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

const ThemeProviderContext = createContext({
  theme: "system",
  setTheme: () => null,
});

export function ThemeProvider({
  children,
  defaultTheme = "system",
  storageKey = "pcfw-ui-theme",
  ...props
}) {
  const [theme, setTheme] = useState(
    () => localStorage.getItem(storageKey) || defaultTheme,
  );

  useEffect(() => {
    const root = window.document.documentElement;
    root.classList.remove("light", "dark");

    if (theme === "system") {
      const systemTheme = window.matchMedia("(prefers-color-scheme: dark)")
        .matches
        ? "dark"
        : "light";
      root.classList.add(systemTheme);
      return;
    }

    root.classList.add(theme);
  }, [theme]);

  return (
    <ThemeProviderContext.Provider
      {...props}
      value={{
        theme,
        setTheme: (theme) => {
          localStorage.setItem(storageKey, theme);
          setTheme(theme);
        },
      }}
    >
      {children}
    </ThemeProviderContext.Provider>
  );
}

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