frontend/src/components/layout/ModeToggle.tsx

import { Moon, Sun } from "lucide-react";
import { useEffect, useState } from "react";
import { Button } from "@/components/ui/button";

export function ModeToggle() {
  const [theme, setTheme] = useState(() => {
    // Check local storage or default to system preference
    const storedTheme = localStorage.getItem("theme");
    if (storedTheme) return storedTheme;
    
    return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
  });
  
  useEffect(() => {
    const root = window.document.documentElement;
    
    if (theme === "dark") {
      root.classList.add("dark");
    } else {
      root.classList.remove("dark");
    }
    
    localStorage.setItem("theme", theme);
  }, [theme]);
  
  const toggleTheme = () => {
    setTheme(theme === "light" ? "dark" : "light");
  };
  
  return (
    <Button variant="outline" size="icon" onClick={toggleTheme} className="h-9 w-9">
      <Sun className="h-4 w-4 rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
      <Moon className="absolute h-4 w-4 rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100" />
      <span className="sr-only">Toggle theme</span>
    </Button>
  );
}