// Helene Martin, CSE 143
// A LinkedIntList stores an ordered list of integers.
// This version adds:
// - a constructor that builds a list
// - add at an index (not discussed in class)
// - addSorted

// LinkedIntList and ArrayIntList are different implementations of the 
// List Abstract Data Type (ADT).

public class LinkedIntList {
   private ListNode front;

   // Initializes a new empty list.
   public LinkedIntList() {
      front = null;
   }

   // Build a new list with nodes of values n to 0.
   // Pre: n >= 0
   public LinkedIntList(int n) {
      if (n < 0) {
         throw new IllegalArgumentException();
      }
      for (int i = 0; i <= n; i++) {
         front = new ListNode(i, front);

         // same as:
         // ListNode temp = new ListNode(i, front);
         // front = temp;
      }

      // we started by writing out some examples to find pattern
      // // n = 1
      // temp = new ListNode(1, front);
      // front = temp;
      //
      // // n = 2
      // temp = new ListNode(2, front);
      // front = temp;
   }

   // Adds the given value to the end of the list.
   public void add(int value) {
      if (front == null) {
         front = new ListNode(value);
      } else {
         ListNode current = front;
         while (current.next != null) {
            current = current.next;
         }

         current.next = new ListNode(value);
      }
   }

   // Adds a value at a given index.
   // Pre: 0 <= index <= size, throws a NullPointerException if index > size.
   public void add(int index, int value) {
      if (index == 0) {
         front = new ListNode(value, front);
      } else {
         ListNode current = front;
         for (int i = 0; i < index - 1; i++) {
            current = current.next;
         }
         ListNode temp = new ListNode(value, current.next);
         current.next = temp;
         // also ok: current.next = new ListNode(value, current.next);
      }
   }

   // Adds the value in sorted (non-decreasing) order.
   // Pre: list is sorted
   // Post: list is sorted
   public void addSorted(int value) {
      if (front == null || value < front.data) {
         front = new ListNode(value, front);
      } else {
         ListNode current = front;

         while (current.next != null && current.next.data < value) {
            current = current.next;
         }

         current.next = new ListNode(value, current.next);
      }
   }

   // Returns the value at the given index.
   // Pre: 0 <= index < size
   // Throws NullPointerException if index >= size
   public int get(int index) {
      ListNode current = front;

      for (int i = 0; i < index; i++) {
         current = current.next;
      }

      return current.data;
   }

   // Returns a comma-separated String representation of this list.
   public String toString() {
      if (front == null) {
         return "[]";
      } else {
         String result = "[" + front.data;
         ListNode current = front.next;
         while (current != null) {
            result += ", " + current.data;
            current = current.next;
         }
         result += "]";
         return result;
      }
   }
}