import type { Metadata } from 'next';
import Link from 'next/link';
import { PageHeader, Section, Note } from '@/components/ui/section';
import { EmptyState } from '@/components/ui/empty-state';
import { Freshness } from '@/components/ui/freshness';
import { Badge } from '@/components/ui/badge';
import { SourceBadge } from '@/components/ui/source-badge';
import { listGeographiesWithObservations, topCancersFor, allSitesObservations, WHO_REGION_LABEL } from '@/lib/queries/geography';
import { listSources } from '@/lib/queries/sources';
import { fmtInt, fmtValue, humanize, toDate, unitLabel } from '@/lib/format';

export const metadata: Metadata = {
  title: 'Countries',
  description: 'Geographies with cancer epidemiology observations in CancerIndex: years covered, sources, and the latest-year figures per country.',
  alternates: { canonical: '/countries' },
};
export const revalidate = 3600;

/**
 * /countries (§47): every geography that carries at least one epidemiology observation, with its year span,
 * the sources behind it and either the all-sites totals (when the source publishes one) or the top cancer by
 * deaths / new cases for the latest year. Geographies without data are not listed — nothing is invented.
 */
export default async function CountriesPage() {
  const [geos, sources] = await Promise.all([listGeographiesWithObservations(), listSources()]);
  const epiSources = sources.filter((s) => ['cdc-uscs', 'cdc-wonder', 'seer', 'seer-explorer', 'iarc-globocan'].includes(s.slug));

  const details = await Promise.all(
    geos.map(async (g) => {
      const [allSites, deaths, cases] = await Promise.all([allSitesObservations(g.id, g.max_year, 'all'), topCancersFor(g, 'mortality_count', g.max_year, 'all', 1), topCancersFor(g, 'incidence_count', g.max_year, 'all', 1)]);
      return { g, allSites, deaths, cases };
    }),
  );
  const freshest = geos.map((g) => toDate(g.last_updated)).filter((d): d is Date => !!d).sort((a, b) => b.getTime() - a.getTime())[0] ?? null;

  return (
    <div>
      <PageHeader kicker="Geographies" title="Countries with epidemiology data" lede="Population statistics are attached per geography, year and sex, exactly as published by a registry or statistical agency. This page lists only geographies for which at least one observation has been ingested.">
        <p className="mt-3 flex flex-wrap items-center gap-1.5 text-[12.5px] text-ink-3">
          Epidemiology sources:
          {epiSources.map((s) => (
            <span key={s.slug} className="inline-flex items-center gap-1">
              <SourceBadge p={{ sourceSlug: s.slug, sourceName: s.name, license: s.license, layer: 'raw' }} compact />
              <Badge tone={s.status === 'active' ? 'ok' : s.status === 'review' || s.status === 'awaiting_credentials' ? 'warn' : 'neutral'}>{humanize(s.status)}</Badge>
            </span>
          ))}
        </p>
      </PageHeader>

