"""Order model definitions."""

import logging
import os
import sys
from datetime import datetime
from decimal import Decimal

from django.contrib.auth.models import User
from django.core.exceptions import ValidationError
from django.core.validators import MinValueValidator
from django.db import models, transaction
from django.db.models import F, Q, Sum
from django.db.models.functions import Coalesce
from django.db.models.signals import post_save
from django.dispatch.dispatcher import receiver
from django.urls import reverse
from django.utils.translation import gettext_lazy as _

from djmoney.contrib.exchange.exceptions import MissingRate
from djmoney.contrib.exchange.models import convert_money
from djmoney.money import Money
from mptt.models import TreeForeignKey

import common.models as common_models
import InvenTree.helpers
import InvenTree.ready
import InvenTree.tasks
import InvenTree.validators
import order.validators
import stock.models
import users.models as UserModels
from common.notifications import InvenTreeNotificationBodies
from common.settings import currency_code_default
from company.models import Address, Company, Contact, SupplierPart
from generic.states import StateTransitionMixin
from InvenTree.exceptions import log_error
from InvenTree.fields import (
    InvenTreeModelMoneyField,
    InvenTreeURLField,
    RoundingDecimalField,
)
from InvenTree.helpers import decimal2string
from InvenTree.helpers_model import getSetting, notify_responsible
from InvenTree.models import (
    InvenTreeAttachment,
    InvenTreeBarcodeMixin,
    InvenTreeNotesMixin,
    MetadataMixin,
    ReferenceIndexingMixin,
)
from InvenTree.status_codes import (
    PurchaseOrderStatus,
    PurchaseOrderStatusGroups,
    ReturnOrderLineStatus,
    ReturnOrderStatus,
    ReturnOrderStatusGroups,
    SalesOrderStatus,
    SalesOrderStatusGroups,
    StockHistoryCode,
    StockStatus,
)
from part import models as PartModels
from plugin.events import trigger_event

logger = logging.getLogger('inventree')


class TotalPriceMixin(models.Model):
    """Mixin which provides 'total_price' field for an order."""

    class Meta:
        """Meta for MetadataMixin."""

        abstract = True

    def save(self, *args, **kwargs):
        """Update the total_price field when saved."""
        # Recalculate total_price for this order
        self.update_total_price(commit=False)
        super().save(*args, **kwargs)

    total_price = InvenTreeModelMoneyField(
        null=True,
        blank=True,
        allow_negative=False,
        verbose_name=_('Total Price'),
        help_text=_('Total price for this order'),
    )

    order_currency = models.CharField(
        max_length=3,
        verbose_name=_('Order Currency'),
        blank=True,
        null=True,
        help_text=_('Currency for this order (leave blank to use company default)'),
        validators=[InvenTree.validators.validate_currency_code],
    )

    @property
    def currency(self):
        """Return the currency associated with this order instance.

        Rules:
        - If the order_currency field is set, return that
        - Otherwise, return the currency associated with the company
        - Finally, return the default currency code
        """
        if self.order_currency:
            return self.order_currency

        if self.company:
            return self.company.currency_code

        # Return default currency code
        return currency_code_default()

    def update_total_price(self, commit=True):
        """Recalculate and save the total_price for this order."""
        self.total_price = self.calculate_total_price(target_currency=self.currency)

        if commit:
            self.save()

    def calculate_total_price(self, target_currency=None):
        """Calculates the total price of all order lines, and converts to the specified target currency.

        If not specified, the default system currency is used.

        If currency conversion fails (e.g. there are no valid conversion rates),
        then we simply return zero, rather than attempting some other calculation.
        """
        # Set default - see B008
        if target_currency is None:
            target_currency = currency_code_default()

        total = Money(0, target_currency)

        # order items
        for line in self.lines.all():
            if not line.price:
                continue

            try:
                total += line.quantity * convert_money(line.price, target_currency)
            except MissingRate:
                # Record the error, try to press on
                kind, info, data = sys.exc_info()

                log_error('order.calculate_total_price')
                logger.exception("Missing exchange rate for '%s'", target_currency)

                # Return None to indicate the calculated price is invalid
                return None

        # extra items
        for line in self.extra_lines.all():
            if not line.price:
                continue

            try:
                total += line.quantity * convert_money(line.price, target_currency)
            except MissingRate:
                # Record the error, try to press on

                log_error('order.calculate_total_price')
                logger.exception("Missing exchange rate for '%s'", target_currency)

                # Return None to indicate the calculated price is invalid
                return None

        # set decimal-places
        total.decimal_places = 4

        return total


class Order(
    StateTransitionMixin,
    InvenTreeBarcodeMixin,
    InvenTreeNotesMixin,
    MetadataMixin,
    ReferenceIndexingMixin,
):
    """Abstract model for an order.

    Instances of this class:

    - PuchaseOrder
    - SalesOrder

    Attributes:
        reference: Unique order number / reference / code
        description: Long form description (required)
        notes: Extra note field (optional)
        creation_date: Automatic date of order creation
        created_by: User who created this order (automatically captured)
        issue_date: Date the order was issued
        complete_date: Date the order was completed
        responsible: User (or group) responsible for managing the order
    """

    class Meta:
        """Metaclass options. Abstract ensures no database table is created."""

        abstract = True

    def save(self, *args, **kwargs):
        """Custom save method for the order models.

        Ensures that the reference field is rebuilt whenever the instance is saved.
        """
        self.reference_int = self.rebuild_reference_field(self.reference)

        if not self.creation_date:
            self.creation_date = datetime.now().date()

        super().save(*args, **kwargs)

    def clean(self):
        """Custom clean method for the generic order class."""
        super().clean()

        # Check that the referenced 'contact' matches the correct 'company'
        if self.company and self.contact:
            if self.contact.company != self.company:
                raise ValidationError({
                    'contact': _('Contact does not match selected company')
                })

    @classmethod
    def overdue_filter(cls):
        """A generic implementation of an 'overdue' filter for the Model class.

        It requires any subclasses to implement the get_status_class() class method
        """
        today = datetime.now().date()
        return (
            Q(status__in=cls.get_status_class().OPEN)
            & ~Q(target_date=None)
            & Q(target_date__lt=today)
        )

    @property
    def is_overdue(self):
        """Method to determine if this order is overdue.

        Makes use of the overdue_filter() method to avoid code duplication
        """
        return (
            self.__class__.objects.filter(pk=self.pk)
            .filter(self.__class__.overdue_filter())
            .exists()
        )

    description = models.CharField(
        max_length=250,
        blank=True,
        verbose_name=_('Description'),
        help_text=_('Order description (optional)'),
    )

    project_code = models.ForeignKey(
        common_models.ProjectCode,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        verbose_name=_('Project Code'),
        help_text=_('Select project code for this order'),
    )

    link = InvenTreeURLField(
        blank=True, verbose_name=_('Link'), help_text=_('Link to external page')
    )

    target_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Target Date'),
        help_text=_(
            'Expected date for order delivery. Order will be overdue after this date.'
        ),
    )

    creation_date = models.DateField(
        blank=True, null=True, verbose_name=_('Creation Date')
    )

    created_by = models.ForeignKey(
        User,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        related_name='+',
        verbose_name=_('Created By'),
    )

    responsible = models.ForeignKey(
        UserModels.Owner,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        help_text=_('User or group responsible for this order'),
        verbose_name=_('Responsible'),
        related_name='+',
    )

    contact = models.ForeignKey(
        Contact,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        verbose_name=_('Contact'),
        help_text=_('Point of contact for this order'),
        related_name='+',
    )

    address = models.ForeignKey(
        Address,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        verbose_name=_('Address'),
        help_text=_('Company address for this order'),
        related_name='+',
    )

    @classmethod
    def get_status_class(cls):
        """Return the enumeration class which represents the 'status' field for this model."""
        raise NotImplementedError(f'get_status_class() not implemented for {__class__}')


class PurchaseOrder(TotalPriceMixin, Order):
    """A PurchaseOrder represents goods shipped inwards from an external supplier.

