"""Instance administration (SPEC §6.1).

The backend seam for the admin panel. Today it carries only the registration
gate — the first account on a fresh install becomes the administrator and closes
signup behind itself, and this is how that gets reopened. Further instance-wide
options land here as the panel grows.
"""

from __future__ import annotations

import datetime as dt
from typing import Annotated

from fastapi import APIRouter, Depends
from sqlalchemy.ext.asyncio import AsyncSession

from app.db import get_session
from app.identity.deps import CurrentAdmin, require_csrf
from app.identity.schemas import AdminSettingsIn, AdminSettingsOut
from app.identity.service import app_settings
from app.models import AppSettings

router = APIRouter(prefix="/admin", tags=["admin"])

DbSession = Annotated[AsyncSession, Depends(get_session)]


def _out(row: AppSettings) -> AdminSettingsOut:
    return AdminSettingsOut(
        registration_open=row.registration_open,
        default_quota_bytes=row.default_quota_bytes,
    )


@router.get("/settings", response_model=AdminSettingsOut)
async def read_settings(admin: CurrentAdmin, db: DbSession) -> AdminSettingsOut:
    return _out(await app_settings(db))


@router.put("/settings", response_model=AdminSettingsOut, dependencies=[Depends(require_csrf)])
async def write_settings(
    body: AdminSettingsIn, admin: CurrentAdmin, db: DbSession
) -> AdminSettingsOut:
    """Merge the supplied fields into the settings row.

    Changing ``default_quota_bytes`` affects users created afterwards only —
    nothing here rewrites an existing ``users.quota_bytes``.
    """
    row = await app_settings(db, for_update=True)
    if body.registration_open is not None:
        row.registration_open = body.registration_open
    if body.default_quota_bytes is not None:
        row.default_quota_bytes = body.default_quota_bytes
    row.updated_at = dt.datetime.now(dt.UTC)
    await db.commit()
    return _out(row)