Add stock_amount to product and reflect it in product detail template. (#213)

src/shop/migrations/0054_auto_20180415_1159.py

@@ -0,0 +1,34 @@
+# Generated by Django 2.0.4 on 2018-04-15 16:59
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('shop', '0053_auto_20180318_0906'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='product',
+            name='stock_amount',
+            field=models.IntegerField(blank=True, help_text='Initial amount available in stock if there is a limited supply, e.g. fridge space', null=True),
+        ),
+        migrations.AlterField(
+            model_name='epaypayment',
+            name='order',
+            field=models.OneToOneField(on_delete=django.db.models.deletion.PROTECT, to='shop.Order'),
+        ),
+        migrations.AlterField(
+            model_name='invoice',
+            name='customorder',
+            field=models.OneToOneField(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, to='shop.CustomOrder'),
+        ),
+        migrations.AlterField(
+            model_name='invoice',
+            name='order',
+            field=models.OneToOneField(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, to='shop.Order'),
+        ),
+    ]

src/shop/models.py

@@ -318,6 +318,15 @@ class Product(CreatedUpdatedModel, UUIDModel):
         blank=True
     )
 
+    stock_amount = models.IntegerField(
+        help_text=(
+            'Initial amount available in stock if there is a limited '
+            'supply, e.g. fridge space'
+        ),
+        null=True,
+        blank=True
+    )
+
     objects = ProductQuerySet.as_manager()
 
     def __str__(self):
@@ -333,8 +342,17 @@ class Product(CreatedUpdatedModel, UUIDModel):
             )
 
     def is_available(self):
+        """ Is the product available or not?
+
+        Checks for the following:
+
+        - Whether now is in the self.available_in
+        - If a stock is defined, that there are items left
+        """
         now = timezone.now()
-        return now in self.available_in
+        time_available = now in self.available_in
+        stock_available = (self.stock_amount - self.left_in_stock()) > 0
+        return time_available and stock_available
 
     def is_old(self):
         now = timezone.now()
@@ -346,6 +364,16 @@ class Product(CreatedUpdatedModel, UUIDModel):
         now = timezone.now()
         return self.available_in.lower > now
 
+    def left_in_stock(self):
+        sold = OrderProductRelation.objects.filter(
+            product=self,
+            order__paid=True,
+        ).aggregate(Sum('quantity'))['quantity__sum']
+
+        total_left = self.stock_amount - (sold or 0)
+
+        return total_left
+
 
 class OrderProductRelation(CreatedUpdatedModel):
     order = models.ForeignKey('shop.Order', on_delete=models.PROTECT)

src/shop/templates/product_detail.html

@@ -25,6 +25,15 @@
 
     <hr />
 
+    {% if product.stock_amount %}
+    <h3>
+      <small>Availability</small><br />
+      <bold>{{ product.left_in_stock }}</bold> available<br />
+    </h3>
+
+    <hr />
+    {% endif %}
+
     <h3>Add to order</h3>
 
     {% if user.is_authenticated %}