      <Section id="list" kicker="Coverage" title={`${fmtInt(geos.length)} ${geos.length === 1 ? 'geography' : 'geographies'} with observations`} description="Years covered, distinct cancer entities with at least one observation, and the latest-year figures. Totals across all cancer sites are shown only when the source itself publishes an all-sites row; sites are never summed by CancerIndex.">
        {geos.length === 0 ? (
          <EmptyState title="No geography has observations yet">
            Country pages appear as soon as a licensed registry connector ingests observations. IARC / GLOBOCAN stays under license review and SEER awaits credentials, so global coverage is not available yet.
          </EmptyState>
        ) : (
          <>
            <div className="ci-table-wrap">
              <table className="ci-table">
                <thead>
                  <tr>
                    <th>Geography</th>
                    <th>ISO3</th>
                    <th>WHO region</th>
                    <th className="num">Years</th>
                    <th className="num">Cancers</th>
                    <th className="num">Observations</th>
                    <th>Sources</th>
                    <th>Latest year</th>
                    <th>Highest annual deaths</th>
                    <th>Highest annual new cases</th>
                  </tr>
                </thead>
                <tbody>
                  {details.map(({ g, allSites, deaths, cases }) => {
                    const total = (metric: string) => allSites.find((a) => a.metric === metric);
                    const td = total('mortality_count');
                    const tc = total('incidence_count');
                    const d0 = deaths.rows[0];
                    const c0 = cases.rows[0];
                    return (
                      <tr key={g.id}>
                        <td>
                          <Link className="ci-link font-medium" href={`/country/${g.slug}`}>
                            {g.name}
                          </Link>
                          <span className="ml-1.5 text-[11.5px] text-ink-3">{humanize(g.kind)}</span>
                        </td>
                        <td className="ci-mono">{g.iso3 ?? '—'}</td>
                        <td className="text-[12.5px] text-ink-2">{g.who_region ? WHO_REGION_LABEL[g.who_region] ?? g.who_region : '—'}</td>
                        <td className="num">
                          {g.min_year}–{g.max_year}
                        </td>
                        <td className="num">{fmtInt(g.n_cancers)}</td>
                        <td className="num">{fmtInt(g.n_obs)}</td>
                        <td>
                          <span className="inline-flex flex-wrap gap-1">
                            {(g.sources ?? []).map((s) => (
                              <SourceBadge key={s.slug} p={{ sourceSlug: s.slug, sourceName: s.name }} compact />
                            ))}
                          </span>
                        </td>
                        <td className="ci-num">{g.max_year}</td>
                        <td className="text-[12.5px]">
                          {td ? (
                            <span>
                              All sites: <span className="ci-num font-medium">{fmtValue(td.value, td.unit)}</span> {unitLabel(td.unit)} ({td.year})
                            </span>
                          ) : d0 ? (
                            <span>
                              <Link className="ci-link" href={`/cancer/${d0.slug}`}>
                                {d0.canonical_name}
                              </Link>{' '}
                              <span className="ci-num font-medium">{fmtValue(d0.value, d0.unit)}</span> <span className="text-ink-3">({deaths.year})</span>
                            </span>
                          ) : (
                            <span className="text-ink-4">—</span>
                          )}
                        </td>
                        <td className="text-[12.5px]">
                          {tc ? (
                            <span>
                              All sites: <span className="ci-num font-medium">{fmtValue(tc.value, tc.unit)}</span> {unitLabel(tc.unit)} ({tc.year})
                            </span>
                          ) : c0 ? (
                            <span>
                              <Link className="ci-link" href={`/cancer/${c0.slug}`}>
                                {c0.canonical_name}
                              </Link>{' '}
                              <span className="ci-num font-medium">{fmtValue(c0.value, c0.unit)}</span> <span className="text-ink-3">({cases.year})</span>
                            </span>
                          ) : (
                            <span className="text-ink-4">—</span>
                          )}
                        </td>
                      </tr>
                    );
                  })}
                </tbody>
              </table>
            </div>
            <p className="mt-2 text-[12px] text-ink-3">"Highest annual deaths / new cases" is the top single site group for the latest year of that metric, both sexes, all ages — not a national total. Where a source publishes an all-sites aggregate it is shown instead and labelled "All sites".</p>
            <Freshness dataUpdatedAt={freshest} extra={`${fmtInt(geos.reduce((n, g) => n + g.n_obs, 0))} observations in total`} />
          </>
        )}
      </Section>

      <Section id="status" kicker="Coverage status" title="Why only these geographies?" level={3}>
        <Note>
          CancerIndex publishes population statistics only from sources whose license has been reviewed (CLAUDE.md §10.4). U.S. Cancer Statistics (CDC, NPCR/SEER incidence and NVSS mortality) is approved and ingested. The IARC Global Cancer Observatory (GLOBOCAN), which would provide estimates for 185 countries, is under license review; the SEER API awaits credentials. Until then no country outside the United States has observations, and no global ranking of countries is shown. Estimates are never substituted for registry counts.
        </Note>
        <p className="mt-2 text-[13px]">
          <Link className="ci-link" href="/sources">
            Source registry and license status →
          </Link>{' '}
          ·{' '}
          <Link className="ci-link" href="/methodology#country-scopes">
            Methodology: country scopes →
          </Link>
        </p>
      </Section>
    </div>
  );
}