"""Shared host-side inspection of FDS root filesystems (standard library only)."""
import hashlib
import pathlib
import plistlib


def package_db(root):
    with (root / "var/db/xbps/pkgdb-0.38.plist").open("rb") as stream:
        db = plistlib.load(stream)
    return {name: props for name, props in db.items() if not name.startswith("_")}


def rooted(root, name):
    """Resolve guest symlinks inside root, including absolute links, never on host."""
    todo = list(pathlib.PurePosixPath(name).parts)
    parts = []
    links = 0
    while todo:
        part = todo.pop(0)
        if part in ("/", "."):
            continue
        if part == "..":
            if parts:
                parts.pop()
            continue
        candidate = root.joinpath(*parts, part)
        if candidate.is_symlink():
            links += 1
            if links > 40:
                raise ValueError(f"Symlink loop: {name}")
            target = candidate.readlink()
            if target.is_absolute():
                parts = []
            todo = list(target.parts) + todo
        else:
            parts.append(part)
    return root.joinpath(*parts)


def digest(path):
    with path.open("rb") as stream:
        return hashlib.file_digest(stream, "sha256").hexdigest()