/**
 * A generic Doubly Linked List implementation.
 * 
 * @author gtowell Created: Jan 2020 Modified: Nov 2020
 */
public class DoubleLinkedList<T extends Comparable<T>> implements LinkedListInterface<T> {

    /**
     * The node class. Each element in the linked list is an instance of Node
     */
    protected class Node<V extends Comparable<V>> {
        /** The data item in the node. An instance of the data */
        public Comparable<V> data;
        /** The next item in the linked list */
        public Node<V> next;
        /** The previous item in the linked list */
        public Node<V> prev;

        /**
         * Node constructor. Takes a data item and the preceding and trailing nodes.
         */
        public Node(Comparable<V> data, Node<V> prev, Node<V> next) {
            this.data = data;
            this.next = next;
            this.prev = prev;
        }
    }

    /** The start, first element, of the linked list */
    protected Node<T> head = null;

    /** THe last element in the linked list */
    protected Node<T> tail = null;

    /** The number of items in the linked list */
    protected int size = 0;

    /**
     * The number of items in the linked list
     * 
     * @return the number of items in the linked list
     */
    @Override
    public int size() {
        return size;
    }

    /**
     * Returns true iff the linked list has no elements
     * 
     * @return true iff the linked list has no elements
     */
    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * Get the first element in the linked list
     * 
     * @return the first element in the linked list or null if list is empty
     */
    @Override
    public Comparable<T> first() {
        if (head == null)
            return null;
        return head.data;
    }

    /**
     * The last element in the linked list
     * 
     * @return the last elment or null if list is empty
     */
    @Override
    public Comparable<T> last() {
        if (head == null)
            return null;
        return tail.data;
    }

    /**
     * Remove the first item from the list
     * 
     * @return the first item, or null if the list is empty
     */
    @Override
    public Comparable<T> removeFirst() {
        if (head == null)
            return null;
        Comparable<T> rtn = head.data;
        head = head.next;
        if (head == null)
            tail = null;
        else
            head.prev = null;
        size--;
        return rtn;
    }

    /**
     * Remove the last item from the list
     * 
     * @return the last item, or null if the list is empty
     */
    @Override
    @SuppressWarnings("unchecked")
    public Comparable<T> removeLast() {
        if (head == null)
            return null;
        Comparable<T> rtn = tail.data;
        if (head == tail) {
            head = null;
            size = 0;
            tail = null;
            return (T) rtn;
        }
        tail = tail.prev;
        tail.next = null;
        size--;
        return rtn;
    }

    /**
     * Remove the specified rabbit from the list
     * 
     * @param r the item to be removed
     * @return the removed item, or null is the item was not in the list
     */
    @Override
    @SuppressWarnings("unchecked")
    public Comparable<T> remove(Comparable<T> r) {
        // Do something much like find, but need to trak the previous node
        Node<T> curr = head;
        while (curr != null) {
            if (0 == curr.data.compareTo((T) r)) {
                break;
            }
            curr = curr.next;
        }
        if (curr == null) {
            // 1. the rabbit was not found
            return null;
        }
        size--;
        if (curr.prev != null)
            curr.prev.next = curr.next;
        if (curr.next != null)
            curr.next.prev = curr.prev;
        if (curr == tail)
            tail = curr.prev;
        return r;
    }

    /**
     * Find a rabbit in the list by its iD
     * 
     * @param iD
     * @return the found rabbit, or null if a match could not be found
     */
    @Override
    @SuppressWarnings("unchecked")
    public Comparable<T> find(Comparable<T> rr) {
        Node<T> curr = head;
        while (curr != null) {
            if (0 == curr.data.compareTo((T) rr)) {
                return (T) curr.data;
            }
            curr = curr.next;
        }
        return null;
    }

    public String toString() {
        StringBuffer s = new StringBuffer();
        for (Node<T> n = head; n != null; n = n.next) {
            s.append(n.data.toString());
            s.append("\n");
        }
        return s.toString();
    }

    /**
     * Example usage with Rabbits
     * 
     * @param args
     */
    public static void main(String[] args) {
        DoubleLinkedList<Rabbit> llr = new DoubleLinkedList<>();
        Rabbit ar = new Rabbit(BreedEnum.Angora, "A1", 2);
        llr.addFirst(ar);
        llr.addFirst(new Rabbit(BreedEnum.DwarfDutch, "DD1", 3));
        llr.addLast(new Rabbit(BreedEnum.FrenchLop, "FL1", 4));
        System.out.println(llr);
        // llr.removeFirst();
        // llr.removeLast();
        llr.remove(ar);
        System.out.println();
        System.out.println(llr);
    }

    /**
     * Add an element at the end of the list
     * 
     * @param c the element to be added
     */
    @Override
    public void addLast(Comparable<T> c) {
        Node<T> newNode = new Node<>(c, tail, null);
        if (head == null) {
            head = newNode;
            tail = newNode;
            size = 1;
            return;
        }
        tail.next = newNode;
        tail = newNode;
        size++;
    }

    /**
     * Add a element at the front of the list
     * 
     * @param c the Element to be added
     */
    @Override
    public void addFirst(Comparable<T> c) {
        Node<T> newNode = new Node<>(c, null, head);
        if (head == null) {
            head = newNode;
            tail = newNode;
            size = 1;
            return;
        }
        head.prev = newNode;
        head = newNode;
        size++;
    }

}