"""Filename rules for uploads: spaces become dashes, duplicates get -2, -3, ..."""
import os
import re
from collections.abc import Callable


def clean_name(filename: str) -> str:
    """Keep only the base name and turn every run of whitespace into one dash."""
    base = filename.replace("\\", "/").rsplit("/", 1)[-1].strip()
    base = re.sub(r"\s+", "-", base)
    return base or "upload"


def split_name(name: str) -> tuple[str, str]:
    """('clip', '.mp4'); a name with no extension gives ('README', '')."""
    return os.path.splitext(name)


def next_free_name(stem: str, ext: str, exists: Callable[[str], bool], limit: int = 1000) -> str:
    """First of stem+ext, stem-2+ext, stem-3+ext, ... that does not exist yet."""
    for n in range(1, limit + 1):
        name = f"{stem}{ext}" if n == 1 else f"{stem}-{n}{ext}"
        if not exists(name):
            return name
    raise RuntimeError(f"no free name for {stem}{ext} after {limit} tries")