import type { Metadata } from 'next';
import Link from 'next/link';
import { StatsComposition } from '@/components/stats/stats-composition';
import { StatsDensity } from '@/components/stats/stats-density';
import { StatsHeadline } from '@/components/stats/stats-headline';
import { StatsHistory } from '@/components/stats/stats-history';
import { ConnectorStrip, Note } from '@/components/stats/shared';
import { Container, PageHeader, Section } from '@/components/ui/section';
import { Unavailable } from '@/components/ui/unavailable';
import { api, safe } from '@/lib/api';
import { fmtAgo, fmtDateTime, fmtInt } from '@/lib/format';
import { routes, SITE_NAME, SITE_URL } from '@/lib/site';

export const revalidate = 300;

const TITLE = 'Global statistics — satellites, debris, launches and orbital density';
const DESC = 'Live statistics of everything in Earth orbit: active satellites, objects on orbit, debris, rocket bodies, launches since 1957, constellation shares and orbital density by altitude and inclination. Real catalogue data with transparent sources.';

export async function generateMetadata(): Promise<Metadata> {
  const url = `${SITE_URL}${routes.stats()}`;
  return {
    title: TITLE,
    description: DESC,
    alternates: { canonical: url },
    openGraph: { title: `${TITLE} | ${SITE_NAME}`, description: DESC, url, type: 'website', siteName: SITE_NAME },
    twitter: { card: 'summary_large_image', title: `${TITLE} | ${SITE_NAME}`, description: DESC },
  };
}

export default async function StatsPage() {
  const [stats, density] = await Promise.all([safe(api.stats()), safe(api.density())]);
  const snapshot = stats?.data ?? null;

  return (
    <Container>
      <PageHeader eyebrow="Statistics" title="Everything in Earth orbit, by the numbers" lede="A dashboard of the whole catalogue: how many objects fly, who operates them, how fast the population grows and where it concentrates. Every number is read from the latest SatelliteIndex snapshot — nothing is estimated or hardcoded.">
        {snapshot && (
          <p className="mono mt-4 text-xs text-ink-3">
            Computed {fmtAgo(snapshot.computed_at)} · {fmtDateTime(snapshot.computed_at)} · {fmtInt(snapshot.connectors.length)} connectors
          </p>
        )}
      </PageHeader>

      {!snapshot ? (
        <div className="py-8">
          <Unavailable what="Statistics snapshot" />
          <Note className="mt-3">The statistics API did not answer. Live catalogue browsing may still work on <Link href={routes.satellites()} className="text-accent hover:underline">/satellites</Link>.</Note>
        </div>
      ) : (
        <>
          <Section eyebrow="Headline" title="Catalogue at a glance" className="pt-0 md:pt-0">
            <StatsHeadline snapshot={snapshot} />
          </Section>

          <Section eyebrow="Composition" title="What is up there" action={{ href: routes.satellites('on_orbit=true'), label: 'Browse objects' }}>
            <StatsComposition snapshot={snapshot} />
          </Section>

          <Section eyebrow="History" title="Seven decades of launches and decays" action={{ href: routes.launches(), label: 'All launches' }}>
            <StatsHistory snapshot={snapshot} />
          </Section>

          <Section eyebrow="Orbital density" title="Where objects concentrate" action={{ href: routes.debris(), label: 'Debris growth' }}>
            <StatsDensity density={density?.data ?? null} fallbackBuckets={snapshot.orbital_buckets} />
          </Section>

          <Section eyebrow="Rankings" title="Leaders and movers" action={{ href: routes.rankings(), label: 'All rankings' }}>
            <ul className="grid gap-3 sm:grid-cols-2 lg:grid-cols-4">
              {[
                { href: routes.rankings('constellations'), label: 'Largest constellations', hint: 'by active satellites' },
                { href: routes.rankings('operators'), label: 'Largest operators', hint: 'by active payloads' },
                { href: routes.rankings('countries'), label: 'Countries', hint: 'by active payloads' },
                { href: routes.rankings('countries-debris'), label: 'Debris by country', hint: 'objects on orbit' },
                { href: routes.rankings('launches'), label: 'Busiest launch sites', hint: 'launches since 1957' },
                { href: routes.rankings('fastest-growing'), label: 'Fastest-growing constellations', hint: 'launched last 365 d vs fleet' },
                { href: routes.rankings('congested-shells'), label: 'Most populated LEO shells', hint: '50 km bands, object counts' },
                { href: routes.rankings('launch-years'), label: 'Launch years', hint: 'launches and payloads per year' },
              ].map((r) => (
                <li key={r.href}>
                  <Link href={r.href} className="flex min-h-[64px] flex-col justify-center border-t border-rule py-3 transition-colors hover:border-accent/60">
                    <span className="text-sm font-medium text-ink">{r.label} →</span>
                    <span className="text-xs text-ink-3">{r.hint}</span>
                  </Link>
                </li>
              ))}
            </ul>
          </Section>

          <Section eyebrow="Sources" title="Connector freshness" action={{ href: routes.sources(), label: 'All sources' }}>
            <ConnectorStrip connectors={snapshot.connectors} />
            <Note className="mt-4">
              Fresh = last success within 3× the connector interval · aging = within 12× · stale beyond that. Orbit class, mission type, constellation membership, activity score and orbital density are derived metrics documented on{' '}
              <Link href={routes.methodology()} className="text-accent hover:underline">/methodology</Link>.
            </Note>
          </Section>
        </>
      )}
    </Container>
  );
}