Context, Redux Toolkit i Zustand w zarządzaniu stanem w React

1. Wprowadzenie

Wybór sposobu zarządzania stanem w React to jedna z decyzji architektonicznych, której błędne przyjęcie powoduje poważne problemy w dłuższej perspektywie. Lokalna funkcja useState wystarcza do izolowanych interfejsów użytkownika, jednak aplikacje szybko wymagają wspólnego zarządzania autoryzacją, tematem, stanem odtwarzacza oraz cache’ami serwerowymi. Narzędzia do tego celu rozwijały się wraz z samym Reactem.

Początkowy React opierał się na lokalnym stanie i przenoszeniu wartości przez właściwości. Flux (2014), a następnie Redux (2015) uczyniły jedyny, przewidywalny magazyn z reduktorami standardem dla dużych zespołów. MobX (2015) oferował obserwowalne elementy jako lżejszą alternatywę. React 16.3 (2018) wprowadził nowoczesną API Context, dzięki której wartości globalne mogły być zarządzane bez użycia zewnętrznych bibliotek. React 16.8 (2019) dodał useReducer umożliwiający przejścia typu Redux wewnątrz React. Zustand (2019) zmniejszył ilość kodu szablonowego dzięki magazynowi opartemu na hookach. Jotai (2020) oraz Recoil (2020) wprowadziły modele stanu atomowego i pochodnego. TanStack Query (wcześniej React Query, 2020) oddzielił kwestie związane ze stanem serwera – cacheowanie, paginację, mutacje – od stanu interfejsu klienta.

Przykład działającej mapy wygląda tak:

• Lokalne useState — flagi i wartości interfejsu, które nigdy nie opuszczają jednego komponentu.

Context — Aplikacje średniej wielkości z globalnymi elementami o niskiej częstotliwości użycia (temat, autoryzacja, lokalizacja).

useReducer + Context — Złożone przejścia, które nadal powinny pozostać w React.

Redux Toolkit — Duże zespoły, zaawansowane middleware, narzędzia deweloperskie oraz procesy typu enterprise.

Zustand — Aplikacje średniej do dużej wielkości, które wymagają prostej API oraz wysokiej wydajności.

TanStack Query — Stan serwera, niezależnie od wybranej bazy danych klienckiej.

Szkic portalu wideo wykorzystuje te same obszary — temat, autoryzacja, kursy, odtwarzacz — w ramach Context, Redux Toolkit i Zustand, a następnie łączy je z TanStack Query.

2. Koncepcje z szczegółowym wyjaśnieniem

Context API — Wbudowany stan globalny

Context przekazuje wartości wzdłuż drzewa bez używania threading props. Jest wbudowany w React, nie wymaga żadnego pakietu i nadaje się do aktualizacji o średniej częstotliwości, takich jak temat, autoryzacja, język oraz flagi funkcjonalne.

W tym wzorcu biorą udział trzy elementy: createContext() tworzy kontekst (z opcjonalną wartością domyślną), Context.Provider publikuje wartość value, a useContext(Context) odczytuje ją w potomnych elementach. Gdy wartość dostarczana przez provider się zmienia, wszystkie elementy korzystające z niej są ponownie renderowane.

Koszt takiego rozsyłania informacji ma znaczenie – elementy korzystające z kontekstu są ponownie renderowane nawet wtedy, gdy potrzebują tylko jednej wartości. Środkami łagodzącymi są m.in. dzielenie kontekstów według częstotliwości aktualizacji, zapamiętywanie wartości provider za pomocą useMemo lub użycie specjalnych narzędzi pomocniczych, takich jak use-context-selector.

Portal wideo może przechowywać informacje o temacie, autoryzacji oraz stanie odtwarzacza w oddzielnych kontekstach:

// contexts/ThemeContext.tsx
'use client';

import { createContext, useContext, useState, useEffect, useCallback, ReactNode } from 'react';

type Theme = 'light' | 'dark' | 'system';
type ActualTheme = 'light' | 'dark';

interface ThemeContextType {
  theme: Theme;
  actualTheme: ActualTheme;
  setTheme: (theme: Theme) => void;
  toggleTheme: () => void;
}

const ThemeContext = createContext<ThemeContextType | undefined>(undefined);

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setTheme] = useState<Theme>(() => {
    if (typeof window !== 'undefined') {
      const saved = localStorage.getItem('theme') as Theme;
      if (saved && ['light', 'dark', 'system'].includes(saved)) return saved;
    }
    return 'system';
  });

  const [actualTheme, setActualTheme] = useState<ActualTheme>('light');

  // Detect system preference
  useEffect(() => {
    const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');

    const updateActualTheme = () => {
      if (theme === 'system') {
        setActualTheme(mediaQuery.matches ? 'dark' : 'light');
      } else {
        setActualTheme(theme as ActualTheme);
      }
    };

    updateActualTheme();
    mediaQuery.addEventListener('change', updateActualTheme);
    return () => mediaQuery.removeEventListener('change', updateActualTheme);
  }, [theme]);

  // Persist to localStorage and apply to document
  useEffect(() => {
    localStorage.setItem('theme', theme);

    if (actualTheme === 'dark') {
      document.documentElement.classList.add('dark');
    } else {
      document.documentElement.classList.remove('dark');
    }
  }, [theme, actualTheme]);

  const toggleTheme = useCallback(() => {
    setTheme(prev => {
      if (prev === 'light') return 'dark';
      if (prev === 'dark') return 'system';
      return 'light';
    });
  }, []);

  const value = useMemo(() => ({
    theme,
    actualTheme,
    setTheme,
    toggleTheme,
  }), [theme, actualTheme, toggleTheme]);

  return (
    <ThemeContext.Provider value={value}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  const context = useContext(ThemeContext);
  if (context === undefined) {
    throw new Error('useTheme must be used within a ThemeProvider');
  }
  return context;
}

// contexts/AuthContext.tsx
'use client';

import { createContext, useContext, useState, useEffect, useCallback, ReactNode } from 'react';
import { useRouter } from 'next/navigation';

interface User {
  id: string;
  name: string;
  email: string;
  avatar?: string;
  role: 'user' | 'instructor' | 'admin';
}

interface AuthContextType {
  user: User | null;
  isLoading: boolean;
  isAuthenticated: boolean;
  login: (email: string, password: string) => Promise<void>;
  loginWithGoogle: () => void;
  logout: () => void;
  register: (name: string, email: string, password: string) => Promise<void>;
  hasPermission: (permission: string) => boolean;
}

const AuthContext = createContext<AuthContextType | undefined>(undefined);

export function AuthProvider({ children }: { children: ReactNode }) {
  const [user, setUser] = useState<User | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const router = useRouter();

  // Check for existing session on mount
  useEffect(() => {
    const checkSession = async () => {
      try {
        const response = await fetch('/api/auth/session');
        if (response.ok) {
          const userData = await response.json();
          setUser(userData);
        }
      } catch (error) {
        console.error('Session check failed:', error);
      } finally {
        setIsLoading(false);
      }
    };

    checkSession();
  }, []);

  const login = useCallback(async (email: string, password: string) => {
    setIsLoading(true);
    try {
      const response = await fetch('/api/auth/login', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ email, password }),
      });

      if (!response.ok) throw new Error('Login failed');

      const userData = await response.json();
      setUser(userData);
      router.push('/dashboard');
    } finally {
      setIsLoading(false);
    }
  }, [router]);

  const loginWithGoogle = useCallback(() => {
    window.location.href = '/api/auth/google';
  }, []);

  const logout = useCallback(async () => {
    await fetch('/api/auth/logout', { method: 'POST' });
    setUser(null);
    router.push('/');
  }, [router]);

  const register = useCallback(async (name: string, email: string, password: string) => {
    setIsLoading(true);
    try {
      const response = await fetch('/api/auth/register', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ name, email, password }),
      });

      if (!response.ok) throw new Error('Registration failed');

      const userData = await response.json();
      setUser(userData);
      router.push('/dashboard');
    } finally {
      setIsLoading(false);
    }
  }, [router]);

  const hasPermission = useCallback((permission: string): boolean => {
    if (!user) return false;
    if (user.role === 'admin') return true;
    // Check specific permissions based on role
    const permissions: Record<string, string[]> = {
      user: ['view_courses', 'enroll_courses', 'leave_reviews'],
      instructor: ['view_courses', 'create_courses', 'edit_courses', 'view_analytics'],
      admin: ['*'],
    };
    return permissions[user.role]?.includes(permission) || permissions[user.role]?.includes('*') || false;
  }, [user]);

  const value = useMemo(() => ({
    user,
    isLoading,
    isAuthenticated: !!user,
    login,
    loginWithGoogle,
    logout,
    register,
    hasPermission,
  }), [user, isLoading, login, loginWithGoogle, logout, register, hasPermission]);

  return (
    <AuthContext.Provider value={value}>
      {children}
    </AuthContext.Provider>
  );
}

export function useAuth() {
  const context = useContext(AuthContext);
  if (context === undefined) {
    throw new Error('useAuth must be used within an AuthProvider');
  }
  return context;
}

