unit Change;

interface

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

type
  TChangeForm = class(TForm)
    ComboBox1: TComboBox;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    Edit4: TEdit;
    Button1: TButton;
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure ComboBox1DropDown(Sender: TObject);
    procedure ComboBox1Click(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Edit2KeyPress(Sender: TObject; var Key: Char);
    procedure Edit3KeyPress(Sender: TObject; var Key: Char);
    procedure Edit4KeyPress(Sender: TObject; var Key: Char);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  ChangeForm: TChangeForm;
  ChangeIndex: Integer;
  Flag: Boolean;

implementation

Uses
   Base, ChangeMenu, Add, DeleteRef, Menu;

{$R *.dfm}

procedure TChangeForm.Button1Click(Sender: TObject);
var
   i: Integer;
   Temp: TRef;
begin
   Inc(ChangeIndex);
   seek(MyFile, ChangeIndex - 1);
   Temp.Topic := Edit1.Text;
   Temp.Author := Edit2.Text;
   Temp.Str := StrToInt(Edit3.Text);
   Temp.Date := Edit4.Text;
   Write(MyFile, Temp);
   for i := ChangeIndex to FileSize(MyFile) - 3 do
   begin
      seek(MyFile, i + 1);
      read(MyFile, Temp);
      seek(MyFile, i);
      Write(MyFile, Temp);
   end;
   seek(MyFile, FileSize(MyFile));
   truncate(MyFile);
   Reset(MyFile);
   i := 0;
   While not eof(MyFile) do
   begin
      Read(MyFile, Ref[i]);
      Inc(i);
   end;
   n := i;
   ComboBox1.Clear;
   ChangeForm.Hide;
   BaseForm.Show;
end;

procedure TChangeForm.ComboBox1Click(Sender: TObject);
begin
   Button1.Visible := True;
   ChangeIndex := ComboBox1.Items.IndexOf(ComboBox1.Text);
   Edit1.Text := Ref[ChangeIndex].Topic;
   Edit2.Text := Ref[ChangeIndex].Author;
   Edit3.Text := IntToStr(Ref[ChangeIndex].Str);
   Edit4.Text := Ref[ChangeIndex].Date;
   Edit1.Visible := True;
   Edit2.Visible := True;
   Edit3.Visible := True;
   Edit4.Visible := True;
   Label1.Visible := True;
   Label2.Visible := True;
   Label3.Visible := True;
   Label4.Visible := True;
end;

procedure TChangeForm.ComboBox1DropDown(Sender: TObject);
var
   i: Integer;
begin
   ComboBox1.Clear;
   for i := 0 to n - 1 do
      ComboBox1.Items.Add(Ref[i].Topic);
end;

procedure TChangeForm.Edit2KeyPress(Sender: TObject; var Key: Char);
const
   Digit: set of Char = ['a'..'z', #8, 'A'..'Z'];
begin
   with (Sender as TEdit) do
   begin
      if not(Key in Digit) then
         Key := #0;
   end;
end;

procedure TChangeForm.Edit3KeyPress(Sender: TObject; var Key: Char);
const
   Digit: set of Char = ['0'..'9', #8];
begin
   with (Sender as TEdit) do
   begin
      if not(Key in Digit) then
         Key := #0;
   end;
end;

procedure TChangeForm.Edit4KeyPress(Sender: TObject; var Key: Char);
const
   Digit: set of Char = ['0'..'9', #8, '.'];
begin
   with (Sender as TEdit) do
   begin
      if not(Key in Digit) then
         Key := #0;
   end;
end;

procedure TChangeForm.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
   BaseForm.Show;
   MenuForm.Hide;
   ChangeMenuForm.Hide;
   AddForm.Hide;
   DeleteForm.Hide;
   ChangeForm.Hide;
end;

procedure TChangeForm.FormShow(Sender: TObject);
begin
   ComboBox1.Clear;
   Button1.Visible := False;
   Edit1.Visible := False;
   Edit2.Visible := False;
   Edit3.Visible := False;
   Edit4.Visible := False;
   Label1.Visible := False;
   Label2.Visible := False;
   Label3.Visible := False;
   Label4.Visible := False;
end;

end.