added buy_products method to Account

cash/models.py

@@ -1,6 +1,7 @@
 from django.db import models
 from django.contrib.auth.models import User
 
+
 class Account(models.Model):
 	user = models.OneToOneField(User)
 	card_number = models.CharField(max_length=32, unique=True)
@@ -11,6 +12,42 @@ class Account(models.Model):
 	def __unicode__(self):
 		return self.user.username
 
+	def buy_products(self, products):
+		# TODO place it somewhere else
+		MAX_DEBIT = -3500
+		BUY_SUBJECT = 'Artikel gekauft'
+
+		if min(products.values()) <= 0:
+			raise ValueError('Non-positive amount in products dict.')
+
+		total_value = sum(map(lambda p: p.price * products[p], products.keys()))
+		if self.credit - total_value >= MAX_DEBIT:
+			self.credit -= total_value
+			self.save()
+
+			descr = ''
+			for product in products.keys():
+				amount = products[product]
+
+				logentry = SalesLogEntry(account=self, product=product,
+										 count=amount, unit_price=product.price)
+				logentry.save()
+
+				descr += '%dx %s\n' % (amount, product.name)
+
+			transaction = Transaction(account=self, subject=BUY_SUBJECT,
+									  amount=total_value,
+									  description=descr)
+			transaction.save()
+
+			return True
+		else:
+			return False
+
+	def buy_product(self, product, amount=1):
+		return self.buy_products({product: amount})
+
+
 class ProductCategory(models.Model):
 	name = models.CharField(max_length=32, unique=True)
 	comment = models.CharField(max_length=128, blank=True)
@@ -50,3 +87,4 @@ class SalesLogEntry(models.Model):
 	timestamp = models.DateTimeField(auto_now_add=True)
 
 	
+