<form id='login' action='log_in.php' method='post' accept-charset='UTF-8'>
<fieldset >
<legend>Login</legend>
<input type='hidden' name='submitted' id='submitted' value='1'/>

<label for='username' >Username:
</label>


<input type='text' name='username' id='username'/>

<label for='password' >Password:
</label>

<input type='password' name='password' id='password'/>


<label for='confirm_password' > Confirm Password:
</label>

<input type='password' name='confirm_password' id='confirm_password'/>



<input type='submit' name='Submit' value='Submit' />

</fieldset>
</form>

<?php



if (isset($_POST["Submit"])){
    $errors = array();
    $user = $_POST['username'];
    $password = $_POST['password'];
    $hash = password_hash($password, PASSWORD_DEFAULT);
    $log_name = "validation.log";
    $log_timestamp = date("Y-m-d", time());
    $log_data = $user . " " . $hash . " " . $log_timestamp;

//checks the username for the REGEX requirements
    if(preg_match("/^[0-9a-zA-Z_]{6,12}$/", $_POST["username"]) === 0)
    $errors[] ="Invalid username. A username must contain 6-12 characters and can only use numbers, letters, and underscores.";
//checks the password for the REGEX requirements
    if(preg_match("/^.*(?=.{8,16})(?=.*[0-9])(?=.*[a-z])(?=.*[A-Z]).*$/", $_POST["password"]) === 0)
    $errors[] ="Invalid password. Password must be 8-16 characters and contain at least one uppercase letter, one number, one special character and no spaces.";
//Makes sure the passwords match
    if ($_POST["password"] !==  $_POST["confirm_password"])
    $errors[] ="Passwords do not match.";
//checks if username is blank
    if (empty($_POST['username']))
    $errors[] ="Username cannot be left blank.";
//checks if password is blank
    if(empty($_POST["password"]))
    $errors[] ="Password cannot be left blank.";
//checks to see that the user entered their password twice
    if(empty($_POST["confirm_password"]))
    $errors[] ="Please enter your password in the Confirm Password field. It cannot be left blank.";
//prints out any errors
    if (count($errors) > 0){
        foreach ($errors as $error)
            echo $error."<br/>";
        }
// if successful, writes data into a log file and prints the password hash
    else{
        echo $hash;
        file_put_contents($log_name, $log_data);

    }
}

?>