implement some client side function to shadow Product

src/pay_center/Product.php

@@ -9,6 +9,7 @@
 namespace neoteched\rpc\pay_center;
 
 use x2ts\IAssignable;
+use x2ts\rpc\RPCWrapper;
 
 class Product implements IAssignable {
     use AssignTrait;
@@ -26,4 +27,30 @@ class Product implements IAssignable {
     public $ctime = 0;
 
     public $mtime = 0;
+
+    private static $userBought = [];
+
+    public static function userBought(int $userId) {
+        if (!array_key_exists($userId, self::$userBought)) {
+            self::$userBought[$userId] = RPCWrapper::rpc('pay_center')
+                ->call('boughtProductHash', $userId);
+        }
+        return self::$userBought[$userId];
+    }
+
+    public static function boughtProductNames(int $userId): array {
+        return array_keys(self::userBought($userId));
+    }
+
+    public static function boughtProducts(int $userId) {
+        return RPCWrapper::rpc('pay_center')->call('boughtProducts', $userId);
+    }
+
+    public static function boughtProductCount(int $userId): int {
+        return count(self::userBought($userId));
+    }
+
+    public static function hasBought(string $name, int $userId): bool {
+        return array_key_exists($name, self::userBought($userId));
+    }
 }
\ No newline at end of file