"""Target management for Synology Chat channel.

ID normalization, validation, and format hints for user/group targeting.
"""

from __future__ import annotations


_CHANNEL_PREFIX = "synologychat:"


def normalize_target(target: str) -> str:
    """Strip channel prefix from a target identifier if present.

    Handles both 'synologychat:' and 'synology-chat:' prefixes.
    """
    if target.startswith("synologychat:"):
        return target[len("synologychat:") :]
    if target.startswith("synology-chat:"):
        return target[len("synology-chat:") :]
    return target


def looks_like_id(value: str) -> bool:
    """Check if a value looks like a Synology Chat user/channel ID.

    Synology Chat IDs are generally pure numeric strings.
    """
    return bool(value and value.isdigit())


def target_format_hint() -> str:
    """Return the expected format for target identifiers."""
    return (
        "Synology Chat 目标格式：\n"
        "- 用户 ID：纯数字字符串，例如 '12345'\n"
        "- 频道 ID：纯数字字符串，例如 '67890'\n"
        "- 可通过 user_list / channel_list API 获取可用 ID\n"
        "- 支持前缀格式 'synologychat:<id>'（自动剥离）\n"
    )


def build_target_label(user_id: str, channel_id: str | None = None) -> str:
    """Build a human-readable label for a target."""
    if channel_id:
        return f"synologychat:{channel_id}:{user_id}"
    return f"synologychat:{user_id}"