// contexts/VideoPlayerContext.tsx - Complex state with Context + useReducer
'use client';

import { createContext, useContext, useReducer, useCallback, ReactNode } from 'react';

// State types
interface VideoState {
  isPlaying: boolean;
  currentTime: number;
  duration: number;
  volume: number;
  isMuted: boolean;
  playbackRate: number;
  quality: 'auto' | '1080p' | '720p' | '480p';
  subtitlesEnabled: boolean;
  subtitleTrack: string | null;
  bookmarks: Bookmark[];
  showNotes: boolean;
  notes: string;
}

interface Bookmark {
  id: string;
  timestamp: number;
  note: string;
}

// Action types
type VideoAction =
  | { type: 'PLAY' }
  | { type: 'PAUSE' }
  | { type: 'TOGGLE_PLAY' }
  | { type: 'SET_TIME'; payload: number }
  | { type: 'SET_DURATION'; payload: number }
  | { type: 'SET_VOLUME'; payload: number }
  | { type: 'TOGGLE_MUTE' }
  | { type: 'SET_PLAYBACK_RATE'; payload: number }
  | { type: 'SET_QUALITY'; payload: VideoState['quality'] }
  | { type: 'TOGGLE_SUBTITLES' }
  | { type: 'ADD_BOOKMARK'; payload: { timestamp: number; note: string } }
  | { type: 'REMOVE_BOOKMARK'; payload: string }
  | { type: 'TOGGLE_NOTES' }
  | { type: 'SET_NOTES'; payload: string }
  | { type: 'RESET' };

// Reducer
const initialState: VideoState = {
  isPlaying: false,
  currentTime: 0,
  duration: 0,
  volume: 80,
  isMuted: false,
  playbackRate: 1,
  quality: 'auto',
  subtitlesEnabled: false,
  subtitleTrack: null,
  bookmarks: [],
  showNotes: false,
  notes: '',
};

function videoReducer(state: VideoState, action: VideoAction): VideoState {
  switch (action.type) {
    case 'PLAY':
      return { ...state, isPlaying: true };
    case 'PAUSE':
      return { ...state, isPlaying: false };
    case 'TOGGLE_PLAY':
      return { ...state, isPlaying: !state.isPlaying };
    case 'SET_TIME':
      return { ...state, currentTime: Math.max(0, Math.min(action.payload, state.duration)) };
    case 'SET_DURATION':
      return { ...state, duration: action.payload };
    case 'SET_VOLUME': {
      const newVolume = Math.max(0, Math.min(100, action.payload));
      return { ...state, volume: newVolume, isMuted: newVolume === 0 };
    }
    case 'TOGGLE_MUTE':
      return { ...state, isMuted: !state.isMuted };
    case 'SET_PLAYBACK_RATE':
      return { ...state, playbackRate: action.payload };
    case 'SET_QUALITY':
      return { ...state, quality: action.payload };
    case 'TOGGLE_SUBTITLES':
      return { ...state, subtitlesEnabled: !state.subtitlesEnabled };
    case 'ADD_BOOKMARK': {
      const newBookmark: Bookmark = {
        id: Date.now().toString(),
        timestamp: action.payload.timestamp,
        note: action.payload.note,
      };
      return { ...state, bookmarks: [...state.bookmarks, newBookmark] };
    }
    case 'REMOVE_BOOKMARK':
      return { ...state, bookmarks: state.bookmarks.filter(b => b.id !== action.payload) };
    case 'TOGGLE_NOTES':
      return { ...state, showNotes: !state.showNotes };
    case 'SET_NOTES':
      return { ...state, notes: action.payload };
    case 'RESET':
      return initialState;
    default:
      return state;
  }
}

// Context type
interface VideoPlayerContextType {
  state: VideoState;
  play: () => void;
  pause: () => void;
  togglePlay: () => void;
  setTime: (time: number) => void;
  setDuration: (duration: number) => void;
  setVolume: (volume: number) => void;
  toggleMute: () => void;
  setPlaybackRate: (rate: number) => void;
  setQuality: (quality: VideoState['quality']) => void;
  toggleSubtitles: () => void;
  addBookmark: (timestamp: number, note: string) => void;
  removeBookmark: (id: string) => void;
  toggleNotes: () => void;
  setNotes: (notes: string) => void;
  reset: () => void;
}

const VideoPlayerContext = createContext<VideoPlayerContextType | undefined>(undefined);

export function VideoPlayerProvider({ children }: { children: ReactNode }) {
  const [state, dispatch] = useReducer(videoReducer, initialState);

  const play = useCallback(() => dispatch({ type: 'PLAY' }), []);
  const pause = useCallback(() => dispatch({ type: 'PAUSE' }), []);
  const togglePlay = useCallback(() => dispatch({ type: 'TOGGLE_PLAY' }), []);
  const setTime = useCallback((time: number) => dispatch({ type: 'SET_TIME', payload: time }), []);
  const setDuration = useCallback((duration: number) => dispatch({ type: 'SET_DURATION', payload: duration }), []);
  const setVolume = useCallback((volume: number) => dispatch({ type: 'SET_VOLUME', payload: volume }), []);
  const toggleMute = useCallback(() => dispatch({ type: 'TOGGLE_MUTE' }), []);
  const setPlaybackRate = useCallback((rate: number) => dispatch({ type: 'SET_PLAYBACK_RATE', payload: rate }), []);
  const setQuality = useCallback((quality: VideoState['quality']) => dispatch({ type: 'SET_QUALITY', payload: quality }), []);
  const toggleSubtitles = useCallback(() => dispatch({ type: 'TOGGLE_SUBTITLES' }), []);
  const addBookmark = useCallback((timestamp: number, note: string) =>
    dispatch({ type: 'ADD_BOOKMARK', payload: { timestamp, note } }), []);
  const removeBookmark = useCallback((id: string) => dispatch({ type: 'REMOVE_BOOKMARK', payload: id }), []);
  const toggleNotes = useCallback(() => dispatch({ type: 'TOGGLE_NOTES' }), []);
  const setNotes = useCallback((notes: string) => dispatch({ type: 'SET_NOTES', payload: notes }), []);
  const reset = useCallback(() => dispatch({ type: 'RESET' }), []);

  const value = useMemo(() => ({
    state,
    play,
    pause,
    togglePlay,
    setTime,
    setDuration,
    setVolume,
    toggleMute,
    setPlaybackRate,
    setQuality,
    toggleSubtitles,
    addBookmark,
    removeBookmark,
    toggleNotes,
    setNotes,
    reset,
  }), [state, play, pause, togglePlay, setTime, setDuration, setVolume, toggleMute,
      setPlaybackRate, setQuality, toggleSubtitles, addBookmark, removeBookmark,
      toggleNotes, setNotes, reset]);

  return (
    <VideoPlayerContext.Provider value={value}>
      {children}
    </VideoPlayerContext.Provider>
  );
}

export function useVideoPlayer() {
  const context = useContext(VideoPlayerContext);
  if (context === undefined) {
    throw new Error('useVideoPlayer must be used within a VideoPlayerProvider');
  }
  return context;
}

Dostawcy są tworzeni u korzenia struktury układu:

// app/layout.tsx - App with multiple Context providers
import { ThemeProvider } from '@/contexts/ThemeContext';
import { AuthProvider } from '@/contexts/AuthContext';
import { VideoPlayerProvider } from '@/contexts/VideoPlayerContext';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  return (
    <html lang="en">
      <body>
        <ThemeProvider>
          <AuthProvider>
            <VideoPlayerProvider>
              {children}
            </VideoPlayerProvider>
          </AuthProvider>
        </ThemeProvider>
      </body>
    </html>
  );
}

Konsumenty pozostają proste:

// components/ThemeToggle.tsx - Using Context
'use client';

import { useTheme } from '@/contexts/ThemeContext';
import { Sun, Moon, Monitor } from 'lucide-react';

export function ThemeToggle() {
  const { theme, setTheme, actualTheme } = useTheme();

  return (
    <div className="flex items-center gap-1 bg-gray-100 dark:bg-gray-800 rounded-lg p-1">
      <button
        onClick={() => setTheme('light')}
        className={`p-2 rounded ${theme === 'light' ? 'bg-white dark:bg-gray-700 shadow-sm' : ''}`}
        aria-label="Light mode"
      >
        <Sun className="w-4 h-4" />
      </button>
      <button
        onClick={() => setTheme('dark')}
        className={`p-2 rounded ${theme === 'dark' ? 'bg-white dark:bg-gray-700 shadow-sm' : ''}`}
        aria-label="Dark mode"
      >
        <Moon className="w-4 h-4" />
      </button>
      <button
        onClick={() => setTheme('system')}
        className={`p-2 rounded ${theme === 'system' ? 'bg-white dark:bg-gray-700 shadow-sm' : ''}`}
        aria-label="System preference"
      >
        <Monitor className="w-4 h-4" />
      </button>
    </div>
  );
}

Kontekst jest łatwy do wdrożenia i wystarczający, gdy aktualizacje są rzadkie. W przypadku częstych odświeżeń lub złożonych struktur zazwyczaj potrzebna jest baza danych z wąskimi selektorami.

