/**
 * Home Page (SSR)
 * Main landing page with school search and browsing
 */

import { absoluteUrl } from '@/lib/site';
import type { Metadata } from 'next';
import { headers } from 'next/headers';
import { isHandheldUserAgent } from '@/lib/device';
import { fetchSchools, fetchFilters, fetchDataInfo } from '@/lib/api';
import { formatAcademicYear } from '@/lib/utils';
import { HomeView } from '@/components/HomeView';
import { getFlags } from '@/lib/flags';
import { HowItWorksSection } from '@/components/HowItWorksSection';
import { EditorialSection } from '@/components/EditorialSection';

interface HomePageProps {
  searchParams: Promise<{
    search?: string;
    local_authority?: string;
    school_type?: string;
    phase?: string;
    page?: string;
    postcode?: string;
    radius?: string;
    sort?: string;
    gender?: string;
    admissions_policy?: string;
    has_sixth_form?: string;
  }>;
}

/*
 * `title` was the bare string 'Home', which is what the browser tab, the
 * bookmark and the search result all read. `absolute` opts out of the root
 * layout's "%s | schoolcompare" template so the homepage doesn't end up
 * saying the brand twice.
 */
export const metadata: Metadata = {
  /*
   * Intent in the title, differentiator in the description.
   *
   * These queries are owned by the DfE's own "Compare school performance"
   * service, and the old title — brand first, then a near-paraphrase of that
   * service's name — gave a searcher no reason to pick us over it. It drew
   * 0.43% CTR at position 6.1 while the brand query drew 9.16% from the same
   * neighbourhood, so the ranking was never the problem.
   *
   * The title now matches what people type. The description carries the one
   * fact gov.uk does not publish: how close you had to live to get a place.
   */
  title: { absolute: 'Compare Schools Side by Side | schoolcompare' },
  description:
    'Put five English schools on one screen: SATs, GCSE results, Ofsted grades, and how close you had to live to get a place. Free, no sign-up.',
  // This page reads eleven search params. They filter a result set; they do
  // not make a new document. Collapsing every combination onto "/" stops the
  // homepage competing with itself for its own head terms.
  alternates: { canonical: absoluteUrl('/') },
};

// The page reads searchParams, which makes rendering dynamic by default.
// We don't use `force-dynamic` here so the internal filter/data-info fetches
// can still hit Next.js's data cache (configured per-call in lib/api.ts).

export default async function HomePage({ searchParams }: HomePageProps) {
  // Await search params (Next.js 15 requirement)
  const params = await searchParams;

  // Server-read: no flag value reaches the browser bundle. Threaded down to
  // both FilterBar instances via HomeView.
  const flags = await getFlags();
  const autosuggest = flags.school_autosuggest === true;

  // Parse search params
  const page = parseInt(params.page || '1');
  const radius = params.radius ? parseFloat(params.radius) : undefined;

  // Check if user has performed a search
  const hasSearchParams = !!(
    params.search ||
    params.local_authority ||
    params.school_type ||
    params.phase ||
    params.postcode ||
    params.gender ||
    params.admissions_policy ||
    params.has_sixth_form
  );

  // Failures propagate to the retryable error boundary.
  const [filtersData, dataInfo] = await Promise.all([fetchFilters(), fetchDataInfo().catch(() => null)]);

  // Only fetch schools if there are search parameters
  let schoolsData;
  if (hasSearchParams) {
    schoolsData = await fetchSchools({
      search: params.search,
      local_authority: params.local_authority,
      school_type: params.school_type,
      phase: params.phase,
      postcode: params.postcode,
      radius,
      page,
      page_size: 50,
      gender: params.gender,
      admissions_policy: params.admissions_policy,
      has_sixth_form: params.has_sixth_form,
    });
  } else {
    // Empty state by default
    schoolsData = { schools: [], page: 1, page_size: 50, total: 0, total_pages: 0 };
  }

  const resolvedFilters = filtersData || { local_authorities: [], school_types: [], years: [], phases: [], genders: [], admissions_policies: [] };
  // `unique_schools`, not `total_schools` — the latter is not a field this
  // endpoint returns, and reading it silently yielded null on every request.
  const total = dataInfo?.unique_schools ?? null;
  const years = dataInfo?.years_available ?? [];
  /*
   * A postcode search opens on the map for desktop browsers and on the list
   * for phones and tablets. The user agent is the only signal available
   * before the first paint; HomeView falls back to the list if the window
   * turns out too narrow, so a wrong guess costs one swap, not a broken page.
   */
  const initialView = params.postcode
    && !isHandheldUserAgent((await headers()).get('user-agent'))
    ? 'map' : 'list';

  return (
    <HomeView
      autosuggest={autosuggest}
      initialView={initialView}
      initialSchools={schoolsData}
      filters={resolvedFilters}
      totalSchools={total}
      howItWorks={hasSearchParams ? null : <HowItWorksSection />}
      editorial={hasSearchParams ? null : (
        <EditorialSection
          totalSchools={total}
          localAuthorityCount={resolvedFilters.local_authorities.length}
          earliestYearLabel={years.length ? formatAcademicYear(years[0]) : null}
          latestYearLabel={years.length ? formatAcademicYear(years[years.length - 1]) : null}
        />
      )}
    />
  );
}