feat(web): enable Continue with Google auth buttons

apps/web/src/app/(auth)/login/page.tsx

@@ -11,6 +11,11 @@ import { Input } from "@/components/ui/Input";
 import { Button } from "@/components/ui/Button";
 import { PageLoadingState } from "@/components/ui/brand-loader";
 import { api, type ApiError } from "@/lib/api";
+import {
+  buildGoogleOAuthStartUrl,
+  getGoogleAuthErrorMessage,
+  getSafeAuthRedirect,
+} from "@/lib/auth";
 
 const loginSchema = z.object({
   email: z.string().email("Enter a valid email address"),
@@ -21,18 +26,6 @@ type LoginFields = z.infer<typeof loginSchema>;
 
 const DEFAULT_LOGIN_DESTINATION = "/home";
 
-function getSafeRedirectDestination(value: string | null): string | null {
-  if (!value || !value.startsWith("/") || value.startsWith("//")) {
-    return null;
-  }
-
-  if (value === "/login" || value.startsWith("/login?")) {
-    return null;
-  }
-
-  return value;
-}
-
 function LoginForm() {
   const router = useRouter();
   const searchParams = useSearchParams();
@@ -49,9 +42,10 @@ function LoginForm() {
     setServerError(null);
     try {
       await api.post("/auth/login", data);
-      const destination =
-        getSafeRedirectDestination(searchParams.get("redirect")) ??
-        DEFAULT_LOGIN_DESTINATION;
+      const destination = getSafeAuthRedirect(
+        searchParams.get("redirect"),
+        DEFAULT_LOGIN_DESTINATION,
+      );
       router.push(destination);
     } catch (err) {
       setServerError(
@@ -60,6 +54,17 @@ function LoginForm() {
     }
   };
 
+  const handleGoogleSignIn = () => {
+    const destination = getSafeAuthRedirect(
+      searchParams.get("redirect"),
+      DEFAULT_LOGIN_DESTINATION,
+    );
+    window.location.assign(buildGoogleOAuthStartUrl(destination));
+  };
+
+  const oauthError = getGoogleAuthErrorMessage(searchParams.get("error"));
+  const visibleError = serverError ?? oauthError;
+
   return (
     <div>
       <h1 className="font-cabinet font-bold text-2xl text-[var(--color-espresso)] mb-1">
@@ -69,6 +74,31 @@ function LoginForm() {
         Sign in to your twizrr account.
       </p>
 
+      <div className="mb-6 flex flex-col gap-3">
+        <Button
+          type="button"
+          variant="secondary"
+          fullWidth
+          size="lg"
+          onClick={handleGoogleSignIn}
+        >
+          Continue with Google
+        </Button>
+
+        <p className="text-center text-xs text-muted-foreground font-cabinet">
+          Google verifies your email. Phone verification may still be required
+          before checkout.
+        </p>
+
+        <div className="relative flex items-center gap-3 py-1">
+          <div className="flex-1 h-px bg-[var(--border)]" />
+          <span className="text-xs text-muted-foreground font-cabinet shrink-0">
+            or
+          </span>
+          <div className="flex-1 h-px bg-[var(--border)]" />
+        </div>
+      </div>
+
       <form
         onSubmit={handleSubmit(onSubmit)}
         noValidate
@@ -116,12 +146,12 @@ function LoginForm() {
           </Link>
         </div>
 
-        {serverError && (
+        {visibleError && (
           <p
             role="alert"
             className="text-sm text-[var(--color-error)] font-cabinet rounded-md bg-[var(--color-error)]/10 px-3 py-2"
           >
-            {serverError}
+            {visibleError}
           </p>
         )}
 

apps/web/src/app/(auth)/register/page.tsx

@@ -1,15 +1,21 @@
 "use client";
 
-import { useState } from "react";
+import { Suspense, useState } from "react";
 import { useForm, type SubmitHandler } from "react-hook-form";
 import { zodResolver } from "@hookform/resolvers/zod";
 import { z } from "zod";
 import Link from "next/link";
-import { useRouter } from "next/navigation";
+import { useRouter, useSearchParams } from "next/navigation";
 import { ArrowLeft, Eye, EyeOff } from "lucide-react";
 import { Input } from "@/components/ui/Input";
 import { Button } from "@/components/ui/Button";
+import { PageLoadingState } from "@/components/ui/brand-loader";
 import { api, type ApiError } from "@/lib/api";
+import {
+  buildGoogleOAuthStartUrl,
+  getGoogleAuthErrorMessage,
+  getSafeAuthRedirect,
+} from "@/lib/auth";
 
 function calcAge(dobString: string): number {
   const dob = new Date(dobString);
@@ -120,8 +126,11 @@ function StepProgress({ step, total }: { step: number; total: number }) {
   );
 }
 
