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

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

    if(isset($data['warehouse_from'])&&$data['type']=="from"){
        $warehouse = (int)$data['warehouse_from'];
    }
    if(isset($data['warehouse_to'])&&$data['type']=="to"){
        $warehouse = (int)$data['warehouse_to'];
    }

    // Filter zones by operation type and optional SKU:
    //   'to'   = destination → zones with at least one empty rack
    //   'from' + sku → zones currently holding that specific SKU
    //   'from' (no sku) → zones with any occupied rack
    //   other  = all zones in the warehouse (admin / read-only pages)
    $product_sku_filter = "";
    $params = [
        ":company_id" => $company_id,
        ":warehouse"  => $warehouse,
    ];

    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 zone
            FROM md_rack
            WHERE 
                company_id = :company_id AND
                warehouse  = :warehouse
                $product_sku_filter
            ORDER BY CAST(zone AS UNSIGNED), zone";

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

    // Frontend expects objects with a `zone` property — keep that shape.
    $answer["output"]  = $sth->fetchAll(PDO::FETCH_ASSOC);
    $answer["success"] = 1;
    exit(json_encode($answer));
?>