src/context/ThemeContext.tsx

"use client";

import * as React from "react";

type Theme = "dark" | "light";

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

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

/**
 * Theme Provider
 * Manages the dark/light mode for the RM Research Assistant workspace.
 */
export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = React.useState<Theme>("light");

  // Sync with system preferences or localStorage on mount
  React.useEffect(() => {
    const savedTheme = localStorage.getItem("theme") as Theme;
    const systemTheme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
    
    const initialTheme = savedTheme || systemTheme;
    setTheme(initialTheme);
    document.documentElement.classList.toggle("dark", initialTheme === "dark");
  }, []);

  const toggleTheme = React.useCallback(() => {
    setTheme((prev) => {
      const newTheme = prev === "light" ? "dark" : "light";
      localStorage.setItem("theme", newTheme);
      document.documentElement.classList.toggle("dark", newTheme === "dark");
      return newTheme;
    });
  }, []);

  return (
    <ThemeContext.Provider value={{ theme, toggleTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

export const useTheme = () => {
  const context = React.useContext(ThemeContext);
  if (!context) throw new Error("useTheme must be used within a ThemeProvider");
  return context;
};