//
//  ElisUndoManager.m
//  Elis Colors
//
//  Created by 柳 on 09/09/24.
//  Copyright 2009 __MyCompanyName__. All rights reserved.
//

#import "ElisUndoManager.h"


@implementation ElisUndoManager

- (void)awakeFromNib
{
    undoStack = [[NSMutableArray alloc] init];
    index = 0;
}

- (void)pushOperation:(ElisLayer*)layer
{
    NSMutableData* data = [[NSMutableData alloc] init];
    NSKeyedArchiver* encoder = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    
    [layer saveToEncoder:encoder];
    [encoder finishEncoding];
    
//    [undoStack addObject:layer];
//    [undoStack addObject:data];
    [undoStack removeObjectsInRange:NSMakeRange(index, [undoStack count] - index)];
    
    if(index != 0)
        if([data isEqualToData:[undoStack objectAtIndex:index-1]])
            return;
    
    [undoStack insertObject:layer atIndex:index];
    [undoStack insertObject:data atIndex:index+1];
    index += 2;
}

- (void)popOperation
{
    NSData* data = [undoStack objectAtIndex:index-1];
    ElisLayer* layer = [undoStack objectAtIndex:index-2];
    
    NSKeyedUnarchiver* decoder = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];    
    [layer loadFromDecoder:decoder];
    [decoder finishDecoding];
    
    index -= 2;
}

- (void)redoOperation
{
    index += 4;
    [self popOperation];
}

- (BOOL)canUndo
{
    return index != 0;
    return [undoStack count] != 0;
}

- (BOOL)canRedo
{
    return index+2 < [undoStack count];
}

@end