package CIS115.linkedlist;

public class BookList {
    public BookNode head;
    public BookNode tail;
    
    // add a book to the list
    public void add(Book b) {
        // new node holds the book
        BookNode node = new BookNode();
        node.contents = b;
        
        // special case for first node
        if (head == null) {
            head = node;
            tail = node;
        } else {
            // add the new node at end and update tail
            tail.next = node;
            tail = node;
        }
    }
    
    // print the whole list
    public void printList() {
        // start at head
        BookNode current = head;
        System.out.println("List Begins");
        int i = 0; // for readability of output
        
        // keep going through whole list
        while(current != null) {
            System.out.println(i + ". " + current.contents);
            // move down one node
            current = current.next;
            i++;
        }
        System.out.println("List Ends");
    }
    
    // remove and return book at position pos (counting from 0)
    public Book remove (int pos) {
        // current node we are looking at
        BookNode current = head;
        // used to store one node back so we can splice out
        BookNode prev = null;
        
        // to store the book we're removing
        Book result = null;
        
        // loop to find the position, stop if we run out of nodes
        // could use while instead, either way we need &&
        // could go 0 to < pos, but this is more readable "stop at pos"
        // since current started at head already
        for (int i = 1; i <= pos && current != null; i++) {
            prev = current; // chase current
            current = current.next;
        }
        
        // if we found that position
        if (current != null) {
            result = current.contents;
            // special case for first node, need to update head
            if (current == head) {
                head = head.next;
            } else {
                // special case for last node, need to update tail
                if (current == tail) {
                    tail = prev;
                }
                // splice out the current node
                prev.next = current.next;
            }
        }
        
        return result;
    }
}