Step 6：受试者（Subject）+ 访视（Visit）+ 随访进度

backend/app/crud/visit.py

@@ -0,0 +1,60 @@
+import uuid
+from typing import Sequence
+
+from sqlalchemy import select, update as sa_update
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.subject import Subject
+from app.models.visit import Visit
+from app.schemas.visit import VisitCreate, VisitUpdate
+
+
+async def create_visit(
+    db: AsyncSession,
+    *,
+    study_id: uuid.UUID,
+    visit_in: VisitCreate | None,
+    subject: Subject,
+    visit_code: str,
+    visit_name: str,
+    planned_date,
+) -> Visit:
+    visit = Visit(
+        study_id=study_id,
+        subject_id=subject.id,
+        visit_code=visit_code,
+        visit_name=visit_name,
+        planned_date=planned_date,
+        actual_date=None,
+        status="PLANNED",
+        window_start=visit_in.window_start if visit_in else None,
+        window_end=visit_in.window_end if visit_in else None,
+        notes=None,
+    )
+    db.add(visit)
+    await db.commit()
+    await db.refresh(visit)
+    return visit
+
+
+async def list_visits(db: AsyncSession, subject_id: uuid.UUID) -> Sequence[Visit]:
+    result = await db.execute(select(Visit).where(Visit.subject_id == subject_id).order_by(Visit.planned_date))
+    return result.scalars().all()
+
+
+async def get_visit(db: AsyncSession, visit_id: uuid.UUID) -> Visit | None:
+    result = await db.execute(select(Visit).where(Visit.id == visit_id))
+    return result.scalar_one_or_none()
+
+
+async def update_visit(db: AsyncSession, visit: Visit, visit_in: VisitUpdate) -> Visit:
+    update_data = visit_in.model_dump(exclude_unset=True)
+    if update_data:
+        await db.execute(
+            sa_update(Visit)
+            .where(Visit.id == visit.id)
+            .values(**update_data)
+        )
+        await db.commit()
+    await db.refresh(visit)
+    return visit