/**
 * Vendor Reliability Scores
 *
 * Routes:
 *   GET /api/vendor-reliability   — Reliability score 0–100 per vendor
 */
import { Router, Request, Response } from "express";
import { pool } from "../db/client";

export const vendorReliabilityRouter = Router();

// ─── GET /api/vendor-reliability ─────────────────────────────────────────────
vendorReliabilityRouter.get("/", async (_req: Request, res: Response) => {
  try {
    const result = await pool.query<{
      vendor_id: number;
      vendor_name: string;
      last_observation: Date;
      obs_30d: string;
      distinct_skus_60d: string;
      days_since_last: string;
    }>(`
      WITH base AS (
        SELECT
          po.source_vendor_id                                        AS vendor_id,
          MAX(po.time)                                               AS last_observation,
          COUNT(*) FILTER (WHERE po.time > NOW() - INTERVAL '30 days')
                                                                     AS obs_30d,
          COUNT(DISTINCT po.transceiver_id)
            FILTER (WHERE po.time > NOW() - INTERVAL '60 days')
                                                                     AS distinct_skus_60d
        FROM price_observations po
        WHERE po.time > NOW() - INTERVAL '90 days'
        GROUP BY po.source_vendor_id
      )
      SELECT
        b.vendor_id,
        v.name                                                       AS vendor_name,
        b.last_observation,
        b.obs_30d,
        b.distinct_skus_60d,
        EXTRACT(EPOCH FROM (NOW() - b.last_observation)) / 86400.0  AS days_since_last
      FROM base b
      JOIN vendors v ON v.id = b.vendor_id
      ORDER BY b.last_observation DESC
    `);

    const vendors = result.rows.map((row) => {
      const days = parseFloat(row.days_since_last);
      const obs30d = parseInt(row.obs_30d, 10);
      const skus60d = parseInt(row.distinct_skus_60d, 10);

      const freshnessScore =
        days <= 7  ? 40 :
        days <= 14 ? 30 :
        days <= 30 ? 20 :
        days <= 60 ? 10 : 0;

      const frequencyScore = Math.min(Math.round((obs30d / 100) * 30), 30);
      const coverageScore  = Math.min(Math.round((skus60d / 500) * 30), 30);
      const reliabilityScore = freshnessScore + frequencyScore + coverageScore;

      return {
        vendor_id:         row.vendor_id,
        vendor_name:       row.vendor_name,
        reliability_score: reliabilityScore,
        freshness_score:   freshnessScore,
        frequency_score:   frequencyScore,
        coverage_score:    coverageScore,
        last_observation:  row.last_observation.toISOString().slice(0, 10),
        obs_30d:           obs30d,
        distinct_skus_60d: skus60d,
      };
    });

    vendors.sort((a, b) => b.reliability_score - a.reliability_score);

    res.json({ success: true, vendors });
  } catch (err) {
    console.error("GET /api/vendor-reliability error:", err);
    res.status(500).json({ success: false, error: String(err) });
  }
});