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

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 loadActiveFastingSchedule = async (): Promise<FastingSchedule | null> => {
  try {
    const stored = await AsyncStorage.getItem(FASTING_STORAGE_KEYS.activeSchedule);
    if (!stored) return null;

    const parsed = JSON.parse(stored) as Partial<FastingSchedule>;
    if (
      !parsed ||
      typeof parsed.planId !== 'string' ||
      typeof parsed.startISO !== 'string' ||
      typeof parsed.endISO !== 'string'
    ) {
      return null;
    }

    return {
      planId: parsed.planId,
      startISO: parsed.startISO,
      endISO: parsed.endISO,
      createdAtISO: parsed.createdAtISO ?? parsed.startISO,
      updatedAtISO: parsed.updatedAtISO ?? parsed.endISO,
      origin: parsed.origin ?? 'manual',
    };
  } catch (error) {
    console.warn('读取断食计划失败', error);
    return null;
  }
};

export const persistActiveFastingSchedule = async (schedule: FastingSchedule | null) => {
  try {
    if (schedule) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.activeSchedule, JSON.stringify(schedule));
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.activeSchedule);
    }
  } catch (error) {
    console.warn('保存断食计划失败', error);
  }
};

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 = {
  preStartId?: string | null;  // 开始前30分钟
  startId?: string | null;     // 开始时
  preEndId?: string | null;    // 结束前30分钟
  endId?: string | null;       // 结束时
};

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 [preStartId, startId, preEndId, endId] = await Promise.all([
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.preStartNotificationId),
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.startNotificationId),
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.preEndNotificationId),
      AsyncStorage.getItem(FASTING_STORAGE_KEYS.endNotificationId),
    ]);

    return {
      preStartId: preStartId ?? undefined,
      startId: startId ?? undefined,
      preEndId: preEndId ?? 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 {
    // 保存开始前30分钟通知ID
    if (ids.preStartId) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.preStartNotificationId, ids.preStartId);
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.preStartNotificationId);
    }

    // 保存开始时通知ID
    if (ids.startId) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.startNotificationId, ids.startId);
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId);
    }

    // 保存结束前30分钟通知ID
    if (ids.preEndId) {
      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.preEndNotificationId, ids.preEndId);
    } else {
      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.preEndNotificationId);
    }

    // 保存结束时通知ID
    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.preStartNotificationId),
      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId),
      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.preEndNotificationId),
      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.endNotificationId),
    ]);
  } catch (error) {
    console.warn('清除断食通知ID失败', error);
  }
};

// 周期性断食相关的存储函数
export const loadActiveFastingCycle = async (): Promise<any | null> => {
  try {
    const stored = await AsyncStorage.getItem('@fasting_active_cycle');
    if (!stored) return null;
    
    const parsed = JSON.parse(stored);
    return parsed;
  } catch (error) {
    console.warn('读取周期性断食计划失败', error);
    return null;
  }
};

export const saveActiveFastingCycle = async (cycle: any | null): Promise<void> => {
  try {
    if (cycle) {
      await AsyncStorage.setItem('@fasting_active_cycle', JSON.stringify(cycle));
    } else {
      await AsyncStorage.removeItem('@fasting_active_cycle');
    }
  } catch (error) {
    console.error('保存周期性断食计划失败', error);
    throw new Error('保存周期性断食计划失败，请稍后重试');
  }
};

export const loadCurrentCycleSession = async (): Promise<any | null> => {
  try {
    const stored = await AsyncStorage.getItem('@fasting_current_cycle_session');
    if (!stored) return null;
    
    const parsed = JSON.parse(stored);
    return parsed;
  } catch (error) {
    console.warn('读取当前断食会话失败', error);
    return null;
  }
};

export const saveCurrentCycleSession = async (session: any | null): Promise<void> => {
  try {
    if (session) {
      await AsyncStorage.setItem('@fasting_current_cycle_session', JSON.stringify(session));
    } else {
      await AsyncStorage.removeItem('@fasting_current_cycle_session');
    }
  } catch (error) {
    console.error('保存当前断食会话失败', error);
    throw new Error('保存断食会话失败，请稍后重试');
  }
};

export const loadCycleHistory = async (): Promise<any[]> => {
  try {
    const stored = await AsyncStorage.getItem('@fasting_cycle_history');
    if (!stored) return [];
    
    const parsed = JSON.parse(stored);
    return Array.isArray(parsed) ? parsed : [];
  } catch (error) {
    console.warn('读取断食周期历史失败', error);
    return [];
  }
};

export const saveCycleHistory = async (history: any[]): Promise<void> => {
  try {
    await AsyncStorage.setItem('@fasting_cycle_history', JSON.stringify(history));
  } catch (error) {
    console.error('保存断食周期历史失败', error);
    throw new Error('保存断食历史失败，请稍后重试');
  }
};

// 计算下一个断食周期的开始时间
export const calculateNextCycleStart = (
  cycle: { startHour: number; startMinute: number },
  baseDate: Date = new Date()
): Date => {
  const now = dayjs(baseDate);
  const today = now.startOf('day').hour(cycle.startHour).minute(cycle.startMinute).second(0).millisecond(0);
  
  // 如果今天的开始时间已过，则从明天开始
  if (today.isBefore(now)) {
    return today.add(1, 'day').toDate();
  }
  
  return today.toDate();
};

// 获取周期性断食的统计信息
export const getCycleStats = (history: any[]) => {
  const completedCycles = history.filter(session => session.completed);
  const totalCycles = history.length;
  const currentStreak = calculateCurrentStreak(history);
  const longestStreak = calculateLongestStreak(history);
  
  return {
    totalCycles,
    completedCycles: completedCycles.length,
    completionRate: totalCycles > 0 ? (completedCycles.length / totalCycles) * 100 : 0,
    currentStreak,
    longestStreak,
  };
};

// 计算当前连续完成天数
const calculateCurrentStreak = (history: any[]): number => {
  if (history.length === 0) return 0;
  
  let streak = 0;
  const today = dayjs().startOf('day');
  
  for (let i = 0; i < history.length; i++) {
    const session = history[i];
    if (!session.completed) break;
    
    const sessionDate = dayjs(session.cycleDate);
    const expectedDate = today.subtract(i, 'day');
    
    if (sessionDate.isSame(expectedDate, 'day')) {
      streak++;
    } else {
      break;
    }
  }
  
  return streak;
};

// 计算最长连续完成天数
const calculateLongestStreak = (history: any[]): number => {
  if (history.length === 0) return 0;
  
  let longestStreak = 0;
  let currentStreak = 0;
  
  for (const session of history) {
    if (session.completed) {
      currentStreak++;
      longestStreak = Math.max(longestStreak, currentStreak);
    } else {
      currentStreak = 0;
    }
  }
  
  return longestStreak;
};