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

backend/app/models/transaction.py

@@ -0,0 +1,62 @@
+import enum
+import uuid
+from datetime import date, datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import (
+    CheckConstraint,
+    Date,
+    DateTime,
+    Enum,
+    ForeignKey,
+    Index,
+    Integer,
+    String,
+    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 TransactionType(str, enum.Enum):
+    income = "income"
+    expense = "expense"
+
+
+class Transaction(Base):
+    __tablename__ = "transactions"
+    __table_args__ = (
+        CheckConstraint("amount_cents > 0", name="ck_transactions_amount_positive"),
+        Index("ix_transactions_user_date", "user_id", "transaction_date", "deleted_at"),
+        Index("ix_transactions_user_category", "user_id", "category_id", "deleted_at"),
+    )
+
+    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
+    )
+    category_id: Mapped[uuid.UUID] = mapped_column(
+        Uuid, ForeignKey("categories.id"), nullable=False
+    )
+    amount_cents: Mapped[int] = mapped_column(Integer, nullable=False)
+    type: Mapped[TransactionType] = mapped_column(
+        Enum(TransactionType, name="transactiontype", native_enum=False, length=10),
+        nullable=False,
+    )
+    description: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    transaction_date: Mapped[date] = mapped_column(Date, nullable=False)
+    deleted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=False), nullable=True)
+    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()
+    )
+
+    # Relationships — use selectinload() explicitly; lazy="raise" prevents accidental N+1
+    category: Mapped["Category"] = relationship("Category", lazy="raise")