edr-platform/apps/edr-freight-web/backoffice/src/shared/hooks/useDarkMode.ts

import { useEffect, useState } from "react";

// Same storage key/values as main.tsx and FreightDashboardLayout so the
// vendored IAM UI toggle and the host dashboard toggle stay in sync.
const THEME_STORAGE_KEY = "edr-theme";

export const useDarkMode = () => {
  const [isDarkMode, setIsDarkMode] = useState(() => {
    // Initialize from localStorage or system preference
    const savedTheme = localStorage.getItem(THEME_STORAGE_KEY);
    if (savedTheme === "dark" || savedTheme === "light") {
      return savedTheme === "dark";
    }
    return window.matchMedia("(prefers-color-scheme: dark)").matches;
  });

  useEffect(() => {
    // Apply dark mode class on mount and when isDarkMode changes
    if (isDarkMode) {
      document.documentElement.classList.add("dark");
      localStorage.setItem(THEME_STORAGE_KEY, "dark");
    } else {
      document.documentElement.classList.remove("dark");
      localStorage.setItem(THEME_STORAGE_KEY, "light");
    }
  }, [isDarkMode]);

  const toggleDarkMode = () => {
    setIsDarkMode((prev) => !prev);
  };

  return { isDarkMode, toggleDarkMode };
};