Modify transfer log system

inventory/admin.py

@@ -1,5 +1,5 @@
 from django.contrib import admin
-from inventory.models import Warehouse, Inventory, Item
+from inventory.models import Warehouse, Inventory, Item, Category
 
 @admin.register(Warehouse)
 class WarehouseAdmin(admin.ModelAdmin):
@@ -11,4 +11,8 @@ class InventoryAdmin(admin.ModelAdmin):
 
 @admin.register(Item)
 class ItemAdmin(admin.ModelAdmin):
-    list_display = ('name', 'description', 'category', 'weight', 'quantity', 'inventory')
+    list_display = ('name', 'description', 'category', 'weight', 'quantity', 'inventory')
+
+@admin.register(Category)
+class CatergoryAdmin(admin.ModelAdmin):
+    list_display = ('name',)

inventory/apps.py

@@ -3,7 +3,4 @@ from django.apps import AppConfig
 
 class InventoryConfig(AppConfig):
     default_auto_field = 'django.db.models.BigAutoField'
-    name = 'inventory'
+    name = 'inventory'
-
-    def ready(self):
-        import inventory.signals

inventory/migrations/0003_category_alter_inventory_current_stock_and_more.py

@@ -0,0 +1,39 @@
+# Generated by Django 4.2.7 on 2023-11-18 21:22
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('inventory', '0002_alter_inventory_options'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Category',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=255)),
+            ],
+            options={
+                'verbose_name_plural': 'Categories',
+            },
+        ),
+        migrations.AlterField(
+            model_name='inventory',
+            name='current_stock',
+            field=models.IntegerField(default=0),
+        ),
+        migrations.AlterField(
+            model_name='inventory',
+            name='min_stock',
+            field=models.IntegerField(default=0),
+        ),
+        migrations.AlterField(
+            model_name='item',
+            name='category',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.DO_NOTHING, to='inventory.category'),
+        ),
+    ]

inventory/migrations/0004_alter_item_category.py

@@ -0,0 +1,19 @@
+# Generated by Django 4.2.7 on 2023-11-18 21:23
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('inventory', '0003_category_alter_inventory_current_stock_and_more'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='item',
+            name='category',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.DO_NOTHING, to='inventory.category'),
+        ),
+    ]

inventory/migrations/0005_item_previous_inventory_alter_item_description.py

@@ -0,0 +1,24 @@
+# Generated by Django 4.2.7 on 2023-11-18 21:48
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('inventory', '0004_alter_item_category'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='item',
+            name='previous_inventory',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='previous_inventory', to='inventory.inventory'),
+        ),
+        migrations.AlterField(
+            model_name='item',
+            name='description',
+            field=models.TextField(null=True),
+        ),
+    ]

inventory/migrations/0006_remove_item_previous_inventory.py

@@ -0,0 +1,17 @@
+# Generated by Django 4.2.7 on 2023-11-18 22:23
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('inventory', '0005_item_previous_inventory_alter_item_description'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='item',
+            name='previous_inventory',
+        ),
+    ]

inventory/models.py

@@ -1,5 +1,5 @@
 from django.db import models
-
+from django.apps import apps
 
 class Warehouse(models.Model):
     """
@@ -58,11 +58,25 @@ class Inventory(models.Model):
     class Meta:
         verbose_name_plural = 'Inventories'
 
+class Category(models.Model):
+    """
+    Catergory of the item
+
+    :param name: Name of the catergory
+    """
+    name = models.CharField(max_length=255)
+
+    def __str__(self):
+        return f"{self.name}"
+
+    class Meta:
+        verbose_name_plural = 'Categories'
 
 class Item(models.Model):
     """
     Item such as food, drink, furnoture etc.
 
+    :param previous_inventory: Previous inventory that the item belongs to, If null, it means the item is new or never move
     :param inventory: Inventory that the item belongs to
     :param name: Name of the item
     :param description: Description of the item
@@ -71,11 +85,38 @@ class Item(models.Model):
     :param quantity: Quantity of the item
     """
     inventory = models.ForeignKey(Inventory, on_delete=models.CASCADE)
+    category = models.ForeignKey(Category, on_delete=models.DO_NOTHING, null=True)
     name = models.CharField(max_length=255)
-    description = models.TextField()
+    description = models.TextField(null=True)
-    category = models.CharField(max_length=255)
     weight = models.DecimalField(max_digits=10, decimal_places=3)
     quantity = models.IntegerField()
 
