Semi-automatic ordering of products from suppliers (#30)

requirements/base.txt

@@ -13,7 +13,7 @@ six==1.9.0
 requests==2.8.1
 pytz==2015.7
 raven==5.8.1
-pynarlivs==0.9.0
 numpy==1.12.0
 scipy==0.18.1
 scikit-learn==0.18.1
+git+https://github.com/uppsaladatavetare/pynarlivs.git@1726025#egg=pynarlivs

src/shop/admin.py

@@ -11,6 +11,14 @@
 from . import models, api, exceptions
 
 
+def format_out_of_stock_forecast(forecast):
+    if forecast is None:
+        return None
+    fmt = '<span style="color: {};">{}</span>'
+    color = 'red' if forecast <= date.today() else 'default'
+    return fmt.format(color, forecast)
+
+
 class ReadonlyMixin:
     def has_add_permission(self, request, obj=None):
         return False
@@ -19,6 +27,29 @@ def has_delete_permission(self, request, obj=None):
         return False
 
 
+@admin.register(models.BaseStockLevel)
+class BaseStockLevelAdmin(admin.ModelAdmin):
+    list_display = ('product_name', 'level', 'product_qty',
+                    'out_of_stock_forecast',)
+    list_select_related = ('product',)
+
+    def product_name(self, obj):
+        return obj.product.name
+
+    def product_qty(self, obj):
+        return obj.product.qty
+
+    def out_of_stock_forecast(self, obj):
+        return format_out_of_stock_forecast(obj.product.out_of_stock_forecast)
+    out_of_stock_forecast.short_description = _('out of stock forecast')
+    out_of_stock_forecast.allow_tags = True
+    out_of_stock_forecast.admin_order_field = 'product__out_of_stock_forecast'
+
+
+class BaseStockLevelInline(admin.StackedInline):
+    model = models.BaseStockLevel
+
+
 class StocktakeItemInline(ReadonlyMixin, admin.TabularInline):
     model = models.StocktakeItem
     fields = ('product', 'category', 'qty',)
@@ -209,6 +240,35 @@ def queryset(self, request, queryset):
         return queryset
 
 
+@admin.register(models.Supplier)
+class SupplierAdmin(admin.ModelAdmin):
+    list_display = ('name',)
+
+    def order(self, request, obj_id):
+        try:
+            supplier = get_object_or_404(models.Supplier, id=obj_id)
+            supplier_products = api.order_refill(supplier.id)
+            msg = _('Added %d products to the cart at %s.')
+            count = len(supplier_products)
+            self.message_user(request, msg % (count, supplier.name))
+        except exceptions.APIException as e:
+            self.message_user(request, str(e), messages.ERROR)
+        return HttpResponseRedirect(
+            reverse('admin:shop_supplier_change', args=(obj_id,))
+        )
+
+    def get_urls(self):
+        urls = super().get_urls()
+        custom_urls = [
+            url(
+                r'^(?P<obj_id>.+)/order/$',
+                self.admin_site.admin_view(self.order),
+                name='supplier-order',
+            ),
+        ]
+        return custom_urls + urls
+
+
 @admin.register(models.SupplierProduct)
 class SupplierProductAdmin(admin.ModelAdmin):
     list_display = ('name', 'supplier', 'sku', 'product',)
@@ -422,14 +482,13 @@ def has_delete_permission(self, request, obj=None):
 
 @admin.register(models.Product)
 class ProductAdmin(admin.ModelAdmin):
-    list_display = ('name', 'code', 'qty', 'price', 'active',
-                    '_out_of_stock_forecast',)
+    list_display = ('name', 'code', 'qty', 'price', 'active',)
     list_filter = ('active', 'category',)
     search_fields = ('code', 'name',)
     readonly_fields = ('qty', 'date_created', 'date_modified',
                        '_out_of_stock_forecast',)
     ordering = ('name',)
-    inlines = (ProductTransactionCreatorInline,)
+    inlines = (BaseStockLevelInline, ProductTransactionCreatorInline,)
     fieldsets = (
         (None, {
             'fields': (
@@ -452,16 +511,6 @@ class ProductAdmin(admin.ModelAdmin):
         }),
     )
 
