feat: add persistent responsive color themes

src/presentation/providers/theme-provider.jsx

@@ -0,0 +1,86 @@
+import {
+  createContext,
+  useContext,
+  useEffect,
+  useLayoutEffect,
+  useMemo,
+  useState,
+} from "react";
+
+import {
+  normalizeColorSchemePreference,
+  resolveColorScheme,
+} from "../../application/policies/color-scheme.js";
+
+/**
+ * @typedef {{
+ *   preference: "system" | "light" | "dark",
+ *   resolvedTheme: "light" | "dark",
+ *   setPreference: (preference: "system" | "light" | "dark") => void
+ * }} ThemeContextValue
+ */
+
+const ThemeContext = createContext(/** @type {ThemeContextValue | null} */ (null));
+
+function systemPrefersDark() {
+  return (
+    typeof window.matchMedia === "function" &&
+    window.matchMedia("(prefers-color-scheme: dark)").matches
+  );
+}
+
+/**
+ * @param {{
+ *   storage?: import("../../application/ports/storage-port.js").StoragePort,
+ *   children: React.ReactNode
+ * }} props
+ */
+export function ThemeProvider({ storage, children }) {
+  const [preference, updatePreference] = useState(() => {
+    const result = storage?.read("COLOR_SCHEME");
+    return normalizeColorSchemePreference(
+      result?.ok ? result.value : undefined,
+    );
+  });
+  const [darkSystemTheme, setDarkSystemTheme] = useState(systemPrefersDark);
+  const resolvedTheme = resolveColorScheme(preference, darkSystemTheme);
+
+  useEffect(() => {
+    if (typeof window.matchMedia !== "function") return undefined;
+    const query = window.matchMedia("(prefers-color-scheme: dark)");
+    /** @param {MediaQueryListEvent} event */
+    const update = (event) => setDarkSystemTheme(event.matches);
+    setDarkSystemTheme(query.matches);
+    query.addEventListener("change", update);
+    return () => query.removeEventListener("change", update);
+  }, []);
+
+  useLayoutEffect(() => {
+    document.documentElement.dataset.theme = resolvedTheme;
+    document.documentElement.dataset.themePreference = preference;
+    document.documentElement.style.colorScheme = resolvedTheme;
+  }, [preference, resolvedTheme]);
+
+  const value = useMemo(
+    () =>
+      Object.freeze({
+        preference,
+        resolvedTheme,
+        /** @param {"system" | "light" | "dark"} next */
+        setPreference(next) {
+          const normalized = normalizeColorSchemePreference(next);
+          updatePreference(normalized);
+          storage?.write("COLOR_SCHEME", normalized);
+        },
+      }),
+    [preference, resolvedTheme, storage],
+  );
+
+  return <ThemeContext.Provider value={value}>{children}</ThemeContext.Provider>;
+}
+
+export function useTheme() {
+  const theme = useContext(ThemeContext);
+  if (!theme) throw new Error("ThemeProvider is required");
+  return theme;
+}