import re

SIGNAL_PREFIX = re.compile(r"^signal:", re.IGNORECASE)
GROUP_PREFIX = re.compile(r"^group:", re.IGNORECASE)
UUID_PREFIX = re.compile(r"^uuid:", re.IGNORECASE)
USERNAME_PREFIX = re.compile(r"^u:", re.IGNORECASE)
RECIPIENT_PATTERN = re.compile(r"^\+?\d{7,15}$")


def normalize_signal_target(raw: str) -> str | None:
    if not raw:
        return None
    raw = raw.strip()

    lowered = raw.lower()
    if lowered.startswith("signal:group:"):
        return "group:" + raw[len("signal:group:") :]

    if lowered.startswith("signal:"):
        inner = raw[len("signal:") :]
        if inner.lower().startswith("group:"):
            return inner
        return _normalize_recipient(inner)

    if lowered.startswith("group:"):
        return raw

    if lowered.startswith("u:") and not lowered.startswith("uuid:"):
        return "username:" + raw[len("u:") :]

    if lowered.startswith("username:"):
        return raw

    if lowered.startswith("uuid:"):
        return _normalize_uuid(raw[len("uuid:") :])

    if RECIPIENT_PATTERN.match(raw):
        return _normalize_recipient(raw)

    return raw


def parse_signal_target(raw: str) -> tuple[str, str] | None:
    """返回 (kind, value) 或 None; kind ∈ {recipient, groupId, username}"""
    normalized = normalize_signal_target(raw)
    if not normalized:
        return None

    lowered = normalized.lower()
    if lowered.startswith("group:"):
        return ("groupId", normalized[len("group:") :])
    if lowered.startswith("username:"):
        return ("username", normalized[len("username:") :])
    return ("recipient", normalized)


def _normalize_recipient(value: str) -> str:
    value = value.strip()
    if not value.startswith("+"):
        return f"+{value}"
    return value


def _normalize_uuid(value: str) -> str:
    return value.strip().replace("-", "").lower()