Upload app/models/tag_link.py

app/models/tag_link.py

@@ -0,0 +1,50 @@
+"""TagLink model: polymorphic many-to-many between tags and accounts/contacts/deals."""
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import TYPE_CHECKING
+
+from sqlalchemy import ForeignKey, Integer, String, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.models.base import Base, OrgScopedMixin, SoftDeleteMixin, TimestampMixin
+
+if TYPE_CHECKING:
+    from app.models.tag import Tag
+
+
+class TagLinkParentType(str, Enum):
+    """Polymorphic parent type for tag links (no DB FK, validated in service layer)."""
+
+    account = "account"
+    contact = "contact"
+    deal = "deal"
+
+
+class TagLink(Base, TimestampMixin, SoftDeleteMixin, OrgScopedMixin):
+    __tablename__ = "tag_links"
+    __table_args__ = (
+        UniqueConstraint(
+            "tag_id", "parent_type", "parent_id", name="uq_tag_link"
+        ),
+    )
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    tag_id: Mapped[int] = mapped_column(
+        ForeignKey("tags.id"), nullable=False, index=True
+    )
+    parent_type: Mapped[TagLinkParentType] = mapped_column(
+        String(32), nullable=False, index=True
+    )
+    # parent_id is intentionally NOT a DB FK because of polymorphic parent.
+    # Service layer (tag_service.link_tag) validates existence.
+    parent_id: Mapped[int] = mapped_column(Integer, nullable=False, index=True)
+
+    tag: Mapped["Tag"] = relationship("Tag", back_populates="links", lazy="joined")
+
+    def __repr__(self) -> str:
+        return f"<TagLink id={self.id} tag={self.tag_id} parent={self.parent_type}:{self.parent_id}>"
+
+
+__all__ = ["TagLink", "TagLinkParentType"]