Breadcrumbs and tabs for admin pages

it would be good to really spell it out in this issue.

oh yes.. my issue summary really sucks :)

E.g. I get this breadcrumb

Home » Administration » Configuration » Search and metadata (» Configure facet display for Price » Amount)
and no tabs

Instead, breadcrumb should be
Home » Administration » Configuration » Search and metadata » Search API » Products index » Facets( » Price: Amount)

Tabs for the page should be
[Display] [Dependencies] [Filters] ...

You could write a Crumbs plugin :)
Then you only need to specify a few parent-child relationships that are not obvious from the path, and you are done.

This said, it might be better to restructure the paths in a way that they reflect the natural hierarchy. This will also improve the admin menu.

The following, combined with Crumbs, will give a nice breadcrumb on the facet config pages.
E.g. Home » Administration » Configuration » Search and metadata » Search API » Index: Products index » Facets »

/**
 * Implements hook_crumbs_plugins()
 *
 * @param crumbs_InjectedAPI_hookCrumbsPlugins $api
 */
function facetapi_crumbs_plugins($api) {

  foreach (array(
    'dependencies',
    'edit',
    'export',
    'filters',
    'revert',
  ) as $key) {
    $api->routeParentCallback(
      'admin/config/search/facetapi/%/%/%/' . $key,
      $key,
      function($path, $item) {
        list(,,,,$adapter, $realm, $facet) = $item['map'];
        if (!$adapter instanceof FacetapiAdapter || empty($realm['name'])) {
          return NULL;
        }
        return $adapter->getPath($realm['name']);
      }
    );
  }
}

Although, to get the "Index: Products index" to show up instead of just "View index", another implementation is necessary. This time it's search_api.

/**
 * Implements hook_crumbs_plugins()
 *
 * @param crumbs_InjectedAPI_hookCrumbsPlugins $api
 */
function search_api_crumbs_plugins($api) {
  $api->routeTitleCallback(
    'admin/config/search/search_api/index/%',
    'index',
    function($path, $item) {
      $searchApiIndex = $item['map'][5];
      if ($searchApiIndex instanceof SearchApiIndex) {
        return t('Index: @index', array('@index' => $searchApiIndex->name));
      }
      return NULL;
    }
  );
}

Actually the second part is not needed, if search api would fix this issue:
#2700879: Move search_api_admin_item_title() to main *.module file

The first part still totally works, and it would be nice if it could be added somewhere.

Maybe it would be nice if the "admin/config/search/facetapi/%/%/%/edit" would be a "default local task", and "admin/config/search/facetapi/%/%/%" would be the tab root. This would allow jumping between the admin sub-pages of one facet.

If you want to support older PHP versions where closures are not possible, just register a regular callback function. Or create a class.

All the stuff can reside in the main facetapi.module file.

I don't have time to write a patch atm.
But here is a module that I use myself to improve the UI of facetapi.
Should be not too hard to turn this into a patch..

See https://www.drupal.org/project/facetapiuifix

I think it is ok for now to have this as a distinct module, because it depends on Crumbs.