    Attributes:
        supplier: Reference to the company supplying the goods in the order
        supplier_reference: Optional field for supplier order reference code
        received_by: User that received the goods
        target_date: Expected delivery target date for PurchaseOrder completion (optional)
    """

    def get_absolute_url(self):
        """Get the 'web' URL for this order."""
        return reverse('po-detail', kwargs={'pk': self.pk})

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the PurchaseOrder model."""
        return reverse('api-po-list')

    @classmethod
    def get_status_class(cls):
        """Return the PurchasOrderStatus class."""
        return PurchaseOrderStatusGroups

    @classmethod
    def api_defaults(cls, request):
        """Return default values for this model when issuing an API OPTIONS request."""
        defaults = {
            'reference': order.validators.generate_next_purchase_order_reference()
        }

        return defaults

    # Global setting for specifying reference pattern
    REFERENCE_PATTERN_SETTING = 'PURCHASEORDER_REFERENCE_PATTERN'

    @staticmethod
    def filterByDate(queryset, min_date, max_date):
        """Filter by 'minimum and maximum date range'.

        - Specified as min_date, max_date
        - Both must be specified for filter to be applied
        - Determine which "interesting" orders exist between these dates

        To be "interesting":
        - A "received" order where the received date lies within the date range
        - A "pending" order where the target date lies within the date range
        - TODO: An "overdue" order where the target date is in the past
        """
        date_fmt = '%Y-%m-%d'  # ISO format date string

        # Ensure that both dates are valid
        try:
            min_date = datetime.strptime(str(min_date), date_fmt).date()
            max_date = datetime.strptime(str(max_date), date_fmt).date()
        except (ValueError, TypeError):
            # Date processing error, return queryset unchanged
            return queryset

        # Construct a queryset for "received" orders within the range
        received = (
            Q(status=PurchaseOrderStatus.COMPLETE.value)
            & Q(complete_date__gte=min_date)
            & Q(complete_date__lte=max_date)
        )

        # Construct a queryset for "pending" orders within the range
        pending = (
            Q(status__in=PurchaseOrderStatusGroups.OPEN)
            & ~Q(target_date=None)
            & Q(target_date__gte=min_date)
            & Q(target_date__lte=max_date)
        )

        # TODO - Construct a queryset for "overdue" orders within the range

        queryset = queryset.filter(received | pending)

        return queryset

    def __str__(self):
        """Render a string representation of this PurchaseOrder."""
        return f"{self.reference} - {self.supplier.name if self.supplier else _('deleted')}"

    reference = models.CharField(
        unique=True,
        max_length=64,
        blank=False,
        verbose_name=_('Reference'),
        help_text=_('Order reference'),
        default=order.validators.generate_next_purchase_order_reference,
        validators=[order.validators.validate_purchase_order_reference],
    )

    status = models.PositiveIntegerField(
        default=PurchaseOrderStatus.PENDING.value,
        choices=PurchaseOrderStatus.items(),
        help_text=_('Purchase order status'),
    )

    @property
    def status_text(self):
        """Return the text representation of the status field."""
        return PurchaseOrderStatus.text(self.status)

    supplier = models.ForeignKey(
        Company,
        on_delete=models.SET_NULL,
        null=True,
        limit_choices_to={'is_supplier': True},
        related_name='purchase_orders',
        verbose_name=_('Supplier'),
        help_text=_('Company from which the items are being ordered'),
    )

    @property
    def company(self):
        """Accessor helper for Order base class."""
        return self.supplier

    supplier_reference = models.CharField(
        max_length=64,
        blank=True,
        verbose_name=_('Supplier Reference'),
        help_text=_('Supplier order reference code'),
    )

    received_by = models.ForeignKey(
        User,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        related_name='+',
        verbose_name=_('received by'),
    )

    issue_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Issue Date'),
        help_text=_('Date order was issued'),
    )

    complete_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Completion Date'),
        help_text=_('Date order was completed'),
    )

    @transaction.atomic
    def add_line_item(
        self,
        supplier_part,
        quantity,
        group: bool = True,
        reference: str = '',
        purchase_price=None,
    ):
        """Add a new line item to this purchase order.

        This function will check that:
        * The supplier part matches the supplier specified for this purchase order
        * The quantity is greater than zero

        Args:
            supplier_part: The supplier_part to add
            quantity : The number of items to add
            group (bool, optional): If True, this new quantity will be added to an existing line item for the same supplier_part (if it exists). Defaults to True.
            reference (str, optional): Reference to item. Defaults to ''.
            purchase_price (optional): Price of item. Defaults to None.

        Returns:
            The newly created PurchaseOrderLineItem instance

        Raises:
            ValidationError: quantity is smaller than 0
            ValidationError: quantity is not type int
            ValidationError: supplier is not supplier of purchase order
        """
        try:
            quantity = int(quantity)
            if quantity <= 0:
                raise ValidationError({
                    'quantity': _('Quantity must be greater than zero')
                })
        except ValueError:
            raise ValidationError({'quantity': _('Invalid quantity provided')})

        if supplier_part.supplier != self.supplier:
            raise ValidationError({
                'supplier': _('Part supplier must match PO supplier')
            })

        if group:
            # Check if there is already a matching line item (for this PurchaseOrder)
            matches = self.lines.filter(part=supplier_part)

            if matches.count() > 0:
                line = matches.first()

                # update quantity and price
                quantity_new = line.quantity + quantity
                line.quantity = quantity_new
                supplier_price = supplier_part.get_price(quantity_new)

                if line.purchase_price and supplier_price:
                    line.purchase_price = supplier_price / quantity_new

                line.save()

                return line

        line = PurchaseOrderLineItem(
            order=self,
            part=supplier_part,
            quantity=quantity,
            reference=reference,
            purchase_price=purchase_price,
        )

        line.save()

        return line

    # region state changes
    def _action_place(self, *args, **kwargs):
        """Marks the PurchaseOrder as PLACED.

        Order must be currently PENDING.
        """
        if self.is_pending:
            self.status = PurchaseOrderStatus.PLACED.value
            self.issue_date = datetime.now().date()
            self.save()

            trigger_event('purchaseorder.placed', id=self.pk)

            # Notify users that the order has been placed
            notify_responsible(
                self,
                PurchaseOrder,
                exclude=self.created_by,
                content=InvenTreeNotificationBodies.NewOrder,
            )

    def _action_complete(self, *args, **kwargs):
        """Marks the PurchaseOrder as COMPLETE.

