unit UnitNewUser;

interface

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

type
  TFormNewUser = class(TForm)
    lbledtNew_Username: TLabeledEdit;
    lbledtNew_Password: TLabeledEdit;
    btnNew_User: TButton;
    procedure btnNew_UserClick(Sender: TObject);
    procedure lbledtNew_UsernameClick(Sender: TObject);
    procedure lbledtNew_PasswordClick(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
    UserFile, SaveFile: TextFile;
    Textstring, TStr: String;
  end;

var
  FormNewUser: TFormNewUser;

implementation

{$R *.dfm}

procedure TFormNewUser.btnNew_UserClick(Sender: TObject);
var
  ended, closing, used: boolean;
  usrnm, pswrd: string;
  studentno: integer;

begin
  usrnm := lbledtNew_Username.Text; // read in username entered in box
  pswrd := lbledtNew_Password.Text; // read in password entered in box
  ended := false;
  closing := false;
  used := false;
  Try
    StrToInt(usrnm);
  except
    On E: EConvertError do
    begin
      Showmessage('Your Username must be your Student Number!');
      ended := true;
      closing := true;
    end;

  End;

  studentno := StrToInt(usrnm);
  if (studentno < 130000) or (studentno >= 170000) then
  // Addressing the input of a new username to just a student number by limiting it to a 6 digit number between 130000 and 170000
  begin
    Showmessage('Please enter a valid student number!"');
    ended := true;
    closing := true;
  end;
  if (Length(pswrd) < 6) or (Length(pswrd) > 14) then
  begin
    ended := true;
    closing := true;
    Showmessage('Please enter a Password between 6 and 14 characters!')
  end;

  AssignFile(UserFile, 'Usernames.txt');
  // open usernames folder (usernames file has passwords in it)

  Reset(UserFile);

  while (* not EOF(UserFile) or ( *) ended = false do
  Begin
    Readln(UserFile, Textstring); // checking for duplicate usernames

    If (Textstring = usrnm) then
    begin
      ended := true;
      closing := true;
      used := true;
      Showmessage('Username is taken'); // display error message
    end
    else

      Readln(UserFile, Textstring); // read in username and store it in file
    if EOF(UserFile) then
    begin
      ended := true; // tell program it is at the end of the file
    end;

  End;
  CloseFile(UserFile);

  if (used = false) and (closing = false) then
  // if username has not been used before
  begin
    AssignFile(UserFile, 'Usernames.txt'); // create usernames folder
    Append(UserFile);
    AssignFile(SaveFile, 'UserData.txt'); // create usernames folder
    Append(SaveFile);
    Writeln(UserFile, usrnm); // write username entered to file
    Writeln(SaveFile, usrnm);
    Writeln(UserFile, pswrd); // write password entered to file
    CloseFile(UserFile);
    CloseFile(SaveFile);
    Showmessage('Successfully registered!');
    lbledtNew_Username.Text := ''; // clear new username and password box
    lbledtNew_Password.Text := '';
    close;
  end

end;

procedure TFormNewUser.lbledtNew_PasswordClick(Sender: TObject);
begin
  lbledtNew_Password.SelectAll;
end;

procedure TFormNewUser.lbledtNew_UsernameClick(Sender: TObject);
begin
  lbledtNew_Username.SelectAll;
end;

end.