unit MainForm;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  Menus, ActiveX, AxCtrls, ComObj;

type
  TfrmMain = class(TForm)
    MainMenu1: TMainMenu;
    File1: TMenuItem;
    Exit1: TMenuItem;
    N1: TMenuItem;
    Gas1: TMenuItem;
    Oil1: TMenuItem;
    Edit1: TMenuItem;
    CarInformation1: TMenuItem;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Gas1Click(Sender: TObject);
    procedure Oil1Click(Sender: TObject);
    procedure CarInformation1Click(Sender: TObject);
  private
    FRootStorage: IStorage;
    FCarName: string;
    FYear: Integer;
    function ActivateForm(ACaption: string): Boolean;
    { Private declarations }
  public
    { Public declarations }
    property RootStorage: IStorage read FRootStorage;
  end;

var
  frmMain: TfrmMain;

implementation

uses GasForm, OilForm, CarInfoForm;

{$R *.DFM}

procedure TfrmMain.FormCreate(Sender: TObject);
var
  stm: IStream;
  OS: TOleStream;
  Reader: TReader;
begin
  if not SUCCEEDED(StgOpenStorage('CARS.CAR', nil,
    STGM_READWRITE or STGM_SHARE_EXCLUSIVE,
    nil, 0, FRootStorage)) then
    OleCheck(StgCreateDocFile('CARS.CAR',
      STGM_CREATE or STGM_READWRITE or STGM_SHARE_EXCLUSIVE,
      0, FRootStorage));

  if SUCCEEDED(FRootStorage.OpenStream('Info', nil,
    STGM_READ or STGM_SHARE_EXCLUSIVE, 0, stm)) then begin
    OS := TOleStream.Create(stm);
    try
      Reader := TReader.Create(OS, 1024);
      try
        FCarName := Reader.ReadString;
        FYear := Reader.ReadInteger;
      finally
        Reader.Free;
      end;
    finally
      OS.Free;
    end;
  end else begin
    OleCheck(FRootStorage.CreateStream('Info',
      STGM_CREATE or STGM_READ or STGM_SHARE_EXCLUSIVE, 0, 0, stm));
  end;
end;

procedure TfrmMain.FormDestroy(Sender: TObject);
var
  stm: IStream;
  OS: TOleStream;
  Writer: TWriter;
begin
  OleCheck(FRootStorage.OpenStream('Info', nil, STGM_WRITE or
    STGM_SHARE_EXCLUSIVE, 0, stm));

  OS := TOleStream.Create(stm);
  try
    Writer := TWriter.Create(OS, 1024);
    try
      Writer.WriteString(FCarName);
      Writer.WriteInteger(FYear);
    finally
      Writer.Free;
    end;
  finally
    OS.Free;
  end;
end;

function TfrmMain.ActivateForm(ACaption: string): Boolean;
var
  Index: Integer;
begin
  Result := False;

  for Index := 0 to MDIChildCount - 1 do
    if MDIChildren[Index].Caption = ACaption then begin
      if MDIChildren[Index].WindowState = wsMinimized then
        MDIChildren[Index].WindowState := wsNormal;
      MDIChildren[Index].SetFocus;
      Result := True;
      exit;
    end;
end;

procedure TfrmMain.Gas1Click(Sender: TObject);
var
  frmGas: TfrmGas;
begin
  if not ActivateForm('Gas') then begin
    frmGas := TfrmGas.Create(self);
    frmGas.Show;
  end;
end;

procedure TfrmMain.Oil1Click(Sender: TObject);
var
  frmOil: TfrmOil;
begin
  if not ActivateForm('Oil') then begin
    frmOil := TfrmOil.Create(self);
    frmOil.Show;
  end;
end;

procedure TfrmMain.CarInformation1Click(Sender: TObject);
var
  frmCarInfo: TfrmCarInfo;
begin
  frmCarInfo := TfrmCarInfo.Create(nil);
  try
    frmCarInfo.ecDescription.Text := FCarName;
    frmCarInfo.ecYear.Text := IntToStr(FYear);

    if frmCarInfo.ShowModal = mrOk then begin
      FCarName := frmCarInfo.Description;
      FYear := frmCarInfo.Year;
    end;
  finally
    frmCarInfo.Free;
  end;
end;

end.