-    def _out_of_stock_forecast(self, obj=None):
-        if obj is None or obj.out_of_stock_forecast is None:
-            return None
-        fmt = '<span style="color: {};">{}</span>'
-        forecast = obj.out_of_stock_forecast
-        color = 'red' if forecast <= date.today() else 'default'
-        return fmt.format(color, forecast)
-    _out_of_stock_forecast.allow_tags = True
-    _out_of_stock_forecast.admin_order_field = 'out_of_stock_forecast'
-
     class Media:
         css = {
             'all': (
@@ -477,3 +526,9 @@ class Media:
             'js/thunderpush.js',
             'js/scan-card.js',
         )
+
+    def _out_of_stock_forecast(self, obj):
+        return format_out_of_stock_forecast(obj.out_of_stock_forecast)
+    _out_of_stock_forecast.short_description = _('out of stock forecast')
+    _out_of_stock_forecast.allow_tags = True
+    _out_of_stock_forecast.admin_order_field = 'out_of_stock_forecast'

src/shop/api.py

@@ -1,12 +1,15 @@
 import logging
 import numpy as np
+import math
 from itertools import accumulate
-from datetime import date
+from datetime import date, timedelta
 from django.db import transaction
 from django.db.models import Sum
 from django.db.models.functions import TruncDay
 from django.contrib.contenttypes.models import ContentType
+from django.utils import timezone
 from sklearn.svm import SVR
+from .suppliers.base import SupplierAPIException
 from . import models, enums, suppliers, exceptions
 
 log = logging.getLogger(__name__)
@@ -92,19 +95,20 @@ def list_categories():
 
 
 @transaction.atomic
-def get_supplier_product(supplier_id, sku):
+def get_supplier_product(supplier_id, sku, refresh=False):
     """Returns supplier product for given SKU.
 
     If the product does not exist in the local database, fetch it from the
     supplier.
     """
-    try:
-        return models.SupplierProduct.objects.get(
-            supplier_id=supplier_id,
-            sku=sku
-        )
-    except models.SupplierProduct.DoesNotExist:
-        pass
+    if not refresh:
+        try:
+            return models.SupplierProduct.objects.get(
+                supplier_id=supplier_id,
+                sku=sku
+            )
+        except models.SupplierProduct.DoesNotExist:
+            pass
 
     # Product has not been found in the database. Let's fetch it from
     # the supplier.
@@ -115,11 +119,14 @@ def get_supplier_product(supplier_id, sku):
         log.warning('Product not found (sku: %s, supplier: %s',
                     sku, supplier_id)
         return None
-    product_obj = models.SupplierProduct.objects.create(
+    product_obj, _ = models.SupplierProduct.objects.update_or_create(
         supplier_id=supplier_id,
         sku=sku,
-        price=product_data.price,
-        name=product_data.name
+        defaults={
+            'price': product_data.price,
+            'name': product_data.name,
+            'units': product_data.units,
+        }
     )
     return product_obj
 
@@ -248,7 +255,7 @@ def assign_free_stocktake_chunk(user_id, stocktake_id):
 
 
 @transaction.atomic
-def predict_quantity(product_id, target):
+def predict_quantity(product_id, target, current_date=None):
     """Predicts when a product will reach the target quantity."""
     product_obj = models.Product.objects.get(id=product_id)
     if product_obj.qty <= target:
@@ -275,6 +282,7 @@ def predict_quantity(product_id, target):
         # No data points to base the prediction on.
         return None
 
+    today_ordinal = (current_date or date.today()).toordinal()
     date_offset = trx_objs[0]['date'].toordinal()
 
     # At this point we want to generate data-points that we will feed into a
@@ -306,13 +314,22 @@ def predict_quantity(product_id, target):
     # | y | 100 | 95 | 85 | 83 | 80 |
     # +---+-----+----+----+----+----+
     #
+    # Also, in case of the stock quantity not changing for a couple of days
+    # we insert additional data point at the current's day offset x
+    # with the current quantity of the product.
+    #
     # The cryptic code below does just that.
     x = [trx_obj['date'].toordinal() - date_offset for trx_obj in trx_objs]
     x = [-1] + x
-    x = np.asarray(x).reshape(-1, 1)
 
     y = [trx_obj['aggregated_qty'] for trx_obj in trx_objs]
     y = [initial_qty] + y
+
+    if today_ordinal not in x:
+        x.append(today_ordinal - date_offset)
+        y.append(0)
+
+    x = np.asarray(x).reshape(-1, 1)
     y = np.asarray(list(accumulate(y)))
 
