Add ability to batch search Rummager

This commit enables the new batch search endpoint to be called on Rummager, where each of the individual queries to be batched is encoded in a readable string as part of the query string.

Co-authored-by: Oscar Wyatt <oscar.wyatt@digital.cabinet-office.gov.uk>

lib/gds_api/rummager.rb

@@ -70,6 +70,21 @@ def search(args, additional_headers = {})
       get_json(request_url, additional_headers)
     end
 
+    # Perform a batch search.
+    #
+    # @param searches [Array] An array valid search queries. Maximum of 6. See Rummager documentation for options.
+    #
+    # # @see https://github.com/alphagov/rummager/blob/master/doc/search-api.md
+    def batch_search(searches, additional_headers = {})
+      url_friendly_searches = []
+      searches.each_with_index do |search, index|
+        url_friendly_searches << { index => search }
+      end
+      searches_query = { search: url_friendly_searches }
+      request_url = "#{base_url}/batch_search?.json?search=#{Rack::Utils.build_nested_query(searches_query)}"
+      get_json(request_url, additional_headers)
+    end
+
     # Perform a search, returning the results as an enumerator.
     #
     # The enumerator abstracts away rummager's pagination and fetches new pages when

test/rummager_test.rb

@@ -5,6 +5,7 @@
   before(:each) do
     stub_request(:get, /example.com\/advanced_search/).to_return(body: "[]")
     stub_request(:get, /example.com\/search/).to_return(body: "[]")
+    stub_request(:get, /example.com\/batch_search/).to_return(body: "[]")
   end
 
   # tests for #advanced_search
@@ -138,6 +139,20 @@
     assert_requested :get, /.*/, headers: { "authorization" => "token" }
   end
 
+  it "#batch_search should issue a single request containing all queries" do
+    GdsApi::Rummager.new("http://example.com").batch_search([{ q: 'self assessment' }, { q: 'tax return' }])
+
+    assert_requested :get, /\[\]\[0\]\[q\]=self assessment/
+    assert_requested :get, /\[\]\[1\]\[q\]=tax return/
+  end
+
+  it "#batch_search should return the search deserialized from json" do
+    batch_search_results = [{ "title" => "document-title" }, { "title" => "document-title-2" }]
+    stub_request(:get, /example.com\/batch_search/).to_return(body: batch_search_results.to_json)
+    results = GdsApi::Rummager.new("http://example.com").batch_search([{ q: 'self assessment' }, { q: 'tax return' }])
+    assert_equal batch_search_results, results.to_hash
+  end
+
   # tests for search_enum
   it "#search_enum returns two pages - last page is half full" do
     stub_request(:get, /example.com\/search/)