        Order must be currently PLACED.
        """
        if self.status == PurchaseOrderStatus.PLACED:
            self.status = PurchaseOrderStatus.COMPLETE.value
            self.complete_date = datetime.now().date()

            self.save()

            # Schedule pricing update for any referenced parts
            for line in self.lines.all():
                if line.part and line.part.part:
                    line.part.part.schedule_pricing_update(create=True)

            trigger_event('purchaseorder.completed', id=self.pk)

    @transaction.atomic
    def place_order(self):
        """Attempt to transition to PLACED status."""
        return self.handle_transition(
            self.status, PurchaseOrderStatus.PLACED.value, self, self._action_place
        )

    @transaction.atomic
    def complete_order(self):
        """Attempt to transition to COMPLETE status."""
        return self.handle_transition(
            self.status, PurchaseOrderStatus.COMPLETE.value, self, self._action_complete
        )

    @transaction.atomic
    def cancel_order(self):
        """Attempt to transition to CANCELLED status."""
        return self.handle_transition(
            self.status, PurchaseOrderStatus.CANCELLED.value, self, self._action_cancel
        )

    @property
    def is_pending(self):
        """Return True if the PurchaseOrder is 'pending'."""
        return self.status == PurchaseOrderStatus.PENDING.value

    @property
    def is_open(self):
        """Return True if the PurchaseOrder is 'open'."""
        return self.status in PurchaseOrderStatusGroups.OPEN

    @property
    def can_cancel(self):
        """A PurchaseOrder can only be cancelled under the following circumstances.

        - Status is PLACED
        - Status is PENDING
        """
        return self.status in [
            PurchaseOrderStatus.PLACED.value,
            PurchaseOrderStatus.PENDING.value,
        ]

    def _action_cancel(self, *args, **kwargs):
        """Marks the PurchaseOrder as CANCELLED."""
        if self.can_cancel:
            self.status = PurchaseOrderStatus.CANCELLED.value
            self.save()

            trigger_event('purchaseorder.cancelled', id=self.pk)

            # Notify users that the order has been canceled
            notify_responsible(
                self,
                PurchaseOrder,
                exclude=self.created_by,
                content=InvenTreeNotificationBodies.OrderCanceled,
            )

    # endregion

    def pending_line_items(self):
        """Return a list of pending line items for this order.

        Any line item where 'received' < 'quantity' will be returned.
        """
        return self.lines.filter(quantity__gt=F('received'))

    def completed_line_items(self):
        """Return a list of completed line items against this order."""
        return self.lines.filter(quantity__lte=F('received'))

    @property
    def line_count(self):
        """Return the total number of line items associated with this order."""
        return self.lines.count()

    @property
    def completed_line_count(self):
        """Return the number of complete line items associated with this order."""
        return self.completed_line_items().count()

    @property
    def pending_line_count(self):
        """Return the number of pending line items associated with this order."""
        return self.pending_line_items().count()

    @property
    def is_complete(self):
        """Return True if all line items have been received."""
        return self.lines.count() > 0 and self.pending_line_items().count() == 0

    @transaction.atomic
    def receive_line_item(
        self, line, location, quantity, user, status=StockStatus.OK.value, **kwargs
    ):
        """Receive a line item (or partial line item) against this PurchaseOrder."""
        # Extract optional batch code for the new stock item
        batch_code = kwargs.get('batch_code', '')

        # Extract optional list of serial numbers
        serials = kwargs.get('serials', None)

        # Extract optional notes field
        notes = kwargs.get('notes', '')

        # Extract optional barcode field
        barcode = kwargs.get('barcode', None)

        # Prevent null values for barcode
        if barcode is None:
            barcode = ''

        if self.status != PurchaseOrderStatus.PLACED:
            raise ValidationError(
                "Lines can only be received against an order marked as 'PLACED'"
            )

        try:
            if quantity < 0:
                raise ValidationError({
                    'quantity': _('Quantity must be a positive number')
                })
            quantity = InvenTree.helpers.clean_decimal(quantity)
        except TypeError:
            raise ValidationError({'quantity': _('Invalid quantity provided')})

        # Create a new stock item
        if line.part and quantity > 0:
            # Calculate received quantity in base units
            stock_quantity = line.part.base_quantity(quantity)

            # Calculate unit purchase price (in base units)
            if line.purchase_price:
                unit_purchase_price = line.purchase_price
                unit_purchase_price /= line.part.base_quantity(1)
            else:
                unit_purchase_price = None

            # Determine if we should individually serialize the items, or not
            if type(serials) is list and len(serials) > 0:
                serialize = True
            else:
                serialize = False
                serials = [None]

            for sn in serials:
                item = stock.models.StockItem(
                    part=line.part.part,
                    supplier_part=line.part,
                    location=location,
                    quantity=1 if serialize else stock_quantity,
                    purchase_order=self,
                    status=status,
                    batch=batch_code,
                    serial=sn,
                    purchase_price=unit_purchase_price,
                )

                # Assign the provided barcode
                if barcode:
                    item.assign_barcode(barcode_data=barcode, save=False)

                item.save(add_note=False)

                tracking_info = {'status': status, 'purchaseorder': self.pk}

                item.add_tracking_entry(
                    StockHistoryCode.RECEIVED_AGAINST_PURCHASE_ORDER,
                    user,
                    notes=notes,
                    deltas=tracking_info,
                    location=location,
                    purchaseorder=self,
                    quantity=quantity,
                )

        # Update the number of parts received against the particular line item
        # Note that this quantity does *not* take the pack_quantity into account, it is "number of packs"
        line.received += quantity
        line.save()

        # Has this order been completed?
        if len(self.pending_line_items()) == 0:
            if common_models.InvenTreeSetting.get_setting(
                'PURCHASEORDER_AUTO_COMPLETE', True
            ):
                self.received_by = user
                self.complete_order()  # This will save the model

        # Issue a notification to interested parties, that this order has been "updated"
        notify_responsible(
            self,
            PurchaseOrder,
            exclude=user,
            content=InvenTreeNotificationBodies.ItemsReceived,
        )


class SalesOrder(TotalPriceMixin, Order):
    """A SalesOrder represents a list of goods shipped outwards to a customer."""

    def get_absolute_url(self):
        """Get the 'web' URL for this order."""
        return reverse('so-detail', kwargs={'pk': self.pk})

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrder model."""
        return reverse('api-so-list')

    @classmethod
    def get_status_class(cls):
        """Return the SalesOrderStatus class."""
        return SalesOrderStatusGroups

    @classmethod
    def api_defaults(cls, request):
        """Return default values for this model when issuing an API OPTIONS request."""
        defaults = {'reference': order.validators.generate_next_sales_order_reference()}

        return defaults

    # Global setting for specifying reference pattern
    REFERENCE_PATTERN_SETTING = 'SALESORDER_REFERENCE_PATTERN'

    @staticmethod
    def filterByDate(queryset, min_date, max_date):
        """Filter by "minimum and maximum date range".