     # Fit the SVR model using above data. We rely here on the linear kernel as
@@ -331,3 +348,70 @@ def update_out_of_stock_forecast(product_id):
     product_obj = models.Product.objects.get(id=product_id)
     product_obj.out_of_stock_forecast = predict_quantity(product_id, target=0)
     product_obj.save()
+
+
+def order_from_supplier(product_id, qty, supplier_id=None):
+    """Orders the cheapest product from a supplier."""
+    products = models.SupplierProduct.objects.filter(product_id=product_id)
+
+    if supplier_id is not None:
+        products = products.filter(supplier_id=supplier_id)
+
+    # A product can be associated with several different supplier products from
+    # the same supplier. Supplier products are also most often sold in batches,
+    # which means you usually cannot purchase the exact amount you need.
+    # Following section of the code takes care of calculating the minimum cost
+    # of each product while taking `qty` into account. It will then try to
+    # purchase the cheapest one and if not possible (for example out of stock),
+    # continue onto next one.
+    def minimum_qty(sp):
+        return math.ceil(qty / sp.qty)
+
+    def cost(sp):
+        # Calculate the minimum quantity of the supplier product that needs to
+        # be purchased in order to reach `qty`.
+        return minimum_qty(sp) * sp.qty * sp.unit_price
+
+    products = sorted(products, key=cost)
+    for product in products:
+        supplier = product.supplier
+        supplier_api = suppliers.get_supplier_api(supplier.internal_name)
+        try:
+            supplier_api.order_product(product.sku, minimum_qty(product))
+            return product
+        except SupplierAPIException:
+            # Log the error and try the next product.
+            log.warning('Failed to order product SKU %d from %s.',
+                        product.sku, supplier.internal_name)
+    else:
+        msg = 'Could not order {}.'.format(product.sku)
+        raise exceptions.APIException(msg)
+
+
+def order_refill(supplier_id, current_date=None):
+    """Orders products that will run out of stock before the next delivery."""
+    def next_weekday(d, weekday):
+        days_ahead = weekday - d.weekday()
+        if days_ahead <= 0:
+            days_ahead += 7
+        return d + timedelta(days_ahead)
+
+    today = current_date or timezone.now().date()
+    supplier = models.Supplier.objects.get(id=supplier_id)
+    delivery_weekday = supplier.delivers_on
+    first_delivery = next_weekday(today, delivery_weekday)
+    second_delivery = next_weekday(first_delivery, delivery_weekday)
+    # Get base stock levels for the products that will run out of the stock
+    # before the second delivery.
+    base_levels = models.BaseStockLevel.objects.filter(
+        product__out_of_stock_forecast__lt=second_delivery
+    )
+    ordered = []
+    for base_level in base_levels:
+        sp = order_from_supplier(
+            base_level.product.id,
+            base_level.level,
+            supplier_id=supplier.id
+        )
+        ordered.append(sp)
+    return ordered

src/shop/enums.py

@@ -21,3 +21,17 @@ class TrxType(enum.Enum):
 class TrxStatus(enum.Enum):
     FINALIZED = 0
     CANCELED = 1
+
+
+class Weekdays(enum.Enum):
+    MONDAY = 0
+    TUESDAY = 1
+    WEDNESDAY = 2
+    THURSDAY = 3
+    FRIDAY = 4
+    SATURDAY = 5
+    SUNDAY = 6
+
+    @classmethod
+    def choices(cls):
+        return [(x.value, x.name) for x in cls]

src/shop/management/commands/update_supplier_products.py

@@ -0,0 +1,16 @@
+import shop.api
+from django.core.management.base import BaseCommand
+from shop.models import SupplierProduct
+
+
+class Command(BaseCommand):
+    def handle(self, *args, **options):
+        products = shop.api.list_products()
+        products = SupplierProduct.objects.all()
+        for product in products:
+            print('Updating {}...'.format(product))
+            shop.api.get_supplier_product(
+                product.supplier.id,
+                product.sku,
+                refresh=True
+            )

src/shop/migrations/0018_auto_20170228_1103.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.5 on 2017-02-28 11:03
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('shop', '0017_auto_20170222_2204'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='supplierproduct',
+            name='units',
+            field=models.SmallIntegerField(default=1),
+        ),
+    ]

src/shop/migrations/0019_auto_20170228_2012.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.5 on 2017-02-28 20:12
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('shop', '0018_auto_20170228_1103'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='supplier',
+            name='delivers_on',
+            field=models.SmallIntegerField(choices=[(0, 'MONDAY'), (1, 'TUESDAY'), (2, 'WEDNESDAY'), (3, 'THURSDAY'), (4, 'FRIDAY'), (5, 'SATURDAY'), (6, 'SUNDAY')], default=0),
+            preserve_default=False,
+        ),
+    ]