"""Kernel DB seam for the temper_rejects page-module.

Mirrors ``modules/fastpress/press/_db.py``: DB access goes ONLY through the
kernel, re-exported here so the coupling to ``app.db`` lives in one place. This
page READS tempered carts + reject reasons and performs one narrow WRITE (insert a
reject row), so it exposes both the SELECT-only proxy and a transactional
connection::

    from .._db import run_select_query, transaction

The base scaffold's API (``api/routes.py``) returns SAMPLE data and does NOT import
this yet — wiring the real reads + the ``POST /reject`` write is the next step
(see the TODO in ``api/routes.py``).

NOTE: no connection happens at import — SQLAlchemy's engine is lazy.
"""
from __future__ import annotations

from contextlib import contextmanager

from app.db.mariadb import engine, run_select_query, cached_select  # noqa: F401  (kernel DB layer)

__all__ = ["run_select_query", "cached_select", "transaction", "engine"]


@contextmanager
def transaction():
    """Yield a transactional connection: commit on clean exit, rollback on error.

    Thin wrapper over the kernel engine's ``begin()`` — same shape as fastpress's
    reject write (``modules/fastpress/press/rejects.py``), which this page's real
    ``POST /reject`` will follow (one INSERT into ``production.rejects``)."""
    with engine.begin() as conn:
        yield conn