Redux Toolkit dla dużych, skoordynowanych baz danych

RTK to narzędzie wspierane przez obecne aplikacje Redux. Eliminuje ono tradycyjne procedury i oferuje pomocniki do konfiguracji bazy danych, definiowania fragmentów danych, pisania funkcji asynchronicznych oraz pobierania danych za pomocą RTK Query.

Główne elementy budulcowe:

• Slices — Reduktorzy i akcje są umieszczane w jednym pliku za pomocą createSlice.
• createAsyncThunk — Standardowe procesy oczekiwania/uzyskania/wykluczenia dla zadań asynchronicznych.

RTK Query — Pobieranie danych i cache zintegrowane ze sklepem.

Selectory — Wartości uzyskiwane z stanu w sposób pochodny i zapamiętywany.

Middleware — Funkcje typu thunk (włączone) oraz logowanie lub inne narzędzia w zależności od potrzeb.

RTK nadaje się do dużych baz kodu z skomplikowanymi interakcjami stanów, wieloma współpracownikami, debugowaniem typu „time-travel”, intensywnym wykorzystaniem middleware oraz preferencją dla aktualizacji w pełni przewidywalnych.

Sklep portalu wideo może łączyć kursy, odtwarzacz, ustawienia użytkownika oraz fragment API:

// store/index.ts - Redux store configuration
import { configureStore } from '@reduxjs/toolkit';
import { setupListeners } from '@reduxjs/toolkit/query';
import coursesReducer from './slices/coursesSlice';
import videoPlayerReducer from './slices/videoPlayerSlice';
import userPreferencesReducer from './slices/userPreferencesSlice';
import { apiSlice } from './services/apiSlice';

export const store = configureStore({
  reducer: {
    courses: coursesReducer,
    videoPlayer: videoPlayerReducer,
    userPreferences: userPreferencesReducer,
    [apiSlice.reducerPath]: apiSlice.reducer,
  },
  middleware: (getDefaultMiddleware) =>
    getDefaultMiddleware().concat(apiSlice.middleware),
  devTools: process.env.NODE_ENV !== 'production',
});

// Enable refetchOnFocus/refetchOnReconnect behaviors
setupListeners(store.dispatch);

// Infer types for TypeScript
export type RootState = ReturnType<typeof store.getState>;
export type AppDispatch = typeof store.dispatch;

// store/hooks.ts - Typed hooks
import { TypedUseSelectorHook, useDispatch, useSelector } from 'react-redux';
import type { RootState, AppDispatch } from './index';

export const useAppDispatch = () => useDispatch<AppDispatch>();
export const useAppSelector: TypedUseSelectorHook<RootState> = useSelector;

// store/slices/coursesSlice.ts - Courses slice with createSlice and createAsyncThunk
import { createSlice, createAsyncThunk, PayloadAction } from '@reduxjs/toolkit';

interface Course {
  id: string;
  title: string;
  description: string;
  thumbnail: string;
  price: number;
  rating: number;
  enrolledCount: number;
  instructor: {
    id: string;
    name: string;
    avatar: string;
  };
  isEnrolled: boolean;
}

interface CoursesState {
  items: Course[];
  featured: Course[];
  recommended: Course[];
  searchResults: Course[];
  currentCourse: Course | null;
  isLoading: boolean;
  error: string | null;
  filters: {
    category: string | null;
    level: string | null;
    sortBy: 'newest' | 'popular' | 'rating' | 'price_low' | 'price_high';
    searchTerm: string;
  };
  pagination: {
    page: number;
    totalPages: number;
    totalItems: number;
  };
}

const initialState: CoursesState = {
  items: [],
  featured: [],
  recommended: [],
  searchResults: [],
  currentCourse: null,
  isLoading: false,
  error: null,
  filters: {
    category: null,
    level: null,
    sortBy: 'popular',
    searchTerm: '',
  },
  pagination: {
    page: 1,
    totalPages: 1,
    totalItems: 0,
  },
};

// Async thunks
export const fetchCourses = createAsyncThunk(
  'courses/fetchCourses',
  async (params: { page?: number; category?: string; sortBy?: string } = {}) => {
    const queryParams = new URLSearchParams();
    if (params.page) queryParams.append('page', params.page.toString());
    if (params.category) queryParams.append('category', params.category);
    if (params.sortBy) queryParams.append('sort', params.sortBy);

    const response = await fetch(`/api/courses?${queryParams}`);
    if (!response.ok) throw new Error('Failed to fetch courses');
    return response.json();
  }
);

export const fetchCourseById = createAsyncThunk(
  'courses/fetchCourseById',
  async (courseId: string) => {
    const response = await fetch(`/api/courses/${courseId}`);
    if (!response.ok) throw new Error('Failed to fetch course');
    return response.json();
  }
);

export const fetchFeaturedCourses = createAsyncThunk(
  'courses/fetchFeaturedCourses',
  async () => {
    const response = await fetch('/api/courses/featured');
    return response.json();
  }
);

export const fetchRecommendedCourses = createAsyncThunk(
  'courses/fetchRecommendedCourses',
  async () => {
    const response = await fetch('/api/courses/recommended');
    return response.json();
  }
);

export const searchCourses = createAsyncThunk(
  'courses/searchCourses',
  async (searchTerm: string) => {
    const response = await fetch(`/api/courses/search?q=${encodeURIComponent(searchTerm)}`);
    return response.json();
  }
);

export const enrollInCourse = createAsyncThunk(
  'courses/enrollInCourse',
  async (courseId: string, { rejectWithValue }) => {
    try {
      const response = await fetch(`/api/courses/${courseId}/enroll`, {
        method: 'POST',
      });
      if (!response.ok) {
        const error = await response.json();
        return rejectWithValue(error.message);
      }
      return { courseId, enrolled: true };
    } catch (error) {
      return rejectWithValue('Enrollment failed');
    }
  }
);

const coursesSlice = createSlice({
  name: 'courses',
  initialState,
  reducers: {
    setFilters: (state, action: PayloadAction<Partial<CoursesState['filters']>>) => {
      state.filters = { ...state.filters, ...action.payload };
      state.pagination.page = 1; // Reset pagination when filters change
    },
    resetFilters: (state) => {
      state.filters = initialState.filters;
      state.pagination.page = 1;
    },
    setPage: (state, action: PayloadAction<number>) => {
      state.pagination.page = action.payload;
    },
    clearSearchResults: (state) => {
      state.searchResults = [];
      state.filters.searchTerm = '';
    },
    updateCourseEnrollment: (state, action: PayloadAction<{ courseId: string; isEnrolled: boolean }>) => {
      const { courseId, isEnrolled } = action.payload;

      // Update in items list
      const itemIndex = state.items.findIndex(c => c.id === courseId);
      if (itemIndex !== -1) {
        state.items[itemIndex].isEnrolled = isEnrolled;
        if (isEnrolled) {
          state.items[itemIndex].enrolledCount += 1;
        } else {
          state.items[itemIndex].enrolledCount -= 1;
        }
      }

      // Update in featured list
      const featuredIndex = state.featured.findIndex(c => c.id === courseId);
      if (featuredIndex !== -1) {
        state.featured[featuredIndex].isEnrolled = isEnrolled;
      }

      // Update current course
      if (state.currentCourse?.id === courseId) {
        state.currentCourse.isEnrolled = isEnrolled;
      }
    },
  },
  extraReducers: (builder) => {
    builder
      // fetchCourses
      .addCase(fetchCourses.pending, (state) => {
        state.isLoading = true;
        state.error = null;
      })
      .addCase(fetchCourses.fulfilled, (state, action) => {
        state.isLoading = false;
        state.items = action.payload.courses;
        state.pagination = {
          page: action.payload.page,
          totalPages: action.payload.totalPages,
          totalItems: action.payload.total,
        };
      })
      .addCase(fetchCourses.rejected, (state, action) => {
        state.isLoading = false;
        state.error = action.error.message || 'Failed to fetch courses';
      })
      // fetchCourseById
      .addCase(fetchCourseById.pending, (state) => {
        state.isLoading = true;
        state.currentCourse = null;
      })
      .addCase(fetchCourseById.fulfilled, (state, action) => {
        state.isLoading = false;
        state.currentCourse = action.payload;
      })
      .addCase(fetchCourseById.rejected, (state, action) => {
        state.isLoading = false;
        state.error = action.error.message || 'Failed to fetch course';
      })
      // fetchFeaturedCourses
      .addCase(fetchFeaturedCourses.fulfilled, (state, action) => {
        state.featured = action.payload;
      })
      // fetchRecommendedCourses
      .addCase(fetchRecommendedCourses.fulfilled, (state, action) => {
        state.recommended = action.payload;
      })
      // searchCourses
      .addCase(searchCourses.fulfilled, (state, action) => {
        state.searchResults = action.payload;
      })
      // enrollInCourse
      .addCase(enrollInCourse.fulfilled, (state, action) => {
        const { courseId, enrolled } = action.payload;
        coursesSlice.caseReducers.updateCourseEnrollment(state, {
          type: 'courses/updateCourseEnrollment',
          payload: { courseId, isEnrolled: enrolled },
        });
      });
  },
});

export const { setFilters, resetFilters, setPage, clearSearchResults, updateCourseEnrollment } = coursesSlice.actions;
export default coursesSlice.reducer;

