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/**

    Copyright 2004, 2007 Engineering Ingegneria Informatica S.p.A.

    This file is part of Spago.

    Spago is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2.1 of the License, or
    any later version.

    Spago is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with Spago; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

**/
package it.eng.spago.navigation;

import it.eng.spago.base.Constants;
import it.eng.spago.navigation.NavigationException;
import it.eng.spago.tracing.TracerSingleton;

import java.util.ArrayList;

public class LightNavigator {

	// ArrayList used as stack (last-in-first-out)
	private ArrayList list = new ArrayList();

	/**
	 * Adds a MarkedRequest element to the stack.
	 * @param markedRequest the MarkedRequest object to be added to the stack
	 */
	public void add(MarkedRequest markedRequest) throws NavigationException {
		if (markedRequest == null) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.CRITICAL, "LightNavigator: " +
			"add: the MarkedRequest object at input is null.");
			throw new NavigationException ("The MarkedRequest object at input is null.");
		}
		list.add(0, markedRequest);
	}
	
	/**
	 * Retrieves the MarkedRequest object at the desired position in the stack and deletes 
	 * the more recent MarkedRequest objects present in the stack.
	 * 
	 * @param i The int representing the position of the stack.
	 * @throws NavigationException if the position at input is not present in the stack
	 */
	public MarkedRequest goBackToPosition(int i) throws NavigationException {
//		 Index i must be 0 < i < list.size()-1, the request at index 0 is the request for the current page
		if (i < 0 || i > list.size() -1 ) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.CRITICAL, "LightNavigator: " +
			"goBackToPosition: the position " + i +" is not present in the stack.");
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.DEBUG, "The requests stack is:\n" + this.toString());
			throw new NavigationException ("Index of the required request is not correct.");
		}
		MarkedRequest markedRequest = (MarkedRequest) list.get(i);
		for (int j = 0; j < i; j++) {
			list.remove(0);
		}
		return markedRequest;
	}
	
	/**
	 * Deletes the more recent MarkedRequest object in the stack and adds 
	 * the MarkedRequest passed at input in the first position of the stack.
	 * 
	 * @param markedRequest the MarkedRequest object that will replace the more recent MarkedRequest in the stack
	 * @throws NavigationException if teh MarkedRequest object at input is null of if the stack is empty.
	 */
	public void replaceLast(MarkedRequest markedRequest) throws NavigationException {
		if (markedRequest == null) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.CRITICAL, "LightNavigator: " +
			"replaceLast: the MarkedRequest object at input is null.");
			throw new NavigationException ("The MarkedRequest object at input is null.");
		}
		if (list.size() == 0) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.CRITICAL, "LightNavigator: " +
			"replaceLast: the stack is empty: it is not possible to substitute the request.");
			throw new NavigationException ("The stack is empty: it is not possible to substitute the request.");
		}
		// removes the most recent request
		list.remove(0);
		// adds the request at input in the first position
		list.add(0, markedRequest);
	}
	
	/**
	 * Resets the stack.
	 *
	 */
	public void reset() {
		list = new ArrayList();
	}
	
	/**
	 * Retrieves the more recent MarkedRequest object in the stack with the mark passed at input 
	 * and deletes the more recent MarkedRequest objects present in the stack.
	 * 
	 * @param mark The string mark of the desired MarkedRequest object in the stack.
	 * @throws NavigationException if there are no MarkedRequest objects with the mark passed at input.
	 */
	public MarkedRequest goBackToMark(String mark) throws NavigationException{
		if (mark == null) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.MAJOR, "LightNavigator: " +
					"goBackToMark: the input mark is null.");
			throw new NavigationException ("The input mark for navigation research cannot be null.");
		}
		MarkedRequest toReturn = null;
		int i = 1; 
		while (i <= list.size()) {
			MarkedRequest markedRequest = (MarkedRequest) list.get(i - 1);
			if (mark.equalsIgnoreCase(markedRequest.getMark())) {
				toReturn = markedRequest;
				break;
			}
			i++;
		}
		if (toReturn == null) {
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.MAJOR, "LightNavigator: " +
				"goBackToMark: Request with mark '" + mark + "' not found.");
			TracerSingleton.log(Constants.NOME_MODULO, TracerSingleton.DEBUG, "The requests stack is:\n" + this.toString());
			throw new NavigationException ("Request with mark '" + mark + "' not found.");
		}
		for (int j = 0; j < i - 1; j++) {
			list.remove(0);
		}
		return toReturn;
	}

	public String toString () {
		String toReturn = "";
		for (int i = 0 ; i < list.size(); i++) {
			toReturn += "Position " + i + ":\n"; 
			toReturn += list.get(i).toString();
			toReturn += "\n-------------------------------------------\n";
		}
		return toReturn;
	}
}