feat: src/useTheme.ts (#12)

Author: tapiwamakandigona

src/useTheme.ts

@@ -0,0 +1,19 @@
+import { useState, useEffect } from "react";
+
+export type Theme = "dark" | "light";
+
+export function useTheme(): [Theme, () => void] {
+  const [theme, setTheme] = useState<Theme>(() => {
+    const saved = localStorage.getItem("theme");
+    if (saved === "light" || saved === "dark") return saved;
+    return window.matchMedia("(prefers-color-scheme: light)").matches ? "light" : "dark";
+  });
+
+  useEffect(() => {
+    document.documentElement.setAttribute("data-theme", theme);
+    localStorage.setItem("theme", theme);
+  }, [theme]);
+
+  const toggle = () => setTheme(prev => prev === "dark" ? "light" : "dark");
+  return [theme, toggle];
+}