"""
Bootstrap service — idempotent startup initialisation.

Ensures a default media library exists as soon as the first user is available.
Called from three places:
  1. AppConfig.ready()          – every server start (DB already populated)
  2. post_migrate signal        – after `manage.py migrate` runs
  3. auth.setup_admin endpoint  – immediately after the first user is created
"""
import logging

logger = logging.getLogger(__name__)

DEFAULT_LIBRARY_NAME = "Default Library"

# One-shot flag: after the first request triggers the bootstrap, disconnect
# the signal so we don't repeat the DB check on every subsequent request.
_startup_bootstrap_done = False


def ensure_default_library():
    """
    Create a default media library if none exists yet.

    Idempotent — safe to call multiple times; does nothing when a library
    already exists.  Returns the newly-created Library, or None if no action
    was taken (either a library already exists, or no users exist yet to be
    the owner).
    """
    from core.models import Library, AppUser

    if Library.objects.exists():
        return None  # Already bootstrapped

    # Need an owner — prefer the first superuser, fall back to any user.
    owner = (
        AppUser.objects.filter(is_superuser=True).order_by("date_joined").first()
        or AppUser.objects.order_by("date_joined").first()
    )
    if owner is None:
        # No users yet — setup_admin will call us again once the first user exists.
        logger.debug("ensure_default_library: no users yet, skipping.")
        return None

    library = Library.objects.create(
        owner_user=owner,
        name=DEFAULT_LIBRARY_NAME,
        visibility="public",
        description=(
            "Default media library. "
            "Add media sources here to start building your channels."
        ),
    )
    logger.info(
        "Bootstrap: created default library '%s' (id=%d) owned by '%s'.",
        library.name,
        library.id,
        owner.username,
    )
    return library


# ---------------------------------------------------------------------------
# Signal handlers — wired up in CoreConfig.ready()
# ---------------------------------------------------------------------------

def _on_post_migrate(sender, **kwargs):
    """Run bootstrap after every successful migration."""
    try:
        ensure_default_library()
    except Exception as exc:  # pragma: no cover
        logger.warning("ensure_default_library failed in post_migrate: %s", exc)


def _on_first_request(sender, **kwargs):
    """
    One-shot: run bootstrap on the very first HTTP request after server start.
    Disconnects itself immediately so subsequent requests pay zero overhead.
    """
    global _startup_bootstrap_done
    if _startup_bootstrap_done:
        return
    _startup_bootstrap_done = True

    from django.core.signals import request_started
    request_started.disconnect(_on_first_request)

    try:
        ensure_default_library()
    except Exception as exc:  # pragma: no cover
        logger.warning("ensure_default_library failed on first request: %s", exc)