/**
 * Individual School Page (SSR)
 * Dynamic route for school details with full SEO optimization
 * URL format: /school/138267-school-name-here
 */

import { APIFetchError, fetchSchoolDetails, fetchSchools, fetchNationalAverages } from '@/lib/api';
import { notFound, redirect } from 'next/navigation';
import { SchoolDetailShell } from '@/components/school/SchoolDetailShell';
import { NearbyPlaces } from '@/components/school/NearbyPlaces';
import { shouldRenderNearby } from '@/components/school/NearbySchoolsSection';
import { schoolBreadcrumbJsonLd, type SchoolPlace } from '@/lib/jsonld';
import { PrimarySchoolSections } from '@/components/school/PrimarySchoolSections';
import { SecondarySchoolSections } from '@/components/school/SecondarySchoolSections';
import {
  computeSchoolFlags, buildNavItems,
  computeSecondaryFlags, buildSecondaryNavItems,
} from '@/lib/schoolSections';
import { parseSchoolSlug, schoolUrl } from '@/lib/utils';
import type { NationalAverages } from '@/lib/types';
import { absoluteUrl } from '@/lib/site';
import type { Metadata } from 'next';

/**
 * Enumerate every school for static generation at build time.
 *
 * Set PRERENDER_SCHOOLS=1 in the build environment to enable. When disabled
 * (or when the API can't be reached), we return an empty list and the route
 * falls back to ISR on first request — `dynamicParams = true` covers it.
 */
export async function generateStaticParams(): Promise<Array<{ slug: string }>> {
  if (process.env.PRERENDER_SCHOOLS !== '1') return [];

  const params: Array<{ slug: string }> = [];
  const PAGE_SIZE = 500;
  let page = 1;
  let totalPages = 1;

  try {
    do {
      const res = await fetchSchools({ page, page_size: PAGE_SIZE });
      for (const s of res.schools) {
        const path = schoolUrl(s.urn, s.school_name);
        const slug = path.replace('/school/', '');
        params.push({ slug });
      }
      totalPages = res.total_pages || 1;
      page += 1;
    } while (page <= totalPages);
  } catch (error) {
    console.warn('generateStaticParams: API unreachable, falling back to on-demand ISR.', error);
    return [];
  }

  console.log(`generateStaticParams: prebuilding ${params.length} school pages.`);
  return params;
}

interface SchoolPageProps {
  params: Promise<{ slug: string }>;
}

export async function generateMetadata({ params }: SchoolPageProps): Promise<Metadata> {
  const { slug } = await params;
  const urn = parseSchoolSlug(slug);

  if (!urn || urn < 100000 || urn > 999999) {
    return {
      title: 'School Not Found',
    };
  }

  try {
    const data = await fetchSchoolDetails(urn);
    const { school_info } = data;

    const canonicalPath = schoolUrl(urn, school_info.school_name);
    const phaseStr = (school_info.phase ?? '').toLowerCase();
    const isAllThrough = phaseStr === 'all-through';
    const isSecondary = !isAllThrough && (
      phaseStr.includes('secondary')
      || (data.yearly_data ?? []).some((d: any) => d.attainment_8_score != null)
    );
    const la = school_info.local_authority ? ` in ${school_info.local_authority}` : '';
    const title = `${school_info.school_name} | ${school_info.local_authority || 'England'}`;
    const description = isAllThrough
      ? `View KS2 SATs and GCSE results for ${school_info.school_name}${la}. All-through school covering primary and secondary education.`
      : isSecondary
        ? `View GCSE results, Attainment 8, Progress 8 and school statistics for ${school_info.school_name}${la}.`
        : `View KS2 performance data, results, and statistics for ${school_info.school_name}${la}. Compare reading, writing, and maths results.`;

    return {
      title,
      description,
      keywords: isAllThrough
        ? `${school_info.school_name}, KS2 results, GCSE results, all-through school, ${school_info.local_authority}, SATs, Attainment 8`
        : isSecondary
          ? `${school_info.school_name}, GCSE results, secondary school, ${school_info.local_authority}, Attainment 8, Progress 8`
          : `${school_info.school_name}, KS2 results, primary school, ${school_info.local_authority}, school performance, SATs results`,
      openGraph: {
        title,
        description,
        type: 'website',
        url: absoluteUrl(canonicalPath),
        siteName: 'schoolcompare',
      },
      twitter: {
        card: 'summary',
        title,
        description,
      },
      alternates: {
        canonical: absoluteUrl(canonicalPath),
      },
    };
  } catch {
    return {
      title: 'School Not Found',
    };
  }
}

// ISR: regenerate at most once a week per slug. School data updates annually,
// so a 7-day cache is plenty and gives sub-100ms TTFB on cache hits.
export const revalidate = 604800;
export const dynamicParams = true;

export default async function SchoolPage({ params }: SchoolPageProps) {
  const { slug } = await params;
  const urn = parseSchoolSlug(slug);

  // Validate URN format
  if (!urn || urn < 100000 || urn > 999999) {
    notFound();
  }

