from functools import wraps
import warnings


def rank_zero_only(fn):

    @wraps(fn)
    def wrapped_fn(*args, **kwargs):
        if rank_zero_only.rank == 0:
            return fn(*args, **kwargs)

    return wrapped_fn


try:
    # add the attribute to the function but don't overwrite in case Trainer has already set it
    getattr(rank_zero_only, 'rank')
except AttributeError:
    rank_zero_only.rank = 0


def _warn(*args, **kwargs):
    warnings.warn(*args, **kwargs)


rank_zero_warn = rank_zero_only(_warn)