import base64
import binascii
from datetime import datetime

from fastapi import HTTPException


def encode(*parts: object) -> str:
    raw = "|".join(str(p) for p in parts).encode()
    return base64.urlsafe_b64encode(raw).decode().rstrip("=")


def decode(cursor: str, count: int) -> list[str]:
    pad = "=" * (-len(cursor) % 4)
    try:
        raw = base64.urlsafe_b64decode(cursor + pad).decode()
    except (binascii.Error, ValueError) as exc:
        raise HTTPException(status_code=400, detail="invalid cursor") from exc
    parts = raw.split("|", count - 1)
    if len(parts) != count:
        raise HTTPException(status_code=400, detail="invalid cursor")
    return parts


def decode_datetime(value: str) -> datetime:
    try:
        return datetime.fromisoformat(value)
    except ValueError as exc:
        raise HTTPException(status_code=400, detail="invalid cursor") from exc