// store/slices/videoPlayerSlice.ts
import { createSlice, PayloadAction } from '@reduxjs/toolkit';

interface Bookmark {
  id: string;
  timestamp: number;
  note: string;
}

interface VideoPlayerState {
  isPlaying: boolean;
  currentTime: number;
  duration: number;
  volume: number;
  isMuted: boolean;
  playbackRate: number;
  quality: 'auto' | '1080p' | '720p' | '480p';
  subtitlesEnabled: boolean;
  subtitlesTrack: string | null;
  bookmarks: Bookmark[];
  showNotes: boolean;
  notes: string;
  currentVideoId: string | null;
  currentCourseId: string | null;
}

const initialState: VideoPlayerState = {
  isPlaying: false,
  currentTime: 0,
  duration: 0,
  volume: 80,
  isMuted: false,
  playbackRate: 1,
  quality: 'auto',
  subtitlesEnabled: false,
  subtitlesTrack: null,
  bookmarks: [],
  showNotes: false,
  notes: '',
  currentVideoId: null,
  currentCourseId: null,
};

const videoPlayerSlice = createSlice({
  name: 'videoPlayer',
  initialState,
  reducers: {
    setCurrentVideo: (state, action: PayloadAction<{ videoId: string; courseId: string }>) => {
      state.currentVideoId = action.payload.videoId;
      state.currentCourseId = action.payload.courseId;
      state.currentTime = 0;
      state.isPlaying = false;
      state.bookmarks = [];
    },
    play: (state) => {
      state.isPlaying = true;
    },
    pause: (state) => {
      state.isPlaying = false;
    },
    togglePlay: (state) => {
      state.isPlaying = !state.isPlaying;
    },
    setTime: (state, action: PayloadAction<number>) => {
      state.currentTime = Math.max(0, Math.min(action.payload, state.duration));
    },
    setDuration: (state, action: PayloadAction<number>) => {
      state.duration = action.payload;
    },
    setVolume: (state, action: PayloadAction<number>) => {
      const volume = Math.max(0, Math.min(100, action.payload));
      state.volume = volume;
      if (volume === 0) state.isMuted = true;
      else if (state.isMuted) state.isMuted = false;
    },
    toggleMute: (state) => {
      state.isMuted = !state.isMuted;
    },
    setPlaybackRate: (state, action: PayloadAction<number>) => {
      state.playbackRate = action.payload;
    },
    setQuality: (state, action: PayloadAction<VideoPlayerState['quality']>) => {
      state.quality = action.payload;
    },
    toggleSubtitles: (state) => {
      state.subtitlesEnabled = !state.subtitlesEnabled;
    },
    addBookmark: (state, action: PayloadAction<{ timestamp: number; note: string }>) => {
      const newBookmark: Bookmark = {
        id: Date.now().toString(),
        timestamp: action.payload.timestamp,
        note: action.payload.note,
      };
      state.bookmarks.push(newBookmark);
    },
    removeBookmark: (state, action: PayloadAction<string>) => {
      state.bookmarks = state.bookmarks.filter(b => b.id !== action.payload);
    },
    toggleNotes: (state) => {
      state.showNotes = !state.showNotes;
    },
    setNotes: (state, action: PayloadAction<string>) => {
      state.notes = action.payload;
    },
    seekForward: (state) => {
      state.currentTime = Math.min(state.duration, state.currentTime + 10);
    },
    seekBackward: (state) => {
      state.currentTime = Math.max(0, state.currentTime - 10);
    },
    resetPlayer: (state) => {
      return { ...initialState, currentCourseId: state.currentCourseId };
    },
  },
});

export const {
  setCurrentVideo,
  play,
  pause,
  togglePlay,
  setTime,
  setDuration,
  setVolume,
  toggleMute,
  setPlaybackRate,
  setQuality,
  toggleSubtitles,
  addBookmark,
  removeBookmark,
  toggleNotes,
  setNotes,
  seekForward,
  seekBackward,
  resetPlayer,
} = videoPlayerSlice.actions;

export default videoPlayerSlice.reducer;

// store/slices/userPreferencesSlice.ts
import { createSlice, PayloadAction } from '@reduxjs/toolkit';

interface UserPreferencesState {
  theme: 'light' | 'dark' | 'system';
  language: string;
  autoplay: boolean;
  quality: 'auto' | '1080p' | '720p' | '480p';
  subtitlesEnabled: boolean;
  subtitlesLanguage: string;
  volume: number;
  playbackRate: number;
  notifications: {
    email: boolean;
    push: boolean;
    courseUpdates: boolean;
    newContent: boolean;
  };
  recentSearches: string[];
  bookmarksView: 'grid' | 'list';
  sortPreferences: {
    courses: 'newest' | 'popular' | 'rating';
    videos: 'recent' | 'popular';
  };
}

const loadFromLocalStorage = (): Partial<UserPreferencesState> => {
  if (typeof window === 'undefined') return {};
  try {
    const saved = localStorage.getItem('userPreferences');
    if (saved) return JSON.parse(saved);
  } catch (error) {
    console.error('Failed to load preferences:', error);
  }
  return {};
};

const initialState: UserPreferencesState = {
  theme: 'system',
  language: 'en',
  autoplay: true,
  quality: 'auto',
  subtitlesEnabled: false,
  subtitlesLanguage: 'en',
  volume: 80,
  playbackRate: 1,
  notifications: {
    email: true,
    push: false,
    courseUpdates: true,
    newContent: true,
  },
  recentSearches: [],
  bookmarksView: 'grid',
  sortPreferences: {
    courses: 'popular',
    videos: 'recent',
  },
  ...loadFromLocalStorage(),
};

const userPreferencesSlice = createSlice({
  name: 'userPreferences',
  initialState,
  reducers: {
    setTheme: (state, action: PayloadAction<UserPreferencesState['theme']>) => {
      state.theme = action.payload;
      this.persist(state);
    },
    setLanguage: (state, action: PayloadAction<string>) => {
      state.language = action.payload;
      this.persist(state);
    },
    setAutoplay: (state, action: PayloadAction<boolean>) => {
      state.autoplay = action.payload;
      this.persist(state);
    },
    setQuality: (state, action: PayloadAction<UserPreferencesState['quality']>) => {
      state.quality = action.payload;
      this.persist(state);
    },
    setSubtitlesEnabled: (state, action: PayloadAction<boolean>) => {
      state.subtitlesEnabled = action.payload;
      this.persist(state);
    },
    setSubtitlesLanguage: (state, action: PayloadAction<string>) => {
      state.subtitlesLanguage = action.payload;
      this.persist(state);
    },
    setVolume: (state, action: PayloadAction<number>) => {
      state.volume = action.payload;
      this.persist(state);
    },
    setPlaybackRate: (state, action: PayloadAction<number>) => {
      state.playbackRate = action.payload;
      this.persist(state);
    },
    updateNotifications: (state, action: PayloadAction<Partial<UserPreferencesState['notifications']>>) => {
      state.notifications = { ...state.notifications, ...action.payload };
      this.persist(state);
    },
    addRecentSearch: (state, action: PayloadAction<string>) => {
      const term = action.payload.trim();
      if (!term) return;
      state.recentSearches = [
        term,
        ...state.recentSearches.filter(s => s !== term),
      ].slice(0, 10);
      this.persist(state);
    },
    clearRecentSearches: (state) => {
      state.recentSearches = [];
      this.persist(state);
    },
    setBookmarksView: (state, action: PayloadAction<'grid' | 'list'>) => {
      state.bookmarksView = action.payload;
      this.persist(state);
    },
    setSortPreference: (state, action: PayloadAction<{ type: 'courses' | 'videos'; value: string }>) => {
      state.sortPreferences[action.payload.type] = action.payload.value as any;
      this.persist(state);
    },
    resetPreferences: () => initialState,
  },
});

