import React, { createContext, useContext, useReducer, useEffect } from 'react';
import { storage } from '../lib/storage';

const AppContext = createContext();

const initialState = {
  currentUser: null, // will hold user object if logged in
  users: [],         // array of registered users
  weekNumber: 1,     // current learning week
  isLoading: true
};

function appReducer(state, action) {
  switch (action.type) {
    case 'INIT_APP':
      return {
        ...state,
        users: action.payload.users,
        weekNumber: action.payload.weekNumber,
        isLoading: false
      };
    case 'LOGIN':
      return {
        ...state,
        currentUser: action.payload
      };
    case 'LOGOUT':
      return {
        ...state,
        currentUser: null
      };
    case 'REGISTER_USER':
      return {
        ...state,
        users: [...state.users, action.payload]
      };
    case 'ADVANCE_WEEK':
      return {
        ...state,
        weekNumber: state.weekNumber + 1
      };
    default:
      return state;
  }
}

export function AppProvider({ children }) {
  const [state, dispatch] = useReducer(appReducer, initialState);

  // Initialize app state from storage
  useEffect(() => {
    const loadState = () => {
      let users = storage.get('users:registry');
      
      // Seed first admin if no users exist
      if (!users || users.length === 0) {
        const initialAdmin = {
          id: 'u_1',
          name: 'Admin',
          role: 'admin',
          pin: '0000',
          registeredAt: new Date().toISOString()
        };
        users = [initialAdmin];
        storage.set('users:registry', users);
        
        // Also seed initial empty leaderboard
        storage.set('leaderboard:current', []);
      }
      
      const storedWeek = storage.get('admin:current_week') || 1;

      // Automatically login if we saved session (optional, simpler to require login per session)
      const sessionUserId = sessionStorage.getItem('respellion_session');
      if (sessionUserId) {
        const user = users.find(u => u.id === sessionUserId);
        if (user) {
          dispatch({ type: 'LOGIN', payload: user });
        }
      }

      dispatch({ 
        type: 'INIT_APP', 
        payload: { users, weekNumber: storedWeek } 
      });
    };

    loadState();
  }, []);

  // Expose dispatch actions as convenient methods
  const login = (userId, pin) => {
    const user = state.users.find(u => u.id === userId && u.pin === pin);
    if (user) {
      sessionStorage.setItem('respellion_session', user.id);
      dispatch({ type: 'LOGIN', payload: user });
      return true;
    }
    return false;
  };

  const logout = () => {
    sessionStorage.removeItem('respellion_session');
    dispatch({ type: 'LOGOUT' });
  };

  return (
    <AppContext.Provider value={{ state, dispatch, login, logout }}>
      {children}
    </AppContext.Provider>
  );
}

export function useApp() {
  return useContext(AppContext);
}