<?php

final class JakeDatasourceEngineExtension
  extends PhabricatorDatasourceEngineExtension {

  public function newDatasourcesForCompositeDatasource(
    PhabricatorTypeaheadCompositeDatasource $datasource) {

    $can_extend =
      ($datasource instanceof PhabricatorPeopleUserFunctionDatasource) ||
      ($datasource instanceof PhabricatorPeopleOwnerDatasource);

    if (!$can_extend) {
      return array();
    }

    return array(
      new JakeDatasource(),
    );
  }

}

<?php

final class JakeDatasource
  extends PhabricatorTypeaheadDatasource {

  public function getBrowseTitle() {
    return pht('Browse Jakes');
  }

  public function getPlaceholderText() {
    return pht('Type users-named-jake()...');
  }

  public function getDatasourceApplicationClass() {
    return 'PhabricatorPeopleApplication';
  }

  public function getDatasourceFunctions() {
    return array(
      'users-named-jake' => array(
        'name' => pht('Users Named Jake'),
        'summary' => pht('Use users named Jake.'),
        'description' => pht(
          "This function allows you to select all users named Jake."),
      ),
    );
  }

  public function loadResults() {
    if ($this->getViewer()->getPHID()) {
      $results = array($this->renderJakeFunctionToken());
    } else {
      $results = array();
    }

    return $this->filterResultsAgainstTokens($results);
  }

  protected function evaluateFunction($function, array $argv_list) {
    $results = array();
    foreach ($argv_list as $argv) {
      foreach ($this->loadJakePHIDs() as $jake_phid) {
        $results[] = $jake_phid;
      }
    }
    return $results;
  }

  public function renderFunctionTokens($function, array $argv_list) {
    $tokens = array();
    foreach ($argv_list as $argv) {
      $tokens[] = PhabricatorTypeaheadTokenView::newFromTypeaheadResult(
        $this->renderJakeFunctionToken());
    }
    return $tokens;
  }

  private function renderJakeFunctionToken() {
    return $this->newFunctionResult()
      ->setName(pht('Users Named Jake'))
      ->setPHID('users-named-jake()')
      ->setIcon('fa-user')
      ->setUnique(true)
      ->addAttribute(pht('Select users named Jake.'));
  }

  private function loadJakePHIDs() {
    $users = id(new PhabricatorUser())->loadAllWhere(
      'realName LIKE %>',
      'Jake ');

    $jake_phids = mpull($users, 'getPHID');

    return array_values($jake_phids);
  }

}