1 files changed, 28 insertions, 0 deletions
diff --git a/frontend/src/lib/theme.ts b/frontend/src/lib/theme.ts
new file mode 100644
index 0000000..ad949a4
--- /dev/null
+++ b/frontend/src/lib/theme.ts
@@ -0,0 +1,28 @@
+// 主题切换（round3）：默认 mint；.theme-amber 类挂 <html> 切到 amber 变量组。
+// 两套 token 都是 app.css 里的 CSS 变量组，本模块只负责持久化与挂类。
+
+export type BrandTheme = 'mint' | 'amber';
+const KEY = 'sl-brand-theme';
+
+export function currentTheme(): BrandTheme {
+  if (typeof document === 'undefined' || typeof localStorage === 'undefined') return 'mint';
+  const stored = localStorage.getItem(KEY);
+  return stored === 'amber' ? 'amber' : 'mint';
+}
+
+export function applyTheme(t: BrandTheme): void {
+  if (typeof document === 'undefined') return;
+  if (t === 'amber') document.documentElement.classList.add('theme-amber');
+  else document.documentElement.classList.remove('theme-amber');
+  if (typeof localStorage !== 'undefined') localStorage.setItem(KEY, t);
+}
+
+export function toggleTheme(): BrandTheme {
+  const next: BrandTheme = currentTheme() === 'mint' ? 'amber' : 'mint';
+  applyTheme(next);
+  return next;
+}
+
+if (typeof document !== 'undefined') {
+  applyTheme(currentTheme());
+}