// Helper to persist to localStorage
function persist(state: UserPreferencesState) {
  if (typeof window === 'undefined') return;
  const { ...persistable } = state;
  localStorage.setItem('userPreferences', JSON.stringify(persistable));
}

export const {
  setTheme,
  setLanguage,
  setAutoplay,
  setQuality,
  setSubtitlesEnabled,
  setSubtitlesLanguage,
  setVolume,
  setPlaybackRate,
  updateNotifications,
  addRecentSearch,
  clearRecentSearches,
  setBookmarksView,
  setSortPreference,
  resetPreferences,
} = userPreferencesSlice.actions;

export default userPreferencesSlice.reducer;

// store/services/apiSlice.ts - RTK Query for data fetching
import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react';

export interface Course {
  id: string;
  title: string;
  description: string;
  thumbnail: string;
  price: number;
  rating: number;
  enrolledCount: number;
  instructor: {
    id: string;
    name: string;
    avatar: string;
  };
  isEnrolled?: boolean;
}

export interface Video {
  id: string;
  title: string;
  duration: number;
  url: string;
  thumbnail: string;
  order: number;
  isFree: boolean;
}

export const apiSlice = createApi({
  reducerPath: 'api',
  baseQuery: fetchBaseQuery({
    baseUrl: '/api',
    prepareHeaders: (headers) => {
      const token = localStorage.getItem('access_token');
      if (token) {
        headers.set('authorization', `Bearer ${token}`);
      }
      return headers;
    },
  }),
  tagTypes: ['Course', 'Courses', 'Video', 'Progress', 'Bookmark'],
  endpoints: (builder) => ({
    // Query endpoints
    getCourses: builder.query<{ courses: Course[]; total: number; page: number }, { page?: number; category?: string; sort?: string }>({
      query: (params) => ({
        url: '/courses',
        params,
      }),
      providesTags: (result) =>
        result
          ? [
              ...result.courses.map(({ id }) => ({ type: 'Course' as const, id })),
              { type: 'Courses', id: 'LIST' },
            ]
          : [{ type: 'Courses', id: 'LIST' }],
    }),

    getCourse: builder.query<Course, string>({
      query: (id) => `/courses/${id}`,
      providesTags: (result, error, id) => [{ type: 'Course', id }],
    }),

    getCourseVideos: builder.query<Video[], string>({
      query: (courseId) => `/courses/${courseId}/videos`,
      providesTags: (result, error, courseId) => [
        { type: 'Course', id: courseId },
        { type: 'Video', id: 'LIST' },
      ],
    }),

    getVideoProgress: builder.query<{ position: number; percentage: number; completed: boolean }, string>({
      query: (videoId) => `/progress/${videoId}`,
      providesTags: (result, error, videoId) => [{ type: 'Progress', id: videoId }],
    }),

    getBookmarks: builder.query<Video[], void>({
      query: () => '/bookmarks',
      providesTags: ['Bookmark'],
    }),

    // Mutation endpoints
    enrollInCourse: builder.mutation<{ success: boolean }, string>({
      query: (courseId) => ({
        url: `/courses/${courseId}/enroll`,
        method: 'POST',
      }),
      invalidatesTags: (result, error, courseId) => [
        { type: 'Course', id: courseId },
        { type: 'Courses', id: 'LIST' },
      ],
    }),

    updateProgress: builder.mutation<void, { videoId: string; position: number; percentage: number }>({
      query: ({ videoId, position, percentage }) => ({
        url: `/progress/${videoId}`,
        method: 'POST',
        body: { position, percentage },
      }),
      invalidatesTags: (result, error, { videoId }) => [
        { type: 'Progress', id: videoId },
      ],
    }),

    toggleBookmark: builder.mutation<{ isBookmarked: boolean }, string>({
      query: (videoId) => ({
        url: `/bookmarks/${videoId}`,
        method: 'POST',
      }),
      invalidatesTags: ['Bookmark'],
      async onQueryStarted(videoId, { dispatch, queryFulfilled }) {
        // Optimistic update example
        const patchResult = dispatch(
          apiSlice.util.updateQueryData('getBookmarks', undefined, (draft) => {
            // Optimistically add/remove bookmark
          })
        );
        try {
          await queryFulfilled;
        } catch {
          patchResult.undo();
        }
      },
    }),

    submitReview: builder.mutation<void, { courseId: string; rating: number; comment: string }>({
      query: ({ courseId, rating, comment }) => ({
        url: `/courses/${courseId}/reviews`,
        method: 'POST',
        body: { rating, comment },
      }),
      invalidatesTags: (result, error, { courseId }) => [{ type: 'Course', id: courseId }],
    }),
  }),
});

// Auto-generated hooks
export const {
  useGetCoursesQuery,
  useGetCourseQuery,
  useGetCourseVideosQuery,
  useGetVideoProgressQuery,
  useGetBookmarksQuery,
  useEnrollInCourseMutation,
  useUpdateProgressMutation,
  useToggleBookmarkMutation,
  useSubmitReviewMutation,
} = apiSlice;

Komponenty następnie wysyłają polecenia i dokonują wyborów za pomocą typowanych hooków:

// components/CourseListRedux.tsx - React component using Redux
'use client';

import { useEffect } from 'react';
import { useAppDispatch, useAppSelector } from '@/store/hooks';
import { fetchCourses, setFilters, setPage } from '@/store/slices/coursesSlice';
import { useGetCoursesQuery } from '@/store/services/apiSlice';
import { RootState } from '@/store';

export function CourseListRedux() {
  // Using traditional Redux slices
  const dispatch = useAppDispatch();
  const { items: courses, isLoading, filters, pagination } = useAppSelector(
    (state: RootState) => state.courses
  );

  // Using RTK Query for automatic caching
  const { data: apiCourses, isLoading: apiLoading } = useGetCoursesQuery({
    page: pagination.page,
    category: filters.category || undefined,
    sort: filters.sortBy,
  });

  useEffect(() => {
    dispatch(fetchCourses({
      page: pagination.page,
      category: filters.category || undefined,
      sortBy: filters.sortBy,
    }));
  }, [dispatch, pagination.page, filters.category, filters.sortBy]);

  const handleFilterChange = (category: string | null) => {
    dispatch(setFilters({ category }));
  };

  const handleSortChange = (sortBy: typeof filters.sortBy) => {
    dispatch(setFilters({ sortBy }));
  };

  if (isLoading) {
    return <div className="flex justify-center p-8"><div className="animate-spin rounded-full h-8 w-8 border-b-2 border-blue-600"></div></div>;
  }

  return (
    <div className="container mx-auto px-4 py-8">
      {/* Filters */}
      <div className="mb-6 flex gap-4">
        <select
          value={filters.category || ''}
          onChange={(e) => handleFilterChange(e.target.value || null)}
          className="px-3 py-2 border rounded-lg"
        >
          <option value="">All Categories</option>
          <option value="react">React</option>
          <option value="typescript">TypeScript</option>
          <option value="nextjs">Next.js</option>
        </select>

        <select
          value={filters.sortBy}
          onChange={(e) => handleSortChange(e.target.value as any)}
          className="px-3 py-2 border rounded-lg"
        >
          <option value="newest">Newest</option>
          <option value="popular">Most Popular</option>
          <option value="rating">Highest Rated</option>
          <option value="price_low">Price: Low to High</option>
          <option value="price_high">Price: High to Low</option>
        </select>
      </div>

      {/* Course Grid */}
      <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
        {courses.map((course) => (
          <CourseCardRedux key={course.id} course={course} />
        ))}
      </div>

      {/* Pagination */}
      {pagination.totalPages > 1 && (
        <div className="mt-8 flex justify-center gap-2">
          {Array.from({ length: pagination.totalPages }, (_, i) => i + 1).map((p) => (
            <button
              key={p}
              onClick={() => dispatch(setPage(p))}
              className={`px-3 py-1 rounded ${
                p === pagination.page
                  ? 'bg-blue-600 text-white'
                  : 'bg-gray-200 hover:bg-gray-300'
              }`}
            >
              {p}
            </button>
          ))}
        </div>
      )}
    </div>
  );
}

function CourseCardRedux({ course }: { course: Course }) {
  const [enroll] = useEnrollInCourseMutation();

  return (
    <div className="bg-white rounded-lg shadow-sm overflow-hidden">
      <img src={course.thumbnail} alt={course.title} className="w-full h-48 object-cover" />
      <div className="p-4">
        <h3 className="font-semibold text-lg">{course.title}</h3>
        <p className="text-sm text-gray-600 mt-1">{course.instructor.name}</p>
        <div className="flex items-center gap-2 mt-2">
          <span className="text-yellow-500">★</span>
          <span>{course.rating}</span>
          <span className="text-gray-400">•</span>
          <span>{course.enrolledCount.toLocaleString()} students</span>
        </div>
        <div className="mt-3 flex justify-between items-center">
          <span className="text-xl font-bold">${course.price}</span>
          {!course.isEnrolled ? (
            <button
              onClick={() => enroll(course.id)}
              className="px-4 py-2 bg-blue-600 text-white rounded hover:bg-blue-700"
            >
              Enroll
            </button>
          ) : (
            <span className="px-4 py-2 bg-green-100 text-green-700 rounded">Enrolled ✓</span>
          )}
        </div>
      </div>
    </div>
  );
}

Struktura RTK dobrze się skaluje i jest dobrze udokumentowana; wadą jest większa złożoność w porównaniu z Context lub Zustand przy małych ekranach.

