'use client';

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

import {
  isThemeMode,
  resolveTheme,
  THEME_MEDIA_QUERY,
  THEME_STORAGE_KEY,
  type ResolvedTheme,
  type ThemeMode,
} from '@/lib/theme/theme';

interface ThemeContextValue {
  themeMode: ThemeMode;
  resolvedTheme: ResolvedTheme;
  setThemeMode: (mode: ThemeMode) => void;
}

const ThemeContext = createContext<ThemeContextValue | null>(null);

interface ThemeProviderProps {
  children: ReactNode;
}

function getSystemPreference() {
  return window.matchMedia(THEME_MEDIA_QUERY).matches;
}

function applyTheme(mode: ThemeMode) {
  const resolvedTheme = resolveTheme(mode, getSystemPreference());
  const root = document.documentElement;

  root.dataset.themeMode = mode;
  root.dataset.theme = resolvedTheme;
  root.style.colorScheme = resolvedTheme;
  window.localStorage.setItem(THEME_STORAGE_KEY, mode);

  return resolvedTheme;
}

export function ThemeProvider({ children }: ThemeProviderProps) {
  const [themeMode, setThemeModeState] = useState<ThemeMode>('system');
  const [resolvedTheme, setResolvedTheme] = useState<ResolvedTheme>('dark');

  useEffect(() => {
    const root = document.documentElement;
    const domThemeMode = root.dataset.themeMode;
    const nextThemeMode = isThemeMode(domThemeMode) ? domThemeMode : 'system';
    const nextResolvedTheme = applyTheme(nextThemeMode);

    setThemeModeState(nextThemeMode);
    setResolvedTheme(nextResolvedTheme);
  }, []);

  useEffect(() => {
    const mediaQuery = window.matchMedia(THEME_MEDIA_QUERY);

    const handleChange = () => {
      if (themeMode !== 'system') {
        return;
      }

      setResolvedTheme(applyTheme('system'));
    };

    mediaQuery.addEventListener('change', handleChange);

    return () => {
      mediaQuery.removeEventListener('change', handleChange);
    };
  }, [themeMode]);

  const setThemeMode = useCallback((mode: ThemeMode) => {
    setThemeModeState(mode);
    setResolvedTheme(applyTheme(mode));
  }, []);

  const value = useMemo(
    () => ({
      themeMode,
      resolvedTheme,
      setThemeMode,
    }),
    [resolvedTheme, setThemeMode, themeMode],
  );

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

export function useTheme() {
  const context = useContext(ThemeContext);

  if (!context) {
    throw new Error('useTheme must be used within ThemeProvider');
  }

  return context;
}