/**********************************************
    * Copyright (C) 2009 Lukas Laag
    * This file is part of lib-gwt-svg-chess.
    * 
    * libgwtsvg-chess is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    * 
   * libgwtsvg-chess 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 General Public License for more details.
   * 
   * You should have received a copy of the GNU General Public License
   * along with libgwtsvg-chess.  If not, see http://www.gnu.org/licenses/
   **********************************************/
  package org.vectomatic.svg.chess;
  
  import com.google.gwt.core.client.GWT;
  import com.google.gwt.event.logical.shared.ValueChangeEvent;
  import com.google.gwt.event.logical.shared.ValueChangeHandler;
  import com.google.gwt.user.client.History;
  
  public class HistoryManagerMozilla extends HistoryManager {
  	/**
  	 * True if the handler for the browser back/forward button is activated, false otherwise
  	 */
  	private boolean undoActivated;
  	
  	/**
  	 * The main application
  	 */
  	private Main main;
  	
  	@Override
  	public void initialize(Main mainApp) {
  		main = mainApp;
  		// Add undo-redo support through the browser back/forward buttons
  		History.addValueChangeHandler(new ValueChangeHandler<String>() {
  			@Override
  			public void onValueChange(ValueChangeEvent<String> event) {
  				GWT.log("Main.onValueChange(" + History.getToken() + ", " + undoActivated + ")", null);
  				if (undoActivated) {
  					int targetMoveNumber = getCurrentToken();
  					if (targetMoveNumber != -1) {
  						int moveNumber = main.board.getMoveNumber();
  						switch(main.getMode()) {
  							case whitesVsBlacks:
  								break;
  							case whitesVsComputer:
  								if (targetMoveNumber < moveNumber) {
  									if (targetMoveNumber % 2 == 1) {
  										targetMoveNumber--;
  										History.back();
  									}
  								} else if (targetMoveNumber > moveNumber) {
  									if (targetMoveNumber % 2 == 1 && targetMoveNumber < main.lastMoveNumber) {
  										targetMoveNumber++;
  										History.forward();
  									}
  								}
  								break;
  							case blacksVsComputer:
  								if (targetMoveNumber < moveNumber) {
  									if (targetMoveNumber % 2 == 0) {
  										targetMoveNumber--;
  										History.back();
  									}
  								} else if (targetMoveNumber > moveNumber) {
  									if (targetMoveNumber % 2 == 0 && targetMoveNumber < main.lastMoveNumber) {
  										targetMoveNumber++;
  										History.forward();
  									}
  								}
  								break;
  							case computerVsComputer:
  								return;
  						}
  						assert targetMoveNumber >= -1;
  						assert targetMoveNumber <= main.lastMoveNumber;
  						if (moveNumber == -1) {
  							main.board.startPosition();
  						} else {
  							main.board.undoMove(targetMoveNumber);
  						}
  						// Calls to nextMove will trigger a ValueChangeEvent due
  						// to calls to History.back and History.forward
  						// This event must be ignored
  						main.chessboard.update(true);
  						main.nextMove();
  						return;
  					}
  				}
  				undoActivated = true;
  			}
  		});
  		History.fireCurrentHistoryState();
  		undoActivated = true;
 	}
 
 	
 	/**
 	 * Return the carballo index of the current move as
 	 * parsed from the browser undo/redo stack
 	 * @return
 	 */
 	private int getCurrentToken() {
 		int moveNumber = -1;
 		try {
 			String token = History.getToken();
 			int index = token.indexOf('_');
 			if (index != -1) {
 				moveNumber = Integer.parseInt(token.substring(0, index));				
 			}
 		} catch (NumberFormatException e) {
 		}
 		return moveNumber;
 	}
 	
 	@Override
 	public void addMove() {
 		int moveNumber = main.board.getMoveNumber();
 		History.newItem(Integer.toString(moveNumber) + "_" + main.board.getSanMove(moveNumber - 1), false);
 	}
 
 	@Override
 	public void setMove(int moveNumber) {
 		int moveCount = main.board.getMoveNumber() - (moveNumber == -1 ? 0 : moveNumber);
 		undoActivated = false;
 		if (moveCount > 0) {
 			for (int i = 0; i < moveCount; i++) {
 				History.back();
 			}
 		} else if (moveCount < 0) {
 			for (int i = 0; i < -moveCount; i++) {
 				History.forward();
 			}
 		}
 	}
 
 }