.now(),
"order_id": order_id
},
dry_run=dry_run)
except TransitionValidationError:
result = False
# Short circuit, we know we cannot commit anything
if backordered_quantity == quantity:
return result
maximum_committable_quantity = quantity - backordered_quantity
maximum_verified_quantity = max(
0, effective_quantity - self.on_hand_buffer)
verified_quantity = min(maximum_verified_quantity,
maximum_committable_quantity)
unverified_quantity = max(
0, maximum_committable_quantity - maximum_verified_quantity)
try:
self.transition(
"commit",
{"quantity": verified_quantity + unverified_quantity}, {
"quantity": verified_quantity,
"unverified_quantity": unverified_quantity,
"order_id": order_id,
"date": datetime.now()
},
dry_run=dry_run)
except TransitionValidationError:
result = False
return result
def fulfill_commitment(self, quantity, order_id, invoice_id):
try:
now = datetime.now()
self.transition("fulfill", {
"quantity": quantity,
"order_id": order_id,
"date": now
}, {
"quantity": quantity,
"order_id": order_id,
"invoice_id": invoice_id,
"date": now
})
except TransitionValidationError:
return False
return True
def backorder_commitment(self, quantity, order_id):
try:
now = datetime.now()
self.transition("backorder_commitment", {
"quantity": quantity,
"order_id": order_id,
"date": now
}, {
"quantity": quantity,
"order_id": order_id,
"date": now,
"allocated": 0
})
except TransitionValidationError:
return False
return True
def revert(self, quantity, order_id):
try:
now = datetime.now()
self.transition("revert", {
"quantity": quantity,
"order_id": order_id,
"date": now
}, {"quantity": quantity})
except TransitionValidationError:
return False
return True
def needs_stock_verified(self, order_id):
return not self.committed.is_verified(order_id)
def verify_stock_level(self, quantity):
# XXX: Ensure atomicity
expected_quantity = self.physical_quantity_on_hand()
now = datetime.now()
# Verify the quantity which was physically counted
self.tracker.action("verify", {"quantity": quantity})()
# Propagate any lost stock into backorders
if quantity < expected_quantity:
for item in self.committed.get_unverified():
self.transition(
"verify_out_of_stock", {
"quantity": item.unverified_quantity,
"order_id": item.order_id,
"date": now
}, {
"quantity": item.unverified_quantity,
"order_id": item.order_id,
"date": now
})
# Declare lost quantity
lost_quantity = expected_quantity - quantity
self.lost_stock(lost_quantity)
elif expected_quantity < quantity:
found_quantity = quantity - expected_quantity
self.found_stock(found_quantity)
# Backorder methods
def find_backorder_for_order(self, order_id):
return self.backorders.get(order_id)
def quantity_backordered(self, order_id=None):
return self.backorders.quantity(order_id=order_id)
def fulfill_backorder(self, quantity, order_id):
now = datetime.now()
try:
self.transition("allocate", {"quantity": quantity}, {
"quantity": 0,
"date": now,
"order_id": order_id,
"allocated": quantity
})
self.transition(
"fulfill_backorder", {
"quantity": 0,
"date": now,
"order_id": order_id,
"allocated": quantity
}, {
"quantity": quantity,
"order_id": order_id,
"date": now
})
except TransitionValidationError:
return False
return True
def cancel_backorder(self, order_id):
# Cancel the entire backorder and return any allocated stock to OnHand
try:
self.transition(
"cancel_backorder", {
"quantity": 0,
"date": datetime.now(),
"order_id": order_id,
"allocated": 0
}, {"quantity": TransitionParameter("allocated")})
except TransitionValidationError:
return False
return True
# Fulfilled item methods
def find_fulfillment_for_invoice(self, invoice_id):
return self.fulfilled.get(invoice_id)
def quantity_fulfilled(self, invoice_id=None):
return self.fulfilled.quantity(invoice_id=invoice_id)
# Purchase order methods
def find_purchase_order(self, purchase_order_id):
return self.purchase_orders.get(purchase_order_id)
def quantity_purchased(self, purchase_order_id=None):
return self.purchase_orders.quantity(
purchase_order_id=purchase_order_id)
def purchase_item(self, quantity, purchase_order_id, eta_date=None):
self.purchase_orders.track({
"quantity": quantity,
"purchase_order_id": purchase_order_id,
"date": datetime.now(),
"eta_date": eta_date if eta_date else None
})
def deliver_purchase_order(self, quantity, purchase_order_id):
try:
self.transition(
"delivery", {
"quantity": quantity,
"purchase_order_id": purchase_order_id,
"date": datetime.now()
}, {"quantity": quantity})
except TransitionValidationError:
return False
return True
def cancel_purchase_order(self, purchase_order_id):
