school_compare/nextjs-app/app/(frontend)/compare/page.tsx

/**
 * Compare Page (SSR)
 * Side-by-side comparison of schools with metrics
 */

import { fetchComparison, fetchMetrics } from '@/lib/api';
import { ComparisonView } from '@/components/ComparisonView';
import { absoluteUrl } from '@/lib/site';
import type { Metadata } from 'next';

interface ComparePageProps {
  searchParams: Promise<{
    urns?: string;
    metric?: string;
  }>;
}

/**
 * Indexability depends on the query string, so this cannot be a static export.
 *
 * Bare /compare is the landing page for the "compare schools" head term and
 * stays indexable. /compare?urns=… is an unbounded parameter space — 25,193
 * schools make ~317 million pairs — so it goes noindex. It stays `follow` and
 * keeps a canonical to the bare path, so the links out to each school page
 * still count.
 */
export async function generateMetadata(
  { searchParams }: ComparePageProps,
): Promise<Metadata> {
  const { urns } = await searchParams;

  const base: Metadata = {
    // Deliberately not the homepage's phrase. Two pages chasing "compare
    // schools" is how a site competes with itself; this one takes the tool
    // phrasing instead.
    title: 'School Comparison Tool: Primary and Secondary Schools | schoolcompare',
    description:
      'Put up to five primary and five secondary schools in England in one table: SATs and GCSE results against the England average, Ofsted grades, and the distance places were offered.',
    keywords:
      'school comparison, compare schools, Ofsted comparison, school admissions, KS2 comparison, primary school performance',
    alternates: { canonical: absoluteUrl('/compare') },
  };

  if (!urns) return base;

  return { ...base, robots: { index: false, follow: true } };
}

// Dynamic via searchParams; remove force-dynamic so internal data fetches
// can still use Next.js's per-call revalidate cache.

export default async function ComparePage({ searchParams }: ComparePageProps) {
  const { urns: urnsParam, metric: metricParam } = await searchParams;

  const urns = urnsParam?.split(',').map(Number).filter(Boolean) || [];
  const selectedMetric = metricParam || 'rwm_expected_pct';

  try {
    // Fetch comparison + metrics in parallel — they are independent.
    const [comparisonResponse, metricsResponse] = await Promise.all([
      urns.length > 0
        ? fetchComparison(urnsParam!).catch((error) => {
            console.error('Failed to fetch comparison:', error);
            return null;
          })
        : Promise.resolve(null),
      fetchMetrics(),
    ]);

    const metricsArray = metricsResponse?.metrics || [];

    return (
      <ComparisonView
        initialData={comparisonResponse?.comparison ?? null}
        initialNationalAverages={comparisonResponse?.national_averages}
        initialBenchmarks={comparisonResponse?.benchmarks}
        initialUrns={urns}
        metrics={metricsArray}
        selectedMetric={selectedMetric}
      />
    );
  } catch (error) {
    console.error('Error fetching data for compare page:', error);

    // Return error state with empty metrics
    return (
      <ComparisonView
        initialData={null}
        initialUrns={urns}
        metrics={[]}
        selectedMetric={selectedMetric}
      />
    );
  }
}