        - Specified as min_date, max_date
        - Both must be specified for filter to be applied
        - Determine which "interesting" orders exist between these dates

        To be "interesting":
        - A "completed" order where the completion date lies within the date range
        - A "pending" order where the target date lies within the date range
        - TODO: An "overdue" order where the target date is in the past
        """
        date_fmt = '%Y-%m-%d'  # ISO format date string

        # Ensure that both dates are valid
        try:
            min_date = datetime.strptime(str(min_date), date_fmt).date()
            max_date = datetime.strptime(str(max_date), date_fmt).date()
        except (ValueError, TypeError):
            # Date processing error, return queryset unchanged
            return queryset

        # Construct a queryset for "completed" orders within the range
        completed = (
            Q(status__in=SalesOrderStatusGroups.COMPLETE)
            & Q(shipment_date__gte=min_date)
            & Q(shipment_date__lte=max_date)
        )

        # Construct a queryset for "pending" orders within the range
        pending = (
            Q(status__in=SalesOrderStatusGroups.OPEN)
            & ~Q(target_date=None)
            & Q(target_date__gte=min_date)
            & Q(target_date__lte=max_date)
        )

        # TODO: Construct a queryset for "overdue" orders within the range

        queryset = queryset.filter(completed | pending)

        return queryset

    def __str__(self):
        """Render a string representation of this SalesOrder."""
        return f"{self.reference} - {self.customer.name if self.customer else _('deleted')}"

    reference = models.CharField(
        unique=True,
        max_length=64,
        blank=False,
        verbose_name=_('Reference'),
        help_text=_('Order reference'),
        default=order.validators.generate_next_sales_order_reference,
        validators=[order.validators.validate_sales_order_reference],
    )

    customer = models.ForeignKey(
        Company,
        on_delete=models.SET_NULL,
        null=True,
        limit_choices_to={'is_customer': True},
        related_name='return_orders',
        verbose_name=_('Customer'),
        help_text=_('Company to which the items are being sold'),
    )

    @property
    def company(self):
        """Accessor helper for Order base."""
        return self.customer

    status = models.PositiveIntegerField(
        default=SalesOrderStatus.PENDING.value,
        choices=SalesOrderStatus.items(),
        verbose_name=_('Status'),
        help_text=_('Purchase order status'),
    )

    @property
    def status_text(self):
        """Return the text representation of the status field."""
        return SalesOrderStatus.text(self.status)

    customer_reference = models.CharField(
        max_length=64,
        blank=True,
        verbose_name=_('Customer Reference '),
        help_text=_('Customer order reference code'),
    )

    shipment_date = models.DateField(
        blank=True, null=True, verbose_name=_('Shipment Date')
    )

    shipped_by = models.ForeignKey(
        User,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        related_name='+',
        verbose_name=_('shipped by'),
    )

    @property
    def is_pending(self):
        """Return True if this order is 'pending'."""
        return self.status == SalesOrderStatus.PENDING

    @property
    def is_open(self):
        """Return True if this order is 'open' (either 'pending' or 'in_progress')."""
        return self.status in SalesOrderStatusGroups.OPEN

    @property
    def stock_allocations(self):
        """Return a queryset containing all allocations for this order."""
        return SalesOrderAllocation.objects.filter(
            line__in=[line.pk for line in self.lines.all()]
        )

    def is_fully_allocated(self):
        """Return True if all line items are fully allocated."""
        for line in self.lines.all():
            if not line.is_fully_allocated():
                return False

        return True

    def is_overallocated(self):
        """Return true if any lines in the order are over-allocated."""
        for line in self.lines.all():
            if line.is_overallocated():
                return True

        return False

    def is_completed(self):
        """Check if this order is "shipped" (all line items delivered)."""
        return self.lines.count() > 0 and all(
            line.is_completed() for line in self.lines.all()
        )

    def can_complete(self, raise_error=False, allow_incomplete_lines=False):
        """Test if this SalesOrder can be completed.

        Throws a ValidationError if cannot be completed.
        """
        try:
            # Order without line items cannot be completed
            if self.lines.count() == 0:
                raise ValidationError(
                    _('Order cannot be completed as no parts have been assigned')
                )

            # Only an open order can be marked as shipped
            elif not self.is_open:
                raise ValidationError(_('Only an open order can be marked as complete'))

            elif self.pending_shipment_count > 0:
                raise ValidationError(
                    _('Order cannot be completed as there are incomplete shipments')
                )

            elif not allow_incomplete_lines and self.pending_line_count > 0:
                raise ValidationError(
                    _('Order cannot be completed as there are incomplete line items')
                )

        except ValidationError as e:
            if raise_error:
                raise e
            else:
                return False

        return True

    # region state changes
    def place_order(self):
        """Deprecated version of 'issue_order'."""
        self.issue_order()

    def _action_place(self, *args, **kwargs):
        """Change this order from 'PENDING' to 'IN_PROGRESS'."""
        if self.status == SalesOrderStatus.PENDING:
            self.status = SalesOrderStatus.IN_PROGRESS.value
            self.issue_date = datetime.now().date()
            self.save()

            trigger_event('salesorder.issued', id=self.pk)

    def _action_complete(self, *args, **kwargs):
        """Mark this order as "complete."""
        user = kwargs.pop('user', None)

        if not self.can_complete(**kwargs):
            return False

        self.status = SalesOrderStatus.SHIPPED.value
        self.shipped_by = user
        self.shipment_date = datetime.now()

        self.save()

        # Schedule pricing update for any referenced parts
        for line in self.lines.all():
            line.part.schedule_pricing_update(create=True)

        trigger_event('salesorder.completed', id=self.pk)

        return True

    @property
    def can_cancel(self):
        """Return True if this order can be cancelled."""
        return self.is_open

    def _action_cancel(self, *args, **kwargs):
        """Cancel this order (only if it is "open").

        Executes:
        - Mark the order as 'cancelled'
        - Delete any StockItems which have been allocated
        """
        if not self.can_cancel:
            return False

        self.status = SalesOrderStatus.CANCELLED.value
        self.save()

        for line in self.lines.all():
            for allocation in line.allocations.all():
                allocation.delete()

        trigger_event('salesorder.cancelled', id=self.pk)

        # Notify users that the order has been canceled
        notify_responsible(
            self,
            SalesOrder,
            exclude=self.created_by,
            content=InvenTreeNotificationBodies.OrderCanceled,
        )

        return True

    @transaction.atomic
    def issue_order(self):
        """Attempt to transition to IN_PROGRESS status."""
        return self.handle_transition(
            self.status, SalesOrderStatus.IN_PROGRESS.value, self, self._action_place
        )

    @transaction.atomic
    def complete_order(self, user, **kwargs):
        """Attempt to transition to SHIPPED status."""
        return self.handle_transition(
            self.status,
            SalesOrderStatus.SHIPPED.value,
            self,
            self._action_complete,
            user=user,
            **kwargs,
        )

    @transaction.atomic
    def cancel_order(self):
        """Attempt to transition to CANCELLED status."""
        return self.handle_transition(
            self.status, SalesOrderStatus.CANCELLED.value, self, self._action_cancel
        )

    # endregion

    @property
    def line_count(self):
        """Return the total number of lines associated with this order."""
        return self.lines.count()

    def completed_line_items(self):
        """Return a queryset of the completed line items for this order."""
        return self.lines.filter(shipped__gte=F('quantity'))

    def pending_line_items(self):
        """Return a queryset of the pending line items for this order."""
        return self.lines.filter(shipped__lt=F('quantity'))

    @property
    def completed_line_count(self):
        """Return the number of completed lines for this order."""
        return self.completed_line_items().count()

    @property
    def pending_line_count(self):
        """Return the number of pending (incomplete) lines associated with this order."""
        return self.pending_line_items().count()

    def completed_shipments(self):
        """Return a queryset of the completed shipments for this order."""
        return self.shipments.exclude(shipment_date=None)

    def pending_shipments(self):
        """Return a queryset of the pending shipments for this order."""
        return self.shipments.filter(shipment_date=None)

    @property
    def shipment_count(self):
        """Return the total number of shipments associated with this order."""
        return self.shipments.count()

    @property
    def completed_shipment_count(self):
        """Return the number of completed shipments associated with this order."""
        return self.completed_shipments().count()

    @property
    def pending_shipment_count(self):
        """Return the number of pending shipments associated with this order."""
        return self.pending_shipments().count()


@receiver(post_save, sender=SalesOrder, dispatch_uid='sales_order_post_save')
def after_save_sales_order(sender, instance: SalesOrder, created: bool, **kwargs):
    """Callback function to be executed after a SalesOrder is saved.