self.tracker.action("cancel_purchase_order",
{"purchase_order_id": purchase_order_id})()
# Lost and Found methods
def quantity_lost(self):
return self.lost.quantity()
def quantity_found(self):
return self.found.quantity()
def lost_stock(self, quantity):
self.transition("lost", {"quantity": quantity}, {
"quantity": quantity,
"date": datetime.now()
})
def found_stock(self, quantity):
self.transition("found", {
"quantity": quantity,
"date": datetime.now()
}, {"quantity": quantity})
class InventoryItem(Entity):
"""
An inventory item is responsible for tracking items of a specific SKU in the following states:
- on hand: location of each unsold item
- committed: location of each item which has been committed to a order/sale
- backorders: item quantity on backorder due to a specific order
- purchase orders: item quantity awaiting delivery from a purchase order issues to a supplied
- fulfillments: items which have been sold
Actions which can be performed on an inventory item:
- Enter new stock
- Commit stock for sale
- Fulfill sale commitment
- Fulfill backorders -> commit for sale
- Create purchase order for expected delivery of stock
- Track lost & found stock
"""
def __init__(self, sku, on_hand_buffer=None):
self.sku = sku
# Minimum on hand quantity before we need to physically verify stock levels, off by default
self.on_hand_buffer = on_hand_buffer if on_hand_buffer else 0
self.tracker = TrackingStateMachine()
self.tracker.add_state(OnHandState("OnHand"))
self.tracker.add_state(CommittedState("Committed"))
self.tracker.add_state(BackorderState("Backorder"))
self.tracker.add_state(FulfilledState("Fulfilled"))
self.tracker.add_state(PurchaseOrderState("PurchaseOrder"))
self.tracker.add_state(LostAndFoundState("Lost"))
self.tracker.add_state(LostAndFoundState("Found"))
self.tracker.add_transition("commit", "OnHand", "Committed")
self.tracker.add_transition("allocate", "OnHand", "Backorder")
self.tracker.add_transition("fulfill_backorder", "Backorder", "Committed")
self.tracker.add_transition("cancel_backorder", "Backorder", "OnHand")
self.tracker.add_action("verify", "Committed")
self.tracker.add_transition("verify_out_of_stock", "Committed", "Backorder")
self.tracker.add_transition("backorder_commitment", "Committed", "Backorder")
self.tracker.add_transition("revert", "Committed", "OnHand")
self.tracker.add_transition("fulfill", "Committed", "Fulfilled")
self.tracker.add_transition("delivery", "PurchaseOrder", "OnHand")
self.tracker.add_action("cancel_purchase_order", "PurchaseOrder")
self.tracker.add_transition("lost", "OnHand", "Lost")
self.tracker.add_transition("found", "Found", "OnHand")
# Some shortcut attributes
self.on_hand = self.tracker.state("OnHand")
self.committed = self.tracker.state("Committed")
self.verification = self.tracker.state("Verify")
self.backorders = self.tracker.state("Backorder")
self.fulfilled = self.tracker.state("Fulfilled")
self.purchase_orders = self.tracker.state("PurchaseOrder")
self.lost = self.tracker.state("Lost")
self.found = self.tracker.state("Found")
def transition(self, *args, **kwargs):
self.tracker.transition(*args, **kwargs)
# On Hand methods
def enter_stock_on_hand(self, quantity):
try:
self.on_hand.track({"quantity": quantity})
except TransitionValidationError:
return False
return True
def effective_quantity_on_hand(self):
return self.on_hand.quantity()
def physical_quantity_on_hand(self):
physical_quantity = self.on_hand.quantity()
committed_quantity = self.committed.quantity()
return physical_quantity + committed_quantity
# Commited Items methods
def find_committed_for_order(self, order_id):
return self.committed.get(key=order_id)
def quantity_committed(self):
return self.committed.quantity()
def commit(self, quantity, order_id, dry_run=None):
result = True
effective_quantity = self.effective_quantity_on_hand()
backordered_quantity = max(0, quantity - effective_quantity)
if backordered_quantity > 0:
try:
# Create a backorder for quantity we know is impossible to commit
self.backorders.track({"quantity": backordered_quantity,
"date": datetime.now(),
"order_id": order_id},
dry_run=dry_run)
except TransitionValidationError:
result = False
# Short circuit, we know we cannot commit anything
if backordered_quantity == quantity:
return result
maximum_committable_quantity = quantity - backordered_quantity
maximum_verified_quantity = max(0, effective_quantity - self.on_hand_buffer)
verified_quantity = min(maximum_verified_quantity, maximum_committable_quantity)
