add captcha support

src/services/captcha.ts

@@ -0,0 +1,28 @@
+import { conf } from '@/config';
+import { StatusError } from '@/services/error';
+
+export async function isValidCaptcha(token: string): Promise<boolean> {
+  if (!conf.captcha.secret)
+    throw new Error('isValidCaptcha() is called but no secret set');
+  const res = await fetch('https://www.google.com/recaptcha/api/siteverify', {
+    method: 'POST',
+    body: JSON.stringify({
+      secret: conf.captcha.secret,
+      response: token,
+    }),
+    headers: {
+      'content-type': 'application/json',
+    },
+  });
+  const json = await res.json();
+  return !!json.success;
+}
+
+export async function assertCaptcha(token?: string) {
+  // early return if captchas arent enabled
+  if (!conf.captcha.enabled) return;
+  if (!token) throw new StatusError('captcha token is required', 400);
+
+  const isValid = await isValidCaptcha(token);
+  if (!isValid) throw new StatusError('captcha token is invalid', 400);
+}