from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime, timezone


@dataclass(frozen=True)
class BuiltinActivationCode:
    """内置激活码：固定自然月有效期，过期后不可再激活。"""

    code: str
    label: str  # 如 2026-01，便于识别
    expires_at: str  # ISO8601 UTC，到达时刻起作废


def _month_label(year: int, month: int) -> str:
    return f"{year}-{month:02d}"


def _month_expiry(year: int, month: int) -> str:
    """每月 1 日 0 点（UTC）为界：该月码在下一月 1 日 0 点作废。"""
    if month == 12:
        end_year, end_month = year + 1, 1
    else:
        end_year, end_month = year, month + 1
    dt = datetime(end_year, end_month, 1, 0, 0, 0, tzinfo=timezone.utc)
    return dt.isoformat()


# 12 个 GUID 激活码：2026-05 起连续 12 个月（至 2027-04），过期作废
_BUILTIN_CODE_GUIDS = (
    "2A76F0DD-F7A0-480D-B0B2-8B4B41C283AA",
    "12205DF6-02DE-4054-8C68-564543727A0F",
    "729754A0-99BF-49AA-970A-2C3BFE793E1E",
    "DCCE3DD5-C843-4C59-B033-CAA7E8DBA618",
    "0CAC138E-8635-4511-8A8D-2EDBB55F60A3",
    "4AEFA1D2-E852-41F1-880A-0EC76C544DFC",
    "C2FC0006-28A7-4018-8DF3-CC7A589CFAB6",
    "6C0F914D-CB48-4EF0-A5A4-A954FD2C48E2",
    "488D70D7-472D-44EC-9573-AA40E1FFC2F8",
    "C79718F6-6828-413B-98DA-42A0BC323D70",
    "E1A4FA71-E258-4FE6-B60E-D4CA6831D0B2",
    "C0DAA98A-678A-4F6D-A04B-38F824D104A8",
)

_START_YEAR = 2026
_START_MONTH = 5


def _builtin_month_sequence() -> list[tuple[int, int]]:
    months: list[tuple[int, int]] = []
    year, month = _START_YEAR, _START_MONTH
    for _ in range(len(_BUILTIN_CODE_GUIDS)):
        months.append((year, month))
        if month == 12:
            year, month = year + 1, 1
        else:
            month += 1
    return months


BUILTIN_ACTIVATION_CODES: tuple[BuiltinActivationCode, ...] = tuple(
    BuiltinActivationCode(
        guid,
        _month_label(year, month),
        _month_expiry(year, month),
    )
    for guid, (year, month) in zip(_BUILTIN_CODE_GUIDS, _builtin_month_sequence(), strict=True)
)

_CODE_INDEX: dict[str, BuiltinActivationCode] = {
    entry.code: entry for entry in BUILTIN_ACTIVATION_CODES
}


def normalize_activation_code(code: str) -> str:
    text = code.strip().upper().replace(" ", "")
    hex_only = text.replace("-", "")
    if len(hex_only) == 32 and all(c in "0123456789ABCDEF" for c in hex_only):
        return (
            f"{hex_only[0:8]}-{hex_only[8:12]}-{hex_only[12:16]}-"
            f"{hex_only[16:20]}-{hex_only[20:32]}"
        )
    return text


def lookup_builtin_code(code: str) -> BuiltinActivationCode | None:
    return _CODE_INDEX.get(normalize_activation_code(code))


def get_builtin_code_for_period(period_label: str | None = None) -> BuiltinActivationCode | None:
    """按月份标签（如 2026-05）查找内置激活码；默认当前 UTC 月。"""
    label = period_label or current_period_label()
    for entry in BUILTIN_ACTIVATION_CODES:
        if entry.label == label:
            return entry
    return None


def current_period_label(*, now: datetime | None = None) -> str:
    """当前自然月标签（UTC），与 BuiltinActivationCode.label 一致。"""
    moment = now or datetime.now(timezone.utc)
    if moment.tzinfo is None:
        moment = moment.replace(tzinfo=timezone.utc)
    else:
        moment = moment.astimezone(timezone.utc)
    return _month_label(moment.year, moment.month)


def is_builtin_code_current_month(
    entry: BuiltinActivationCode, *, now: datetime | None = None
) -> bool:
    return entry.label == current_period_label(now=now)


def is_builtin_code_expired(entry: BuiltinActivationCode, *, now: datetime | None = None) -> bool:
    moment = now or datetime.now(timezone.utc)
    exp = datetime.fromisoformat(entry.expires_at.replace("Z", "+00:00"))
    if exp.tzinfo is None:
        exp = exp.replace(tzinfo=timezone.utc)
    return moment >= exp