    - If the SALESORDER_DEFAULT_SHIPMENT setting is enabled, create a default shipment
    - Ignore if the database is not ready for access
    - Ignore if data import is active
    """
    if (
        not InvenTree.ready.canAppAccessDatabase(allow_test=True)
        or InvenTree.ready.isImportingData()
    ):
        return

    if created:
        # A new SalesOrder has just been created

        if getSetting('SALESORDER_DEFAULT_SHIPMENT'):
            # Create default shipment
            SalesOrderShipment.objects.create(order=instance, reference='1')

        # Notify the responsible users that the sales order has been created
        notify_responsible(instance, sender, exclude=instance.created_by)


class PurchaseOrderAttachment(InvenTreeAttachment):
    """Model for storing file attachments against a PurchaseOrder object."""

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the PurchaseOrderAttachment model."""
        return reverse('api-po-attachment-list')

    def getSubdir(self):
        """Return the directory path where PurchaseOrderAttachment files are located."""
        return os.path.join('po_files', str(self.order.id))

    order = models.ForeignKey(
        PurchaseOrder, on_delete=models.CASCADE, related_name='attachments'
    )


class SalesOrderAttachment(InvenTreeAttachment):
    """Model for storing file attachments against a SalesOrder object."""

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrderAttachment class."""
        return reverse('api-so-attachment-list')

    def getSubdir(self):
        """Return the directory path where SalesOrderAttachment files are located."""
        return os.path.join('so_files', str(self.order.id))

    order = models.ForeignKey(
        SalesOrder, on_delete=models.CASCADE, related_name='attachments'
    )


class OrderLineItem(MetadataMixin, models.Model):
    """Abstract model for an order line item.

    Attributes:
        quantity: Number of items
        reference: Reference text (e.g. customer reference) for this line item
        note: Annotation for the item
        target_date: An (optional) date for expected shipment of this line item.
    """

    class Meta:
        """Metaclass options. Abstract ensures no database table is created."""

        abstract = True

    def save(self, *args, **kwargs):
        """Custom save method for the OrderLineItem model.

        Calls save method on the linked order
        """
        super().save(*args, **kwargs)
        self.order.save()

    def delete(self, *args, **kwargs):
        """Custom delete method for the OrderLineItem model.

        Calls save method on the linked order
        """
        super().delete(*args, **kwargs)
        self.order.save()

    quantity = RoundingDecimalField(
        verbose_name=_('Quantity'),
        help_text=_('Item quantity'),
        default=1,
        max_digits=15,
        decimal_places=5,
        validators=[MinValueValidator(0)],
    )

    @property
    def total_line_price(self):
        """Return the total price for this line item."""
        if self.price:
            return self.quantity * self.price

    reference = models.CharField(
        max_length=100,
        blank=True,
        verbose_name=_('Reference'),
        help_text=_('Line item reference'),
    )

    notes = models.CharField(
        max_length=500,
        blank=True,
        verbose_name=_('Notes'),
        help_text=_('Line item notes'),
    )

    link = InvenTreeURLField(
        blank=True, verbose_name=_('Link'), help_text=_('Link to external page')
    )

    target_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Target Date'),
        help_text=_(
            'Target date for this line item (leave blank to use the target date from the order)'
        ),
    )


class OrderExtraLine(OrderLineItem):
    """Abstract Model for a single ExtraLine in a Order.

    Attributes:
        price: The unit sale price for this OrderLineItem
    """

    class Meta:
        """Metaclass options. Abstract ensures no database table is created."""

        abstract = True

    description = models.CharField(
        max_length=250,
        blank=True,
        verbose_name=_('Description'),
        help_text=_('Line item description (optional)'),
    )

    context = models.JSONField(
        blank=True,
        null=True,
        verbose_name=_('Context'),
        help_text=_('Additional context for this line'),
    )

    price = InvenTreeModelMoneyField(
        max_digits=19,
        decimal_places=6,
        null=True,
        blank=True,
        allow_negative=True,
        verbose_name=_('Price'),
        help_text=_('Unit price'),
    )


class PurchaseOrderLineItem(OrderLineItem):
    """Model for a purchase order line item.

    Attributes:
        order: Reference to a PurchaseOrder object
    """

    # Filter for determining if a particular PurchaseOrderLineItem is overdue
    OVERDUE_FILTER = (
        Q(received__lt=F('quantity'))
        & ~Q(target_date=None)
        & Q(target_date__lt=datetime.now().date())
    )

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the PurchaseOrderLineItem model."""
        return reverse('api-po-line-list')

    def clean(self):
        """Custom clean method for the PurchaseOrderLineItem model.

        Ensure the supplier part matches the supplier
        """
        super().clean()

        if self.order.supplier and self.part:
            # Supplier part *must* point to the same supplier!
            if self.part.supplier != self.order.supplier:
                raise ValidationError({'part': _('Supplier part must match supplier')})

    def __str__(self):
        """Render a string representation of a PurchaseOrderLineItem instance."""
        return '{n} x {part} from {supplier} (for {po})'.format(
            n=decimal2string(self.quantity),
            part=self.part.SKU if self.part else 'unknown part',
            supplier=self.order.supplier.name if self.order.supplier else _('deleted'),
            po=self.order,
        )

    order = models.ForeignKey(
        PurchaseOrder,
        on_delete=models.CASCADE,
        related_name='lines',
        verbose_name=_('Order'),
        help_text=_('Purchase Order'),
    )

    def get_base_part(self):
        """Return the base part.Part object for the line item.

        Note: Returns None if the SupplierPart is not set!
        """
        if self.part is None:
            return None
        return self.part.part

    part = models.ForeignKey(
        SupplierPart,
        on_delete=models.SET_NULL,
        blank=False,
        null=True,
        related_name='purchase_order_line_items',
        verbose_name=_('Part'),
        help_text=_('Supplier part'),
    )

    received = models.DecimalField(
        decimal_places=5,
        max_digits=15,
        default=0,
        verbose_name=_('Received'),
        help_text=_('Number of items received'),
    )

    purchase_price = InvenTreeModelMoneyField(
        max_digits=19,
        decimal_places=6,
        null=True,
        blank=True,
        verbose_name=_('Purchase Price'),
        help_text=_('Unit purchase price'),
    )

    @property
    def price(self):
        """Return the 'purchase_price' field as 'price'."""
        return self.purchase_price

    destination = TreeForeignKey(
        'stock.StockLocation',
        on_delete=models.SET_NULL,
        verbose_name=_('Destination'),
        related_name='po_lines',
        blank=True,
        null=True,
        help_text=_('Where does the Purchaser want this item to be stored?'),
    )

    def get_destination(self):
        """Show where the line item is or should be placed.

