AgentCompany/landing/components/theme/theme-provider.tsx

"use client";

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

const storageKey = "agentcompany-theme";

type ThemeMode = "light" | "dark";

type ThemeContextValue = {
  theme: ThemeMode;
  setTheme: (theme: ThemeMode) => void;
  toggleTheme: () => void;
};

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

function resolveTheme(): ThemeMode {
  if (typeof window === "undefined") {
    return "light";
  }

  const stored = localStorage.getItem(storageKey);
  if (stored === "light" || stored === "dark") {
    return stored;
  }

  return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
}

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setThemeState] = useState<ThemeMode>(resolveTheme);

  useEffect(() => {
    const root = document.documentElement;
    if (theme === "dark") {
      root.classList.add("dark");
    } else {
      root.classList.remove("dark");
    }
    localStorage.setItem(storageKey, theme);
  }, [theme]);

  useEffect(() => {
    const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
    const handleChange = (event: MediaQueryListEvent) => {
      if (!localStorage.getItem(storageKey)) {
        setThemeState(event.matches ? "dark" : "light");
      }
    };

    mediaQuery.addEventListener("change", handleChange);
    return () => mediaQuery.removeEventListener("change", handleChange);
  }, []);

  const setTheme = useCallback((nextTheme: ThemeMode) => {
    setThemeState(nextTheme);
  }, []);

  const toggleTheme = useCallback(() => {
    setThemeState((currentTheme) => (currentTheme === "light" ? "dark" : "light"));
  }, []);

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

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