Zustand — Minimalistyczne zarządzanie stanem

Zustand jest przeznaczony dla zespołów, które chcą semantyki sklepu bez zbędnych procedur Redux – szczególnie gdy wydajność i krótka API są ważniejsze niż formalny słownik działań.

Portal może rozdzielić kwestie związane z kursami i graczami pomiędzy sklepami Zustand za pomocą funkcji persist, DevTools oraz powiązanych middleware:

// store/zustand/courseStore.ts
import { create } from 'zustand';
import { persist, devtools, subscribeWithSelector } from 'zustand/middleware';
import { immer } from 'zustand/middleware/immer';

interface Course {
  id: string;
  title: string;
  description: string;
  thumbnail: string;
  price: number;
  rating: number;
  enrolledCount: number;
  instructor: {
    id: string;
    name: string;
    avatar: string;
  };
  isEnrolled: boolean;
}

interface FilterState {
  category: string | null;
  level: string | null;
  sortBy: 'newest' | 'popular' | 'rating' | 'price_low' | 'price_high';
  searchTerm: string;
}

interface CourseStore {
  // State
  courses: Course[];
  featured: Course[];
  recommended: Course[];
  currentCourse: Course | null;
  isLoading: boolean;
  error: string | null;
  filters: FilterState;
  page: number;
  totalPages: number;
  hasMore: boolean;

  // Actions
  fetchCourses: () => Promise<void>;
  fetchCourseById: (id: string) => Promise<void>;
  fetchFeatured: () => Promise<void>;
  fetchRecommended: () => Promise<void>;
  searchCourses: (term: string) => Promise<void>;
  enrollInCourse: (courseId: string) => Promise<boolean>;
  setFilter: <K extends keyof FilterState>(key: K, value: FilterState[K]) => void;
  resetFilters: () => void;
  setPage: (page: number) => void;
  clearError: () => void;

  // Selectors (computed)
  getFilteredAndSortedCourses: () => Course[];
}

const initialFilters: FilterState = {
  category: null,
  level: null,
  sortBy: 'popular',
  searchTerm: '',
};

// Create store with multiple middleware
export const useCourseStore = create<CourseStore>()(
  devtools(
    persist(
      subscribeWithSelector(
        immer((set, get) => ({
          // Initial state
          courses: [],
          featured: [],
          recommended: [],
          currentCourse: null,
          isLoading: false,
          error: null,
          filters: initialFilters,
          page: 1,
          totalPages: 1,
          hasMore: true,

          // Actions
          fetchCourses: async () => {
            set({ isLoading: true, error: null }, false, 'courses/fetch/start');

            try {
              const { page, filters } = get();
              const params = new URLSearchParams();
              params.append('page', page.toString());
              if (filters.category) params.append('category', filters.category);
              if (filters.sortBy) params.append('sort', filters.sortBy);
              if (filters.searchTerm) params.append('search', filters.searchTerm);

              const response = await fetch(`/api/courses?${params}`);
              if (!response.ok) throw new Error('Failed to fetch courses');

              const data = await response.json();

              set((state) => {
                state.courses = page === 1 ? data.courses : [...state.courses, ...data.courses];
                state.totalPages = data.totalPages;
                state.hasMore = data.hasMore;
                state.isLoading = false;
              }, false, 'courses/fetch/success');
            } catch (error) {
              set({ error: (error as Error).message, isLoading: false }, false, 'courses/fetch/error');
            }
          },

          fetchCourseById: async (id: string) => {
            set({ isLoading: true, error: null }, false, 'course/fetch/start');

            try {
              const response = await fetch(`/api/courses/${id}`);
              if (!response.ok) throw new Error('Course not found');

              const course = await response.json();
              set({ currentCourse: course, isLoading: false }, false, 'course/fetch/success');
            } catch (error) {
              set({ error: (error as Error).message, isLoading: false }, false, 'course/fetch/error');
            }
          },

          fetchFeatured: async () => {
            try {
              const response = await fetch('/api/courses/featured');
              const featured = await response.json();
              set({ featured }, false, 'courses/featured/success');
            } catch (error) {
              console.error('Failed to fetch featured:', error);
            }
          },

          fetchRecommended: async () => {
            try {
              const response = await fetch('/api/courses/recommended');
              const recommended = await response.json();
              set({ recommended }, false, 'courses/recommended/success');
            } catch (error) {
              console.error('Failed to fetch recommended:', error);
            }
          },

          searchCourses: async (term: string) => {
            if (!term.trim()) {
              set(
                (state) => {
                  state.filters.searchTerm = '';
                  state.page = 1;
                },
                false,
                'courses/search/clear'
              );
              await get().fetchCourses();
              return;
            }

            set(
              (state) => {
                state.filters.searchTerm = term;
                state.page = 1;
                state.isLoading = true;
              },
              false,
              'courses/search/start'
            );

            try {
              const response = await fetch(`/api/courses/search?q=${encodeURIComponent(term)}`);
              const data = await response.json();

              set(
                (state) => {
                  state.courses = data.courses;
                  state.totalPages = data.totalPages;
                  state.hasMore = data.hasMore;
                  state.isLoading = false;
                },
                false,
                'courses/search/success'
              );
            } catch (error) {
              set({ error: (error as Error).message, isLoading: false }, false, 'courses/search/error');
            }
          },

          enrollInCourse: async (courseId: string) => {
            try {
              const response = await fetch(`/api/courses/${courseId}/enroll`, {
                method: 'POST',
              });

              if (!response.ok) return false;

              // Update local state
              set((state) => {
                // Update in courses list
                const courseIndex = state.courses.findIndex(c => c.id === courseId);
                if (courseIndex !== -1) {
                  state.courses[courseIndex].isEnrolled = true;
                  state.courses[courseIndex].enrolledCount += 1;
                }

                // Update current course
                if (state.currentCourse?.id === courseId) {
                  state.currentCourse.isEnrolled = true;
                }
              }, false, 'courses/enroll/success');

              return true;
            } catch (error) {
              console.error('Enrollment failed:', error);
              return false;
            }
          },

          setFilter: <K extends keyof FilterState>(key: K, value: FilterState[K]) => {
            set(
              (state) => {
                state.filters[key] = value;
                state.page = 1; // Reset pagination on filter change
              },
              false,
              `courses/filter/${String(key)}`
            );
            get().fetchCourses();
          },

          resetFilters: () => {
            set(
              (state) => {
                state.filters = initialFilters;
                state.page = 1;
              },
              false,
              'courses/filters/reset'
            );
            get().fetchCourses();
          },

          setPage: (page: number) => {
            set({ page }, false, 'courses/page/set');
            get().fetchCourses();
          },

          clearError: () => set({ error: null }, false, 'courses/error/clear'),

          // Selector: get filtered and sorted courses (computed)
          getFilteredAndSortedCourses: () => {
            const { courses, filters } = get();
            let result = [...courses];

            // Apply filters
            if (filters.category) {
              // In real app, filter by category
            }

            if (filters.level) {
              // Filter by level
            }

            // Apply sorting
            switch (filters.sortBy) {
              case 'newest':
                result.sort((a, b) => 0); // Add sorting logic
                break;
              case 'popular':
                result.sort((a, b) => b.enrolledCount - a.enrolledCount);
                break;
              case 'rating':
                result.sort((a, b) => b.rating - a.rating);
                break;
              case 'price_low':
                result.sort((a, b) => a.price - b.price);
                break;
              case 'price_high':
                result.sort((a, b) => b.price - a.price);
                break;
            }

            return result;
          },
        }))
      ),
      {
        name: 'course-store', // localStorage key
        partialize: (state) => ({
          // Only persist these fields
          filters: state.filters,
          page: state.page,
        }),
      }
    ),
    { name: 'CourseStore' } // Redux DevTools name
  )
);

// Selector hooks for performance
export const useCourses = () => useCourseStore((state) => state.courses);
export const useFeatured = () => useCourseStore((state) => state.featured);
export const useRecommended = () => useCourseStore((state) => state.recommended);
export const useCurrentCourse = () => useCourseStore((state) => state.currentCourse);
export const useCourseLoading = () => useCourseStore((state) => state.isLoading);
export const useCourseError = () => useCourseStore((state) => state.error);
export const useFilters = () => useCourseStore((state) => state.filters);
export const usePagination = () => useCourseStore((state) => ({ page: state.page, totalPages: state.totalPages }));