-export default function RegisterPage() {
+const DEFAULT_REGISTER_DESTINATION = "/explore";
+
+function RegisterForm() {
   const router = useRouter();
+  const searchParams = useSearchParams();
 
   const [step, setStep] = useState(1);
   const [serverError, setServerError] = useState<string | null>(null);
@@ -150,6 +159,14 @@ export default function RegisterPage() {
     router.push(`/verify-email?${params.toString()}`);
   }
 
+  function startGoogleAuth() {
+    const destination = getSafeAuthRedirect(
+      searchParams.get("redirect"),
+      DEFAULT_REGISTER_DESTINATION,
+    );
+    window.location.assign(buildGoogleOAuthStartUrl(destination));
+  }
+
   const form2 = useForm<Step2Fields>({
     resolver: zodResolver(step2Schema),
     defaultValues: { email: data.email, password: data.password },
@@ -210,6 +227,8 @@ export default function RegisterPage() {
     }
   };
 
+  const oauthError = getGoogleAuthErrorMessage(searchParams.get("error"));
+
   return (
     <div>
       {step > 1 && (
@@ -235,13 +254,32 @@ export default function RegisterPage() {
           </p>
 
           <div className="flex flex-col gap-3">
-            <Button variant="secondary" fullWidth size="lg" disabled>
-              Continue with Google - coming soon
+            <Button
+              type="button"
+              variant="secondary"
+              fullWidth
+              size="lg"
+              onClick={startGoogleAuth}
+            >
+              Continue with Google
             </Button>
+            <p className="text-center text-xs text-muted-foreground font-cabinet">
+              Google verifies your email. Phone verification may still be
+              required before checkout.
+            </p>
             <Button variant="secondary" fullWidth size="lg" disabled>
               Continue with Apple - coming soon
             </Button>
 
+            {oauthError && (
+              <p
+                role="alert"
+                className="text-sm text-[var(--color-error)] font-cabinet rounded-md bg-[var(--color-error)]/10 px-3 py-2"
+              >
+                {oauthError}
+              </p>
+            )}
+
             <div className="relative flex items-center gap-3 py-1">
               <div className="flex-1 h-px bg-[var(--border)]" />
               <span className="text-xs text-muted-foreground font-cabinet shrink-0">
@@ -459,3 +497,11 @@ export default function RegisterPage() {
     </div>
   );
 }
+
+export default function RegisterPage() {
+  return (
+    <Suspense fallback={<PageLoadingState label="Loading registration..." />}>
+      <RegisterForm />
+    </Suspense>
+  );
+}

apps/web/src/lib/auth.ts

@@ -1,5 +1,14 @@
 import { api } from "@/lib/api";
 
+const API_BASE = (process.env.NEXT_PUBLIC_API_URL ?? "").replace(/\/$/, "");
+
+const AUTH_ROUTE_PREFIXES = [
+  "/login",
+  "/register",
+  "/forgot-password",
+  "/verify-email",
+];
+
 export type GoogleOnboardingPrefill = {
   providerEmail: string;
   providerEmailVerified: boolean;
@@ -20,6 +29,51 @@ export type CompleteGoogleOnboardingResponse = {
   redirectTo: string;
 };
 
+export function getSafeAuthRedirect(
+  value: string | null | undefined,
+  fallback: string,
+): string {
+  if (!value || !value.startsWith("/") || value.startsWith("//")) {
+    return fallback;
+  }
+
+  if (AUTH_ROUTE_PREFIXES.some((prefix) => value.startsWith(prefix))) {
+    return fallback;
+  }
+
+  return value;
+}
+
+export function buildGoogleOAuthStartUrl(redirectPath: string): string {
+  const params = new URLSearchParams({ redirect: redirectPath });
+  return `${API_BASE}/auth/google?${params.toString()}`;
+}
+
+export function getGoogleAuthErrorMessage(error: string | null): string | null {
+  if (!error) {
+    return null;
+  }
+
+  const normalized = error.trim().toUpperCase();
+
+  if (
+    normalized.includes("EMAIL") &&
+    (normalized.includes("UNVERIFIED") || normalized.includes("NOT_VERIFIED"))
+  ) {
+    return "Google email must be verified.";
+  }
+
+  if (normalized.includes("SESSION") || normalized.includes("EXPIRED")) {
+    return "Google session expired. Please try again.";
+  }
+
+  if (normalized.includes("GOOGLE") || normalized.includes("OAUTH")) {
+    return "Google sign-in failed. Please try again.";
+  }
+
+  return "Authentication failed. Please try again.";
+}
+
 export function getGoogleOnboardingPrefill(
   sessionId: string,
 ): Promise<GoogleOnboardingPrefill> {