"""FastAPI dependencies — per-request wiring (SD-0001 §6.2 platform/deps).

Yields a pooled connection per request. The pool lives on app.state, built once in
create_app(). Later slices add the current-session and mailer dependencies here.
"""
from __future__ import annotations

from collections.abc import Iterator

import psycopg
from fastapi import Request


def get_conn(request: Request) -> Iterator[psycopg.Connection]:
    """A pooled connection for the duration of one request."""
    pool = request.app.state.pool
    with pool.connection() as conn:
        yield conn