unit LoginUnit;

interface

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

type
  TfrmLogin = class(TForm)
    btnEnter: TButton;
    ledtUsername: TLabeledEdit;
    btnExit: TButton;
    medtPassword: TMaskEdit;
    Label1: TLabel;
    procedure btnEnterClick(Sender: TObject);
    procedure btnExitClick(Sender: TObject);


//record for username and password
Type TCredentials = Record
  Username : String[15];
  Password : String[20];
  UserType : String[7];
End;

  private
    { Private declarations }
  public
    { Public declarations }
    UserArray : array [1..500] of TCredentials;//array storing sorted usernames + passwords
    i : integer;
  end;


var
  frmLogin: TfrmLogin;

implementation

{$R *.dfm}

Uses
  TeacherMenuUnit , StudentMenuUnit , TeachersReportUnit;


procedure TfrmLogin.btnEnterClick(Sender: TObject);
var
  FileArray : array [1..500] of TCredentials;  //Stores content from file in separate indexes
  LoginFile : TextFile;
  userptr , fileptr , counter : Integer;
  credentials : String;
  TeacherValid , StudentValid : Boolean;
begin

  //storing usernames and passwords into array 'FileArray' in separate indexes:
  i := 1;
  assignfile(LoginFile , 'LoginDetails.txt');
  Reset(LoginFile);
  while not EOF(LoginFile) do
    Begin
      readln(LoginFile , credentials); //store username/password from file
      FileArray[i].Username := credentials; //write username/password to array
      i := i + 1; //increment array index by one
    End;
  CloseFile(LoginFile);

  //store username with coresponding passwords in the same index in array 'UserArray'
  userptr := 1;
  fileptr := 1;
  i := i DIV 3;  //makes sure no extra array indexes are used
  for counter := 1 to i do
    Begin
      //store username in one index:
      UserArray[userptr].Username := FileArray[fileptr].Username;
      //store password in same index:
      UserArray[userptr].Password := FileArray[fileptr + 1].Username;
      //store user type in same index:
      UserArray[userptr].UserType := FileArray[fileptr + 2].Username;
      userptr := userptr + 1; //increment userarray by one
      fileptr := fileptr + 3  //increment filearray by two (goes to next username)
    End;


  //Search for username and password in array
  TeacherValid := False;
  StudentValid := False;

  for counter := 1 to i do
    Begin
      //comparing username and password to array

      //teacher login prerequisites
      if (UserArray[counter].Username = ledtUsername.Text)
         AND (UserArray[counter].Password = medtPassword.Text)
         AND (UserArray[counter].UserType = 'Teacher') then
        Begin
          TeacherValid := True;
        End;

      //student login prerequisites
      if (UserArray[counter].Username = ledtUsername.Text)
         AND (UserArray[counter].Password = medtPassword.Text)
         AND (UserArray[counter].UserType = 'Student') then
        Begin
          StudentValid := True;
        End;
    End;


  //Teacher logging in
  if TeacherValid = True then
    Begin
      ShowMessage('Login Successful');
      frmTeacherMenu.Show; //Display Teacher's Menu
      frmLogin.Hide;
    End

  //Student logging in
  Else if StudentValid = True then
    Begin
      ShowMessage('Login Successful');
      frmStudentMenu.Show; //Display Student's Menu
      frmLogin.Hide;
    End

  //when both username and password left blank:
  Else if (medtPassword.Text = '') AND (ledtUsername.Text = '') then
    ShowMessage('Please enter a username and password before logging in')

  //when no username entered
  Else if ledtUsername.Text = '' then
    ShowMessage('Please enter a username')

  //when no password entered
  Else if medtPassword.Text = '' then
    ShowMessage('Please enter a Password')

  //incorrect login details
  Else
    Begin
        //create custom messagebox
      IF Application.Messagebox('Incorrect Login Details, Please Try Again',
                                  'Incorrect',
                                  MB_RetryCancel or MB_IconError) = IDCancel then
        Begin
          Close;   //closes the form when 'Cancel' is clicked in messagebox
        End
      ELSE
        Begin
          ledtUsername.Text := ''; //clears username
          medtPassword.Text := ''; //clears password
        End;
    End;
End;




procedure TfrmLogin.btnExitClick(Sender: TObject);
begin
  frmLogin.Close; //closes login form
end;

end.