// This file contains excerpts from the textbook Concrete
// Abstractions: An Introduction to Computer Science Using Scheme, by
// Max Hailperin, Barbara Kaiser, and Karl Knight, Copyright (c) 1998
// by the authors. Full text is available for free at
// http://www.gustavus.edu/+max/concrete-abstractions.html

public class ItemList extends Object {

  private Item[] itemVector;
  private int numItems;

  public ItemList(){
    itemVector = new Item[10];
    numItems = 0;
  }

  public boolean empty(){
    return numItems == 0;
  }

  public void display(){
    for(int index = 0; index < numItems; index = index + 1){
      System.out.print(index + 1);
      System.out.print(") ");
      itemVector[index].display();
      System.out.println();
    }
    System.out.print("Total: ");
    CompuDuds.displayPrice(totalPrice());
    System.out.println();
  }

  public int totalPrice(){
    int sum = 0;
    for(int i = 0; i < numItems; i += 1){
      sum += itemVector[i].price();
    }
    return sum;
  }

  public void add(Item item){
    if(numItems == itemVector.length){
      grow();
      add(item);
    } else {
      itemVector[numItems] = item;
      numItems++;
    }
  }

  public void delete(Item item){
    for(int i = 0; i < numItems; i++){
      if(itemVector[i] == item){
        for(int j = i + 1; j < numItems; j++){
          itemVector[j - 1] = itemVector[j];
        }
        itemVector[numItems - 1] = null;
        numItems--;
        return;
      }
    }
    System.err.println
      ("Error: ItemList delete done with Item not in list.");
    System.exit(1);
  }

  public Item choose(){
    if(empty()){
      System.err.println("Error: choose done on empty ItemList.");
      System.exit(1);
    }
    System.out.println("Which item?");
    display();
    return
      itemVector[CompuDuds.inputIntegerInRange(1, numItems) - 1];
  }

  private void grow(){
    Item[] newItemVector = new Item[itemVector.length * 2];
    for(int i = 0; i < itemVector.length; i++){
      newItemVector[i] = itemVector[i];
    }
    itemVector = newItemVector;
  }
}