Extract Category model into src/models/category.py

src/models/category.py

@@ -0,0 +1,56 @@
+from pydantic import Field, computed_field
+from sqlalchemy import ForeignKey, String, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from src.models._common import BaseModelDb, ExportBaseModel, _hash
+
+
+class Category(ExportBaseModel):
+    name: str = Field(pattern=r"[^:\r\n]+")
+    parent: Category | None = None
+
+    @computed_field  # type: ignore[prop-decorator]
+    @property
+    def hash_id(self) -> str:
+        return _hash(self.name, self.parent)
+
+    @classmethod
+    def from_str(cls, s: str) -> Category | None:
+        if not s:
+            return None
+        components = s.split(":")
+        name = components[-1]
+        rest = ":".join(components[:-1])
+        return cls(name=name, parent=cls.from_str(rest))
+
+    def to_str(self) -> str | None:
+        if not self.parent:
+            return self.name
+        else:
+            return f"{self.parent.to_str()}:{self.name}"
+
+    def __str__(self):
+        return self.to_str()
+
+    def __repr__(self):
+        return f'Category.from_str("{self.__str__()}")'
+
+
+class CategoryDb(BaseModelDb):
+    __tablename__ = "category"
+    __table_args__ = (
+        UniqueConstraint("name", "parent_id", name="uq_category_name_parent"),
+    )
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    parent_id: Mapped[int | None] = mapped_column(
+        ForeignKey("category.id"), nullable=True
+    )
+
+    # Relationships
+    parent = relationship(
+        "CategoryDb", remote_side="CategoryDb.id", back_populates="children"
+    )
+    children = relationship("CategoryDb", back_populates="parent")
+    budgets = relationship("CategoryBudgetDb", back_populates="category")