export class LinkedListNode<T> {
   constructor(public value: T | null, public next: LinkedListNode<T> | null = null) {}
}

export class LinkedList<T> {
   constructor(public head: LinkedListNode<T> | null = null, public tail: LinkedListNode<T> | null = null) {
      this.head = null;
      this.tail = null;
   }

   empty() {
      return this.head === null;
   }

   prepend(value: T) {
      const newNode = new LinkedListNode<T>(value, this.head);
      this.head = newNode;
      if (!this.tail) {
         this.tail = newNode;
      }
      return this;
   }

   append(value: T) {
      const newNode = new LinkedListNode(value);
      if (!this.head) {
         this.head = newNode;
         this.tail = newNode;

         return this;
      }
      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
      this.tail!.next = newNode;
      this.tail = newNode;
      return this;
   }

   deleteHead() {
      if (!this.head) {
         return null;
      }
      const deletedHead = this.head;
      if (this.head.next) {
         this.head = this.head.next;
      } else {
         this.head = null;
         this.tail = null;
      }
      return deletedHead;
   }
}