<?php
    session_start();
    require '../../../assets/utils/db_auth.php';

    // Returns active serials for a given product_sku + optional lot_number
    // "Active" = EXISTS in an occupied md_rack
    $product_sku = $data['product_sku'] ?? '';
    $lot_number  = $data['lot_number']  ?? '';

    if (empty($product_sku)) {
        $answer['output']  = [];
        $answer['success'] = 1;
        exit(json_encode($answer));
    }

    // Discover all warehouses
    $sth = $pdo2->prepare(
        "SELECT id, warehouse_name FROM md_warehouse
         WHERE company_id = :company_id AND status = 1"
    );
    $sth->execute([':company_id' => $company_id]);
    $warehouses = $sth->fetchAll(PDO::FETCH_ASSOC);

    $active_serials = [];

    foreach ($warehouses as $wh) {
        $safe  = preg_replace('/[^a-zA-Z0-9_]/', '', $wh['warehouse_name']);
        $table = "td_stock_{$safe}";

        $sql = "SELECT DISTINCT s.serial_number
                FROM `{$table}` s
                WHERE s.company_id   = :company_id
                  AND s.product_sku  = :product_sku
                  AND s.type         = 'in'
                  AND s.serial_number IS NOT NULL
                  AND EXISTS (
                      SELECT 1 FROM md_rack r
                      WHERE r.company_id  = s.company_id
                        AND r.td_stock_id = s.id
                        AND r.product_sku IS NOT NULL
                  )";

        $params = [
            ':company_id'  => $company_id,
            ':product_sku' => $product_sku,
        ];

        if (!empty($lot_number)) {
            $sql .= " AND s.lot_number = :lot_number";
            $params[':lot_number'] = $lot_number;
        }

        $sth = $pdo2->prepare($sql);
        $sth->execute($params);

        foreach ($sth->fetchAll(PDO::FETCH_ASSOC) as $row) {
            $active_serials[$row['serial_number']] = $row['serial_number'];
        }
    }

    $answer['output']  = array_values($active_serials);
    $answer['success'] = 1;
    exit(json_encode($answer));
?>