"""Rendezvous (highest random weight) hashing."""
from __future__ import annotations

import hashlib
from typing import Any, Iterable


def _weight(key: Any, node: Any) -> int:
    h = hashlib.sha256(repr(key).encode() + b"\x00" + repr(node).encode()).digest()
    return int.from_bytes(h[:8], "big")


def _nodes(nodes: Iterable[Any]) -> list[Any]:
    seen = []
    seen_set = set()
    for n in nodes:
        if n not in seen_set:
            seen_set.add(n)
            seen.append(n)
    return seen


def rendezvous(key: Any, nodes: Iterable[Any]) -> Any | None:
    ns = _nodes(nodes)
    if not ns:
        return None
    best = None
    best_w = -1
    for n in ns:
        w = _weight(key, n)
        if w > best_w:
            best_w = w
            best = n
    return best


def rendezvous_topk(key: Any, nodes: Iterable[Any], k: int) -> list[Any]:
    ns = _nodes(nodes)
    if k <= 0 or not ns:
        return []
    indexed = sorted(range(len(ns)), key=lambda i: (-_weight(key, ns[i]), i))
    return [ns[i] for i in indexed[:k]]


def weights(key: Any, nodes: Iterable[Any]) -> list[tuple[Any, int]]:
    ns = _nodes(nodes)
    out = [(n, _weight(key, n)) for n in ns]
    out.sort(key=lambda t: (-t[1], ns.index(t[0])))
    return out