package service.bean;

import java.util.*;
import java.io.*;

/** @author Eric La Force
 *  @version %I% %G%
 *  This is a class that encapsulates the server delay module
*/

public class ServerDelayModule{
	Hashtable priority;
	/** Contructor that initiates the priority hash table.  The priority
	 *  hash table is used for the equation parsing.
	 *
	 */
	public ServerDelayModule(){
		priority = new Hashtable(4);
		
		// priority table for operators
		// the higher the key value, the higher the priority
		priority.put("(",new Integer(2));
		priority.put(")",new Integer(2));
		priority.put("/",new Integer(1));
		priority.put("*",new Integer(1));
		priority.put("+",new Integer(0));
		priority.put("-",new Integer(0));
		
		//this is bottom of the stack.  dont put anything below -1
		priority.put("bottom", new Integer(-1));
	}
	
	/** computes the server delay by parsing out the equation associated
	 *  with this server (in the prediction.xml under the XMLDataContentTree
	 *  and the parameters associated with that equation.
	 * @param requestdatasize  is the size of the request.  
	 * @return the server delay
	 */
	public double getServerDelay(double requestdatasize){
		double delay = 0;
		
		// returns the xml file in a string
		String xmlDescription = invokeXML();
		
        // write parse code here
		ArrayList listOfVariables = new ArrayList();
		ArrayList parameters = new ArrayList();
		StringTokenizer tokens = new StringTokenizer(xmlDescription,",");
		
		while(tokens.hasMoreElements()){
			listOfVariables.add(tokens.nextToken());
		}
		
		// add parameters into parameter array list
		// the parameters should always go from [6] to [size of listOfVariables - 1]
		for (int i = 6; i < listOfVariables.size(); i++){
			//parameters.add(new Double(Double.parseDouble((String)listOfVariables.get(i))));
			parameters.add(listOfVariables.get(i));
		}
		//System.out.println(parameters);
		// parse equation - right now it only deals with + and - and / and *
		String equation = (String) listOfVariables.get(5);
		
		//skip the "Sd =" part
		String equationWithoutSd = equation.substring(4,equation.length());
		
		// get all the variable names  should equal the number of parameters
		// make sure the equation is space delimited i.e spaces between parens
		// such as Sd = Tqd + Tcpudelay + Tdisk - TTestValue
		tokens = new StringTokenizer(equationWithoutSd, " ");
		
		/* build postfix expression */
		String postfix = "";
		Stack postfixStack = new Stack();
		// this is so the algorithm knows to push the first operator on
		postfixStack.push("bottom");
		while(tokens.hasMoreTokens()){
			String currentTok = tokens.nextToken();
			
			// open paren
			if(currentTok.equals("(")){
				postfixStack.push(currentTok);
			}
			
			// close paren
			else if(currentTok.equals(")")){
				while(!(((String)(postfixStack.peek())).equals("("))){
					String temp = (String)postfixStack.pop();
					postfix += temp + ",";
				}
			}
			
			//operators
			else if(currentTok.equals("+") || currentTok.equals("-") || currentTok.equals("*") || currentTok.equals("/")){
				boolean endLoop = false;
				while(endLoop == false){
					// if nothing on the stack
					if(postfixStack.size() == 0){
						postfixStack.push(currentTok);
						endLoop = true;
					}
					
					//if open paren is on top of the stack
					else if(((String)postfixStack.peek()).equals("(")){
						postfixStack.push(currentTok);
						endLoop = true;
					}
					
					// has higher priority than what is currently on top of the stack
				    else if(hasHigherPriority(currentTok,((String)postfixStack.peek()))){
						postfixStack.push(currentTok);
						endLoop = true;
					}
					
					// does not have higher priority or is equal priority
					else{
						String temp = (String)postfixStack.pop();
						postfix += temp + ",";
					}
				} 
				
			}
			
			// must be an operand
			else{
				postfix += currentTok + ",";
			}
		}
		
		// append what operators are on the stack to the postfix expression
		while(!(postfixStack.isEmpty())){
			String temp = (String)postfixStack.pop();
			if(temp.equals("+") || temp.equals("-") || temp.equals("*") || temp.equals("/")){
				postfix += temp + ",";
			}	
		}
		
		//System.out.println(postfix);
		// evaluate postfix expression into delay
		Stack evaluation = new Stack();
		tokens = new StringTokenizer(postfix,",");
		int index = 0;
		while(tokens.hasMoreTokens()){
			String currentTok = tokens.nextToken();
			//System.out.println("currentTok = " + currentTok);
			if(currentTok.equals("requestdatasize")){
				evaluation.push(new String("" + requestdatasize));
		//		System.out.println("in the requestdatasize");
			}
			
			else if(currentTok.equals("+") || currentTok.equals("-") || currentTok.equals("*") || currentTok.equals("/")){
				String s1 = (String)evaluation.pop();
				String s2 = (String)evaluation.pop();
			    double operand01 = Double.parseDouble(s1);
				double operand02 = Double.parseDouble(s2);
				double pushOperand = 0.0;
				if(currentTok.equals("+")){
					pushOperand = operand02 + operand01;
					evaluation.push("" + pushOperand);	
				}
				
				else if(currentTok.equals("-")){
					pushOperand = operand02 - operand01;
					evaluation.push("" + pushOperand);
				}
				
				else if(currentTok.equals("*")){
					pushOperand = operand02 * operand01;
					evaluation.push("" + pushOperand);
				}
				
				// divide
				else{
					pushOperand = operand02 / operand01;
					evaluation.push("" + pushOperand);
				}
		//		System.out.println("pushOperand = " + pushOperand);
			}
			
			else{
		//		System.out.println("parameters.get() returns " +parameters.get(index) + " at " + index);
				evaluation.push((parameters.get(index)));  //index matches up the variables name of the equation with the actual parameters
				index++;
			}
		}
		
        //should only have the delay left on the stack
		 if(evaluation.size() == 1){
			 delay = Double.parseDouble((String)evaluation.pop());
		 }
	
		 else{
			 System.out.println("Something went wrong with the stacks");
		 }

		return delay;
	}
	
	/** contacts the XMLContentTree to parse out the xml file
	 * 
	 * @return string that holds all the web server delay info
	 */
	private String invokeXML(){
		String string = "";
		
		WebService ws;
		String URLTwo = "http://localhost:9080/XMLDataContentTree/services/XMLDataContentTree";
		String targetNameSpaceTwo = "http://bean.service";
		String serviceNameTwo = "XMLDataContentTree";
				
		ws = new WebService(URLTwo, targetNameSpaceTwo, serviceNameTwo);
		string = (String) ws.invokeMethod( "unmarshallIt", "string", new Object [] {} );
				
		return string;
	}
	
	private boolean hasHigherPriority(String token, String topOfStack){
		Integer temp = (Integer)priority.get(token);
		//System.out.println(temp.intValue());
		Integer temp2 = (Integer)priority.get(topOfStack);
		
		// return true if temp is greater than temp2 (aka has a higher priority)
		return (temp.intValue() > temp2.intValue());
	}
}