var ScrollerWindow = new Class({

    initialize: function(items, size, start) {
    
        if(start == undefined) start = 0;
    
        this.left = start;
        this.right = start + size - 1;
        this.items = items;
    },
    
    next: function() {

        if(this.left > 0) {
        
            this.left--;
            this.right--;
            
            return this.items[this.left];
        }
        
        return null;
    },
    
    previous: function() {
    
        if(this.right < (this.items.length - 1)) {
        
            this.right++;
            this.left++;
            
            return this.items[this.right];
        }
        
        return null;
    },
    
    isFirst: function() {
    
        if(this.left == 0) {
        
            return true;
        }
        
        return false;
    },
    
    isLast: function() {
    
        if(this.right == (this.items.length - 1)) {
        
            return true;
        }
        
        return false;
    }

});