/**
 * /api/relations — read typed relations for an entity.
 *
 * GET /api/relations?class=person&id=j-edgar-hoover
 *   → Returns relations where this entity is source OR target,
 *     grouped by relation_type and direction.
 */
import { NextRequest } from "next/server";
import { pgQuery } from "@/lib/retrieval/db";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

function json(data: unknown, status = 200) {
  return new Response(JSON.stringify(data), {
    status,
    headers: { "content-type": "application/json" },
  });
}

interface Relation {
  source_class: string;
  source_id: string;
  relation_type: string;
  target_class: string;
  target_id: string;
  evidence_ref: string | null;
  confidence: string;
}

export async function GET(req: NextRequest) {
  const u = new URL(req.url);
  const cls = u.searchParams.get("class") ?? "";
  const id = u.searchParams.get("id") ?? "";
  if (!cls || !id) return json({ error: "class and id required" }, 400);

  try {
    const outgoing = await pgQuery<Relation>(
      `SELECT source_class, source_id, relation_type, target_class, target_id,
              evidence_ref, confidence
       FROM public.relations
       WHERE source_class = $1 AND source_id = $2
       ORDER BY confidence DESC, relation_type, target_class, target_id
       LIMIT 200`,
      [cls, id],
    );
    const incoming = await pgQuery<Relation>(
      `SELECT source_class, source_id, relation_type, target_class, target_id,
              evidence_ref, confidence
       FROM public.relations
       WHERE target_class = $1 AND target_id = $2
       ORDER BY confidence DESC, relation_type, source_class, source_id
       LIMIT 200`,
      [cls, id],
    );
    return json({ outgoing, incoming });
  } catch (e) {
    return json({ error: "db_unavailable", message: (e as Error).message }, 503);
  }
}