Add a hook to alter the block delta

On a recent project, I ran into an issue with the hash that gets generated off $searcher, $realm_name, $facet_name. We have a fairly typical dev, stage, prod setup. Each of our searchers are for different environment setups with different solr servers. This is working for us, until we use context to place blocks on our site.

Since the searcher changes by environment, the hash changes and a block that was displaying in dev no longer displays in stage. This adds a drupal_alter to the hash so we can alter it to have essentially the same hash in all environments. Example implementation provided.

function example_facetapi_hash_alter(&$hash, $delta) {
  preg_match('/(.+@)(.+?)(:.+)/', $delta, $matches);
  $delta = $matches[1] . EXAMPLE_SEARCHER_ID . $matches[3];
  $hash = substr(drupal_hash_base64($delta), 0, 32);
  $hash = strtr($hash, array('-' => '0', '_' => '1'));
}