Autocomplete uid to name and name to uid

username.php

<?php

function axelerant_custom_username_form($form, &$form_state) {
  $default_user = user_load(3);

  $form['name'] = array(
    '#type' => 'textfield',
    '#title' => t('Search for Contributor'),
    '#autocomplete_path' => 'user/autocomplete',
    '#default_value' => $default_user->name,
    '#required' => TRUE,
  );
  
  return $form;
}

/**
 * Implements hook_actions_delete().
 */
function axelerant_custom_username_form_submit($form, &$form_state) {
  $name = trim($form_state['values']['name']);
  $user = user_load_by_name($name);
  // form_set_value($form['name'], $user->uid, $form_state);
}