/*
 * List.java
 *
 * Created on March 28, 2007, 5:51 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package exercise5;
import java.util.*;
public class List implements Element {
    
    private static class EleArrList extends ArrayList<Element> {
        
    }
    
    private static class linkListNode {
        EleArrList _data;
        linkListNode _next;
        @SuppressWarnings("unchecked")
        public linkListNode(EleArrList L){
            _data = (EleArrList)(L.clone());
            _next = null;
        }
    }
    static private linkListNode _head = null;
    static private linkListNode _tail = null;
    private linkListNode _ptr;
    
    List(){
        // this is a dummy
    }
    
    List(EleArrList L) {
        linkListNode N = new linkListNode(L);
        // case 1: link list is empty
        if (_head==null){
            _head = N;
            _tail = N;
            _ptr = _head;
            return;
        }
        // case two: check if the List is already in the link list
        linkListNode current = _head;
        while (current!=null){
            if (current._data.equals(L)==true){
                _ptr = current;
                return;
            }
            current = current._next;
        }
        // case three: add a List to link list
        _tail._next = N;
        _tail = _tail._next;
        _ptr = N;
        return;
    }
    
    public static List nil(){
        EleArrList L = new EleArrList();
        return new List(L);
    }
    
    public static List cons(Element x, List k){
        @SuppressWarnings("unchecked")
        EleArrList L = (EleArrList)k._ptr._data.clone();
        L.add(0,x);
        return new List(L);
    }
    
    public Element getMember(int i) throws BadIndexException{
        if ((i<0)||(i>(_ptr._data.size()-1))) {
            throw new BadIndexException(this,i);
        }
        return (Element)(_ptr._data.get(i));
    }
    
    public static List take(int i, List k) throws BadIndexException {
        @SuppressWarnings("unchecked")
        EleArrList L = (EleArrList)(k._ptr._data.clone());
        int len = L.size();
        if ((i<0)||(i>len)) {
            throw new BadIndexException(k,i);
        }
        for (int count=i; count<len; count++){
            L.remove(i);
        }
        return new List(L);
    }
    
    public static List drop(int i, List k) throws BadIndexException {
        @SuppressWarnings("unchecked")
        EleArrList L = (EleArrList)(k._ptr._data.clone());
        int len = L.size();
        if ((i<0)||(i>len)) {
            throw new BadIndexException(k,i);
        }
        for (int count=0; count<i; count++){
            L.remove(0);
        }
        return new List(L);
    }
    
    public boolean same(Element e) {
        if (this._ptr==((List)e)._ptr){
            return true;
        } else {
            return false;
        }
    }
    
    public String toString() {
        String s = "[";
        int len = this._ptr._data.size();
        for (int i=0; i<len-1; i++){
            s = s+this._ptr._data.get(i).toString()+",";
        }
        if (len>0) {
            s = s+this._ptr._data.get(len-1).toString()+"]";
        }else{
            s = s+"]";
        }
        return s;
    }
    
}