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<?php
  $user_name = '';
  $user_email = '';
  $username = '';
  $password = '';
  $verify = '';
  $email = '';
  $have_error = false;
  include "validation_function.php";
  if(isset($_POST['username']) && isset($_POST['password']) && isset($_POST['verify'])){
    $user_name = $_POST['username'];
    $user_email = $_POST['email'];
    if(!valid_user_name($_POST['username'])){
      $username = "That's not a valid username.";
      $have_error = true;
    }
    if(!valid_password($_POST['password'])){
      $password = "That wasn't a valid password.";
      $have_error = true;
    }
    else if($_POST['password'] !== $_POST['verify']){
      $verify = "Your passwords didn't match.";
      $have_error = true;
    }
    if(!valid_email($_POST['email'])){
      $email = "That's not a valid email";
      $have_error = true;
    }
    if(!$have_error){
      header('Location: thanks.php?username='.$_POST['username']);
      return;
    }
  }
?>
<!DOCTYPE html>
<html>
  <head>
    <title>Sign Up</title>
    <style type="text/css">
      .label {text-align: right}
      .error {color: red}
    </style>
  </head>
  <body>
    <h2>Signup</h2>
    <form method="post">
      <table>
        <tr>
          <td class="label">
            Username
          </td>
          <td>
            <input type="text" name="username" value="<?= htmlentities($user_name)?>">
          </td>
          <td class="error">
            <?= $username ?>
          </td>
        </tr>
        <tr>
          <td class="label">
            Password
          </td>
          <td>
            <input type="password" name="password" value="">
          </td>
          <td class="error">
            <?= $password ?>
          </td>
        </tr>
        <tr>
          <td class="label">
            Verify Password
          </td>
          <td>
            <input type="password" name="verify" value="">
          </td>
          <td class="error">
            <?= $verify ?>
          </td>
        </tr>
        <tr>
          <td class="label">
            Email (optional)
          </td>
          <td>
            <input type="text" name="email" value="<?= htmlentities($user_email)?>">
          </td>
          <td class="error">
              <?= $email ?>
          </td>
        </tr>
      </table>
      <input type="submit">
    </form>
  </body>
</html>