package linkedList;

public class SinglyLinkedList<T extends Comparable<T>> implements List<T> {

	private Node<T> top;
	private int listSize;

	//Creates a node and sets the size of the list
	public SinglyLinkedList(){
		top = new Node<T>(null);
		listSize = 0;
	}

	//Inserts element at a specific position
	public void add(int index, T value) throws ListAccessError {
		Node<T> addNode = new Node<T>(value);
		Node<T> nextE = top;
		if(index > (listSize + 1)) throw new ListAccessError("You can't add an element to an index greater than the list size");
		//For each element less than index skip over then move each element one
		//more pointer
		for (int i = 1; i < index && nextE.next() != null; i++) {
			nextE = nextE.next();
		}
		//Set the pointer to the next node
		addNode.setNext(nextE.next());
		//Set this node to the old node pointer
		nextE.setNext(addNode);
		//Increment the size
		listSize++;
	}

	//Gets the element at a specific index
	public T get(int index) throws ListAccessError{
		//Index needs to be more than 1 since index 0 is top
		if (index <= 0)
			throw new ListAccessError("This is the top index");
		//Starts any counting from the next element after the top
		Node <T> nextE = top.next();
		//Each element less than the index is ignored
		for (int i = 1; i < index; i++) {
			if (nextE.next() == null)
				throw new ListAccessError("There is no node to get");
			nextE = nextE.next();
		}
		//Returns the value of the next index from index - 1 i.e index
		return nextE.value();
	}

	//Removes specific element
	public T remove(int index)  throws ListAccessError{
		//If the index is the same as top or greater than the list size throw an error
		if (index < 1 || index > listSize)
			throw new ListAccessError ("Index not within specified list");
		//Each element less than the specific index is ignored
		Node<T> nextE = top;
		for (int i = 1; i < index; i++) {
			//If there isn't pointer to the next node throw error
			if (nextE.next() == null)
				throw new ListAccessError ("There is no node to remove");
			nextE = nextE.next();
		}
		//Assigns value of removed item to elementValue
		T elementValue = nextE.next().value();
		//Sets the current node pointer to the pointer after the removed node
		nextE.setNext(nextE.next().next());
		//Reduces list size by 1
		listSize--;
		return elementValue;
	}

	//Return True or False depending on whether list is empty
	public boolean isEmpty(){
		return(top == null);
	}

	//For outputing the test
	public String toString() {
		Node<T> indexE = top.next();
		String testOutput = "";
		while (indexE != null) {
			testOutput += "[" + indexE.value().toString() + "]";
			indexE = indexE.next();
		}
		return testOutput;
	}

	//Main method
	public static void main(String[] args) throws ListAccessError {
		SinglyLinkedList<String> newList = new SinglyLinkedList<String>();

		//Add elements to SinglyLinkedList
		newList.add(1,"1");
		newList.add(2,"2");
		newList.add(3,"3");
		newList.add(4,"4");
		newList.add(5,"5");
		newList.add(2, "6");

		//Test that methods work
		try{
			System.out.println("List: " + newList);
			System.out.println("Get 2nd element: " + newList.get(2));
			System.out.println("Remove 2nd element: " + newList.remove(2));
			System.out.println("List size: " + newList.listSize);
			System.out.println("Update list: " + newList);
		} finally {
			System.out.println("Is list empty?: " + newList.isEmpty());
		}
}
}