var
  AllPlaceholders: TCatalogPlaceHolders;

  procedure ConvertVersionSet(AMainVersion: TCatalogItem);
  var
    ACatItems: TCatalogItems;
    APlaceholders: TCatalogPlaceHolders;
    APh: TCatalogPlaceHolder;
    AStackID: String;
    i: Integer;
    AVersion: TCatalogItem;
    AMarkers: Integer;
  begin
    {
      1. Retrieve all items in the set
      2. Retrieve the placeholders used in this version set
      3. Destroy the version set
      4. Create a new stack

    }

    ACatItems := TCatalogItems.Create(TCatalogItem, '');
    APlaceholders := TCatalogPlaceHolders.Create(TCatalogPlaceHolder, '');
    try
      PublicCatalog.EnumVersionsForItem(AMainVersion, ACatItems);
      PublicCatalog.EnumPlaceHoldersForMainVersion(APlaceholders, AMainVersion.GUID, True);
      APlaceholders.Disconnect;

      {
        ACatItems now contains the versions. Add the main version so
        that ACatItems contains the full set of catalog items that need
        to become a stack
      }
      ACatItems.Disconnect;  // disconnect from the dataset so that we
                             // can use it independently of the database
      AMainVersion.CopyTo(ACatItems, False);  // add the main version...in other
                                              // words: the last item is always
                                              // the old main version.

      // reset all the stack markers
      for i := 0 to ACatItems.Count - 1 do
      begin
        AVersion := ACatItems.Items[i];
        AVersion.GroupMarkers := 0;
      end;

      //Say2(AMainVersion.FileName, IntToStr(ACatItems.Count) + '-->' + IntToStr(APlaceholders.Count));

      // create the stack
      AStackID := NewGUID;
      PublicCatalog.StackItems(ACatItems, AStackID, AMainVersion);  // set the main version as the

      // for every version that had a placeholder, determine the stack markers
      for i := 0 to APlaceholders.Count - 1 do
      begin
        APh := AllPlaceholders.FindItem(APlaceholders.Items[i].GUID);
        if Assigned(APh) and (APh.idOrder <> -1) then
        begin
          AVersion := ACatItems.FindItem(APlaceholders.Items[i]._VersionGUID);
          if Assigned(AVersion) then
          begin
            AMarkers := AVersion.GroupMarkers;
            Include(AMarkers, APh.idOrder);
            AVersion.GroupMarkers := AMarkers;
          end;
        end;
      end;

      // update the stack markers
      for i := 0 to ACatItems.Count - 1 do
      begin
        AVersion := ACatItems.Items[i];
        if AVersion.GroupMarkers <> 0 then
        begin
          //Say2(AVersion.FileName, IntToStr(AVersion.GroupMarkers));
          PublicCatalog.UpdateItemGroupMarkers(AVersion.GUID, AVersion.GroupMarkers);
        end;
      end;

      // destroy the version set
      PublicCatalog.DestroyVersionSetForItem(AMainVersion);
    finally
      APlaceholders.Free;
      ACatItems.Free;
    end;
  end;

  procedure MapPlaceHolders;
  var
    APh: TCatalogPlaceHolder;
    i: Integer;
  begin
    for i := 0 to AllPlaceholders.Count - 1 do
    begin
      APh := AllPlaceholders.Items[i];
      if APh.PlaceHolderType = vptAlbumDisplay then
        APh.idOrder := sMarkerWhite
      else if APh.PlaceHolderType = vptWebDisplay then
        APh.idOrder := sMarkerRed
      else if APh.PlaceHolderType = vptSlideDisplay then
        APh.idOrder := sMarkerOrange
      else if APh.PlaceHolderType = vptEmail then
        APh.idOrder := sMarkerYellow
      else if APh.PlaceHolderType = vptPrint then
        APh.idOrder := sMarkerAqua
      else if i <= sMarkerBlack then
        APh.idOrder := i
      else
        APh.idOrder := -1;
    end;
  end;

  procedure ConvertVersionSets(AMainVersions: TCatalogItems);
  var
    AProgress: TxomProgress;
    i: Integer;
    AOld: Boolean;
  begin
    AOld := PublicOptions.AutoQuickSync;
    PublicOptions.AutoQuickSync := False;

    AProgress := TxomProgress.Create(nil);
    AllPlaceholders := TCatalogPlaceHolders.Create(TCatalogPlaceHolder, '');
    try
      PublicCatalog.EnumPlaceHolders(AllPlaceholders, False);
      // map the place holders
      MapPlaceHolders;

      AProgress.Caption := 'Convert version sets to stacks';
      AProgress.Max := AMainVersions.Count;
      AProgress.Pos := 0;
      AProgress.CanCancel := True;
      for i := 0 to AMainVersions.Count - 1 do
      begin
        AProgress.Pos := i + 1;
        if AProgress.Cancel then
        begin
          Say('Cancelled.');
          break;
        end;
        ConvertVersionSet(AMainVersions.Items[i]);
      end;
    finally
      AllPlaceholders.Free;
      AProgress.Free;
      PublicOptions.AutoQuickSync := AOld;
    end;
  end;

var
  AMainVersions: TCatalogItems;
begin
  AMainVersions := TCatalogItems.Create(TCatalogItem, '');
  try
    PublicCatalog.EnumAllMainVersions(AMainVersions);
    if AMainVersions.Count = 0 then
      Say('No version sets found.')
    else if AskYN('Are you sure you want to convert your ' + IntToStr(AMainVersions.Count) + ' Version Set' + iif(AMainVersions.Count = 1, '', 's') + ' to Stacks?') then
      ConvertVersionSets(AMainVersions);
  finally
    AMainVersions.Free;
  end;
end;