import Link from 'next/link';
import { Section } from '@/components/ui/section';
import { EmptyState } from '@/components/ui/empty-state';
import { PathChainView } from '@/components/graph/path-chain';
import { defaultFocus, focusCancerIds, loadPaths, resolveFocus } from '@/lib/queries/graph';
import { fmtInt } from '@/lib/format';

/**
 * Home teaser for the knowledge graph: three strongest gene → variant → drug chains for the
 * most-connected cancer (chosen from the data at request time, never hardcoded) and a link to /graph.
 */
export async function GraphModule({ limit = 3 }: { limit?: number }) {
  const ref = await defaultFocus();
  const focus = ref ? await resolveFocus(ref) : null;
  const chains = focus ? await loadPaths(focus, await focusCancerIds(focus), limit) : [];
  return (
    <Section
      id="graph"
      kicker="Knowledge graph"
      title={focus ? `Paths through ${focus.label}` : 'Knowledge graph'}
      description="Cancer → gene → variant → drug → approval → trials, as the sources state each hop: CIViC evidence level and direction, regulatory authority and date, registry trial counts. No edge is inferred by CancerIndex."
      actions={
        <Link href={focus ? `/graph?focus=cancer:${encodeURIComponent(focus.ref)}` : '/graph'} className="ci-link">
          Explore the graph →
        </Link>
      }
    >
      {!focus || chains.length === 0 ? (
        <EmptyState compact knows={[{ label: 'Open the graph', href: '/graph' }]}>
          No knowledge edge with a sensitivity direction is loaded yet, so no chain can be shown.
        </EmptyState>
      ) : (
        <>
          <ol className="m-0 list-none p-0">
            {chains.map((c) => (
              <PathChainView key={`${c.variant.id}:${c.drug.id}`} chain={c} compact />
            ))}
          </ol>
          <p className="mt-2 text-[12px] text-ink-3">
            {fmtInt(chains.length)} of the strongest chains for the cancer with the most knowledge edges ({focus.label}); ranked by source-native evidence level, then support. Not treatment guidance.
          </p>
        </>
      )}
    </Section>
  );
}