import AsyncStorage from '@react-native-async-storage/async-storage';
import { createAsyncThunk, createSlice, PayloadAction } from '@reduxjs/toolkit';

export type PlanMode = 'daysOfWeek' | 'sessionsPerWeek';

export type PlanGoal =
  | 'postpartum_recovery' // 产后恢复
  | 'fat_loss' // 减脂塑形
  | 'posture_correction' // 体态矫正
  | 'core_strength' // 核心力量
  | 'flexibility' // 柔韧灵活
  | 'rehab' // 康复保健
  | 'stress_relief'; // 释压放松

export type TrainingPlan = {
  id: string;
  createdAt: string; // ISO
  startDate: string; // ISO (当天或下周一)
  mode: PlanMode;
  daysOfWeek: number[]; // 0(日) - 6(六)
  sessionsPerWeek: number; // 1..7
  goal: PlanGoal | '';
  startWeightKg?: number;
  preferredTimeOfDay?: 'morning' | 'noon' | 'evening' | '';
};

export type TrainingPlanState = {
  current?: TrainingPlan | null;
  draft: Omit<TrainingPlan, 'id' | 'createdAt'>;
};

const STORAGE_KEY = '@training_plan';

function nextMondayISO(): string {
  const now = new Date();
  const day = now.getDay();
  const diff = (8 - day) % 7 || 7; // 距下周一的天数
  const next = new Date(now);
  next.setDate(now.getDate() + diff);
  next.setHours(0, 0, 0, 0);
  return next.toISOString();
}

const initialState: TrainingPlanState = {
  current: null,
  draft: {
    startDate: new Date(new Date().setHours(0, 0, 0, 0)).toISOString(),
    mode: 'daysOfWeek',
    daysOfWeek: [1, 3, 5],
    sessionsPerWeek: 3,
    goal: '',
    startWeightKg: undefined,
    preferredTimeOfDay: '',
  },
};

export const loadTrainingPlan = createAsyncThunk('trainingPlan/load', async () => {
  const str = await AsyncStorage.getItem(STORAGE_KEY);
  if (!str) return null;
  try {
    return JSON.parse(str) as TrainingPlan;
  } catch {
    return null;
  }
});

export const saveTrainingPlan = createAsyncThunk(
  'trainingPlan/save',
  async (_: void, { getState }) => {
    const s = (getState() as any).trainingPlan as TrainingPlanState;
    const draft = s.draft;
    const plan: TrainingPlan = {
      id: `plan_${Date.now()}`,
      createdAt: new Date().toISOString(),
      ...draft,
    };
    await AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(plan));
    return plan;
  }
);

const trainingPlanSlice = createSlice({
  name: 'trainingPlan',
  initialState,
  reducers: {
    setMode(state, action: PayloadAction<PlanMode>) {
      state.draft.mode = action.payload;
    },
    toggleDayOfWeek(state, action: PayloadAction<number>) {
      const d = action.payload;
      const set = new Set(state.draft.daysOfWeek);
      if (set.has(d)) set.delete(d); else set.add(d);
      state.draft.daysOfWeek = Array.from(set).sort();
    },
    setSessionsPerWeek(state, action: PayloadAction<number>) {
      const n = Math.min(7, Math.max(1, action.payload));
      state.draft.sessionsPerWeek = n;
    },
    setGoal(state, action: PayloadAction<TrainingPlan['goal']>) {
      state.draft.goal = action.payload;
    },
    setStartWeight(state, action: PayloadAction<number | undefined>) {
      state.draft.startWeightKg = action.payload;
    },
    setStartDate(state, action: PayloadAction<string>) {
      state.draft.startDate = action.payload;
    },
    setPreferredTime(state, action: PayloadAction<TrainingPlan['preferredTimeOfDay']>) {
      state.draft.preferredTimeOfDay = action.payload;
    },
    setStartDateNextMonday(state) {
      state.draft.startDate = nextMondayISO();
    },
    resetDraft(state) {
      state.draft = initialState.draft;
    },
  },
  extraReducers: (builder) => {
    builder
      .addCase(loadTrainingPlan.fulfilled, (state, action) => {
        state.current = action.payload;
        // 若存在历史计划，初始化 draft 基于该计划（便于编辑）
        if (action.payload) {
          const { id, createdAt, ...rest } = action.payload;
          state.draft = { ...rest };
        }
      })
      .addCase(saveTrainingPlan.fulfilled, (state, action) => {
        state.current = action.payload;
      });
  },
});

export const {
  setMode,
  toggleDayOfWeek,
  setSessionsPerWeek,
  setGoal,
  setStartWeight,
  setStartDate,
  setPreferredTime,
  setStartDateNextMonday,
  resetDraft,
} = trainingPlanSlice.actions;

export default trainingPlanSlice.reducer;