// taken from http://www.codeproject.com/jscript/Observer_Pattern_JS.asp

function ArrayList()
{
   this.aList = []; //initialize with an empty array
}
        
ArrayList.prototype.Count = function()
{
   return this.aList.length;
}
        
ArrayList.prototype.Add = function( object )
{
   //Object are placed at the end of the array
   return this.aList.push( object );
}

ArrayList.prototype.GetAt = function( index ) //Index must be a number
{
   if( index > -1 && index < this.aList.length )
      return this.aList[index];
   else
      return undefined; //Out of bound array, return undefined
}
        
ArrayList.prototype.Clear = function()
{
   this.aList = [];
}

ArrayList.prototype.RemoveAt = function ( index ) // index must be a number
{
   var m_count = this.aList.length;
            
   if ( m_count > 0 && index > -1 && index < this.aList.length ) 
   {
      switch( index )
      {
         case 0:
            this.aList.shift();
            break;
         case m_count - 1:
            this.aList.pop();
            break;
         default:
            var head   = this.aList.slice( 0, index );
            var tail   = this.aList.slice( index + 1 );
            this.aList = head.concat( tail );
            break;
      }
   }
}

ArrayList.prototype.Insert = function ( object, index )
{
   var m_count       = this.aList.length;
   var m_returnValue = -1;

   if ( index > -1 && index <= m_count ) 
   {
      switch(index)
      {
         case 0:
            this.aList.unshift(object);
            m_returnValue = 0;
            break;
         case m_count:
            this.aList.push(object);
            m_returnValue = m_count;
            break;
         default:
            var head      = this.aList.slice(0, index - 1);
            var tail      = this.aList.slice(index);
            this.aList    = this.aList.concat(tail.unshift(object));
            m_returnValue = index;
            break;
      }
   }
            
   return m_returnValue;
}

ArrayList.prototype.IndexOf = function( object, startIndex )
{
   var m_count       = this.aList.length;
   var m_returnValue = - 1;
            
   if ( startIndex > -1 && startIndex < m_count ) 
   {
      var i = startIndex;

      while( i < m_count )
      {
         if ( this.aList[i] == object )
         {
            m_returnValue = i;
            break;
         }
                    
         i++;
      }
   }
            
   return m_returnValue;
}
        
        
ArrayList.prototype.LastIndexOf = function( object, startIndex )
{
   var m_count       = this.aList.length;
   var m_returnValue = - 1;
            
   if ( startIndex > -1 && startIndex < m_count ) 
   {
      var i = m_count - 1;
                
      while( i >= startIndex )
      {
         if ( this.aList[i] == object )
         {
            m_returnValue = i;
            break;
         }
                    
         i--;
      }
   }
            
   return m_returnValue;
}

function Observer()
{
   this.Update = function()
   {
      return;
   }
}


function Subject()
{
   this.observers = new ArrayList();
}

Subject.prototype.Notify = function()
{
   var m_count = this.observers.Count();
   
   for( var i = 0; i < m_count; i++ )
      this.observers.GetAt(i).Update.apply(this,arguments);
}

Subject.prototype.AddObserver = function( observer )
{
   if( !observer.Update )
      throw 'Wrong parameter';

   this.observers.Add( observer );
}

Subject.prototype.RemoveObserver = function( observer )
{
   if( !observer.Update )
      throw 'Wrong parameter';
   
   this.observers.RemoveAt(this.observers.IndexOf( observer, 0 ));
}



function inherits(base, extension)
{
   for ( var property in base )
   {
      try
      {
         extension[property] = base[property];
      }
      catch( warning ){}
   }
}