import os

from celery import Celery
from celery.contrib.django.task import DjangoTask
from celery.signals import worker_process_init
from kombu.serialization import register

from paperless.signed_pickle import signed_pickle_dumps
from paperless.signed_pickle import signed_pickle_loads

# Set the default Django settings module for the 'celery' program.
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")

# ---------------------------------------------------------------------------
# Signed-pickle serializer: pickle with HMAC-SHA256 integrity verification.
#
# Protects against malicious pickle injection via an exposed Redis broker.
# Messages are signed on the producer side and verified before deserialization
# on the worker side using Django's SECRET_KEY.
# ---------------------------------------------------------------------------

register(
    "signed-pickle",
    signed_pickle_dumps,
    signed_pickle_loads,
    content_type="application/x-signed-pickle",
    content_encoding="binary",
)


class FileMoveScopedTask(DjangoTask):
    """
    Run every task inside a document file move scope, so each document a task
    changes is moved once when the task ends, after its writes have committed.
    The scope also flushes when the task raises, for writes that committed
    before the failure.

    Subclasses DjangoTask because a custom task_cls replaces the Django fixup's
    default, and delay_on_commit lives there.
    """

    def __call__(self, *args, **kwargs):
        # Function-local: this module is imported by paperless/__init__.py
        # before Django apps are loaded.
        from documents.file_moves import defer_file_moves

        with defer_file_moves():
            return super().__call__(*args, **kwargs)


app = Celery("paperless", task_cls=FileMoveScopedTask)

# Using a string here means the worker doesn't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
#   should have a `CELERY_` prefix.
app.config_from_object("django.conf:settings", namespace="CELERY")

# Load task modules from all registered Django apps.
app.autodiscover_tasks()


@worker_process_init.connect
def on_worker_process_init(**kwargs) -> None:  # pragma: no cover
    """
    Register built-in parsers eagerly in each Celery worker process.

    This registers only the built-in parsers (no entrypoint discovery) so
    that workers can begin consuming documents immediately.  Entrypoint
    discovery for third-party parsers is deferred to the first call of
    get_parser_registry() inside a task, keeping worker_process_init
    well within its 4-second timeout budget.
    """
    from paperless.parsers.registry import init_builtin_parsers

    init_builtin_parsers()