Compute and display consumable count and price in admin

manuels/admin.py

@@ -28,10 +28,18 @@ class TeacherAdmin(ExportMixin, admin.ModelAdmin):
 
 @admin.register(Level)
 class LevelAdmin(admin.ModelAdmin):
-    list_display = ['name', 'order']
+    list_display = ['name', 'order', 'consumable_count', 'consumable_price']
     list_editable = ['order']
     list_display_links = ['name']
 
+    def consumable_count(self, obj: Level):
+        return obj.consumable_count
+    consumable_count.short_description = 'Nombre de consommable(s)'
+
+    def consumable_price(self, obj: Level):
+        return f'{obj.consumable_price:.2f}€'
+    consumable_price.short_description = 'Coût des consommables'
+
 
 class BookResource(resources.ModelResource):
     class Meta:

manuels/models.py

@@ -8,6 +8,7 @@ from django.contrib.postgres.fields import CIEmailField
 from django.core.exceptions import ValidationError
 from django.core.mail import EmailMultiAlternatives
 from django.db import models
+from django.db.models import Sum
 from django.template.loader import render_to_string
 from django.urls import reverse
 
@@ -115,6 +116,17 @@ class Level(BaseModel):
     def __str__(self):
         return self.name
 
+    @property
+    def consumable_count(self):
+        return self.book_set.filter(consumable=True).count()
+
+    @property
+    def consumable_price(self):
+        price = self.book_set.filter(consumable=True).aggregate(Sum('price')).get('price__sum', 0)
+        if price is None:
+            return 0
+        return price
+
 
 class Editor(BaseModel):
     class Meta: