import dayjs from 'dayjs';
import duration from 'dayjs/plugin/duration';
import isSameOrAfter from 'dayjs/plugin/isSameOrAfter';
import isSameOrBefore from 'dayjs/plugin/isSameOrBefore';
import AsyncStorage from '@/utils/kvStore';
import { FASTING_STORAGE_KEYS } from '@/constants/Fasting';

dayjs.extend(duration);
dayjs.extend(isSameOrAfter);
dayjs.extend(isSameOrBefore);

export type FastingPhase = 'upcoming' | 'fasting' | 'completed';

export const calculateFastingWindow = (start: Date, fastingHours: number) => {
  const startDate = dayjs(start).second(0).millisecond(0);
  const endDate = startDate.add(fastingHours, 'hour');

  return {
    start: startDate.toDate(),
    end: endDate.toDate(),
  };
};

export const getFastingPhase = (start?: Date | null, end?: Date | null, now: Date = new Date()): FastingPhase => {
  if (!start || !end) {
    return 'completed';
  }

  const nowJs = dayjs(now);
  const startJs = dayjs(start);
  const endJs = dayjs(end);

  if (nowJs.isBefore(startJs)) {
    return 'upcoming';
  }
  if (nowJs.isSameOrAfter(startJs) && nowJs.isBefore(endJs)) {
    return 'fasting';
  }
  return 'completed';
};

export const getPhaseLabel = (phase: FastingPhase) => {
  switch (phase) {
    case 'fasting':
      return '断食中';
    case 'upcoming':
      return '可饮食';
    case 'completed':
      return '可饮食';
    default:
      return '可饮食';
  }
};

export const formatDayDescriptor = (date: Date | null | undefined, now: Date = new Date()) => {
  if (!date) return '--';

  const target = dayjs(date);
  const today = dayjs(now).startOf('day');

  if (target.isSame(today, 'day')) {
    return '今天';
  }
  if (target.isSame(today.subtract(1, 'day'), 'day')) {
    return '昨天';
  }
  if (target.isSame(today.add(1, 'day'), 'day')) {
    return '明天';
  }
  return target.format('MM-DD');
};

export const formatTime = (date: Date | null | undefined) => {
  if (!date) return '--:--';
  return dayjs(date).format('HH:mm');
};

export const formatCountdown = (target: Date | null | undefined, now: Date = new Date()) => {
  if (!target) return '--:--:--';

  const diff = dayjs(target).diff(now);
  if (diff <= 0) {
    return '00:00:00';
  }

  const dur = dayjs.duration(diff);
  const hours = String(Math.floor(dur.asHours())).padStart(2, '0');
  const minutes = String(dur.minutes()).padStart(2, '0');
  const seconds = String(dur.seconds()).padStart(2, '0');

  return `${hours}:${minutes}:${seconds}`;
};

export const buildDisplayWindow = (start?: Date | null, end?: Date | null) => {
  return {
    startDayLabel: formatDayDescriptor(start ?? null),
    startTimeLabel: formatTime(start ?? null),
    endDayLabel: formatDayDescriptor(end ?? null),
    endTimeLabel: formatTime(end ?? null),
  };
};

export const loadPreferredPlanId = async (): Promise<string | null> => {
  try {
    return await AsyncStorage.getItem(FASTING_STORAGE_KEYS.preferredPlanId);
  } catch (error) {
    console.warn('加载断食首选计划ID失败', error);
    return null;
  }
};

export const savePreferredPlanId = async (planId: string) => {
  try {
    await AsyncStorage.setItem(FASTING_STORAGE_KEYS.preferredPlanId, planId);
  } catch (error) {
    console.warn('保存断食首选计划ID失败', error);
  }
};

export type FastingNotificationIds = {
  startId?: string | null;
  endId?: string | null;
};

export const getFastingNotificationsRegistered = async (): Promise<boolean> => {
  try {
    const value = await AsyncStorage.getItem(FASTING_STORAGE_KEYS.notificationsRegistered);
    return value === 'true';
  } catch (error) {
    console.warn('读取断食通知注册状态失败', error);
    return false;
  }
};

export const setFastingNotificationsRegistered = async (registered: boolean) => {
  try {
    if (registered) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.notificationsRegistered, 'true');
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.notificationsRegistered);
    }
  } catch (error) {
    console.warn('更新断食通知注册状态失败', error);
  }
};

export const loadStoredFastingNotificationIds = async (): Promise<FastingNotificationIds> => {
  try {
    const [startId, endId] = await Promise.all([
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.startNotificationId),
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.endNotificationId),
    ]);

    return {
      startId: startId ?? undefined,
      endId: endId ?? undefined,
    };
  } catch (error) {
    console.warn('读取断食通知ID失败', error);
    return {};
  }
};

export const saveFastingNotificationIds = async (ids: FastingNotificationIds) => {
  try {
    if (ids.startId) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.startNotificationId, ids.startId);
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId);
    }

    if (ids.endId) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.endNotificationId, ids.endId);
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.endNotificationId);
    }
  } catch (error) {
    console.warn('保存断食通知ID失败', error);
  }
};

export const clearFastingNotificationIds = async () => {
  try {
    await Promise.all([
      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId),
      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.endNotificationId),
    ]);
  } catch (error) {
    console.warn('清除断食通知ID失败', error);
  }
};