Command Pattern at Work in a Database Application

#include "StdAfx.h"
#include "GDataBaseCommand.h"
#include "DataGrid.h"

#include "Resource.h"

struct BookMarkVsCommand
{
	CGDataBaseCommand* pCmd;
	_variant_t vBookMark;

	BookMarkVsCommand()
	{
		vBookMark.vt = VT_EMPTY;
		pCmd = NULL;
	}
};
CArray<BookMarkVsCommand, BookMarkVsCommand&> m_mapBookMarksVsCommands;

void SetCommandInfoAt(CGDataBaseCommand* pCmd, _variant_t vBookMark)
{
	// check if add command exists 
	for(int i = m_mapBookMarksVsCommands.GetSize() - 1; i >=0 ; i--)
	{
		if(m_mapBookMarksVsCommands[i].pCmd == pCmd)
		{
			m_mapBookMarksVsCommands[i].vBookMark = vBookMark;
			return;
		}
	}

	BookMarkVsCommand info;
	info.pCmd = pCmd;	
	info.vBookMark = vBookMark;	
	m_mapBookMarksVsCommands.Add(info);		
}

variant_t GetBookMark(CGDataBaseCommand* pCmd)
{
	for(int i = m_mapBookMarksVsCommands.GetSize() - 1; i >=0 ; i--)
	{
		if(m_mapBookMarksVsCommands[i].pCmd  == pCmd)
		{
			return m_mapBookMarksVsCommands[i].vBookMark;
		}
	}	

	_variant_t vt;
	vt.vt = VT_EMPTY;

	return vt;
}

void UpdateBookMarks(_variant_t vOldBookMark, _variant_t vNewBookMark)
{
	for(int i = m_mapBookMarksVsCommands.GetSize() - 1; i >=0 ; i--)
	{
		if(m_mapBookMarksVsCommands[i].vBookMark == vOldBookMark)
		{
			m_mapBookMarksVsCommands[i].vBookMark = vNewBookMark;
		}
	}	
}


CGDBEditRowCommand::CGDBEditRowCommand(_RecordsetPtr pSet, const CDDXFields& fields, CDataGrid* pGrid) 
					: CGDataBaseCommand(pSet, fields)
{
	m_pGrid = pGrid;
	
	m_undoDDXFields.RemoveAll();
	m_undoDDXFields.Append(fields);	
}


BOOL CGDBEditRowCommand::Execute()
{	
	BOOL bRet = FALSE;	

	_variant_t vBookMark = GetBookMark(this);			
	if(vBookMark.vt == VT_EMPTY) // first time
	{		
		SetCommandInfoAt(this, m_pSet->Bookmark);
	}
	else
	{
		m_pSet->Bookmark = vBookMark;
	}
	
	try
	{
		m_undoDDXFields.ReadData(m_pSet);
		
		if( m_DDXFields.WriteData(m_pSet)!=-1)
		{
			try
			{			
				m_pSet->Update();
				
				if(m_pGrid)
				{
					m_pGrid->SetRowFocus(m_pSet->AbsolutePosition);
				}
					
				bRet = TRUE;
			}
			catch(...)
			{
			}			
		}
	}
	catch( _com_error &e )
	{

		CString mes1,mes2,mes3,mes4;

		mes1.Format(_T("Error:%08lx.\n"), e.Error());
		mes2.Format(_T("ErrorMessage:%s.\n"), e.ErrorMessage());
		mes3.Format(_T("Source:%s.\n"), (LPCTSTR) _bstr_t(e.Source()));
		mes4.Format(_T("Description:%s.\n"), (LPCTSTR) _bstr_t(e.Description()));
		MessageBox(NULL, mes1+mes2+mes3+mes4,_T("Undo Error"),MB_ICONERROR);


		return FALSE;
	}		

					
	return bRet;
}
    
BOOL CGDBEditRowCommand::UnExecute()
{
	BOOL bRet = FALSE;
	
	try
	{		
		_variant_t vBookMark = GetBookMark(this);
		if(vBookMark.vt == VT_EMPTY) // first time
		{
			AfxMessageBox(_T("Invalid Command"));
		}
		else
		{
			m_pSet->Bookmark = vBookMark;
		}
		
		if( m_undoDDXFields.WriteData(m_pSet)!=-1)
		{
			try
			{
				m_pSet->Update();				

				if(m_pGrid)
				{
					m_pGrid->SetRowFocus(m_pSet->AbsolutePosition);
				}
				
				bRet = TRUE;				
			}
			catch(...)
			{
			}			
		}	
	}
	catch( _com_error &e )
	{

