unit Login;

interface

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

type

  TUserInfo = record
    Username: String[25];
    Password: String[25];
  end;

  TfrmLogin = class(TForm)
    Label1: TLabel;
    edtUsername: TEdit;
    edtPassword: TEdit;
    btnLogin: TButton;
    btnExit: TButton;
    lblTryAgain: TLabel;
    lblUsername: TLabel;
    lblPassword: TLabel;
    procedure btnExitClick(Sender: TObject);
    procedure btnLoginClick(Sender: TObject);
    procedure edtUsernameKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
    procedure edtPasswordKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
  private

  public
   Info: file of TUserInfo;
  end;

var
  frmLogin: TfrmLogin;
  UserInfo: TUserInfo;


implementation

uses ExamMenu, main, Signup;

{$R *.dfm}

procedure CheckForAllCompleteFields;
begin
  if (frmLogin.edtUsername.Text <> '') and (frmLogin.edtPassword.Text <> '') then
    frmLogin.btnLogin.Enabled := true
                                       //Checks that all the fields are completed
                                     //for signup
end;

procedure TfrmLogin.btnLoginClick(Sender: TObject);
begin
  AssignFile(Info, 'UserInfo.Dat');
  reset(Info);
  while Not Eof(Info) do
  begin
    read (Info,UserInfo);
    if (frmLogin.edtUsername.Text = UserInfo.Username) and
      (frmLogin.edtPassword.Text = UserInfo.Password) then
    begin
      frmExamMenu.Visible := true;
      frmLogin.Visible := false;
      edtUsername.Text := '';                 //Checks user credentials
      edtPassword.Text := '';
    end
    else
      lblTryAgain.Visible := true;

  end;
  closefile(Info)
end;

procedure TfrmLogin.btnExitClick(Sender: TObject); //if exit button is pressed
begin
  frmLogin.Visible := false;
  frmMainMenu.Visible := true
end;

procedure TfrmLogin.edtUsernameKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  CheckForAllCompleteFields;
  edtPassword.Visible := true;
end;

procedure TfrmLogin.edtPasswordKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  CheckForAllCompleteFields;
  edtPassword.Visible := true;
end;

procedure TfrmLogin.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  frmSignup.Visible := true;
  frmLogin.Visible := false;
end;


end.