Moved stuff, added Contains to sliceutils

containers/queues.go

@@ -0,0 +1,95 @@
+package containers
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type Queue[T any] struct {
+	head *ChainElem[T]
+	tail *ChainElem[T]
+}
+
+// isValid checks if the queue is still valid.
+func (q *Queue[T]) isValid() bool {
+	return q.head != nil &&
+		q.tail != nil &&
+		reachable(q.head, q.tail)
+}
+
+// IsEmpty checks if the queue is empty.
+func (q *Queue[T]) IsEmpty() bool {
+	return q.head == q.tail
+}
+
+// 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")
+	}
+
+	e := emptyElem[T]()
+	q.tail.Elem = elem
+	q.tail.Next = e
+	q.tail = e
+
+	return nil
+}
+
+// Pop removes the first element of the queue.
+// 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")
+	}
+	if q.IsEmpty() {
+		return nil, errors.New("empty queue")
+	}
+	Elem := q.head.Elem
+	q.head = q.head.Next
+	return Elem, nil
+}
+
+// Top returns the first element of the queue without removing it.
+// 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")
+	}
+	if q.IsEmpty() {
+		return nil, errors.New("queue empty")
+	}
+	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]{
+		head: empty,
+		tail: empty,
+	}
+}