// visitor-recommendation-ctr — graph-backed CTR replacement for the
// log-scan aggregation that ships with Task 336. Operates on Recommendation
// nodes (materialised from [property-recommended] log lines via backfill)
// joined to :Click events. Output schema matches the log-scan tool's so
// the cutover (separate follow-up task) is a one-line swap.

import { getSession } from "../lib/neo4j.js";

export interface RecommendationCtrParams {
  accountId: string;
  /** Days back from now. Defaults to 7. */
  sinceDays?: number;
  /** Optional listingSlug filter. */
  listingSlug?: string;
}

export interface CtrRow {
  listingSlug: string;
  recommended: number;
  clicked: number;
  ctr: number;
}

export interface CtrSummary {
  windowDays: number;
  totalRecommended: number;
  totalClicked: number;
  ctr: number;
  perListing: CtrRow[];
}

export async function visitorRecommendationCtr(p: RecommendationCtrParams): Promise<CtrSummary> {
  const since = p.sinceDays ?? 7;
  const session = getSession();
  try {
    const result = await session.run(
      `MATCH (rec:Recommendation {accountId: $accountId})
       WHERE rec.recommendedAt >= datetime() - duration({days: $since})
         AND ($slug IS NULL OR rec.listingSlug = $slug)
       OPTIONAL MATCH (rec)-[:FOR_SESSION]->(s:Session)-[:HAS_EVENT]->(cl:Click {label: 'card'})
       WITH rec.listingSlug AS slug,
            count(DISTINCT rec) AS recommended,
            count(DISTINCT cl) AS clicked
       RETURN slug AS listingSlug, recommended, clicked,
              CASE WHEN recommended > 0 THEN toFloat(clicked) / recommended ELSE 0.0 END AS ctr
       ORDER BY recommended DESC`,
      { accountId: p.accountId, since, slug: p.listingSlug ?? null },
    );
    const perListing: CtrRow[] = result.records.map((r) => ({
      listingSlug: r.get("listingSlug") ?? "",
      recommended: Number(r.get("recommended") ?? 0),
      clicked: Number(r.get("clicked") ?? 0),
      ctr: Number(r.get("ctr") ?? 0),
    }));
    const totalRecommended = perListing.reduce((a, b) => a + b.recommended, 0);
    const totalClicked = perListing.reduce((a, b) => a + b.clicked, 0);
    return {
      windowDays: since,
      totalRecommended,
      totalClicked,
      ctr: totalRecommended > 0 ? totalClicked / totalRecommended : 0,
      perListing,
    };
  } finally {
    await session.close();
  }
}