unit DeleteElementsUnit;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Menus, Vcl.StdCtrls;

type
  TDeleteElementsForm = class(TForm)
    NumberEdit: TEdit;
    IndexEdit: TEdit;
    DeleteBtn: TButton;
    MainMenu: TMainMenu;
    NumberLabel: TLabel;
    IndexLabel: TLabel;
    Instruction: TMenuItem;
    procedure FormShow(Sender: TObject);
    procedure DeleteBtnClick(Sender: TObject);
    procedure IndexEditChange(Sender: TObject);
    procedure NumberEditChange(Sender: TObject);
    procedure NumberEditKeyPress(Sender: TObject; var Key: Char);
    procedure IndexEditKeyPress(Sender: TObject; var Key: Char);
    procedure InstructionClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  DeleteElementsForm: TDeleteElementsForm;

implementation

{$R *.dfm}


Uses
     MainUnit, LinkedListUnit;


procedure TDeleteElementsForm.DeleteBtnClick(Sender: TObject);

begin
    TListOperations.delete(Header, StrToInt(IndexEdit.Text), StrToInt(NumberEdit.Text));
    IndexEdit.Text := '';
    NumberEdit.Text := '';
    Main.ListMemo.Text := '';
end;

procedure TDeleteElementsForm.FormShow(Sender: TObject);
begin
    IndexEdit.Text := '';
    NumberEdit.Text := '';
    SystemParametersInfo(SPI_SETBEEP, 0, nil, SPIF_SENDWININICHANGE);
end;

procedure TDeleteElementsForm.IndexEditChange(Sender: TObject);

begin
    if IndexEdit.Text <> '' then
        DeleteBtn.Enabled := true
    else
        DeleteBtn.Enabled := false;
end;

procedure TDeleteElementsForm.IndexEditKeyPress(Sender: TObject; var Key: Char);

begin
    if (IndexEdit.Text <> '') and (Key = #13) then
        DeleteBtnClick(Sender);
    if (IndexEdit.Text = '0') and (Key <> #08) then
        Key := #0;
end;

procedure TDeleteElementsForm.InstructionClick(Sender: TObject);

var
    Separator: String;

begin
    Separator := #13#10;
    MessageDlg('Нужно ввести числа в диапазоне 0..100.', mtInformation, [mbOK], 0);
end;

procedure TDeleteElementsForm.NumberEditChange(Sender: TObject);

begin
    if NumberEdit.Text <> '' then
        DeleteBtn.Enabled := true
    else
        DeleteBtn.Enabled := false;
end;

procedure TDeleteElementsForm.NumberEditKeyPress(Sender: TObject;
  var Key: Char);

begin
    if (NumberEdit.Text <> '') and (Key = #13) then
        DeleteBtnClick(Sender);
    if (NumberEdit.Text = '0') and (Key <> #08) then
        Key := #0;
end;

end.