Use optimistic checkout redirect URL loading strategy to improve checkout load time

.changeset/cute-spies-talk.md

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+---
+"@bigcommerce/catalyst-core": minor
+---
+
+Use optimistic checkout redirect URL loading strategy to improve checkout load time

core/app/[locale]/(default)/cart/_actions/generate-checkout-url.ts

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+'use server';
+
+import { getSessionCustomerAccessToken } from '~/auth';
+import { getChannelIdFromLocale } from '~/channels.config';
+import { client } from '~/client';
+import { graphql } from '~/client/graphql';
+import { getVisitIdCookie, getVisitorIdCookie } from '~/lib/analytics/bigcommerce';
+
+const CheckoutRedirectMutation = graphql(`
+  mutation CheckoutRedirectMutation($cartId: String!, $visitId: UUID, $visitorId: UUID) {
+    cart {
+      createCartRedirectUrls(
+        input: { cartEntityId: $cartId, visitId: $visitId, visitorId: $visitorId }
+      ) {
+        errors {
+          ... on NotFoundError {
+            __typename
+          }
+        }
+        redirectUrls {
+          redirectedCheckoutUrl
+        }
+      }
+    }
+  }
+`);
+
+export interface GenerateCheckoutUrlResult {
+  url: string | null;
+  error?: string;
+}
+
+export async function generateCheckoutUrl(
+  cartId: string,
+  locale: string,
+): Promise<GenerateCheckoutUrlResult> {
+  try {
+    const customerAccessToken = await getSessionCustomerAccessToken();
+    const channelId = getChannelIdFromLocale(locale);
+    const visitId = await getVisitIdCookie();
+    const visitorId = await getVisitorIdCookie();
+
+    const { data } = await client.fetch({
+      document: CheckoutRedirectMutation,
+      variables: { cartId, visitId, visitorId },
+      fetchOptions: { cache: 'no-store' },
+      customerAccessToken,
+      channelId,
+    });
+
+    if (
+      data.cart.createCartRedirectUrls.errors.length > 0 ||
+      !data.cart.createCartRedirectUrls.redirectUrls
+    ) {
+      return { url: null, error: 'Failed to generate checkout URL' };
+    }
+
+    return { url: data.cart.createCartRedirectUrls.redirectUrls.redirectedCheckoutUrl };
+  } catch (error) {
+    // eslint-disable-next-line no-console
+    console.error('Error generating checkout URL:', error);
+
+    return { url: null, error: 'Failed to generate checkout URL' };
+  }
+}

core/app/[locale]/(default)/cart/_components/optimized-cart.tsx

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+'use client';
+
+import { SubmissionResult } from '@conform-to/react';
+import { useEffect, useState } from 'react';
+
+import {
+  CartClient as CartComponent,
+  CartLineItem,
+  CartProps,
+} from '@/vibes/soul/sections/cart/client';
+import { useRouter } from '~/i18n/routing';
+import { isCheckoutUrlValid } from '~/lib/checkout-url-utils';
+
+type CheckoutAction = (
+  lastResult: SubmissionResult | null,
+  formData: FormData,
+) => Promise<SubmissionResult | null>;
+
+interface OptimizedCartProps<LineItem extends CartLineItem> {
+  preGeneratedUrl: string | null;
+  fallbackAction: CheckoutAction;
+  cartProps: CartProps<LineItem>;
+}
+
+export function OptimizedCart<LineItem extends CartLineItem>({
+  preGeneratedUrl,
+  fallbackAction,
+  cartProps,
+}: OptimizedCartProps<LineItem>) {
+  const router = useRouter();
+  const [checkoutUrl, setCheckoutUrl] = useState<string | null>(preGeneratedUrl);
+  const [pageLoadTime] = useState(() => Date.now()); // Capture when this component first mounted
+
+  // Update the stored URL if a new one is provided
+  useEffect(() => {
+    setCheckoutUrl(preGeneratedUrl);
+  }, [preGeneratedUrl]);
+
+  // Custom action that checks URL validity before redirecting
+  const optimizedCheckoutAction: CheckoutAction = async (lastResult, formData) => {
+    // Check if we have a valid pre-generated URL (accounting for clock skew and page load time)
+    if (checkoutUrl && isCheckoutUrlValid(checkoutUrl, pageLoadTime)) {
+      // Direct client-side redirect for better performance
+      router.push(checkoutUrl);
+
+      // Return null to prevent further processing
+      return null;
+    }
+
+    // Fall back to the original server action if URL is invalid or missing
+    return fallbackAction(lastResult, formData);
+  };
+
+  return <CartComponent {...cartProps} checkoutAction={optimizedCheckoutAction} />;
+}