/*
 * Name = Abdulmohsen ali asiri
 * ID = 36110218
 */
package testintegerdll;

public class DLL<T> {

    private DLLNode<T> head, tail;

    public DLL() {
        head = tail = null;
    }

    public boolean isEmpty() {
        return head == null;
    }

    public void clear() {
        head = tail = null;
    }

    public T getFirst() {
        if (head != null) {
            return head.info;
        } else {
            return null;
        }
    }

    public void addToHead(T el) {
        if (head != null) {
            head = new DLLNode<T>(el, head, null);
            head.next.prev = head;
        } else {
            head = tail = new DLLNode<T>(el);
        }
    }

    public void addToTail(T el) {
        if (tail != null) {
            tail = new DLLNode<T>(el, null, tail);
            tail.prev.next = tail;
        } else {
            head = tail = new DLLNode<T>(el);
        }
    }

    public T deleteFromHead() {
        if (isEmpty()) {
            return null;
        }
        T el = head.info;
        if (head == tail) // if only one node on the list;
        {
            head = tail = null;
        } else {              // if more than one node in the list;
            head = head.next;
            head.prev = null;
        }
        return el;
    }

    public T deleteFromTail() {
        if (isEmpty()) {
            return null;
        }
        T el = tail.info;
        if (head == tail) // if only one node on the list;
        {
            head = tail = null;
        } else {              // if more than one node in the list;
            tail = tail.prev;
            tail.next = null;
        }
        return el;
    }

    public void delete(T el) {  // delete the node with an element el;
        DLLNode<T> tmp;
        for (tmp = head; tmp != null && !el.equals(tmp.info); tmp = tmp.next); //locate the item

        if (tmp != null) { // item found
            if (head == tail) //the found item was the only one
            {
                head = tail = null;
            } else if (head == tmp) { //the found item is the first
                head = head.next;
                head.prev = null;
            } else if (tail == tmp) { // the found item is the last
                tail = tail.prev;
                tail.next = null;
            } else { // the found item is in the middle
                tmp.prev.next = tmp.next;
                tmp.next.prev = tmp.prev;
            }
        }
    }

    public void printAll() {
        for (DLLNode<T> tmp = head; tmp != null; tmp = tmp.next) {
            System.out.print(tmp.info + " ");
        }
    }

    public T find(T el) {
        DLLNode<T> tmp;
        for (tmp = head; tmp != null && !tmp.info.equals(el); tmp = tmp.next);
        if (tmp == null) {
            return null;
        } else {
            return tmp.info;
        }
    }

    // node of generic doubly linked list class
    class DLLNode<T> {

        public T info;
        public DLLNode<T> next, prev;

        public DLLNode() {
            next = null;
            prev = null;
        }

        public DLLNode(T el) {
            info = el;
            next = null;
            prev = null;
        }

        public DLLNode(T el, DLLNode<T> n, DLLNode<T> p) {
            info = el;
            next = n;
            prev = p;
        }
    }

    public int length() {
        int count = 0;
        DLLNode<T> tmp = head;
        for (tmp = head; tmp != null; tmp = tmp.next, count++);
        return count;
    }
//start of assignment
    public T get(int index) {
        DLLNode<T> tmp = head;
        int count = 0;

        if (index < 0 || index > length() - 1) {
            return null;
        } else {

            for (tmp = head; count != index; tmp = tmp.next, count++);
            return tmp.info;
        }

    }

    public int indexOf(T el) {
        DLLNode<T> tmp = head;
        int count = 0;
        for (tmp = head; tmp != null && !tmp.info.equals(el); tmp = tmp.next, count++);
        if (tmp == null) {
            return -1;
        } else {
            return count;
        }
    }

    public void replace(int index, T el) {
        DLLNode<T> tmp = head;
        int count = 0;

        for (tmp = head; tmp != null && count != index; tmp = tmp.next, count++);
        if (tmp != null) {
            tmp.info = el;
        }
    }

    public void insertAt(int index, T el) {
        DLLNode<T> tmp = head;
        int count = 0;

        if (index >= 0 && index <= length()) {
            if (index == 0) {
                addToHead(el);
            }
            else if (index == length()) {
                addToTail(el);
            }
            else    {
                for (tmp = head; count != index; tmp = tmp.next, count++);
                tmp.prev.next = tmp.prev = new DLLNode<T>(el, tmp, tmp.prev);
            }
        }

    }

    public T deleteAt(int index) {
        DLLNode<T> tmp = head;
        int count = 0;

        if (index < 0 || index > length() - 1) {
            return null;
        } else if (isEmpty()) {
            return null;
        } else if (length() == 1) {
            T el = head.info;
            clear();
            return el;
        } else if (index == 0) {
            T el = tmp.info;
            head = tmp.next;
            head.prev = null;
            return el;
        } else if (index == length() - 1) {
            T el = tail.info;
            tail = tail.prev;
            tail.next = null;
            return el;
        } else {
            for (tmp = head; count != index; tmp = tmp.next, count++);
            T el = tmp.info;
            tmp.next.prev = tmp.prev;
            tmp.prev.next = tmp.next;
            return el;
        }
    }

}