import React, { createContext, useContext, useEffect, useState } from "react";

type Theme = "dark" | "light" | "system";

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

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

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

const ThemeProviderContext = createContext<ThemeProviderState>(initialState);

export function ThemeProvider({
  children,
  defaultTheme = "system",
  storageKey = "vite-ui-theme",
  ...props
}: ThemeProviderProps) {
  const [theme, setTheme] = React.useState<Theme>(
    () => {
      if (typeof window !== 'undefined') {
        return (localStorage.getItem(storageKey) as Theme) || defaultTheme;
      }
      return defaultTheme;
    }
  );

  React.useEffect(() => {
    if (typeof window !== 'undefined') {
      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: (newTheme: Theme) => {
      if (typeof window !== 'undefined') {
        localStorage.setItem(storageKey, newTheme);
      }
      setTheme(newTheme);
    },
  };

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

export const useTheme = () => {
  const context = React.useContext(ThemeProviderContext);

  if (context === undefined)
    throw new Error("useTheme must be used within a ThemeProvider");

  return context;
};