// store/zustand/videoPlayerStore.ts
import { create } from 'zustand';
import { devtools, persist } from 'zustand/middleware';

interface Bookmark {
  id: string;
  timestamp: number;
  note: string;
}

interface VideoPlayerState {
  // State
  isPlaying: boolean;
  currentTime: number;
  duration: number;
  volume: number;
  isMuted: boolean;
  playbackRate: number;
  quality: 'auto' | '1080p' | '720p' | '480p';
  subtitlesEnabled: boolean;
  subtitlesTrack: string | null;
  bookmarks: Bookmark[];
  showNotes: boolean;
  notes: string;
  currentVideoId: string | null;
  currentCourseId: string | null;

  // Actions
  play: () => void;
  pause: () => void;
  togglePlay: () => void;
  setTime: (time: number) => void;
  setDuration: (duration: number) => void;
  setVolume: (volume: number) => void;
  toggleMute: () => void;
  setPlaybackRate: (rate: number) => void;
  setQuality: (quality: VideoPlayerState['quality']) => void;
  toggleSubtitles: () => void;
  addBookmark: (timestamp: number, note?: string) => void;
  removeBookmark: (id: string) => void;
  toggleNotes: () => void;
  setNotes: (notes: string) => void;
  seekForward: (seconds?: number) => void;
  seekBackward: (seconds?: number) => void;
  reset: () => void;
  loadVideo: (videoId: string, courseId: string) => void;

  // Computed
  getProgressPercentage: () => number;
  getFormattedTime: () => string;
}

export const useVideoPlayerStore = create<VideoPlayerState>()(
  devtools(
    persist(
      (set, get) => ({
        // Initial state
        isPlaying: false,
        currentTime: 0,
        duration: 0,
        volume: 80,
        isMuted: false,
        playbackRate: 1,
        quality: 'auto',
        subtitlesEnabled: false,
        subtitlesTrack: null,
        bookmarks: [],
        showNotes: false,
        notes: '',
        currentVideoId: null,
        currentCourseId: null,

        // Actions
        play: () => set({ isPlaying: true }, false, 'video/play'),
        pause: () => set({ isPlaying: false }, false, 'video/pause'),
        togglePlay: () => set((state) => ({ isPlaying: !state.isPlaying }), false, 'video/togglePlay'),

        setTime: (time: number) => set((state) => ({
          currentTime: Math.max(0, Math.min(time, state.duration))
        }), false, 'video/setTime'),

        setDuration: (duration: number) => set({ duration }, false, 'video/setDuration'),

        setVolume: (volume: number) => {
          const clampedVolume = Math.max(0, Math.min(100, volume));
          set((state) => ({
            volume: clampedVolume,
            isMuted: clampedVolume === 0 ? true : state.isMuted,
          }), false, 'video/setVolume');
        },

        toggleMute: () => set((state) => ({ isMuted: !state.isMuted }), false, 'video/toggleMute'),

        setPlaybackRate: (rate: number) => set({ playbackRate: rate }, false, 'video/setPlaybackRate'),

        setQuality: (quality: VideoPlayerState['quality']) => set({ quality }, false, 'video/setQuality'),

        toggleSubtitles: () => set((state) => ({
          subtitlesEnabled: !state.subtitlesEnabled
        }), false, 'video/toggleSubtitles'),

        addBookmark: (timestamp: number, note: string = '') => {
          const newBookmark: Bookmark = {
            id: Date.now().toString(),
            timestamp,
            note,
          };
          set((state) => ({
            bookmarks: [...state.bookmarks, newBookmark].sort((a, b) => a.timestamp - b.timestamp)
          }), false, 'video/addBookmark');
        },

        removeBookmark: (id: string) => set((state) => ({
          bookmarks: state.bookmarks.filter(b => b.id !== id)
        }), false, 'video/removeBookmark'),

        toggleNotes: () => set((state) => ({ showNotes: !state.showNotes }), false, 'video/toggleNotes'),

        setNotes: (notes: string) => set({ notes }, false, 'video/setNotes'),

        seekForward: (seconds: number = 10) => set((state) => ({
          currentTime: Math.min(state.duration, state.currentTime + seconds)
        }), false, 'video/seekForward'),

        seekBackward: (seconds: number = 10) => set((state) => ({
          currentTime: Math.max(0, state.currentTime - seconds)
        }), false, 'video/seekBackward'),

        reset: () => set({
          isPlaying: false,
          currentTime: 0,
          duration: 0,
          bookmarks: [],
          showNotes: false,
          notes: '',
        }, false, 'video/reset'),

        loadVideo: (videoId: string, courseId: string) => {
          // Reset and load new video
          set({
            currentVideoId: videoId,
            currentCourseId: courseId,
            currentTime: 0,
            duration: 0,
            isPlaying: false,
            bookmarks: [],
          }, false, 'video/load');

          // Fetch saved progress from API (async)
          fetch(`/api/progress/${videoId}`)
            .then(res => res.json())
            .then(data => {
              if (data.position) {
                set({ currentTime: data.position }, false, 'video/restoreProgress');
              }
            })
            .catch(console.error);
        },

        // Computed values
        getProgressPercentage: () => {
          const { currentTime, duration } = get();
          return duration > 0 ? (currentTime / duration) * 100 : 0;
        },

        getFormattedTime: () => {
          const { currentTime, duration } = get();
          const format = (seconds: number) => {
            const hrs = Math.floor(seconds / 3600);
            const mins = Math.floor((seconds % 3600) / 60);
            const secs = Math.floor(seconds % 60);
            if (hrs > 0) return `${hrs}:${mins.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
            return `${mins}:${secs.toString().padStart(2, '0')}`;
          };
          return `${format(currentTime)} / ${format(duration)}`;
        },
      }),
      {
        name: 'video-player-store',
        partialize: (state) => ({
          volume: state.volume,
          playbackRate: state.playbackRate,
          quality: state.quality,
          subtitlesEnabled: state.subtitlesEnabled,
        }),
      }
    ),
    { name: 'VideoPlayerStore' }
  )
);

// Individual selector hooks for better performance
export const useIsPlaying = () => useVideoPlayerStore((state) => state.isPlaying);
export const useCurrentTime = () => useVideoPlayerStore((state) => state.currentTime);
export const useDuration = () => useVideoPlayerStore((state) => state.duration);
export const useVolume = () => useVideoPlayerStore((state) => state.volume);
export const usePlaybackRate = () => useVideoPlayerStore((state) => state.playbackRate);
export const useBookmarks = () => useVideoPlayerStore((state) => state.bookmarks);
export const useVideoPlayerActions = () => useVideoPlayerStore((state) => ({
  play: state.play,
  pause: state.pause,
  togglePlay: state.togglePlay,
  setTime: state.setTime,
  setVolume: state.setVolume,
  toggleMute: state.toggleMute,
  setPlaybackRate: state.setPlaybackRate,
  addBookmark: state.addBookmark,
  removeBookmark: state.removeBookmark,
  seekForward: state.seekForward,
  seekBackward: state.seekBackward,
  loadVideo: state.loadVideo,
}));

Komponenty odczytują tylko wybrane fragmenty stanu sklepu:

// components/ZustandVideoPlayer.tsx - Component using Zustand store
'use client';

import { useEffect, useRef } from 'react';
import {
  useVideoPlayerStore,
  useIsPlaying,
  useCurrentTime,
  useDuration,
  useVolume,
  usePlaybackRate,
  useBookmarks,
  useVideoPlayerActions
} from '@/store/zustand/videoPlayerStore';
import { Play, Pause, Volume2, VolumeX, SkipBack, SkipForward, Bookmark } from 'lucide-react';

export function ZustandVideoPlayer({ videoUrl, videoId, courseId }: {
  videoUrl: string;
  videoId: string;
  courseId: string;
}) {
  const videoRef = useRef<HTMLVideoElement>(null);

  // Individual selectors for precise re-rendering
  const isPlaying = useIsPlaying();
  const currentTime = useCurrentTime();
  const duration = useDuration();
  const volume = useVolume();
  const playbackRate = usePlaybackRate();
  const bookmarks = useBookmarks();
  const progressPercentage = useVideoPlayerStore((state) => state.getProgressPercentage());

  // Actions
  const {
    play,
    pause,
    togglePlay,
    setTime,
    setDuration,
    setVolume,
    toggleMute,
    setPlaybackRate,
    addBookmark,
    seekForward,
    seekBackward,
  } = useVideoPlayerActions();

