phase 6

backend/app/api/boards.py

@@ -7,7 +7,7 @@ from fastapi import APIRouter, Depends, HTTPException, Query, status
 from sqlalchemy.orm import Session
 
 from app.boards.repository import BoardRepository
-from app.boards.schemas import BoardCreate, BoardDetail, BoardSummary, BoardUpdate
+from app.boards.schemas import BoardCreate, BoardDetail, BoardSummary, BoardUpdate, ViewportStateUpdate
 from app.core.deps import get_current_user, get_db
 from app.database.models.user import User
 
@@ -152,6 +152,48 @@ def update_board(
     return BoardDetail.model_validate(board)
 
 
+@router.patch("/{board_id}/viewport", status_code=status.HTTP_204_NO_CONTENT)
+def update_viewport(
+    board_id: UUID,
+    viewport_data: ViewportStateUpdate,
+    current_user: Annotated[User, Depends(get_current_user)],
+    db: Annotated[Session, Depends(get_db)],
+):
+    """
+    Update board viewport state only (optimized for frequent updates).
+
+    This endpoint is designed for high-frequency viewport state updates
+    (debounced pan/zoom/rotate changes) with minimal overhead.
+
+    Args:
+        board_id: Board UUID
+        viewport_data: Viewport state data
+        current_user: Current authenticated user
+        db: Database session
+
+    Raises:
+        HTTPException: 404 if board not found or not owned by user
+    """
+    repo = BoardRepository(db)
+
+    # Convert viewport data to dict
+    viewport_dict = viewport_data.model_dump()
+
+    board = repo.update_board(
+        board_id=board_id,
+        user_id=current_user.id,
+        title=None,
+        description=None,
+        viewport_state=viewport_dict,
+    )
+
+    if not board:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Board {board_id} not found",
+        )
+
+
 @router.delete("/{board_id}", status_code=status.HTTP_204_NO_CONTENT)
 def delete_board(
     board_id: UUID,