try 3

contracts/task3.fc

@@ -14,6 +14,7 @@
 ;; You may delete and rewrite as needed,
 ;; but the final implementation must adhere to the same structure
 
+{-
 cell get_storage() inline {
     slice cs = get_data().begin_parse();
 
@@ -22,6 +23,7 @@ cell get_storage() inline {
 
     return storage;
 }
+-}
 
 cell wrap_storage(int version_id, cell storage) inline {
     ;; add additional data required for versioning in this cell
@@ -58,6 +60,11 @@ cell migrate_one(cell old_storage) { ;; it's just a placeholder that is required
 () recv_internal(int msg_value, int balance, cell in_msg_full, slice in_msg_body) impure {
     int expected_version = in_msg_body~load_uint(32);
 
+    ;; ---
+    ;; here you should check if it's the first call or not based on `expected_version` as stated in the task
+    ;; if it is the first call, wrap the storage and finish execution by returning from the function
+    ;; ---
+
     if (expected_version == 0) {
         set_data(wrap_storage(1, get_data().begin_parse().preload_ref()));
         return();
@@ -71,12 +78,38 @@ cell migrate_one(cell old_storage) { ;; it's just a placeholder that is required
     int version = ds.preload_uint(32);
     cell storage = ds.preload_ref();
 
-    ;; ---
-    ;; here you should check if it's the first call or not based on `expected_version` as stated in the task
-    ;; if it is the first call, wrap the storage and finish execution by returning from the function
-    ;; ---
+    throw_if(200, expected_version < version);
+
+    int setcode = false;
+    if (expected_version > version) {
+        throw_if(200, expected_code.null?());
+        setcode = true;
+    }
+
+    while (version < expected_version) {
+        (slice mig, int found) = migrations.udict_get?(32, version);
+        throw_unless(400, found);
+        int next = mig~load_uint(32);
+        cell mc = mig.preload_maybe_ref();
+        ifnot (mc.null?()) {
+            set_c3(mc.begin_parse().bless());
+            storage = migrate_one(storage);
+        }
+        version = next;
+    }
+
+    throw_if(200, version > expected_version);
+
+    if (setcode) {
+        set_code(expected_code);
+        set_c3(expected_code.begin_parse().bless());
+    }
 
     storage = process_message(storage, msg_value, balance, in_msg_full, payload.begin_parse());
 
-    set_data(wrap_storage(expected_version, storage));
+    set_data(begin_cell()
+        .store_uint(version, 32)
+        .store_ref(storage)
+        .end_cell()
+    );
 }