        NOTE: If a line item gets split when received, only an arbitrary
              stock items location will be reported as the location for the
              entire line.
        """
        for item in stock.models.StockItem.objects.filter(
            supplier_part=self.part, purchase_order=self.order
        ):
            if item.location:
                return item.location
        if self.destination:
            return self.destination
        if self.part and self.part.part and self.part.part.default_location:
            return self.part.part.default_location

    def remaining(self):
        """Calculate the number of items remaining to be received."""
        r = self.quantity - self.received
        return max(r, 0)


class PurchaseOrderExtraLine(OrderExtraLine):
    """Model for a single ExtraLine in a PurchaseOrder.

    Attributes:
        order: Link to the PurchaseOrder that this line belongs to
        title: title of line
        price: The unit price for this OrderLine
    """

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the PurchaseOrderExtraLine model."""
        return reverse('api-po-extra-line-list')

    order = models.ForeignKey(
        PurchaseOrder,
        on_delete=models.CASCADE,
        related_name='extra_lines',
        verbose_name=_('Order'),
        help_text=_('Purchase Order'),
    )


class SalesOrderLineItem(OrderLineItem):
    """Model for a single LineItem in a SalesOrder.

    Attributes:
        order: Link to the SalesOrder that this line item belongs to
        part: Link to a Part object (may be null)
        sale_price: The unit sale price for this OrderLineItem
        shipped: The number of items which have actually shipped against this line item
    """

    # Filter for determining if a particular SalesOrderLineItem is overdue
    OVERDUE_FILTER = (
        Q(shipped__lt=F('quantity'))
        & ~Q(target_date=None)
        & Q(target_date__lt=datetime.now().date())
    )

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrderLineItem model."""
        return reverse('api-so-line-list')

    def clean(self):
        """Perform extra validation steps for this SalesOrderLineItem instance."""
        super().clean()

        if self.part:
            if self.part.virtual:
                raise ValidationError({
                    'part': _('Virtual part cannot be assigned to a sales order')
                })

            if not self.part.salable:
                raise ValidationError({
                    'part': _('Only salable parts can be assigned to a sales order')
                })

    order = models.ForeignKey(
        SalesOrder,
        on_delete=models.CASCADE,
        related_name='lines',
        verbose_name=_('Order'),
        help_text=_('Sales Order'),
    )

    part = models.ForeignKey(
        'part.Part',
        on_delete=models.SET_NULL,
        related_name='sales_order_line_items',
        null=True,
        verbose_name=_('Part'),
        help_text=_('Part'),
        limit_choices_to={'salable': True, 'virtual': False},
    )

    sale_price = InvenTreeModelMoneyField(
        max_digits=19,
        decimal_places=6,
        null=True,
        blank=True,
        verbose_name=_('Sale Price'),
        help_text=_('Unit sale price'),
    )

    @property
    def price(self):
        """Return the 'sale_price' field as 'price'."""
        return self.sale_price

    shipped = RoundingDecimalField(
        verbose_name=_('Shipped'),
        help_text=_('Shipped quantity'),
        default=0,
        max_digits=15,
        decimal_places=5,
        validators=[MinValueValidator(0)],
    )

    def fulfilled_quantity(self):
        """Return the total stock quantity fulfilled against this line item."""
        if not self.pk:
            return 0

        query = self.order.stock_items.filter(part=self.part).aggregate(
            fulfilled=Coalesce(Sum('quantity'), Decimal(0))
        )

        return query['fulfilled']

    def allocated_quantity(self):
        """Return the total stock quantity allocated to this LineItem.

        This is a summation of the quantity of each attached StockItem
        """
        if not self.pk:
            return 0

        query = self.allocations.aggregate(
            allocated=Coalesce(Sum('quantity'), Decimal(0))
        )

        return query['allocated']

    def is_fully_allocated(self):
        """Return True if this line item is fully allocated."""
        if self.order.status == SalesOrderStatus.SHIPPED:
            return self.fulfilled_quantity() >= self.quantity

        return self.allocated_quantity() >= self.quantity

    def is_overallocated(self):
        """Return True if this line item is over allocated."""
        return self.allocated_quantity() > self.quantity

    def is_completed(self):
        """Return True if this line item is completed (has been fully shipped)."""
        return self.shipped >= self.quantity


class SalesOrderShipment(InvenTreeNotesMixin, MetadataMixin, models.Model):
    """The SalesOrderShipment model represents a physical shipment made against a SalesOrder.

    - Points to a single SalesOrder object
    - Multiple SalesOrderAllocation objects point to a particular SalesOrderShipment
    - When a given SalesOrderShipment is "shipped", stock items are removed from stock

    Attributes:
        order: SalesOrder reference
        shipment_date: Date this shipment was "shipped" (or null)
        checked_by: User reference field indicating who checked this order
        reference: Custom reference text for this shipment (e.g. consignment number?)
        notes: Custom notes field for this shipment
    """

    class Meta:
        """Metaclass defines extra model options."""

        # Shipment reference must be unique for a given sales order
        unique_together = ['order', 'reference']

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrderShipment model."""
        return reverse('api-so-shipment-list')

    order = models.ForeignKey(
        SalesOrder,
        on_delete=models.CASCADE,
        blank=False,
        null=False,
        related_name='shipments',
        verbose_name=_('Order'),
        help_text=_('Sales Order'),
    )

    shipment_date = models.DateField(
        null=True,
        blank=True,
        verbose_name=_('Shipment Date'),
        help_text=_('Date of shipment'),
    )

    delivery_date = models.DateField(
        null=True,
        blank=True,
        verbose_name=_('Delivery Date'),
        help_text=_('Date of delivery of shipment'),
    )

    checked_by = models.ForeignKey(
        User,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
        verbose_name=_('Checked By'),
        help_text=_('User who checked this shipment'),
        related_name='+',
    )

    reference = models.CharField(
        max_length=100,
        blank=False,
        verbose_name=_('Shipment'),
        help_text=_('Shipment number'),
        default='1',
    )

    tracking_number = models.CharField(
        max_length=100,
        blank=True,
        unique=False,
        verbose_name=_('Tracking Number'),
        help_text=_('Shipment tracking information'),
    )

    invoice_number = models.CharField(
        max_length=100,
        blank=True,
        unique=False,
        verbose_name=_('Invoice Number'),
        help_text=_('Reference number for associated invoice'),
    )

    link = InvenTreeURLField(
        blank=True, verbose_name=_('Link'), help_text=_('Link to external page')
    )

    def is_complete(self):
        """Return True if this shipment has already been completed."""
        return self.shipment_date is not None

    def is_delivered(self):
        """Return True if this shipment has already been delivered."""
        return self.delivery_date is not None

    def check_can_complete(self, raise_error=True):
        """Check if this shipment is able to be completed."""
        try:
            if self.shipment_date:
                # Shipment has already been sent!
                raise ValidationError(_('Shipment has already been sent'))

            if self.allocations.count() == 0:
                raise ValidationError(_('Shipment has no allocated stock items'))

        except ValidationError as e:
            if raise_error:
                raise e
            else:
                return False

        return True

    @transaction.atomic
    def complete_shipment(self, user, **kwargs):
        """Complete this particular shipment.

