HOWTO:contact form for anonymous users, specific to a node- type.

Hi,

in my project i needed a contact form for anonymous users,
displayed only on a specific node-type and the subject-field should be prefilled
with the node- title and the node id.

I get these working - but I am pretty sure that it could be done in a much more cleaner way
with drupal hooks/modules/api. Due to the fact that i am new to drupal, I would like to hear your opinions
how I can handle things like this in a better, more stable way, without hacking the core.
So here is what I have done:

At first, i patched the drupal contact-module, to allow anonymous users to use the contact form:
http://drupal.org/node/58224
http://drupal.org/files/issues/anonymous-contact-5.3.patch

After that, i enabled the authors-information-block and set it to display only on the specific node- type.
Than i modified the profile module to integrate the authors contact- form on the author-information-block,
by adding the following line:

if ($fields) {
          $profile = _profile_update_user_fields($fields, $account);
          $output .= theme('profile_block', $account, $profile, TRUE);
          // ADDED: display authors contact form beneath his profile information.
          $output .= '<div id="author-contact">'.drupal_get_form('contact_mail_user', $account).'</div>';
        }

Then, I have done some coding in the contact module:
In function contact_mail_user($recipient):

1. Check if we are on the specific node- type:

// Are we on the 'angebot' node type?
  $match = FALSE;
  $types = array('angebot' => 1);
  if (arg(0) == 'node' && is_numeric(arg(1))) {
    $nid = arg(1);
    $node = node_load(array('nid' => $nid));
    $type = $node->type;
    if (isset($types[$type])) {
      $match = TRUE;
    }
  }

2. If we are - do some prefilling of the subject and message field:

// if we are on the node type 'angebot', dont include the 'to'- field, prefill the subject and message fields:
  if ($match) {
//Subject comes with node id and node-title
    $form['subject'] = array('#type' => 'textfield',
      '#title' => t('Subject'),
      '#value' => t('Request to Service No. ').$node->nid.': '.$node->title,
      '#maxlength' => 70,
      '#required' => TRUE,
    );
//prefilled with static text    
     $form['message'] = array('#type' => 'textarea',
      '#title' => t('Message'),
      '#value' => t('I am interested in your service. Please contact me.'),
      '#rows' => 15,
      '#required' => TRUE,
    );
    
      // integrate the nodes authors (email receipient) id in the form, because we will need it later
     // when we will send the mail 
      $form['uid'] = array('#type' => 'hidden',
      '#value' => $recipient->uid,
  );
  
  }
 

And last but not least,
get the authors id (receipient) we have used in the hidden field above.

function contact_mail_user_submit($form_id, $form_values) some lines

  // This comes from the anonymous Contact Form on the Content Node, so catch the authors id
  if ($form_values['uid']) {
    $account = user_load(array('uid' => $form_values['uid'], 'status' => 1));
  } 

Done.