"""Resolve possibly-relative asset references to absolute URLs.

All extractors funnel their raw `src`/`href` values through
`:func:resolve` so the final result always has absolute URLs.
"""

from urllib.parse import urljoin, urlparse


def resolve(base_url: str, ref: str) -> str | None:
    """Turn a raw reference into an absolute http(s) URL.

    Returns None for references we cannot safely absolutize, including
    `javascript:`/`mailto:`/`data:`/`#` when they carry no usable path.
    """
    ref = (ref or "").strip().strip('"').strip("'")
    if not ref or ref.startswith("#"):
        return None

    scheme, netloc = urlparse(ref)[:2]
    if scheme and scheme not in ("http", "https"):
        # keep data: URIs only if explicitly requested by the caller
        if scheme == "data":
            return ref
        return None

    absolute = urljoin(base_url, ref)
    parsed = urlparse(absolute)
    if parsed.scheme not in ("http", "https") or not parsed.netloc:
        return None
    return absolute