  // Sync video element with store
  useEffect(() => {
    const video = videoRef.current;
    if (!video) return;

    if (isPlaying) {
      video.play();
    } else {
      video.pause();
    }
  }, [isPlaying]);

  useEffect(() => {
    const video = videoRef.current;
    if (!video) return;

    video.volume = volume / 100;
  }, [volume]);

  useEffect(() => {
    const video = videoRef.current;
    if (!video) return;

    video.playbackRate = playbackRate;
  }, [playbackRate]);

  useEffect(() => {
    const video = videoRef.current;
    if (!video) return;

    if (Math.abs(video.currentTime - currentTime) > 0.5) {
      video.currentTime = currentTime;
    }
  }, [currentTime]);

  const handleTimeUpdate = () => {
    if (videoRef.current) {
      const time = videoRef.current.currentTime;
      if (Math.abs(time - currentTime) > 0.1) {
        setTime(time);
      }
    }
  };

  const handleLoadedMetadata = () => {
    if (videoRef.current) {
      setDuration(videoRef.current.duration);
    }
  };

  const handleAddBookmark = () => {
    const note = prompt('Add a note for this bookmark:');
    addBookmark(currentTime, note || '');
  };

  const jumpToBookmark = (timestamp: number) => {
    setTime(timestamp);
    if (videoRef.current) {
      videoRef.current.currentTime = timestamp;
    }
  };

  return (
    <div className="bg-black rounded-lg overflow-hidden">
      <video
        ref={videoRef}
        src={videoUrl}
        className="w-full aspect-video"
        onTimeUpdate={handleTimeUpdate}
        onLoadedMetadata={handleLoadedMetadata}
        onPlay={play}
        onPause={pause}
      />

      <div className="p-4 bg-gray-900 text-white">
        {/* Progress Bar */}
        <div className="mb-3">
          <div className="flex justify-between text-sm mb-1">
            <span>{formatTime(currentTime)}</span>
            <span>{formatTime(duration)}</span>
          </div>
          <div className="relative">
            <input
              type="range"
              min="0"
              max={duration}
              value={currentTime}
              onChange={(e) => setTime(parseFloat(e.target.value))}
              className="w-full"
            />
            {/* Bookmark markers on progress bar */}
            <div className="absolute top-0 left-0 right-0 pointer-events-none">
              {bookmarks.map((bookmark) => (
                <div
                  key={bookmark.id}
                  className="absolute w-0.5 h-3 bg-yellow-500 -top-1"
                  style={{ left: `${(bookmark.timestamp / duration) * 100}%` }}
                  title={bookmark.note}
                />
              ))}
            </div>
          </div>
        </div>

        {/* Controls */}
        <div className="flex items-center gap-3 flex-wrap">
          <button
            onClick={togglePlay}
            className="p-2 bg-blue-600 rounded-full hover:bg-blue-700"
          >
            {isPlaying ? <Pause className="w-5 h-5" /> : <Play className="w-5 h-5" />}
          </button>

          <button
            onClick={() => seekBackward(10)}
            className="p-2 bg-gray-700 rounded hover:bg-gray-600"
          >
            <SkipBack className="w-5 h-5" />
          </button>

          <button
            onClick={() => seekForward(10)}
            className="p-2 bg-gray-700 rounded hover:bg-gray-600"
          >
            <SkipForward className="w-5 h-5" />
          </button>

          <button
            onClick={handleAddBookmark}
            className="p-2 bg-gray-700 rounded hover:bg-gray-600"
          >
            <Bookmark className="w-5 h-5" />
          </button>

          <div className="flex items-center gap-2 ml-4">
            <button onClick={toggleMute} className="p-1">
              {volume === 0 ? <VolumeX className="w-5 h-5" /> : <Volume2 className="w-5 h-5" />}
            </button>
            <input
              type="range"
              min="0"
              max="100"
              value={volume}
              onChange={(e) => setVolume(parseInt(e.target.value))}
              className="w-24"
            />
          </div>

          <select
            value={playbackRate}
            onChange={(e) => setPlaybackRate(parseFloat(e.target.value))}
            className="px-2 py-1 bg-gray-800 rounded text-sm"
          >
            <option value="0.5">0.5x</option>
            <option value="0.75">0.75x</option>
            <option value="1">1x</option>
            <option value="1.25">1.25x</option>
            <option value="1.5">1.5x</option>
            <option value="2">2x</option>
          </select>
        </div>

        {/* Bookmarks List */}
        {bookmarks.length > 0 && (
          <div className="mt-4 pt-3 border-t border-gray-700">
            <h4 className="text-sm font-medium mb-2">Bookmarks</h4>
            <div className="flex flex-wrap gap-2">
              {bookmarks.map((bookmark) => (
                <button
                  key={bookmark.id}
                  onClick={() => jumpToBookmark(bookmark.timestamp)}
                  className="px-2 py-1 bg-gray-800 rounded text-xs hover:bg-gray-700"
                >
                  {formatTime(bookmark.timestamp)} - {bookmark.note || 'Untitled'}
                </button>
              ))}
            </div>
          </div>
        )}
      </div>
    </div>
  );
}

function formatTime(seconds: number): string {
  const mins = Math.floor(seconds / 60);
  const secs = Math.floor(seconds % 60);
  return `${mins}:${secs.toString().padStart(2, '0')}`;
}

Zustand pozostaje niewielki, jednocześnie umożliwiając przechowywanie danych i selektywne renderowanie. Jest doskonałym wyborem domyślnym, gdy procedury Redux przeważają nad jego zaletami.

Porównanie i ramy decyzyjne

Wybierz odpowiedni narzędzie w zależności od częstotliwości aktualizacji, wielkości zespołu oraz tego, czy dane znajdują się na serwerze, czy u klienta. Wybierz Context dla rzadko używanych globalnych danych; RTK, gdy dominują narzędzia korporacyjne i middleware; Zustand, gdy wystarczy mała API sklepu; TanStack Query, gdy źródłem prawdy są sieci.

Matryca decyzyjna

Dopasuj narzędzie do ograniczeń: krzywej uczenia się, szablonów kodu, DevTools, głębokości middleware oraz liczby osób edytujących ten sam stan. Wybierz najmniejszą opcję, która zapewnia przewidywalne aktualizacje przy danej wielkości zespołu.

Porównanie wydajności

Context przerysowuje się głównie przy zmianach wartości. Redux i Zustand mogą działać bardziej precyzyjnie. Zmierz czas przewijania odtwarzacza i filtrowanie listy w warunkach zbliżonych do produkcji, zanim podjąłeś ostateczną decyzję.

Integracja z TanStack Query

Trwałe podziały:

• TanStack Query — stan serwera (cache, aktualizacje w tle, mutacje).
• Zustand lub Redux — stan interfejsu klienta (ustawienia, tymczasowy interfejs odtwarzacza).
• Context — globalne zmieniające się rzadko.

// store/combined.ts - Integration example
import { create } from 'zustand';
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';

// Zustand for client state
interface UIStore {
  sidebarOpen: boolean;
  theme: 'light' | 'dark';
  toggleSidebar: () => void;
  setTheme: (theme: 'light' | 'dark') => void;
}

export const useUIStore = create<UIStore>((set) => ({
  sidebarOpen: true,
  theme: 'light',
  toggleSidebar: () => set((state) => ({ sidebarOpen: !state.sidebarOpen })),
  setTheme: (theme) => set({ theme }),
}));

// TanStack Query for server state
export function useCourses() {
  return useQuery({
    queryKey: ['courses'],
    queryFn: () => fetch('/api/courses').then(res => res.json()),
  });
}

export function useEnrollCourse() {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: (courseId: string) =>
      fetch(`/api/courses/${courseId}/enroll`, { method: 'POST' }),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['courses'] });
      queryClient.invalidateQueries({ queryKey: ['enrollments'] });
    },
  });
}

// Component using both
function CoursePage() {
  const { theme } = useUIStore();
  const { data: courses, isLoading } = useCourses();
  const enrollMutation = useEnrollCourse();

  return (
    <div data-theme={theme}>
      {courses?.map(course => (
        <CourseCard
          key={course.id}
          course={course}
          onEnroll={() => enrollMutation.mutate(course.id)}
        />
      ))}
    </div>
  );
}

3. Zakończenie

Kontekst obejmuje wbudowane globalne takie jak theme, auth i player. RTK zajmuje się stanem przedsiębiorstwa opartym na fragmentach za pomocą thunków i RTK Query. Zustand służy do tworzenia skromnych magazynów danych z możliwością przechowywania ich długoterminowo. Powyższa struktura decyzyjna pomaga wybrać odpowiedni narzędzie – TanStack Query zarządza stanem serwera, natomiast Zustand lub Redux odpowiadają za stan kliencki.

Zacznij od prostych globalnych w Kontekście, przejdź do Zustand lub RTK, gdy konieczne będą bardziej specyficzne selektory, a pamięci cache sieciowe przechowuj w TanStack Query zamiast w tych magazynach klienckich.