frontend/src/context/ThemeContext.tsx

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

type Theme = "light" | "dark";

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

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

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setTheme] = useState<Theme>(() => {
    const saved = localStorage.getItem("agentgraph-theme");
    return (saved as Theme) || "light";
  });

  useEffect(() => {
    localStorage.setItem("agentgraph-theme", theme);

    // Update document class
    document.documentElement.classList.remove("light", "dark");
    document.documentElement.classList.add(theme);
  }, [theme]);

  const toggleTheme = () => {
    setTheme((prev) => (prev === "light" ? "dark" : "light"));
  };

  return (
    <ThemeContext.Provider value={{ theme, setTheme, toggleTheme }}>
      {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;
}