"use client";

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

type Theme = "light" | "dark";

const ThemeContext = createContext<{
  theme: Theme;
  setTheme: (t: Theme) => void;
  toggle: () => void;
}>({
  theme: "light",
  setTheme: () => {},
  toggle: () => {},
});

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setThemeState] = useState<Theme>("light");
  const [mounted, setMounted] = useState(false);

  useEffect(() => {
    // Read from localStorage, fall back to system preference
    const stored = localStorage.getItem("theme") as Theme | null;
    if (stored === "dark" || stored === "light") {
      setThemeState(stored);
    } else if (window.matchMedia("(prefers-color-scheme: dark)").matches) {
      setThemeState("dark");
    }
    setMounted(true);
  }, []);

  useEffect(() => {
    if (!mounted) return;
    document.documentElement.classList.toggle("dark", theme === "dark");
    localStorage.setItem("theme", theme);
  }, [theme, mounted]);

  const setTheme = (t: Theme) => setThemeState(t);
  const toggle = () => setThemeState((t) => (t === "dark" ? "light" : "dark"));

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

export function useTheme() {
  return useContext(ThemeContext);
}