const { outputProgress, formatElapsedTime } = require('../metrics-new/utils/progress');

/**
 * Import daily deals from production MySQL to local PostgreSQL.
 *
 * Production has two tables:
 *   - product_daily_deals (deal_id, deal_date, pid, price_id)
 *   - product_current_prices (price_id, pid, price_each, active, ...)
 *
 * We join them in the prod query to denormalize the deal price, avoiding
 * the need to sync the full product_current_prices table.
 *
 * On each sync:
 *   1. Fetch deals from the last 7 days (plus today) from production
 *   2. Upsert into local table
 *   3. Hard delete local deals older than 7 days past their deal_date
 */
async function importDailyDeals(prodConnection, localConnection) {
  outputProgress({
    operation: "Starting daily deals import",
    status: "running",
  });

  const startTime = Date.now();

  try {
    await localConnection.query('BEGIN');

    // Fetch recent daily deals from production (MySQL 5.7, no CTEs)
    // Join product_current_prices to get the actual deal price
    // Only grab last 7 days + today + tomorrow (for pre-scheduled deals)
    const [deals] = await prodConnection.query(`
      SELECT
        pdd.deal_id,
        pdd.deal_date,
        pdd.pid,
        pdd.price_id,
        pcp.price_each as deal_price
      FROM product_daily_deals pdd
      LEFT JOIN product_current_prices pcp ON pcp.price_id = pdd.price_id
      WHERE pdd.deal_date >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
        AND pdd.deal_date <= DATE_ADD(CURDATE(), INTERVAL 1 DAY)
      ORDER BY pdd.deal_date DESC, pdd.pid
    `);

    outputProgress({
      status: "running",
      operation: "Daily deals import",
      message: `Fetched ${deals.length} deals from production`,
      elapsed: formatElapsedTime(startTime),
    });

    let totalInserted = 0;
    let totalUpdated = 0;

    if (deals.length > 0) {
      // Batch upsert — filter to only PIDs that exist locally
      const pids = [...new Set(deals.map(d => d.pid))];
      const existingResult = await localConnection.query(
        `SELECT pid FROM products WHERE pid = ANY($1)`,
        [pids]
      );
      const existingPids = new Set(
        (Array.isArray(existingResult) ? existingResult[0] : existingResult)
          .rows.map(r => Number(r.pid))
      );

      const validDeals = deals.filter(d => existingPids.has(Number(d.pid)));

      if (validDeals.length > 0) {
        // Build batch upsert
        const values = validDeals.flatMap(d => [
          d.deal_date,
          d.pid,
          d.price_id,
          d.deal_price ?? null,
        ]);

        const placeholders = validDeals
          .map((_, i) => `($${i * 4 + 1}, $${i * 4 + 2}, $${i * 4 + 3}, $${i * 4 + 4})`)
          .join(',');

        const upsertQuery = `
          WITH upserted AS (
            INSERT INTO product_daily_deals (deal_date, pid, price_id, deal_price)
            VALUES ${placeholders}
            ON CONFLICT (deal_date, pid) DO UPDATE SET
              price_id = EXCLUDED.price_id,
              deal_price = EXCLUDED.deal_price
            WHERE
              product_daily_deals.price_id IS DISTINCT FROM EXCLUDED.price_id OR
              product_daily_deals.deal_price IS DISTINCT FROM EXCLUDED.deal_price
            RETURNING
              CASE WHEN xmax = 0 THEN true ELSE false END as is_insert
          )
          SELECT
            COUNT(*) FILTER (WHERE is_insert) as inserted,
            COUNT(*) FILTER (WHERE NOT is_insert) as updated
          FROM upserted
        `;

        const result = await localConnection.query(upsertQuery, values);
        const queryResult = Array.isArray(result) ? result[0] : result;
        totalInserted = parseInt(queryResult.rows[0].inserted) || 0;
        totalUpdated = parseInt(queryResult.rows[0].updated) || 0;
      }

      const skipped = deals.length - validDeals.length;
      if (skipped > 0) {
        console.log(`Skipped ${skipped} deals (PIDs not in local products table)`);
      }
    }

    // Hard delete deals older than 7 days past their deal_date
    const deleteResult = await localConnection.query(`
      DELETE FROM product_daily_deals
      WHERE deal_date < CURRENT_DATE - INTERVAL '7 days'
    `);
    const deletedCount = deleteResult.rowCount ??
      (Array.isArray(deleteResult) ? deleteResult[0]?.rowCount : 0) ?? 0;

    // Update sync status
    await localConnection.query(`
      INSERT INTO sync_status (table_name, last_sync_timestamp)
      VALUES ('product_daily_deals', NOW())
      ON CONFLICT (table_name) DO UPDATE SET
        last_sync_timestamp = NOW()
    `);

    await localConnection.query('COMMIT');

    outputProgress({
      status: "complete",
      operation: "Daily deals import completed",
      message: `Inserted ${totalInserted}, updated ${totalUpdated}, deleted ${deletedCount} expired`,
      current: totalInserted + totalUpdated,
      total: totalInserted + totalUpdated,
      duration: formatElapsedTime(startTime),
    });

    return {
      status: "complete",
      recordsAdded: totalInserted,
      recordsUpdated: totalUpdated,
      recordsDeleted: deletedCount,
      totalRecords: totalInserted + totalUpdated,
    };
  } catch (error) {
    console.error("Error importing daily deals:", error);

    try {
      await localConnection.query('ROLLBACK');
    } catch (rollbackError) {
      console.error("Error during rollback:", rollbackError);
    }

    outputProgress({
      status: "error",
      operation: "Daily deals import failed",
      error: error.message,
    });

    throw error;
  }
}

module.exports = importDailyDeals;