generic API response + ICS: warehouse_balance md_rack update

app/ics/api/engine/retrieve_zone.php

@@ -1,32 +1,59 @@
 <?php 
     session_start();
-
     require '../../../assets/utils/db_auth.php';
 
-    $id = (int)$data['id'];
+    // Get warehouse from the form
+    $warehouse = (int)$data['warehouse'];
 
-    // identity source of zone and aisle
-    if(empty($data["type"])){
-        $warehouse = (int)$data['warehouse'];
-    }else{
-        $warehouse = (int)$data['warehouse_'.$data["type"]];
+    if(isset($data['warehouse_from'])&&$data['type']=="from"){
+        $warehouse = (int)$data['warehouse_from'];
+    }
+    if(isset($data['warehouse_to'])&&$data['type']=="to"){
+        $warehouse = (int)$data['warehouse_to'];
     }
 
-    $sql = "SELECT * 
-        FROM md_storage
-        WHERE 
-            company_id = {$company_id} and 
-            warehouse = {$warehouse}";
+    // 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([
-        ":company_id" => $company_id,
-        ":warehouse" => $warehouse
-    ]);
+    $sth->execute($params);
     db_check($sth, $answer);
 
-    $answer["output"] = $sth->fetchAll(PDO::FETCH_ASSOC);
+    // Frontend expects objects with a `zone` property — keep that shape.
+    $answer["output"]  = $sth->fetchAll(PDO::FETCH_ASSOC);
     $answer["success"] = 1;
     exit(json_encode($answer));
-
 ?>