Change queues and stacks

- Make chain element private
- Remove JSON Marshaller from stack and queue
- Remove access to top chain element

containers/stacks.go

@@ -1,13 +1,12 @@
 package containers
 
 import (
-	"encoding/json"
 	"errors"
 )
 
 type Stack[T any] struct {
-	top    *ChainElem[T]
-	bottom *ChainElem[T]
+	top    *chainElem[T]
+	bottom *chainElem[T]
 }
 
 // isValid checks if the stack is valid.
@@ -61,17 +60,6 @@ func (s *Stack[T]) Top() (*T, error) {
 	return s.top.Elem, nil
 }
 
-// MarshalJSON is used by json.Marshal to create a json representation.
-func (s *Stack[T]) MarshalJSON() ([]byte, error) {
-	if !s.isValid() {
-		return nil, errors.New("queue invalid")
-	}
-	if s.IsEmpty() {
-		return nil, errors.New("queue empty")
-	}
-
-	return json.Marshal(s.top)
-}
 func BuildStack[T any]() *Stack[T] {
 	empty := emptyElem[T]()
 	return &Stack[T]{