Auto add lote on internal ship move

stock.py

@@ -32,10 +32,25 @@ class Move(metaclass=PoolMeta):
     current_stock = fields.Function(fields.Float('Current Stock',
         depends=['product']), 'on_change_with_current_stock')
 
-    @fields.depends('current_stock')
+    def next_lot(self, product_id):
+        "Look for the oldest lot or the one closest to the expiration date."
+        Lot = Pool().get('stock.lot')
+        dom = [
+            ('product', '=', product_id),
+            ('active', '=', True),
+            ('quantity', '>', 0),
+        ]
+
+        lots = Lot.search(dom, order=[('create_date', 'ASC')])
+        if lots:
+            return lots[0].id
+
+    @fields.depends('current_stock', 'lot')
     def on_change_product(self, name=None):
         super(Move, self).on_change_product()
         self.current_stock = self.on_change_with_current_stock()
+        if self.product:
+            self.lot = self.next_lot(self.product.id)
 
     @fields.depends('product', 'from_location', 'to_location')
     def on_change_with_current_stock(self, name=None):