from django.db import models, router from django.db.models import F, Value, signals from django.db.models.functions import Coalesce from django.utils.functional import cached_property from django.utils.timezone import now from django.utils.translation import gettext_lazy as _ from django.utils.translation import pgettext_lazy from oscar.apps.partner.exceptions import InvalidStockAdjustment from oscar.core.compat import AUTH_USER_MODEL from oscar.core.utils import get_default_currency from oscar.models.fields import AutoSlugField class AbstractPartner(models.Model): """ A fulfillment partner. An individual or company who can fulfil products. E.g. for physical goods, somebody with a warehouse and means of delivery. Creating one or more instances of the Partner model is a required step in setting up an Oscar deployment. Many Oscar deployments will only have one fulfillment partner. """ code = AutoSlugField(_("Code"), max_length=128, unique=True, populate_from='name') name = models.CharField( pgettext_lazy("Partner's name", "Name"), max_length=128, blank=True) #: A partner can have users assigned to it. This is used #: for access modelling in the permission-based dashboard users = models.ManyToManyField( AUTH_USER_MODEL, related_name="partners", blank=True, verbose_name=_("Users")) @property def display_name(self): return self.name or self.code @property def primary_address(self): """ Returns a partners primary address. Usually that will be the headquarters or similar. This is a rudimentary implementation that raises an error if there's more than one address. If you actually want to support multiple addresses, you will likely need to extend PartnerAddress to have some field or flag to base your decision on. """ addresses = self.addresses.all() if len(addresses) == 0: # intentionally using len() to save queries return None elif len(addresses) == 1: return addresses[0] else: raise NotImplementedError( "Oscar's default implementation of primary_address only " "supports one PartnerAddress. You need to override the " "primary_address to look up the right address") def get_address_for_stockrecord(self, stockrecord): """ Stock might be coming from different warehouses. Overriding this function allows selecting the correct PartnerAddress for the record. That can be useful when determining tax. """ return self.primary_address class Meta: abstract = True app_label = 'partner' ordering = ('name', 'code') permissions = (('dashboard_access', 'Can access dashboard'), ) verbose_name = _('Fulfillment partner') verbose_name_plural = _('Fulfillment partners') def __str__(self): return self.display_name class AbstractStockRecord(models.Model): """ A stock record. This records information about a product from a fulfilment partner, such as their SKU, the number they have in stock and price information. Stockrecords are used by 'strategies' to determine availability and pricing information for the customer. """ product = models.ForeignKey( 'catalogue.Product', on_delete=models.CASCADE, related_name="stockrecords", verbose_name=_("Product")) partner = models.ForeignKey( 'partner.Partner', on_delete=models.CASCADE, verbose_name=_("Partner"), related_name='stockrecords') #: The fulfilment partner will often have their own SKU for a product, #: which we store here. This will sometimes be the same the product's UPC #: but not always. It should be unique per partner. #: See also http://en.wikipedia.org/wiki/Stock-keeping_unit partner_sku = models.CharField(_("Partner SKU"), max_length=128) # Price info: price_currency = models.CharField( _("Currency"), max_length=12, default=get_default_currency) # This is the base price for calculations - tax should be applied by the # appropriate method. We don't store tax here as its calculation is highly # domain-specific. It is NULLable because some items don't have a fixed # price but require a runtime calculation (possible from an external # service). Current field name `price_excl_tax` is deprecated and will be # renamed into `price` in Oscar 2.0. price_excl_tax = models.DecimalField( _("Price (excl. tax)"), decimal_places=2, max_digits=12, blank=True, null=True) # Deprecated - will be removed in Oscar 2.0 price_retail = models.DecimalField( _("Price (retail)"), decimal_places=2, max_digits=12, blank=True, null=True) # Deprecated - will be removed in Oscar 2.0 cost_price = models.DecimalField( _("Cost Price"), decimal_places=2, max_digits=12, blank=True, null=True) #: Number of items in stock num_in_stock = models.PositiveIntegerField( _("Number in stock"), blank=True, null=True) #: The amount of stock allocated to orders