/**
 * COMP 410
 *See inline comment descriptions for methods not described in interface.
 *
*/
package LinkedList_A1;

public class LinkedListImpl implements LIST_Interface {
  Node sentinel; //this will be the entry point to your linked list (the head)

  public LinkedListImpl(){//this constructor is needed for testing purposes. Please don't modify!
    sentinel=new Node(0); //Note that the root's data is not a true part of your data set!
  }

  //implement all methods in interface, and include the getRoot method we made for testing purposes. Feel free to implement private helper methods!
  public void clear() {
      sentinel.next=null;
      sentinel.prev=null;
  }

  public int size() {
      int size = 0;
      if (sentinel.next==null) {return size;}
      else {
          Node curr = sentinel.next;
          while (curr != sentinel) {
            size++;
            curr = curr.next;
          }
          return size;
      }
  }

  public boolean isEmpty() {
      if (this.size() == 0) {return true;}
      else {return false;}
  }


  public boolean insert(double elt, int index) {
      if ((sentinel.next == null) && (index==0)) {
          Node c = new Node(elt);
          sentinel.next = c;
          c.prev = sentinel;
          c.next = sentinel;
          sentinel.prev = c;
          return true;
          }
      else if ((this.size() < index) || (index < 0)) {return false;}
      else {
          Node c = new Node(elt);
          Node curr = sentinel.next; //location of new cell
          int ct = 0;
          while (curr != sentinel) {
              if (ct < index) {curr=curr.next; ct++;}
              else {break;}
          }
          c.prev = curr.prev;
          curr.prev = c;
          c.prev.next = c;
          c.next = curr;
          return true;
      }
  }

  public boolean remove(int index) {
      if ((this.size() <= index) || (index < 0)) {return false;}
      else {
      Node curr = sentinel.next;
      int ct = 0;
      while (curr != sentinel) {
          if (ct<index) {curr=curr.next; ct++;}
          else {break;}
      }
      curr.next.prev = curr.prev;
      curr.prev.next = curr.next;
      return true;
      }
  }

  public double get(int index) {
      if ((this.size() <= index) || (index < 0)) {return Double.NaN;}
      else {
          Node curr = sentinel.next;
          int ct = 0;
          while (curr != sentinel) {
              if (ct<index) {curr=curr.next; ct++;}
              else {break;}
          }
          return curr.data;
      }
  }


  public Node getRoot(){ //leave this method as is, used by the grader to grab your linkedList easily.
    return sentinel;
  }
}