feat: backend core — models, auth, CRUD, tests

backend/app/models/budget.py

@@ -0,0 +1,47 @@
+import uuid
+from datetime import datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import (
+    CheckConstraint,
+    DateTime,
+    ForeignKey,
+    Integer,
+    String,
+    UniqueConstraint,
+    Uuid,
+    func,
+)
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+if TYPE_CHECKING:
+    from app.models.category import Category
+
+
+class Budget(Base):
+    __tablename__ = "budgets"
+    __table_args__ = (
+        UniqueConstraint("user_id", "category_id", "month", name="uq_budgets_user_category_month"),
+        CheckConstraint("limit_cents > 0", name="ck_budgets_limit_positive"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(Uuid, primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        Uuid, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    category_id: Mapped[uuid.UUID] = mapped_column(
+        Uuid, ForeignKey("categories.id"), nullable=False
+    )
+    # Format YYYY-MM
+    month: Mapped[str] = mapped_column(String(7), nullable=False)
+    limit_cents: Mapped[int] = mapped_column(Integer, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=False), nullable=False, server_default=func.now()
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=False), nullable=False, server_default=func.now()
+    )
+
+    category: Mapped["Category"] = relationship("Category", lazy="raise")