"""农历/节气/节日/时辰引擎。

依赖 ``lunar_python``（寿星天文历 Python 版）做历法换算与节气判定；节日按
公历固定日期 + 农历日期两张表命中。全部纯函数，无副作用。
"""

from __future__ import annotations

from datetime import date

from lunar_python import Solar
from pydantic import BaseModel


class LunarDate(BaseModel):
    """农历日期。"""

    year_ganzhi: str
    month: int
    day: int
    is_leap_month: bool


class SolarTermInfo(BaseModel):
    """节气信息。"""

    current_name: str | None
    next_name: str
    days_to_next: int


class Festival(BaseModel):
    """节日命中。"""

    name: str
    calendar: str  # solar / lunar
    locale: str = "zh-CN"


class Shichen(BaseModel):
    """十二时辰。"""

    name: str
    start_hour: int
    end_hour: int


# 十二时辰：name -> (start, end)，跨零点的时辰 end < start（子时 23->1）
_SHICHEN_TABLE: list[tuple[str, int, int]] = [
    ("子", 23, 1),
    ("丑", 1, 3),
    ("寅", 3, 5),
    ("卯", 5, 7),
    ("辰", 7, 9),
    ("巳", 9, 11),
    ("午", 11, 13),
    ("未", 13, 15),
    ("申", 15, 17),
    ("酉", 17, 19),
    ("戌", 19, 21),
    ("亥", 21, 23),
]

# 公历固定节日（month, day） -> name
_SOLAR_FESTIVALS: dict[tuple[int, int], str] = {
    (1, 1): "元旦",
    (2, 14): "情人节",
    (5, 1): "劳动节",
    (10, 1): "国庆节",
    (12, 25): "圣诞节",
}

# lunar_python 的 getJieQiTable() 对跨年带入的节气用大写拼音常量作 key
# （实证于 lunar_python 1.4.8：DA_HAN/DONG_ZHI/JING_ZHE/LI_CHUN/XIAO_HAN/YU_SHUI 等），
# 本表内节气用中文 key。此处把 24 节气拼音常量统一翻成中文，已是中文的保持不变。
_JIEQI_PINYIN_TO_CN: dict[str, str] = {
    "LI_CHUN": "立春",
    "YU_SHUI": "雨水",
    "JING_ZHE": "惊蛰",
    "CHUN_FEN": "春分",
    "QING_MING": "清明",
    "GU_YU": "谷雨",
    "LI_XIA": "立夏",
    "XIAO_MAN": "小满",
    "MANG_ZHONG": "芒种",
    "XIA_ZHI": "夏至",
    "XIAO_SHU": "小暑",
    "DA_SHU": "大暑",
    "LI_QIU": "立秋",
    "CHU_SHU": "处暑",
    "BAI_LU": "白露",
    "QIU_FEN": "秋分",
    "HAN_LU": "寒露",
    "SHUANG_JIANG": "霜降",
    "LI_DONG": "立冬",
    "XIAO_XUE": "小雪",
    "DA_XUE": "大雪",
    "DONG_ZHI": "冬至",
    "XIAO_HAN": "小寒",
    "DA_HAN": "大寒",
}


# 农历节日（lunar_month, lunar_day, is_leap） -> name
_LUNAR_FESTIVALS: dict[tuple[int, int, bool], str] = {
    (1, 1, False): "春节",
    (1, 15, False): "元宵节",
    (5, 5, False): "端午节",
    (7, 7, False): "七夕",
    (8, 15, False): "中秋节",
    (9, 9, False): "重阳节",
    (12, 8, False): "腊八节",
}


def solar_to_lunar(solar_date: date) -> LunarDate:
    """公历日期转农历日期。

    ``lunar_python`` 的 ``getMonth()`` 对闰月返回负数（如 -6 表示闰六月），
    非闰月返回正数；据此推导 ``is_leap_month`` 与展示用的月份数值。
    """
    solar = Solar.fromYmd(solar_date.year, solar_date.month, solar_date.day)
    lunar = solar.getLunar()
    raw_month = lunar.getMonth()
    return LunarDate(
        year_ganzhi=lunar.getYearInGanZhi(),
        month=abs(raw_month),
        day=int(lunar.getDay()),
        is_leap_month=raw_month < 0,
    )


def get_shichen(hour: int) -> Shichen:
    """按 24 小时制小时返回十二时辰。子时跨零点（23 与 0 均属子）。"""
    h = hour % 24
    for name, start, end in _SHICHEN_TABLE:
        if start < end:
            if start <= h < end:
                return Shichen(name=name, start_hour=start, end_hour=end)
        else:  # 跨零点（子时 23->1）
            if h >= start or h < end:
                return Shichen(name=name, start_hour=start, end_hour=end)
    # 理论不可达（24 小时全覆盖）
    raise ValueError(f"无法识别时辰：hour={hour}")


def get_day_period(hour: int) -> str:
    """返回现代时段枚举值（契约字典 day_period）。"""
    h = hour % 24
    if 0 <= h < 5:
        return "凌晨"
    if 5 <= h < 8:
        return "清晨"
    if 8 <= h < 11:
        return "上午"
    if 11 <= h < 13:
        return "中午"
    if 13 <= h < 17:
        return "下午"
    if 17 <= h < 19:
        return "傍晚"
    if 19 <= h < 23:
        return "夜晚"
    return "深夜"  # 23-24


def get_solar_term(solar_date: date) -> SolarTermInfo:
    """返回当日命中的节气与下一节气信息。

    ``lunar_python`` 的 ``getJieQiTable()`` 返回 dict（节气名 -> ``Solar``）；
    值本身即 ``Solar`` 时刻对象，无需再调 ``getSolar()``。据此判定当日是否
    命中某节气，并算出距下一节气的天数。
    """
    solar = Solar.fromYmd(solar_date.year, solar_date.month, solar_date.day)
    lunar = solar.getLunar()
    jieqi = lunar.getJieQiTable()  # dict: 节气名 -> Solar 时刻

    current_name: str | None = None
    for raw_name, moment in jieqi.items():
        if (
            moment.getYear() == solar_date.year
            and moment.getMonth() == solar_date.month
            and moment.getDay() == solar_date.day
        ):
            current_name = _JIEQI_PINYIN_TO_CN.get(raw_name, raw_name)
            break

    # 下一节气：从所有节气时刻中找当前日期之后最近的
    upcoming: list[tuple[int, str, date]] = []
    for raw_name, moment in jieqi.items():
        d = date(moment.getYear(), moment.getMonth(), moment.getDay())
        if d > solar_date:
            upcoming.append(((d - solar_date).days, _JIEQI_PINYIN_TO_CN.get(raw_name, raw_name), d))
    upcoming.sort()
    days_to_next, next_name, _ = upcoming[0]
    return SolarTermInfo(current_name=current_name, next_name=next_name, days_to_next=days_to_next)


def get_festivals(solar_date: date, locale: str = "zh-CN") -> list[Festival]:
    """命中今日的公历与农历节日。"""
    result: list[Festival] = []
    # 公历
    if (solar_date.month, solar_date.day) in _SOLAR_FESTIVALS:
        result.append(
            Festival(
                name=_SOLAR_FESTIVALS[(solar_date.month, solar_date.day)],
                calendar="solar",
                locale=locale,
            )
        )
    # 农历
    lunar = solar_to_lunar(solar_date)
    key = (lunar.month, lunar.day, lunar.is_leap_month)
    if key in _LUNAR_FESTIVALS:
        result.append(Festival(name=_LUNAR_FESTIVALS[key], calendar="lunar", locale=locale))
    return result