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

export type ThemeTypes = 'dark' | 'light' | 'system';

type ThemeProviderProps = {
  children: React.ReactNode;
  defaultTheme?: ThemeTypes;
  storageKey?: string;
};

type ThemeProviderState = {
  theme: ThemeTypes;
  setTheme: (theme: ThemeTypes) => void;
};

const initialState: ThemeProviderState = {
  theme: 'system' as ThemeTypes,
  setTheme: () => null,
};

const ThemeProviderContext = createContext<ThemeProviderState>(initialState);

export function ThemeProvider({ children, defaultTheme = 'system', storageKey = 'vite-ui-theme', ...props }: ThemeProviderProps) {
  const [theme, setTheme] = useState<ThemeTypes>(() => {
    const stored = localStorage.getItem(storageKey);
    if (stored && ['dark', 'light', 'system'].includes(stored)) {
      return stored as ThemeTypes;
    }
    return 'system';
  });

  useEffect(() => {
    const root = window.document.documentElement;

    root.classList.remove('light', 'dark');

    if (theme === 'system') {
      const systemTheme = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
      root.classList.add(systemTheme);
      return;
    }

    root.classList.add(theme);
  }, [theme]);

  const value = {
    theme,
    setTheme: (theme: ThemeTypes) => {
      localStorage.setItem(storageKey, theme);
      setTheme(theme);
    },
  };

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

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