"""Admin upload caption parsing:  <course_id> <kind> [title...]   e.g.  12 exam Midterm 2017"""
from typing import Optional

KIND_ALIASES = {
    "slide": "slide", "slides": "slide", "ppt": "slide",
    "exam": "exam", "exams": "exam", "test": "exam",
    "note": "note", "notes": "note", "module": "note",
    "book": "book", "books": "book",
}


def parse_caption(caption: Optional[str]) -> Optional[tuple[int, str, Optional[str]]]:
    if not caption:
        return None
    parts = caption.strip().split(maxsplit=2)
    if len(parts) < 2 or not parts[0].isdigit():
        return None
    kind = KIND_ALIASES.get(parts[1].lower().lstrip("#"))
    if not kind:
        return None
    title = parts[2].strip() if len(parts) == 3 and parts[2].strip() else None
    return int(parts[0]), kind, title


def clean_title(file_name: Optional[str], caption: Optional[str], fallback: str) -> str:
    """Readable title for bulk uploads: file name without extension, else first caption line."""
    import os

    name = os.path.splitext(file_name)[0] if file_name else ""
    name = name.replace("_", " ").strip()
    if not name and caption:
        name = caption.strip().split("\n")[0].strip()
    return (name or fallback)[:250]