        Executes:
        1. Update any stock items associated with this shipment
        2. Update the "shipped" quantity of all associated line items
        3. Set the "shipment_date" to now
        """
        # Check if the shipment can be completed (throw error if not)
        self.check_can_complete()

        allocations = self.allocations.all()

        # Iterate through each stock item assigned to this shipment
        for allocation in allocations:
            # Mark the allocation as "complete"
            allocation.complete_allocation(user)

        # Update the "shipment" date
        self.shipment_date = kwargs.get('shipment_date', datetime.now())
        self.shipped_by = user

        # Was a tracking number provided?
        tracking_number = kwargs.get('tracking_number', None)

        if tracking_number is not None:
            self.tracking_number = tracking_number

        # Was an invoice number provided?
        invoice_number = kwargs.get('invoice_number', None)

        if invoice_number is not None:
            self.invoice_number = invoice_number

        # Was a link provided?
        link = kwargs.get('link', None)

        if link is not None:
            self.link = link

        # Was a delivery date provided?
        delivery_date = kwargs.get('delivery_date', None)

        if delivery_date is not None:
            self.delivery_date = delivery_date

        self.save()

        trigger_event('salesordershipment.completed', id=self.pk)


class SalesOrderExtraLine(OrderExtraLine):
    """Model for a single ExtraLine in a SalesOrder.

    Attributes:
        order: Link to the SalesOrder that this line belongs to
        title: title of line
        price: The unit price for this OrderLine
    """

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrderExtraLine model."""
        return reverse('api-so-extra-line-list')

    order = models.ForeignKey(
        SalesOrder,
        on_delete=models.CASCADE,
        related_name='extra_lines',
        verbose_name=_('Order'),
        help_text=_('Sales Order'),
    )


class SalesOrderAllocation(models.Model):
    """This model is used to 'allocate' stock items to a SalesOrder. Items that are "allocated" to a SalesOrder are not yet "attached" to the order, but they will be once the order is fulfilled.

    Attributes:
        line: SalesOrderLineItem reference
        shipment: SalesOrderShipment reference
        item: StockItem reference
        quantity: Quantity to take from the StockItem
    """

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the SalesOrderAllocation model."""
        return reverse('api-so-allocation-list')

    def clean(self):
        """Validate the SalesOrderAllocation object.

        Executes:
        - Cannot allocate stock to a line item without a part reference
        - The referenced part must match the part associated with the line item
        - Allocated quantity cannot exceed the quantity of the stock item
        - Allocation quantity must be "1" if the StockItem is serialized
        - Allocation quantity cannot be zero
        """
        super().clean()

        errors = {}

        try:
            if not self.item:
                raise ValidationError({'item': _('Stock item has not been assigned')})
        except stock.models.StockItem.DoesNotExist:
            raise ValidationError({'item': _('Stock item has not been assigned')})

        try:
            if self.line.part != self.item.part:
                variants = self.line.part.get_descendants(include_self=True)
                if self.line.part not in variants:
                    errors['item'] = _(
                        'Cannot allocate stock item to a line with a different part'
                    )
        except PartModels.Part.DoesNotExist:
            errors['line'] = _('Cannot allocate stock to a line without a part')

        if self.quantity > self.item.quantity:
            errors['quantity'] = _('Allocation quantity cannot exceed stock quantity')

        # Ensure that we do not 'over allocate' a stock item
        build_allocation_count = self.item.build_allocation_count()
        sales_allocation_count = self.item.sales_order_allocation_count(
            exclude_allocations={'pk': self.pk}
        )

        total_allocation = (
            build_allocation_count + sales_allocation_count + self.quantity
        )

        if total_allocation > self.item.quantity:
            errors['quantity'] = _('Stock item is over-allocated')

        if self.quantity <= 0:
            errors['quantity'] = _('Allocation quantity must be greater than zero')

        if self.item.serial and self.quantity != 1:
            errors['quantity'] = _('Quantity must be 1 for serialized stock item')

        if self.line.order != self.shipment.order:
            errors['line'] = _('Sales order does not match shipment')
            errors['shipment'] = _('Shipment does not match sales order')

        if len(errors) > 0:
            raise ValidationError(errors)

    line = models.ForeignKey(
        SalesOrderLineItem,
        on_delete=models.CASCADE,
        verbose_name=_('Line'),
        related_name='allocations',
    )

    shipment = models.ForeignKey(
        SalesOrderShipment,
        on_delete=models.CASCADE,
        related_name='allocations',
        verbose_name=_('Shipment'),
        help_text=_('Sales order shipment reference'),
    )

    item = models.ForeignKey(
        'stock.StockItem',
        on_delete=models.CASCADE,
        related_name='sales_order_allocations',
        limit_choices_to={
            'part__salable': True,
            'part__virtual': False,
            'belongs_to': None,
            'sales_order': None,
        },
        verbose_name=_('Item'),
        help_text=_('Select stock item to allocate'),
    )

    quantity = RoundingDecimalField(
        max_digits=15,
        decimal_places=5,
        validators=[MinValueValidator(0)],
        default=1,
        verbose_name=_('Quantity'),
        help_text=_('Enter stock allocation quantity'),
    )

    def get_location(self):
        """Return the <pk> value of the location associated with this allocation."""
        return self.item.location.id if self.item.location else None

    def get_po(self):
        """Return the PurchaseOrder associated with this allocation."""
        return self.item.purchase_order

    def complete_allocation(self, user):
        """Complete this allocation (called when the parent SalesOrder is marked as "shipped").

        Executes:
        - Determine if the referenced StockItem needs to be "split" (if allocated quantity != stock quantity)
        - Mark the StockItem as belonging to the Customer (this will remove it from stock)
        """
        order = self.line.order

        item = self.item.allocateToCustomer(
            order.customer, quantity=self.quantity, order=order, user=user
        )

        # Update the 'shipped' quantity
        self.line.shipped += self.quantity
        self.line.save()

        # Update our own reference to the StockItem
        # (It may have changed if the stock was split)
        self.item = item
        self.save()


class ReturnOrder(TotalPriceMixin, Order):
    """A ReturnOrder represents goods returned from a customer, e.g. an RMA or warranty.

    Attributes:
        customer: Reference to the customer
        sales_order: Reference to an existing SalesOrder (optional)
        status: The status of the order (refer to status_codes.ReturnOrderStatus)
    """

    def get_absolute_url(self):
        """Get the 'web' URL for this order."""
        return reverse('return-order-detail', kwargs={'pk': self.pk})

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the ReturnOrder model."""
        return reverse('api-return-order-list')

    @classmethod
    def get_status_class(cls):
        """Return the ReturnOrderStatus class."""
        return ReturnOrderStatusGroups

    @classmethod
    def api_defaults(cls, request):
        """Return default values for this model when issuing an API OPTIONS request."""
        defaults = {
            'reference': order.validators.generate_next_return_order_reference()
        }

        return defaults

    REFERENCE_PATTERN_SETTING = 'RETURNORDER_REFERENCE_PATTERN'

    def __str__(self):
        """Render a string representation of this ReturnOrder."""
        return f"{self.reference} - {self.customer.name if self.customer else _('no customer')}"

    reference = models.CharField(
        unique=True,
        max_length=64,
        blank=False,
        verbose_name=_('Reference'),
        help_text=_('Return Order reference'),
        default=order.validators.generate_next_return_order_reference,
        validators=[order.validators.validate_return_order_reference],
    )

    customer = models.ForeignKey(
        Company,
        on_delete=models.SET_NULL,
        null=True,
        limit_choices_to={'is_customer': True},
        related_name='sales_orders',
        verbose_name=_('Customer'),
        help_text=_('Company from which items are being returned'),
    )

