<?php
// Include config file
require_once 'config.php';

// Define variables and initialize with empty values
$username = $password = $confirm_password = "";
$username_err = $password_err = $confirm_password_err = "";

// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){

    // Validate username
    if(empty(trim($_POST["username"]))){
        $username_err = "Wpisz nazwę użytkownika";
    } else{
        // Prepare a select statement
        $sql = "SELECT id FROM users WHERE username = ?";

        if($stmt = mysqli_prepare($link, $sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "s", $param_username);

            // Set parameters
            $param_username = trim($_POST["username"]);

            // Attempt to execute the prepared statement
            if(mysqli_stmt_execute($stmt)){
                /* store result */
                mysqli_stmt_store_result($stmt);

                if(mysqli_stmt_num_rows($stmt) == 1){
                    $username_err = "Ta nazwa użytkownika jest już zajęta.";
                } else{
                    $username = trim($_POST["username"]);
                }
            } else{
                echo "Ups! Coś poszło nie tak. Spróbuj ponownie później.";
            }
        }

        // Close statement
        mysqli_stmt_close($stmt);
    }

    // Validate password
    if(empty(trim($_POST['password']))){
        $password_err = "Proszę wprowadzić hasło.";
    } elseif(strlen(trim($_POST['password'])) < 6){
        $password_err = "Hasło musi mieć co najmniej 6 znaków.";
    } else{
        $password = trim($_POST['password']);
    }

    // Validate confirm password
    if(empty(trim($_POST["confirm_password"]))){
        $confirm_password_err = 'Potwierdź hasło.';
    } else{
        $confirm_password = trim($_POST['confirm_password']);
        if($password != $confirm_password){
            $confirm_password_err = 'Hasło nie pasuje.';
        }
    }

    // Check input errors before inserting in database
    if(empty($username_err) && empty($password_err) && empty($confirm_password_err)){

        // Prepare an insert statement
        $sql = "INSERT INTO users (username, password) VALUES (?, ?)";

        if($stmt = mysqli_prepare($link, $sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "ss", $param_username, $param_password);

            // Set parameters
            $param_username = $username;
            $param_password = password_hash($password, PASSWORD_DEFAULT); // Creates a password hash

            // Attempt to execute the prepared statement
            if(mysqli_stmt_execute($stmt)){
                // Redirect to login page
                header("location: login.php");
            } else{
                echo "Coś poszło nie tak. Spróbuj ponownie później.";
            }
        }

        // Close statement
        mysqli_stmt_close($stmt);
    }

    // Close connection
    mysqli_close($link);
}
?>