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

    // Get warehouse, zone, and aisle from the form
    $warehouse = (int)$data['warehouse'];
    $zone      = $data['zone'];
    $aisle     = $data['aisle'];

    if (isset($data['warehouse_from']) && $data['type'] == "from") {
        $warehouse = (int)$data['warehouse_from'];
        $zone      = $data['zone_from'];
        $aisle     = $data['aisle_from'];   
    }
    if (isset($data['warehouse_to']) && $data['type'] == "to") {
        $warehouse = (int)$data['warehouse_to'];
        $zone      = $data['zone_to'];
        $aisle     = $data['aisle_to'];
    }

    // Filter racks by operation type and optional SKU:
    //   'to'   = destination → empty racks only   (product_sku IS NULL)
    //   'from' + sku → racks currently holding that specific SKU
    //   'from' (no sku) → any occupied rack       (product_sku IS NOT NULL)
    //   other  = all racks in the aisle (admin / read-only pages)
    $product_sku_filter = "";
    $params = [
        ":company_id" => $company_id,
        ":warehouse"  => $warehouse,
        ":zone"       => $zone,
        ":aisle"      => $aisle,
    ];

    if ($data["type"] == "to") {
        $product_sku_filter = "AND product_sku IS NULL";

    } elseif ($data["type"] == "from") {
        if (!empty($data["product_sku"])) {
            $product_sku_filter = "AND product_sku = :product_sku";
            $params[":product_sku"] = $data["product_sku"];
        } else {
            $product_sku_filter = "AND product_sku IS NOT NULL";
        }
    }

    if(!empty($data["id"])){
        $product_sku_filter = "";
        unset($params[":product_sku"]);
    }

    $sql = "SELECT DISTINCT rack
            FROM md_rack
            WHERE 
                company_id = :company_id AND
                warehouse  = :warehouse  AND
                `zone`     = :zone       AND
                aisle      = :aisle
                $product_sku_filter
            ORDER BY CAST(rack AS UNSIGNED), rack";

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

    // Return flat array (matches original response shape for the frontend)
    $answer["output"]  = array_column($sth->fetchAll(PDO::FETCH_ASSOC), 'rack');
    $answer["success"] = 1;
    exit(json_encode($answer));
?>