    @property
    def company(self):
        """Accessor helper for Order base class."""
        return self.customer

    status = models.PositiveIntegerField(
        default=ReturnOrderStatus.PENDING.value,
        choices=ReturnOrderStatus.items(),
        verbose_name=_('Status'),
        help_text=_('Return order status'),
    )

    customer_reference = models.CharField(
        max_length=64,
        blank=True,
        verbose_name=_('Customer Reference '),
        help_text=_('Customer order reference code'),
    )

    issue_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Issue Date'),
        help_text=_('Date order was issued'),
    )

    complete_date = models.DateField(
        blank=True,
        null=True,
        verbose_name=_('Completion Date'),
        help_text=_('Date order was completed'),
    )

    # region state changes
    @property
    def is_pending(self):
        """Return True if this order is pending."""
        return self.status == ReturnOrderStatus.PENDING

    @property
    def is_open(self):
        """Return True if this order is outstanding."""
        return self.status in ReturnOrderStatusGroups.OPEN

    @property
    def is_received(self):
        """Return True if this order is fully received."""
        return not self.lines.filter(received_date=None).exists()

    def _action_cancel(self, *args, **kwargs):
        """Cancel this ReturnOrder (if not already cancelled)."""
        if self.status != ReturnOrderStatus.CANCELLED:
            self.status = ReturnOrderStatus.CANCELLED.value
            self.save()

            trigger_event('returnorder.cancelled', id=self.pk)

            # Notify users that the order has been canceled
            notify_responsible(
                self,
                ReturnOrder,
                exclude=self.created_by,
                content=InvenTreeNotificationBodies.OrderCanceled,
            )

    def _action_complete(self, *args, **kwargs):
        """Complete this ReturnOrder (if not already completed)."""
        if self.status == ReturnOrderStatus.IN_PROGRESS:
            self.status = ReturnOrderStatus.COMPLETE.value
            self.complete_date = datetime.now().date()
            self.save()

            trigger_event('returnorder.completed', id=self.pk)

    def place_order(self):
        """Deprecated version of 'issue_order."""
        self.issue_order()

    def _action_place(self, *args, **kwargs):
        """Issue this ReturnOrder (if currently pending)."""
        if self.status == ReturnOrderStatus.PENDING:
            self.status = ReturnOrderStatus.IN_PROGRESS.value
            self.issue_date = datetime.now().date()
            self.save()

            trigger_event('returnorder.issued', id=self.pk)

    @transaction.atomic
    def issue_order(self):
        """Attempt to transition to IN_PROGRESS status."""
        return self.handle_transition(
            self.status, ReturnOrderStatus.IN_PROGRESS.value, self, self._action_place
        )

    @transaction.atomic
    def complete_order(self):
        """Attempt to transition to COMPLETE status."""
        return self.handle_transition(
            self.status, ReturnOrderStatus.COMPLETE.value, self, self._action_complete
        )

    @transaction.atomic
    def cancel_order(self):
        """Attempt to transition to CANCELLED status."""
        return self.handle_transition(
            self.status, ReturnOrderStatus.CANCELLED.value, self, self._action_cancel
        )

    # endregion

    @transaction.atomic
    def receive_line_item(self, line, location, user, note=''):
        """Receive a line item against this ReturnOrder.

        Rules:
        - Transfers the StockItem to the specified location
        - Marks the StockItem as "quarantined"
        - Adds a tracking entry to the StockItem
        - Removes the 'customer' reference from the StockItem
        """
        # Prevent an item from being "received" multiple times
        if line.received_date is not None:
            logger.warning('receive_line_item called with item already returned')
            return

        stock_item = line.item

        deltas = {
            'status': StockStatus.QUARANTINED.value,
            'returnorder': self.pk,
            'location': location.pk,
        }

        if stock_item.customer:
            deltas['customer'] = stock_item.customer.pk

        # Update the StockItem
        stock_item.status = StockStatus.QUARANTINED.value
        stock_item.location = location
        stock_item.customer = None
        stock_item.sales_order = None
        stock_item.save(add_note=False)
        stock_item.clearAllocations()

        # Add a tracking entry to the StockItem
        stock_item.add_tracking_entry(
            StockHistoryCode.RETURNED_AGAINST_RETURN_ORDER,
            user,
            notes=note,
            deltas=deltas,
            location=location,
            returnorder=self,
        )

        # Update the LineItem
        line.received_date = datetime.now().date()
        line.save()

        trigger_event('returnorder.received', id=self.pk)

        # Notify responsible users
        notify_responsible(
            self,
            ReturnOrder,
            exclude=user,
            content=InvenTreeNotificationBodies.ReturnOrderItemsReceived,
        )


class ReturnOrderLineItem(OrderLineItem):
    """Model for a single LineItem in a ReturnOrder."""

    class Meta:
        """Metaclass options for this model."""

        unique_together = [('order', 'item')]

    @staticmethod
    def get_api_url():
        """Return the API URL associated with this model."""
        return reverse('api-return-order-line-list')

    def clean(self):
        """Perform extra validation steps for the ReturnOrderLineItem model."""
        super().clean()

        if self.item and not self.item.serialized:
            raise ValidationError({
                'item': _('Only serialized items can be assigned to a Return Order')
            })

    order = models.ForeignKey(
        ReturnOrder,
        on_delete=models.CASCADE,
        related_name='lines',
        verbose_name=_('Order'),
        help_text=_('Return Order'),
    )

    item = models.ForeignKey(
        stock.models.StockItem,
        on_delete=models.CASCADE,
        related_name='return_order_lines',
        verbose_name=_('Item'),
        help_text=_('Select item to return from customer'),
    )

    received_date = models.DateField(
        null=True,
        blank=True,
        verbose_name=_('Received Date'),
        help_text=_('The date this this return item was received'),
    )

    @property
    def received(self):
        """Return True if this item has been received."""
        return self.received_date is not None

    outcome = models.PositiveIntegerField(
        default=ReturnOrderLineStatus.PENDING.value,
        choices=ReturnOrderLineStatus.items(),
        verbose_name=_('Outcome'),
        help_text=_('Outcome for this line item'),
    )

    price = InvenTreeModelMoneyField(
        null=True,
        blank=True,
        verbose_name=_('Price'),
        help_text=_('Cost associated with return or repair for this line item'),
    )


class ReturnOrderExtraLine(OrderExtraLine):
    """Model for a single ExtraLine in a ReturnOrder."""

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the ReturnOrderExtraLine model."""
        return reverse('api-return-order-extra-line-list')

    order = models.ForeignKey(
        ReturnOrder,
        on_delete=models.CASCADE,
        related_name='extra_lines',
        verbose_name=_('Order'),
        help_text=_('Return Order'),
    )


class ReturnOrderAttachment(InvenTreeAttachment):
    """Model for storing file attachments against a ReturnOrder object."""

    @staticmethod
    def get_api_url():
        """Return the API URL associated with the ReturnOrderAttachment class."""
        return reverse('api-return-order-attachment-list')

    def getSubdir(self):
        """Return the directory path where ReturnOrderAttachment files are located."""
        return os.path.join('return_files', str(self.order.id))

    order = models.ForeignKey(
        ReturnOrder, on_delete=models.CASCADE, related_name='attachments'
    )