Hoàn thành bước 3.3. Interactive Workbook (The Core Viewer)

backend/app/routers/annotations.py

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+from datetime import datetime, timezone
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..dependencies import get_current_user
+from ..models import Annotation, PDF, User
+from ..schemas import AnnotationIn, AnnotationOut
+
+router = APIRouter(prefix="/annotations", tags=["annotations"])
+
+
+def _verify_pdf_ownership(db: Session, pdf_id: int, user_id: int) -> PDF:
+    pdf = db.get(PDF, pdf_id)
+    if not pdf or pdf.user_id != user_id:
+        raise HTTPException(status_code=404, detail="PDF not found.")
+    return pdf
+
+
+# ── GET /api/annotations/{pdf_id}/{page_number} ───────────────────────────────
+
+@router.get("/{pdf_id}/{page_number}", response_model=AnnotationOut)
+def get_annotation(
+    pdf_id: int,
+    page_number: int,
+    current_user: User = Depends(get_current_user),
+    db: Session = Depends(get_db),
+):
+    _verify_pdf_ownership(db, pdf_id, current_user.id)
+
+    ann = (
+        db.query(Annotation)
+        .filter(
+            Annotation.pdf_id == pdf_id,
+            Annotation.user_id == current_user.id,
+            Annotation.page_number == page_number,
+        )
+        .first()
+    )
+
+    # Return empty canvas if no annotation exists yet — not an error
+    if ann is None:
+        return AnnotationOut(
+            id=0,
+            pdf_id=pdf_id,
+            page_number=page_number,
+            canvas_data={},
+            updated_at=datetime.now(timezone.utc),
+        )
+
+    return ann
+
+
+# ── PUT /api/annotations/{pdf_id}/{page_number} ───────────────────────────────
+
+@router.put("/{pdf_id}/{page_number}", response_model=AnnotationOut)
+def upsert_annotation(
+    pdf_id: int,
+    page_number: int,
+    body: AnnotationIn,
+    current_user: User = Depends(get_current_user),
+    db: Session = Depends(get_db),
+):
+    _verify_pdf_ownership(db, pdf_id, current_user.id)
+
+    ann = (
+        db.query(Annotation)
+        .filter(
+            Annotation.pdf_id == pdf_id,
+            Annotation.user_id == current_user.id,
+            Annotation.page_number == page_number,
+        )
+        .first()
+    )
+
+    if ann is None:
+        ann = Annotation(
+            pdf_id=pdf_id,
+            user_id=current_user.id,
+            page_number=page_number,
+            canvas_data=body.canvas_data,
+        )
+        db.add(ann)
+    else:
+        ann.canvas_data = body.canvas_data
+        ann.updated_at = datetime.now(timezone.utc)
+
+    db.commit()
+    db.refresh(ann)
+    return ann