+    __previous_inventory = None
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        try:
+            self.__previous_inventory = self.inventory
+        except:
+            self.__previous_inventory = None
+
+    def save(self, force_insert=False, force_update=False, *args, **kwargs):
+        if self.__previous_inventory == None:
+            super().save(force_insert, force_update, *args, **kwargs)
+            Inventory.objects.filter(id=self.inventory.id).update(current_stock=self.inventory.current_stock + self.quantity)
+            return
+
+        if self.inventory != self.__previous_inventory:
+            Inventory.objects.filter(id=self.__previous_inventory.id).update(current_stock=self.__previous_inventory.current_stock - self.quantity)
+            Inventory.objects.filter(id=self.inventory.id).update(current_stock=self.inventory.current_stock + self.quantity)
+            apps.get_model('transaction', 'Transfer').objects.create(
+                from_warehouse=self.__previous_inventory.warehouse,
+                to_warehouse=self.inventory.warehouse,
+                item=self,
+                quantity=self.quantity,
+            )
+        super().save(force_insert, force_update, *args, **kwargs)
+        self.__previous_inventory = self.inventory
+
     def __str__(self):
         return f"{self.name} - {self.quantity}"

inventory/signals.py

@@ -1,41 +0,0 @@
-from django.db.models.signals import post_save, pre_save
-from django.dispatch import receiver
-from inventory.models import Item
-from transaction.models import Transfer
-
-
-@receiver(pre_save, sender=Item)
-def handle_item_move(sender, instance, **kwargs):
-    """
-    Signal to handle moving an Item to a new Inventory.
-    """
-    if instance.pk:
-        old_item = Item.objects.get(pk=instance.pk)
-        if old_item.inventory != instance.inventory:
-            old_item.inventory.current_stock -= old_item.quantity
-            old_item.inventory.save()
-
-@receiver(post_save, sender=Item)
-def update_inventory_current_stock(sender, instance, **kwargs):
-    """
-    Signal to update current_stock of related Inventory when an Item is created or assigned to a new Inventory.
-    """
-    if kwargs.get('created', False) or instance.pk:
-        instance.inventory.current_stock += instance.quantity
-        instance.inventory.save()
-
-
-@receiver(post_save, sender=Item)
-def create_transfer_instance(sender, instance, **kwargs):
-    """
-    Signal to create a Transfer instance when an Item is transferred between warehouses.
-    """
-    # If the item is being created or updated
-    if kwargs.get('created', False) or instance.pk:
-        if instance.pk and instance.inventory.warehouse != instance.inventory.old_warehouse:
-            Transfer.objects.create(
-                from_warehouse=instance.inventory.old_warehouse,
-                to_warehouse=instance.inventory.warehouse,
-                item=instance,
-                quantity=instance.quantity,
-            )

transaction/admin.py

@@ -20,4 +20,4 @@ class OrderAdmin(admin.ModelAdmin):
 
 @admin.register(Transfer)
 class TransferAdmin(admin.ModelAdmin):
-    list_display = ('from_warehouse', 'to_warehouse', 'item', 'from_date_timestamp', 'to_date_timestamp', 'quantity')
+    list_display = ('from_warehouse', 'to_warehouse', 'item', 'update_time', 'quantity')

transaction/migrations/0003_remove_transfer_from_date_timestamp_and_more.py

@@ -0,0 +1,26 @@
+# Generated by Django 4.2.7 on 2023-11-18 21:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('transaction', '0002_alter_supply_options_alter_order_order_date_and_more'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='transfer',
+            name='from_date_timestamp',
+        ),
+        migrations.RemoveField(
+            model_name='transfer',
+            name='to_date_timestamp',
+        ),
+        migrations.AddField(
+            model_name='transfer',
+            name='update_time',
+            field=models.DateTimeField(auto_now=True),
+        ),
+    ]

transaction/models.py

@@ -87,8 +87,7 @@ class Transfer(models.Model):
     to_warehouse = models.ForeignKey(Warehouse, related_name='transfer_to', on_delete=models.CASCADE)
     item = models.ForeignKey(Item, on_delete=models.CASCADE)
     quantity = models.IntegerField()
-    from_date_timestamp = models.DateTimeField()
+    update_time = models.DateTimeField(auto_now=True)
-    to_date_timestamp = models.DateTimeField()
 
     def __str__(self):
         return f"{self.from_warehouse.name} - {self.to_warehouse.name} - {self.item.name} - {self.quantity}"