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

Yields a pooled connection per request, the process-wide mailer, and the verified session
payload (from the signed cookie). The pool and mailer live on app.state, built once in
create_app(). The storefronts dependency lands in SLICE-3.
"""
from __future__ import annotations

from collections.abc import Iterator
from typing import Any

import psycopg
from fastapi import Request

from app.platform import config, session
from app.platform.mailer import Mailer

SESSION_COOKIE = "ecomm_session"


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


def get_mailer(request: Request) -> Mailer:
    """The process-wide mailer adapter (built from config at startup, INV-8)."""
    return request.app.state.mailer


def get_session(request: Request) -> dict[str, Any] | None:
    """The verified session payload from the cookie, or None if absent/invalid."""
    token = request.cookies.get(SESSION_COOKIE)
    if not token:
        return None
    return session.verify(token, config.session_secret())