From 09de0a19e1a24133bfa14d2c472370fe4bfd6d81 Mon Sep 17 00:00:00 2001
From: mstar <me@mstar.dev>
Date: Thu, 24 Apr 2025 15:52:43 +0200
Subject: [PATCH] Change queues and stacks

- Make chain element private
- Remove JSON Marshaller from stack and queue
- Remove access to top chain element
---
 containers/generics.go | 12 ++++++------
 containers/queues.go   | 42 ++++++++++--------------------------------
 containers/stacks.go   | 16 ++--------------
 3 files changed, 18 insertions(+), 52 deletions(-)

diff --git a/containers/generics.go b/containers/generics.go
index 17c1c4d..9465afd 100644
--- a/containers/generics.go
+++ b/containers/generics.go
@@ -1,15 +1,15 @@
 package containers
 
-type ChainElem[T any] struct {
+type chainElem[T any] struct {
 	Elem *T
-	Next *ChainElem[T]
+	Next *chainElem[T]
 }
 
 // reachable checks if you can reach elem l when starting from elem f.
 // It detects loops and returns false if it runs into one.
-func reachable[T any](f, l *ChainElem[T]) bool {
+func reachable[T any](f, l *chainElem[T]) bool {
 	// Map to keep track of nodes already visited
-	checks := make(map[*ChainElem[T]]bool)
+	checks := make(map[*chainElem[T]]bool)
 	for w := f; w != l; w = w.Next {
 		if w == nil {
 			return false
@@ -26,8 +26,8 @@ func reachable[T any](f, l *ChainElem[T]) bool {
 }
 
 // emptyElem creates a new ChainElem[T] with empty values.
-func emptyElem[T any]() *ChainElem[T] {
-	return &ChainElem[T]{
+func emptyElem[T any]() *chainElem[T] {
+	return &chainElem[T]{
 		Elem: nil,
 		Next: nil,
 	}
diff --git a/containers/queues.go b/containers/queues.go
index b528692..f590293 100644
--- a/containers/queues.go
+++ b/containers/queues.go
@@ -1,13 +1,15 @@
 package containers
 
 import (
-	"encoding/json"
 	"errors"
 )
 
+var ErrInvalidQueue = errors.New("invalid queue")
+var ErrEmptyQueue = errors.New("empty queue")
+
 type Queue[T any] struct {
-	head *ChainElem[T]
-	tail *ChainElem[T]
+	head *chainElem[T]
+	tail *chainElem[T]
 }
 
 // isValid checks if the queue is still valid.
@@ -25,7 +27,7 @@ func (q *Queue[T]) IsEmpty() bool {
 // Push adds a new element to the end of the queue.
 func (q *Queue[T]) Push(elem *T) error {
 	if !q.isValid() {
-		return errors.New("invalid queue")
+		return ErrInvalidQueue
 	}
 
 	e := emptyElem[T]()
@@ -40,10 +42,10 @@ func (q *Queue[T]) Push(elem *T) error {
 // It errors out if there is no element or the queue is invalid.
 func (q *Queue[T]) Pop() (*T, error) {
 	if !q.isValid() {
-		return nil, errors.New("invalid queue")
+		return nil, ErrInvalidQueue
 	}
 	if q.IsEmpty() {
-		return nil, errors.New("empty queue")
+		return nil, ErrEmptyQueue
 	}
 	Elem := q.head.Elem
 	q.head = q.head.Next
@@ -54,38 +56,14 @@ func (q *Queue[T]) Pop() (*T, error) {
 // It errors out if there is no element or the queue is invalid.
 func (q *Queue[T]) Top() (*T, error) {
 	if !q.isValid() {
-		return nil, errors.New("queue invalid")
+		return nil, ErrInvalidQueue
 	}
 	if q.IsEmpty() {
-		return nil, errors.New("queue empty")
+		return nil, ErrEmptyQueue
 	}
 	return q.head.Elem, nil
 }
 
-// HeadElem returns the first ChainElem of the queue without removing it.
-// It errors out if there is no element or the queue is invalid.
-func (q *Queue[T]) HeadElem() (*ChainElem[T], error) {
-	if !q.isValid() {
-		return nil, errors.New("queue invalid")
-	}
-	if q.IsEmpty() {
-		return nil, errors.New("queue empty")
-	}
-	return q.head, nil
-}
-
-// MarshalJSON is used for generating json data when using json.Marshal.
-func (q *Queue[T]) MarshalJSON() ([]byte, error) {
-	if !q.isValid() {
-		return nil, errors.New("queue invalid")
-	}
-	if q.IsEmpty() {
-		return nil, errors.New("queue empty")
-	}
-
-	return json.Marshal(q.head)
-}
-
 func BuildQueue[T any]() *Queue[T] {
 	empty := emptyElem[T]()
 	return &Queue[T]{
diff --git a/containers/stacks.go b/containers/stacks.go
index 57a4b55..101b820 100644
--- a/containers/stacks.go
+++ b/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]{