but not fed back to the master #: stock system. A typical stock update process will set the num_in_stock #: variable to a new value and reset num_allocated to zero num_allocated = models.IntegerField( _("Number allocated"), blank=True, null=True) #: Threshold for low-stock alerts. When stock goes beneath this threshold, #: an alert is triggered so warehouse managers can order more. low_stock_threshold = models.PositiveIntegerField( _("Low Stock Threshold"), blank=True, null=True) # Date information date_created = models.DateTimeField(_("Date created"), auto_now_add=True) date_updated = models.DateTimeField(_("Date updated"), auto_now=True, db_index=True) def __str__(self): msg = "Partner: %s, product: %s" % ( self.partner.display_name, self.product,) if self.partner_sku: msg = "%s (%s)" % (msg, self.partner_sku) return msg class Meta: abstract = True app_label = 'partner' unique_together = ('partner', 'partner_sku') verbose_name = _("Stock record") verbose_name_plural = _("Stock records") @property def net_stock_level(self): """ The effective number in stock (eg available to buy). This is correct property to show the customer, not the num_in_stock field as that doesn't account for allocations. This can be negative in some unusual circumstances """ if self.num_in_stock is None: return 0 if self.num_allocated is None: return self.num_in_stock return self.num_in_stock - self.num_allocated @cached_property def can_track_allocations(self): """Return True if the Product is set for stock tracking.""" return self.product.get_product_class().track_stock # 2-stage stock management model def allocate(self, quantity): """ Record a stock allocation. This normally happens when a product is bought at checkout. When the product is actually shipped, then we 'consume' the allocation. """ # Doesn't make sense to allocate if stock tracking is off. if not self.can_track_allocations: return # Send the pre-save signal signals.pre_save.send( sender=self.__class__, instance=self, created=False, raw=False, using=router.db_for_write(self.__class__, instance=self)) # Atomic update (self.__class__.objects .filter(pk=self.pk) .update(num_allocated=( Coalesce(F('num_allocated'), Value(0)) + quantity))) # Make sure the current object is up-to-date if self.num_allocated is None: self.num_allocated = 0 self.num_allocated += quantity # Send the post-save signal signals.post_save.send( sender=self.__class__, instance=self, created=False, raw=False, using=router.db_for_write(self.__class__, instance=self)) allocate.alters_data = True def is_allocation_consumption_possible(self, quantity): """ Test if a proposed stock consumption is permitted """ return quantity <= min(self.num_allocated, self.num_in_stock) def consume_allocation(self, quantity): """ Consume a previous allocation This is used when an item is shipped. We remove the original allocation and adjust the number in stock accordingly """ if not self.can_track_allocations: return if not self.is_allocation_consumption_possible(quantity): raise InvalidStockAdjustment( _('Invalid stock consumption request')) self.num_allocated -= quantity self.num_in_stock -= quantity self.save() consume_allocation.alters_data = True def cancel_allocation(self, quantity): if not self.can_track_allocations: return # We ignore requests that request a cancellation of more than the # amount already allocated. self.num_allocated -= min(self.num_allocated, quantity) self.save() cancel_allocation.alters_data = True @property def is_below_threshold(self): if self.low_stock_threshold is None: return False return self.net_stock_level < self.low_stock_threshold class AbstractStockAlert(models.Model): """ A stock alert. E.g. used to notify users when a product is 'back in stock'. """ stockrecord = models.ForeignKey( 'partner.StockRecord', on_delete=models.CASCADE, related_name='alerts', verbose_name=_("Stock Record")) threshold = models.PositiveIntegerField(_("Threshold")) OPEN, CLOSED = "Open", "Closed" status_choices = ( (OPEN, _("Open")), (CLOSED, _("Closed")), ) status = models.CharField(_("Status"), max_length=128, default=OPEN, choices=status_choices) date_created = models.DateTimeField(_("Date Created"), auto_now_add=True) date_closed = models.DateTimeField(_("Date Closed"), blank=True, null=True) def close(self): self.status = self.CLOSED self.date_closed = now() self.save() close.alters_data = True def __str__(self): return _('') \ % {'stock': self.stockrecord, 'status': self.status} class Meta: abstract = True app_label = 'partner' ordering = ('-date_created',) verbose_name = _('Stock alert') verbose_name_plural = _('Stock alerts')