feat: add billing core models

apps/users/models.py

@@ -1,5 +1,13 @@
+from __future__ import annotations
+
+import hashlib
+import hmac
+import secrets
+
+from django.conf import settings
 from django.contrib.auth.models import AbstractUser
 from django.db import models
+from django.db.models import Q
 
 
 class User(AbstractUser):
@@ -26,3 +34,94 @@ class User(AbstractUser):
 
     class Meta:
         db_table = "user"
+
+
+class UserWallet(models.Model):
+    user = models.OneToOneField(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.PROTECT,
+        related_name="wallet",
+    )
+    points_balance = models.BigIntegerField(default=0)
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        db_table = "user_wallet"
+        ordering = ("user_id",)
+        constraints = [
+            models.CheckConstraint(
+                condition=Q(points_balance__gte=0),
+                name="user_wallet_points_balance_non_negative",
+            ),
+        ]
+
+    def __str__(self) -> str:
+        return f"{self.user} wallet: {self.points_balance}"
+
+
+class ApiKey(models.Model):
+    KEY_PREFIX_LENGTH = 16
+
+    class Status(models.TextChoices):
+        ACTIVE = "active", "Active"
+        REVOKED = "revoked", "Revoked"
+
+    user = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.PROTECT,
+        related_name="api_keys",
+    )
+    name = models.CharField(max_length=80, blank=True)
+    key_hash = models.CharField(max_length=64, unique=True, editable=False)
+    key_prefix = models.CharField(max_length=32, editable=False)
+    status = models.CharField(
+        max_length=20,
+        choices=Status.choices,
+        default=Status.ACTIVE,
+    )
+    last_used_at = models.DateTimeField(null=True, blank=True)
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        db_table = "api_key"
+        ordering = ("-created_at", "-id")
+        indexes = [
+            models.Index(fields=("user", "status")),
+            models.Index(fields=("key_prefix",)),
+        ]
+
+    def __str__(self) -> str:
+        return f"{self.user} {self.key_prefix}"
+
+    @classmethod
+    def generate_plaintext_key(cls) -> str:
+        return f"sk_cmhub_{secrets.token_urlsafe(32)}"
+
+    @classmethod
+    def hash_key(cls, raw_key: str) -> str:
+        return hashlib.sha256(raw_key.encode("utf-8")).hexdigest()
+
+    @classmethod
+    def build_prefix(cls, raw_key: str) -> str:
+        return raw_key[: cls.KEY_PREFIX_LENGTH]
+
+    @classmethod
+    def create_for_user(cls, user, *, name: str = "") -> tuple["ApiKey", str]:
+        raw_key = cls.generate_plaintext_key()
+        api_key = cls(user=user, name=name)
+        api_key.set_key(raw_key)
+        api_key.save()
+        return api_key, raw_key
+
+    def set_key(self, raw_key: str) -> None:
+        self.key_hash = self.hash_key(raw_key)
+        self.key_prefix = self.build_prefix(raw_key)
+
+    def matches_key(self, raw_key: str) -> bool:
+        return hmac.compare_digest(self.key_hash, self.hash_key(raw_key))
+
+    @property
+    def is_active_key(self) -> bool:
+        return self.status == self.Status.ACTIVE