package org.kuali.common.util.tree;
   
   import static org.kuali.common.util.base.Precondition.checkNotNull;
   
   import com.google.common.base.Function;
   
   public final class NodeStringFunction<T> implements Function<Node<T>, String> {
   
   	public NodeStringFunction(Function<T, String> function) {
  		checkNotNull(function, "function");
  		this.function = function;
  	}
  
  	/**
  	 * Convert the element contained in each node to a string by calling it's toString() method
  	 */
  	public static <T> NodeStringFunction<T> create() {
  		return create(new ToStringFunction<T>());
  	}
  
  	/**
  	 * Convert the element contained in each node to a string by invoking {@code function} on it
  	 */
  	public static <T> NodeStringFunction<T> create(Function<T, String> function) {
  		return new NodeStringFunction<T>(function);
  	}
  
  	private final Function<T, String> function;
  
  	@Override
  	public String apply(Node<T> node) {
  		checkNotNull(node, "node");
  		checkNotNull(node.getElement(), "node.element");
  		return function.apply(node.getElement());
  	}
  
  	private static class ToStringFunction<T> implements Function<T, String> {
  
  		@Override
  		public String apply(T element) {
  			checkNotNull(element, "element");
  			return element.toString();
  		}
  	}
  
  }