# Copyright (C) 2018-2019  The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information

import logging

import pkg_resources

from swh.lister import pattern

logger = logging.getLogger(__name__)


try:
    __version__ = pkg_resources.get_distribution("swh.lister").version
except pkg_resources.DistributionNotFound:
    __version__ = "devel"

USER_AGENT_TEMPLATE = "Software Heritage Lister (%s)"
USER_AGENT = USER_AGENT_TEMPLATE % __version__


LISTERS = {
    entry_point.name.split(".", 1)[1]: entry_point
    for entry_point in pkg_resources.iter_entry_points("swh.workers")
    if entry_point.name.split(".", 1)[0] == "lister"
}


SUPPORTED_LISTERS = list(LISTERS)


def get_lister(lister_name, db_url=None, **conf):
    """Instantiate a lister given its name.

    Args:
        lister_name (str): Lister's name
        conf (dict): Configuration dict (lister db cnx, policy, priority...)

    Returns:
        Tuple (instantiated lister, drop_tables function, init schema function,
        insert minimum data function)

    """
    if lister_name not in LISTERS:
        raise ValueError(
            "Invalid lister %s: only supported listers are %s"
            % (lister_name, SUPPORTED_LISTERS)
        )
    if db_url:
        conf["lister"] = {"cls": "local", "args": {"db": db_url}}

    registry_entry = LISTERS[lister_name].load()()
    lister_cls = registry_entry["lister"]
    if issubclass(lister_cls, pattern.Lister):
        return lister_cls.from_config(**conf)
    else:
        # Old-style lister
        return lister_cls(override_config=conf)