//-- VisitorExample.java

import java.util.ArrayList;


// ************************************************************************
/*
 * VisitorExample.java
 *
 * Provides a simple Visitor Design Pattern Example.
 *
 * The example will construct an object graph of several Order objects
 * each of which aggregates an ArrayList of Item objects. A Visitor will
 * be created which will traverse through the structure and adjust the
 * price of all Item objects.
*/
// ************************************************************************
public class VisitorExample {
	static int MAX_ORDERS = 3;
	static int MAX_ITEMS = 10;


	/** ====================================================
	 * Main used as main driver for the example
	 * ==================================================== */
	public static void main(String[] args) {
		Item item = null;
		Order order = null;

		VisitorExample example = new VisitorExample();

		//-- Create example's sample object graph
		ArrayList orderList = example.createSampleObjectGraph();
		VisitorExample.log(1,
			"ArrayList orderList contains orders = " +
			orderList.size());

		//-- Vist each Order and each Order's Items with the Visitor
		ItemPriceAdjustmentVisitor visitor =
			new ItemPriceAdjustmentVisitor();
		for(int i=0; i < orderList.size(); i++) {
			order = (Order)orderList.get(i);
			order.accept(visitor);
		} //endfor
	} //endmain


	/** ========================================================================
	 *
	 * Create example sample object graph
	 *
	 * ======================================================================== */
	private ArrayList createSampleObjectGraph() {
		Item item = null;
		Order order = null;

		//-- Create example sample object graph
		ArrayList orderList = new ArrayList();
		for(int i=0; i < VisitorExample.MAX_ORDERS; i++) {
			order = new Order();
			order.setOrderId((new java.util.Date()).getTime());
			ArrayList itemList = new ArrayList();
			VisitorExample.log(1, "Order " + order.getOrderId() +
					"has added Item:");
			for(int j=0; j < VisitorExample.MAX_ITEMS; j++) {
				item = new Item();
				item.setItemId((new java.util.Date()).getTime());
				item.setPrice(
				(new Double(java.lang.Math.PI*
					java.lang.Math.random()*8.6f)).floatValue());
				itemList.add(item);
				VisitorExample.log(2, "" + item.getItemId() +
						" has price: " + item.getPrice());
				//-- Pause to let seconds change for new ids...
				for(int wait=0; wait < 50000000; wait++) {}
			}//endfor
			order.setItemList(itemList);
			orderList.add(order);
		} //endfor

		return(orderList);
	} //endmethod: createSampleObjectGraph


	/** ========================================================================
	 *
	 * Used for debug testing
	 *
	 * ======================================================================== */
  public static void log(int aLevel, String aMsg) {
	  boolean showLogTraceToSystemOut = true;
	  if(showLogTraceToSystemOut) {
		  String prefix = "";
		  if(aLevel == 1) {
			  prefix = "   ---> ";
		  } else if(aLevel == 2) {
			  prefix = "     ---> ";
		  } else if(aLevel == 3) {
			  prefix = "       ---> ";
		  } //endif
		  System.out.println(prefix + aMsg);
	  } //endif
  } //endmethod: log
} //endclass: VisitorExample.java


// ************************************************************************
/*
 * Visitor.java
 *
 * Provides a simple Visitor interface for Visitor Design Pattern Example.
*/
// ************************************************************************
interface Visitor {
    public void visit(Object o);
} //endinterface: Visitor.java


// ************************************************************************
/*
 * Visitable.java
 *
 * Provides a simple Visitable interface for Visitor Design Pattern Example.
*/
// ************************************************************************
interface Visitable {
    public void accept(Visitor visitor);
} //endinterface: Visitable



// ************************************************************************
/*
 * Order.java
 *
 * Order object is a container for ArrayList of associated item objects.
*/
// ************************************************************************
class Order implements Visitable {
	private ArrayList items = null;
	private long orderId = 0;

	/* ====================================================
	 * Accepts a Visitor object
	 * ==================================================== */
	public void accept(Visitor visitor) {
		VisitorExample.log(1, "Order " + this.getOrderId() +
				" has accepted a visitor.");
		visitor.visit(this);

		//-- Have the Visitor vist all of my aggregates
		Item item = null;
		for(int i=0; i < items.size(); i++) {
			item = (Item)items.get(i);
			item.accept(visitor);
		} //endfor
	} //endmethod: accept()

	public long getOrderId() { return(orderId); }
	public void setOrderId(long aOrderId) { orderId = aOrderId; }
	public ArrayList getItemList() { return(items); }
	public void setItemList(ArrayList aItems) { items = aItems; }
} //endclass: Order


// ************************************************************************
/*
 * Item.java
 *
 * An Item is an aggregate object of an Order object.
*/
// ************************************************************************
class Item implements Visitable {
	private long itemId = 0;
	private float price = 0.0f;

	/* ====================================================
	 * Accepts a Visitor object
	 * ==================================================== */
	public void accept(Visitor visitor) {
		VisitorExample.log(2, "Item "	+ this.getItemId() +
				" has accepted a visitor.");
		visitor.visit(this);
	} //endmethod: accept()

	public long getItemId() { return(itemId); }
	public void setItemId(long aItemId) { itemId = aItemId; }
	public float getPrice() { return(price); }
	public void setPrice(float aPrice) { price = aPrice; }
} //endclass: Item


// ************************************************************************
/*
 * ItemPriceAdjustmentVisitor.java
 *
 * Business service object to change all of the prices of a given Order’s
 * Items by an increase of 1.33 if the Item’s price is below $22.00.
*/
// ************************************************************************
class ItemPriceAdjustmentVisitor implements Visitor {
	private static final float TARGET_PRICE = 22.0f;
	private static final float ADJUSTMENT_PERCENTAGE = 1.33f;
	private static float currentPrice = 0.0f;
	private static float adjustedPrice = 0.0f;

	/* ====================================================
	 * Defines the business logic to perform on the target
	 * Visitable object via double-dispatch
	 * ==================================================== */
	public void visit(Object o) {
		if( o instanceof Item) {
			currentPrice = ((Item)o).getPrice();
			if(currentPrice <= TARGET_PRICE) {
				adjustedPrice = currentPrice*ADJUSTMENT_PERCENTAGE;
				((Item)o).setPrice(adjustedPrice);
				VisitorExample.log(3, "Price changed from " +
					currentPrice +
					" to " + ((Item)o).getPrice());
			} else {
				VisitorExample.log(3, "Current price " +
					currentPrice +
					" not adjusted as greater than min target price " +
					TARGET_PRICE);
			} //endif
		} else {
			VisitorExample.log(2, "I'm not an Item. Bye...");
		} //endif
	} //endmethod: visit()
} //endclass: ItemPriceAdjustmentVisitor