  // Fetch school data. National averages feed the England-comparison deltas
  // across most sections; fetching them here rather than in a client effect
  // keeps those sections server-renderable and puts the deltas in the initial
  // HTML. They are supplementary, so they degrade to null rather than 404ing
  // the page.
  let data;
  let nationalAvg: NationalAverages | null = null;
  try {
    [data, nationalAvg] = await Promise.all([
      fetchSchoolDetails(urn),
      fetchNationalAverages().catch(() => null),
    ]);
  } catch (error) {
    if (error instanceof APIFetchError && error.status === 404) notFound();
    throw error;
  }

  const { school_info, yearly_data, absence_data, ofsted, census, admissions, admissions_history, admission_distance, deprivation, finance, destinations } = data;
  // Absent on an older API build; the module and the trail both degrade to
  // nothing rather than throwing, which is how this shipped without a
  // lockstep deploy of the two images.
  const places: SchoolPlace[] = data.places ?? [];
  // Absent on an older API build, exactly like `places` above.
  const nearbySchools = data.nearby_schools ?? [];

  // Redirect bare URN to canonical slug URL
  const canonicalSlug = schoolUrl(urn, school_info.school_name).replace('/school/', '');
  if (slug !== canonicalSlug) {
    redirect(`/school/${canonicalSlug}`);
  }

  const phaseStr = (school_info.phase ?? '').toLowerCase();
  const isAllThrough = phaseStr === 'all-through';
  // All-through schools go to PrimarySchoolSections (renders both KS2 + KS4).
  // SecondarySchoolSections is KS4-only, so all-through schools would lose SATs data.
  const isSecondary = !isAllThrough && (
    phaseStr.includes('secondary')
    || yearly_data.some((d: any) => d.attainment_8_score != null)
  );

  // Section list is computed on the server so the client shell never needs to
  // derive it -- and so it can never disagree with what the sections render.
  const sectionInput = {
    schoolInfo: school_info, yearlyData: yearly_data,
    absenceData: absence_data, census: census ?? null,
    deprivation: deprivation ?? null, finance: finance ?? null,
    destinations: destinations ?? null,
  };
  const primaryFlags = computeSchoolFlags(sectionInput);
  const secondaryFlags = computeSecondaryFlags(sectionInput);
  const navInput = {
    ofsted: ofsted ?? null,
    admissions: admissions ?? null,
    admissionDistance: admission_distance ?? null,
    hasLocation: school_info.latitude != null && school_info.longitude != null,
    hasNearbySchools: shouldRenderNearby(nearbySchools),
    yearlyDataLength: yearly_data.length,
  };
  const primaryNavItems = buildNavItems(primaryFlags, navInput);
  const secondaryNavItems = buildSecondaryNavItems(secondaryFlags, navInput);

  /*
   * `School`, not `EducationalOrganization`.
   *
   * Both are valid, but EducationalOrganization is the parent type covering
   * universities, training providers and nurseries alike. School is the
   * specific one, and a type that says what the page is about is the whole
   * point of declaring it. Google's own guidance treats the narrower type as
   * the correct choice where it applies.
   */
  const structuredData = {
    '@context': 'https://schema.org',
    '@graph': [{
    '@type': 'School',
    name: school_info.school_name,
    identifier: school_info.urn.toString(),
    ...(school_info.address && {
      address: {
        '@type': 'PostalAddress',
        streetAddress: school_info.address,
        addressLocality: school_info.local_authority || undefined,
        postalCode: school_info.postcode || undefined,
        addressCountry: 'GB',
      },
    }),
    ...(school_info.latitude && school_info.longitude && {
      geo: {
        '@type': 'GeoCoordinates',
        latitude: school_info.latitude,
        longitude: school_info.longitude,
      },
    }),
    ...(school_info.school_type && {
      additionalType: school_info.school_type,
    }),
    },
    // The trail the page sits at the end of. School pages carried no
    // breadcrumb at all, while every place page already emitted one.
    schoolBreadcrumbJsonLd({
      name: school_info.school_name,
      url: `/school/${slug}`,
      places,
    }),
    ],
  };

  return (
    <>
      <script
        type="application/ld+json"
        dangerouslySetInnerHTML={{ __html: JSON.stringify(structuredData) }}
      />
      {isSecondary ? (
        <SchoolDetailShell
          schoolInfo={school_info}
          yearlyData={yearly_data}
          census={census ?? null}
          navItems={secondaryNavItems}
        >
          <SecondarySchoolSections
            schoolInfo={school_info}
            yearlyData={yearly_data}
            absenceData={absence_data}
            ofsted={ofsted ?? null}
            census={census ?? null}
            admissions={admissions ?? null}
            admissionsHistory={admissions_history ?? []}
            admissionDistance={admission_distance}
            deprivation={deprivation ?? null}
            finance={finance ?? null}
            nationalAvg={nationalAvg}
            destinations={destinations ?? null}
            nearbySchools={nearbySchools}
            flags={secondaryFlags}
          />
        </SchoolDetailShell>
      ) : (
        <SchoolDetailShell
          schoolInfo={school_info}
          yearlyData={yearly_data}
          census={census ?? null}
          navItems={primaryNavItems}
        >
          <PrimarySchoolSections
            schoolInfo={school_info}
            yearlyData={yearly_data}
            absenceData={absence_data}
            ofsted={ofsted ?? null}
            census={census ?? null}
            admissions={admissions ?? null}
            admissionsHistory={admissions_history ?? []}
            admissionDistance={admission_distance ?? null}
            deprivation={deprivation ?? null}
            finance={finance ?? null}
            nationalAvg={nationalAvg}
            nearbySchools={nearbySchools}
            flags={primaryFlags}
          />
        </SchoolDetailShell>
      )}
      <NearbyPlaces places={places} />
    </>
  );
}