		CString mes1,mes2,mes3,mes4;

		mes1.Format(_T("Error:%08lx.\n"), e.Error());
		mes2.Format(_T("ErrorMessage:%s.\n"), e.ErrorMessage());
		mes3.Format(_T("Source:%s.\n"), (LPCTSTR) _bstr_t(e.Source()));
		mes4.Format(_T("Description:%s.\n"), (LPCTSTR) _bstr_t(e.Description()));
		MessageBox(NULL, mes1+mes2+mes3+mes4,_T("Undo Error"),MB_ICONERROR);


		return FALSE;
	}			
	
	return bRet;
}

CGDBAddRowCommand::CGDBAddRowCommand(_RecordsetPtr pSet, const CDDXFields& fields, CDataGrid* pGrid) 
					: CGDataBaseCommand(pSet, fields)
{
	m_pGrid = pGrid;
}

BOOL CGDBAddRowCommand::Execute()
{	
	BOOL bRet = FALSE;

	m_pSet->AddNew();
	if( m_DDXFields.WriteData(m_pSet)!=-1)
	{
		try
		{
			m_pSet->Update();

			_variant_t vBookMark = GetBookMark(this);
			if(vBookMark.vt == VT_EMPTY) // first time
			{
				SetCommandInfoAt(this, m_pSet->Bookmark);
			}
			else
			{
				UpdateBookMarks(vBookMark, m_pSet->Bookmark);
			}

			m_DDXFields.ReadData(m_pSet);			
			
			if(m_pGrid)
			{
				m_pGrid->Invalidate();
				m_pGrid->SetRowFocus(m_pSet->AbsolutePosition);
				m_pGrid->AddNew();
			}																								
			
			bRet = TRUE;
		}
		catch(...)
		{
		}			
	}
				
	return bRet;
}
    
BOOL CGDBAddRowCommand::UnExecute()
{
	BOOL bRet = FALSE;	
	
	try
	{
		_variant_t vBookMark = GetBookMark(this);
		if(vBookMark.vt == VT_EMPTY)
		{
			SetCommandInfoAt(this, m_pSet->Bookmark);
		}
		else
		{
			m_pSet->Bookmark = vBookMark;
		}		
		
		m_DDXFields.ReadData(m_pSet);

		int pos = m_pSet->AbsolutePosition;

		BOOL bBof = pos == 1;
		BOOL bEof = pos == m_pSet->GetRecordCount();
		
		m_pSet->Delete(adAffectCurrent);			
		m_pSet->Update();						
		
		if(m_pGrid)
		{
			m_pGrid->Invalidate();			
			m_pGrid->SetRowFocus(pos-1);
			if(bBof)
			{
				m_pSet->MoveNext();
			}
			if(bEof)
			{
				m_pSet->MovePrevious();
			}
			
			m_pGrid->SetRowCount(m_pSet->GetRecordCount() + 1);
		}

		bRet = TRUE;
	}
	catch( _com_error &e )
	{

		CString mes1,mes2,mes3,mes4;

		mes1.Format(_T("Error:%08lx.\n"), e.Error());
		mes2.Format(_T("ErrorMessage:%s.\n"), e.ErrorMessage());
		mes3.Format(_T("Source:%s.\n"), (LPCTSTR) _bstr_t(e.Source()));
		mes4.Format(_T("Description:%s.\n"), (LPCTSTR) _bstr_t(e.Description()));
		MessageBox(NULL, mes1+mes2+mes3+mes4,_T("Undo Error"),MB_ICONERROR);


		return FALSE;
	}	
	
	return bRet;
}


CGDBDeleteRowCommand::CGDBDeleteRowCommand(_RecordsetPtr pSet, const CDDXFields& fields, CDataGrid* pGrid) 
					: CGDBAddRowCommand(pSet, fields, pGrid), m_bFirstTimeExecution(TRUE)
{
}

BOOL CGDBDeleteRowCommand::Execute()
{	
	if(m_bFirstTimeExecution)
	{
		m_bFirstTimeExecution = FALSE;

		CString strDel,strErrorDesc;
		strDel.LoadString(IDS_GRID_DEL);
		CString strQuestion;

		strQuestion.LoadString(IDS_GRID_DEL_QUESTION);
		if (::MessageBox (AfxGetMainWnd()->GetSafeHwnd(), strQuestion, strDel,  MB_YESNO|MB_DEFBUTTON2 | MB_ICONQUESTION) == IDNO)
			return FALSE;				
	}
	
	BOOL bRet = CGDBAddRowCommand::UnExecute();	

	return bRet;
}

BOOL CGDBDeleteRowCommand::UnExecute()
{	
	BOOL bRet = CGDBAddRowCommand::Execute();	

	return bRet;
}