//server.php

<?php
session_start();

// initializing variables
$username = "";
$email    = "";
$errors = array();

// pripojeni do databeze
$db = mysqli_connect('localhost', 'root', 'usbw', 'users');

// registrace
if (isset($_POST['reg_user'])) {
  // prijima vsechny informace z formulare viz. login.php
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $email = mysqli_real_escape_string($db, $_POST['email']);
  $password_1 = mysqli_real_escape_string($db, $_POST['password_1']);
  $password_2 = mysqli_real_escape_string($db, $_POST['password_2']);

  $level = 1;
  //zkontroluje jestli je vybrana class(celkem harsh code asi pozdeji upravim)
if (empty($class)) {

    array_push($errors, "You have to choose your class!");
  } else {

    $class = mysqli_real_escape_string($db, $_POST['class']);

  }

  // zkontroluje ze je form spravne vyplnen
  if (empty($username)) { array_push($errors, "Username is required"); }
  if (empty($email)) { array_push($errors, "Email is required"); }
  if (empty($password_1)) { array_push($errors, "Password is required"); }
  if ($password_1 != $password_2) {
	array_push($errors, "The two passwords do not match");
  }

  // zkontroluje databazi
  // a potom zkontroluje zda-li neexistuje stejny username nebo email
  $user_check_query = "SELECT * FROM users WHERE username='$username' OR email='$email' LIMIT 1";
  $result = mysqli_query($db, $user_check_query);
  $user = mysqli_fetch_assoc($result);

  if ($user) { // jestlize uzivatel existuje
    if ($user['username'] === $username) {
      array_push($errors, "Username already exists");
    }

    if ($user['email'] === $email) {
      array_push($errors, "Email already exists");
    }
  }

  // jestlize nejsou chyby ve formu provede registraci a zaslani dat do databaze
  if (count($errors) == 0) {
  	$password = md5($password_1);//pro jistotu zahashuju hesla kdo to v dnesni dobe nedela lol
  	$query = "INSERT INTO users (username, email, password, level, class)
  			  VALUES('$username', '$email', '$password', '$level', '$class')";
  	mysqli_query($db, $query);
    $_SESSION['level'] = $level;
  	$_SESSION['username'] = $username;
    $_SESSION['class'] = $class;
  	$_SESSION['success'] = "You are now logged in";
  	header('location: index.php');
  }
}

// ...

// login uzivatele
if (isset($_POST['login_user'])) {
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $password = mysqli_real_escape_string($db, $_POST['password']);

  if (empty($username)) {
    array_push($errors, "Username is required");
  }
  if (empty($password)) {
    array_push($errors, "Password is required");
  }

  if (count($errors) == 0) {
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
    $results = mysqli_query($db, $query);
    if (mysqli_num_rows($results) == 1) {
      $_SESSION['username'] = $username;
      $_SESSION['success'] = "You are now logged in";
      header('location: index.php');
    }else {
      array_push($errors, "Wrong username/password combination");
    }
  }
}

?>