Custom token in Drupal 7

token.txt

/**
 * Implements hook_token_info().
 */
function modulename_token_info() {
  // Add tokens.
  $info['types']['token-type'] = array(
    'name' => t('ModuleName Tokens'),
    'description' => t('ModuleName custom tokens'),
  );

  $info['tokens']['token-type']['token-name'] = array(
    'name' => t('Token Name Token'),
    'description' => t('Does what your tokens do.'),
  );

  return $info;
}

/**
 * Implements hook_tokens().
 */
function modulename_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $replacements = array();

  if ($type == 'token-type') {
    foreach ($tokens as $name => $original) {
      switch ($name) {
        // Get the file id from a media field and return the image url.
        case 'token-name':
          $replacement = // Do something here.
          $replacements[$original] = $replacement;
          break;
      }
    }
  }

  // Return the replacements.
  return $replacements;
}