from __future__ import annotations

import uuid
from typing import Mapping


def parse_contact_user_ids(contact: str | None) -> set[uuid.UUID]:
    ids: set[uuid.UUID] = set()
    for token in _contact_tokens(contact):
        try:
            ids.add(uuid.UUID(token))
        except ValueError:
            continue
    return ids


def build_contact_display(contact: str | None, users: Mapping[uuid.UUID, object]) -> str | None:
    labels: list[str] = []
    for token in _contact_tokens(contact):
        try:
            user_id = uuid.UUID(token)
        except ValueError:
            labels.append(token)
            continue

        user = users.get(user_id)
        label = _user_display_name(user)
        if label:
            labels.append(label)

    return "、".join(labels) if labels else None


def _contact_tokens(contact: str | None) -> list[str]:
    return [part.strip() for part in str(contact or "").split(",") if part.strip()]


def _user_display_name(user: object | None) -> str | None:
    if user is None:
        return None
    for attr in ("full_name", "username", "email"):
        value = getattr(user, attr, None)
        if value:
            return str(value)
    return None