h2. How to Get Facets to Display on Home Page and in Search Results

(note - contribute this to blacklight project and then just link to it in HOW_DO_I doc)

1.  Determine which indexed Solr fields you want to as facets.  

If you have declared them with OM terminology in your datastream models, then they will be the fields in Solr named (something)_facet.
To see what fields are in Solr, go to:

<pre>
  http://localhost:8983/solr/development/admin/schema.jsp
</pre>

where "http://localhost:8983/solr/development" is the base url for your Solr instance.  Click on the "fields" link in the left navigation bar.  You will see a list of all your Solr fields.  Use the "find" function in your web browser to locate all the fields ending with _facet.

Let's say my Solr index has these facet fields:  object_type_facet, set_type_facet, genre_facet
"tag_facet"


2.  Write a test

e.g. features/facets.feature

<pre>
  Feature: Facets on Home Page and Search Results
    I want facets to display and work properly

    Scenario: home page facets
      When I am on the home page
      Then I should see "Format"
      And I should see "Book"

    Scenario: search results facets
      When I am on the home page
      And I fill in "q" with "dor"
      And I press "Search"
      Then I should see "Format"
      And I should see "Book"
</pre>  

3.  Ensure test fails

4.  Indicate the facet fields in a Rails initializer.

Facet fields are initially configured by config/initializers/blacklight_config.rb in your Rails app.  You override these configurations by creating a new file in config/initializers  that MUST sort later alphabetically than blacklight_config.  Your hydra_app_config.rb might look something like this:

<pre>
  # overrides of blacklight_config.rb
  Blacklight.configure(:shared) do |config|
  
    ... 

    # solr fields that will be treated as facets by the blacklight application
    #   The ordering of the field names is the order of the display
    config[:facet] = {
       :field_names => (facet_fields = [
         "object_type_facet",
         "set_type_facet",
         "genre_facet"
         ]),
       :labels => {
         "object_type_facet"=>"Object Type",
         "set_type_facet"=>"Set Type",
         "genre_facet"=>"Genre"
       }   
    }

    # Have BL send all facet field names to Solr. 
    config[:default_solr_params] ||= {}
    config[:default_solr_params][:"facet.field"] = facet_fields

    ...
</pre>

5.  Ensure test passes.