unverified_quantity = max(0, maximum_committable_quantity - maximum_verified_quantity)
try:
self.transition("commit",
{"quantity": verified_quantity + unverified_quantity},
{"quantity": verified_quantity, "unverified_quantity": unverified_quantity,
"order_id": order_id, "date": datetime.now()},
dry_run=dry_run)
except TransitionValidationError:
result = False
return result
def fulfill_commitment(self, quantity, order_id, invoice_id):
try:
now = datetime.now()
self.transition("fulfill",
{"quantity": quantity, "order_id": order_id, "date": now},
{"quantity": quantity, "order_id": order_id, "invoice_id": invoice_id, "date": now})
except TransitionValidationError:
return False
return True
def backorder_commitment(self, quantity, order_id):
try:
now = datetime.now()
self.transition("backorder_commitment",
{"quantity": quantity, "order_id": order_id,"date": now},
{"quantity": quantity, "order_id": order_id, "date": now, "allocated": 0})
except TransitionValidationError:
return False
return True
def revert(self, quantity, order_id):
try:
now = datetime.now()
self.transition("revert",
{"quantity": quantity, "order_id": order_id, "date": now},
{"quantity": quantity})
except TransitionValidationError:
return False
return True
def needs_stock_verified(self, order_id):
return not self.committed.is_verified(order_id)
def verify_stock_level(self, quantity):
# XXX: Ensure atomicity
expected_quantity = self.physical_quantity_on_hand()
now = datetime.now()
# Verify the quantity which was physically counted
self.tracker.action("verify", {"quantity": quantity})()
# Propagate any lost stock into backorders
if quantity < expected_quantity:
for item in self.committed.get_unverified():
self.transition("verify_out_of_stock",
{"quantity": item.unverified_quantity, "order_id": item.order_id, "date": now},
{"quantity": item.unverified_quantity, "order_id": item.order_id, "date": now})
# Declare lost quantity
lost_quantity = expected_quantity - quantity
self.lost_stock(lost_quantity)
elif expected_quantity < quantity:
found_quantity = quantity - expected_quantity
self.found_stock(found_quantity)
# Backorder methods
def find_backorder_for_order(self, order_id):
return self.backorders.get(order_id)
def quantity_backordered(self, order_id=None):
return self.backorders.quantity(order_id=order_id)
def fulfill_backorder(self, quantity, order_id):
now = datetime.now()
try:
self.transition("allocate",
{"quantity": quantity},
{"quantity": 0, "date": now, "order_id": order_id, "allocated": quantity})
self.transition("fulfill_backorder",
{"quantity": 0, "date": now, "order_id": order_id, "allocated": quantity},
{"quantity": quantity, "order_id": order_id, "date": now})
except TransitionValidationError:
return False
return True
def cancel_backorder(self, order_id):
# Cancel the entire backorder and return any allocated stock to OnHand
try:
self.transition("cancel_backorder",
{"quantity": 0, "date": datetime.now(), "order_id": order_id, "allocated": 0},
{"quantity": TransitionParameter("allocated")})
except TransitionValidationError:
return False
return True
# Fulfilled item methods
def find_fulfillment_for_invoice(self, invoice_id):
return self.fulfilled.get(invoice_id)
def quantity_fulfilled(self, invoice_id=None):
return self.fulfilled.quantity(invoice_id=invoice_id)
# Purchase order methods
def find_purchase_order(self, purchase_order_id):
return self.purchase_orders.get(purchase_order_id)
def quantity_purchased(self, purchase_order_id=None):
return self.purchase_orders.quantity(purchase_order_id=purchase_order_id)
def purchase_item(self, quantity, purchase_order_id, eta_date=None):
self.purchase_orders.track({
"quantity": quantity,
"purchase_order_id": purchase_order_id,
"date": datetime.now(),
"eta_date": eta_date if eta_date else None
})
def deliver_purchase_order(self, quantity, purchase_order_id):
try:
self.transition("delivery",
{"quantity": quantity, "purchase_order_id": purchase_order_id, "date": datetime.now()},
{"quantity": quantity})
except TransitionValidationError:
return False
return True
def cancel_purchase_order(self, purchase_order_id):
self.tracker.action("cancel_purchase_order", {"purchase_order_id": purchase_order_id})()
# Lost and Found methods
def quantity_lost(self):
return self.lost.quantity()
def quantity_found(self):
return self.found.quantity()
def lost_stock(self, quantity):
self.transition("lost",
{"quantity": quantity},
{"quantity": quantity, "date": datetime.now()})
def found_stock(self, quantity):
self.transition("found",
{"quantity": quantity, "date": datetime.now()},
{"quantity": quantity})