autocomplete: refactor javascript to use /autocomplete endpoint.

This refactors the autocomplete Javascript to use a single dedicated
/autocomplete.json endpoint instead of a bunch of separate endpoints.

This simplifies the autocomplete Javascript by making it so that instead
of calling a different endpoint for each type of query (for users, wiki
pages, pools, artists, etc), then having to parse the results of each
call to get the data we need, we can call a single endpoint that returns
exactly what we need.

This also means we don't have to parse searches clientside in order to
autocomplete metatags. Instead we can just pass the search term to the
server and let it parse the search, which is easy to do serverside.

Finally, this makes autocomplete easier to test, and it makes it easier
to add more sophisticated autocomplete behavior, since most of the logic
lives serverside.

test/functional/autocomplete_controller_test.rb

@@ -1,6 +1,17 @@
 require "test_helper"
 
 class AutocompleteControllerTest < ActionDispatch::IntegrationTest
+  def autocomplete(query, type)
+    get autocomplete_index_path(search: { query: query, type: type }), as: :json
+    assert_response :success
+
+    response.parsed_body.map { |result| result["value"] }
+  end
+
+  def assert_autocomplete_equals(expected_value, query, type)
+    assert_equal(expected_value, autocomplete(query, type))
+  end
+
   context "Autocomplete controller" do
     context "index action" do
       setup do
@@ -8,9 +19,20 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
       end
 
       should "work for opensearch queries" do
-        get autocomplete_index_path(query: "azur", variant: "opensearch"), as: :json
+        get autocomplete_index_path(search: { query: "azur", type: "opensearch" }), as: :json
+
         assert_response :success
-        assert_equal(["azur", ["azur lane"]], response.parsed_body)
+        assert_equal(["azur", ["azur_lane"]], response.parsed_body)
+      end
+
+      should "work for tag queries" do
+        assert_autocomplete_equals(["azur_lane"], "azur", "tag_query")
+        assert_autocomplete_equals(["azur_lane"], "-azur", "tag_query")
+        assert_autocomplete_equals(["azur_lane"], "~azur", "tag_query")
+        assert_autocomplete_equals(["azur_lane"], "AZUR", "tag_query")
+
+        assert_autocomplete_equals(["rating:safe"], "rating:s", "tag_query")
+        assert_autocomplete_equals(["rating:safe"], "-rating:s", "tag_query")
       end
     end
   end