From d7a705c3b7cd579151d96c7ef8f47222dd12bc98 Mon Sep 17 00:00:00 2001
From: Paul Butcher <paul.butcher@gmail.com>
Date: Fri, 15 Sep 2023 11:57:02 +0100
Subject: [PATCH] join knn filter terms with AND (#716)

---
 .../services/TemplateSearchBuilder.scala      |  5 ++--
 .../api/search/images/ImagesFiltersTest.scala | 24 +++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/search/src/main/scala/weco/api/search/services/TemplateSearchBuilder.scala b/search/src/main/scala/weco/api/search/services/TemplateSearchBuilder.scala
index 3650cafc3..dc3c18cbf 100644
--- a/search/src/main/scala/weco/api/search/services/TemplateSearchBuilder.scala
+++ b/search/src/main/scala/weco/api/search/services/TemplateSearchBuilder.scala
@@ -43,8 +43,9 @@ trait TemplateSearchBuilder extends Encoders {
   // on whether the document contains the term in any searchable field.
   // If there are fields that should be ignored, then this default will
   // be inappropriate, and can be overridden.
-  protected val knnFilter: String = """{
-  |   "multi_match": { "query": "{{query}}" }
+  protected val knnFilter: String =
+    """{
+  |   "multi_match": { "query": "{{query}}", "operator": "AND", "type": "cross_fields"}
   | }""".stripMargin
 
   // Importantly, this is *not* JSON, due to the `{{#` sequences, so must be created and sent as a string.
diff --git a/search/src/test/scala/weco/api/search/images/ImagesFiltersTest.scala b/search/src/test/scala/weco/api/search/images/ImagesFiltersTest.scala
index 7d713d81b..ee0511758 100644
--- a/search/src/test/scala/weco/api/search/images/ImagesFiltersTest.scala
+++ b/search/src/test/scala/weco/api/search/images/ImagesFiltersTest.scala
@@ -354,6 +354,7 @@ class ImagesFiltersTest extends AnyFunSpec with ApiImagesTestBase {
             imagesIndex,
             "images.examples.color-filter-tests.even-less-blue-foot",
             "images.examples.color-filter-tests.blue-foot",
+            "images.examples.color-filter-tests.blue",
             "images.examples.color-filter-tests.orange-foot",
             "images.examples.color-filter-tests.slightly-less-blue-foot"
           )
@@ -374,5 +375,28 @@ class ImagesFiltersTest extends AnyFunSpec with ApiImagesTestBase {
           }
       }
     }
+    it("combines multi-token query terms with AND") {
+      withImagesApi {
+        case (imagesIndex, routes) =>
+          indexTestDocuments(
+            imagesIndex,
+            "images.examples.color-filter-tests.blue", // Green + Dye (subjects)
+            "images.examples.color-filter-tests.blue-foot", // Dye but not Green
+            "images.examples.color-filter-tests.even-less-blue-foot" // Neither Dye nor Green
+          )
+
+          assertJsonResponse(
+            routes,
+            path = f"$rootPath/images?query=green+dye&color=22bbff"
+          ) {
+            Status.OK -> imagesListResponse(
+              ids = Seq(
+                "images.examples.color-filter-tests.blue"
+              ),
+              strictOrdering = true
+            )
+          }
+      }
+    }
   }
 }