from __future__ import annotations

import re

_E164_CLEAN = re.compile(r"[^\d+]")


def normalize_imessage_handle(handle: str) -> str:
    handle = handle.strip()
    for prefix in ("imessage:", "sms:", "auto:"):
        if handle.lower().startswith(prefix):
            handle = handle[len(prefix):]
    if "@" in handle:
        return handle.lower().strip()
    return normalize_e164(handle)


def normalize_e164(handle: str) -> str:
    cleaned = _E164_CLEAN.sub("", handle)
    if not cleaned:
        return handle
    if not cleaned.startswith("+"):
        cleaned = "+" + cleaned
    return cleaned


def parse_target(target: str) -> tuple[str, str | None]:
    """Parse a target string into (format, value)."""
    target = target.strip()
    if target.startswith("chat_guid:"):
        return ("chat_guid", target[len("chat_guid:"):])
    if target.startswith("chat_identifier:"):
        return ("chat_identifier", target[len("chat_identifier:"):])
    return ("handle", normalize_imessage_handle(target))


def build_session_key(
    channel_type: str,
    account_id: str,
    chat_type: str,
    identifier: str,
) -> str:
    return f"{channel_type}:{account_id}:{chat_type}:{identifier}"


def parse_session_key(session_key: str) -> dict | None:
    parts = session_key.split(":")
    if len(parts) < 4:
        return None
    return {
        "channel_type": parts[0],
        "account_id": parts[1],
        "chat_type": parts[2],
        "identifier": ":".join(parts[3:]),
    }