Merge pull request #148 from alphagov/filters2

Make filters more generic

app/services/discovery_engine/query/filters.rb

@@ -1,17 +1,19 @@
 module DiscoveryEngine::Query
   class Filters
+    FILTERABLE_FIELDS = %i[content_purpose_supergroup link part_of_taxonomy_tree].freeze
+
     def initialize(query_params)
       @query_params = query_params
     end
 
     def filter_expression
       expressions = [
-        reject_links_filter,
-        content_purpose_supergroup_filter,
-      ]
+        *query_params_of_type(:reject).map { reject_filter(_1, _2) },
+        *query_params_of_type(:filter).map { any_filter(_1, _2) },
+        *query_params_of_type(:filter_all).map { all_filter(_1, _2) },
+      ].compact
 
       expressions
-        .compact
         .map { surround(_1, delimiter: "(", delimiter_end: ")") }
         .join(" AND ")
         .presence
@@ -21,31 +23,38 @@ def filter_expression
 
     attr_reader :query_params
 
-    def reject_links_filter
-      return nil if query_params[:reject_link].blank?
-
-      values = Array(query_params[:reject_link])
-        .map { filter_string_value(_1) }
-        .join(",")
-
-      "NOT link: ANY(#{values})"
+    def query_params_of_type(type)
+      FILTERABLE_FIELDS
+        .filter_map { [_1, query_params["#{type}_#{_1}".to_sym]] }
+        .to_h
+        .compact_blank
     end
 
-    def content_purpose_supergroup_filter
-      return nil if query_params[:filter_content_purpose_supergroup].blank?
+    def reject_filter(field, value_or_values)
+      string_filter_expression(field, value_or_values, negate: true)
+    end
 
-      values = Array(query_params[:filter_content_purpose_supergroup])
-        .map { filter_string_value(_1) }
-        .join(",")
+    def all_filter(field, value_or_values)
+      Array(value_or_values)
+        .map { string_filter_expression(field, _1) }
+        .join(" AND ")
+        .presence
+    end
 
-      "content_purpose_supergroup: ANY(#{values})"
+    def any_filter(field, value_or_values)
+      string_filter_expression(field, value_or_values)
     end
 
-    # Input strings need to be wrapped in double quotes and have double quotes or backslashes
-    # escaped for Discovery Engine's filter syntax
-    def filter_string_value(str)
-      escaped_str = str.gsub(/(["\\])/, '\\\\\1')
-      surround(escaped_str, delimiter: '"')
+    def string_filter_expression(field, value_or_values, negate: false)
+      values = Array(value_or_values).map do |value|
+        # Input strings need to be wrapped in double quotes and have double quotes or backslashes
+        # escaped for Discovery Engine's filter syntax
+        escaped_value = value.gsub(/(["\\])/, '\\\\\1')
+        surround(escaped_value, delimiter: '"')
+      end
+      return if values.blank?
+
+      "#{negate ? 'NOT ' : ''}#{field}: ANY(#{values.join(',')})"
     end
 
     def surround(str, delimiter:, delimiter_end: delimiter)

spec/services/discovery_engine/query/filters_spec.rb

@@ -8,7 +8,7 @@
       it { is_expected.to be_nil }
     end
 
-    context "with reject_link" do
+    context "with a reject filter" do
       context "with an empty parameter" do
         let(:query_params) { { q: "garden centres", reject_link: "" } }
 
@@ -28,30 +28,63 @@
       end
     end
 
-    context "with filter_content_purpose_supergroup" do
+    context "with an 'any' filter" do
       context "with an empty parameter" do
         let(:query_params) { { q: "garden centres", filter_content_purpose_supergroup: "" } }
 
         it { is_expected.to be_nil }
       end
 
       context "with a single parameter" do
-        let(:query_params) { { q: "garden centres", filter_content_purpose_supergroup: "services" } }
+        let(:query_params) do
+          { q: "garden centres", filter_content_purpose_supergroup: "services" }
+        end
 
         it { is_expected.to eq('(content_purpose_supergroup: ANY("services"))') }
       end
 
       context "with several parameters" do
-        let(:query_params) { { q: "garden centres", filter_content_purpose_supergroup: %w[services guidance] } }
+        let(:query_params) do
+          { q: "garden centres", filter_content_purpose_supergroup: %w[services guidance] }
+        end
 
         it { is_expected.to eq('(content_purpose_supergroup: ANY("services","guidance"))') }
       end
     end
 
+    context "with an 'all' filter" do
+      context "with an empty parameter" do
+        let(:query_params) { { q: "garden centres", filter_all_part_of_taxonomy_tree: "" } }
+
+        it { is_expected.to be_nil }
+      end
+
+      context "with a single parameter" do
+        let(:query_params) { { q: "garden centres", filter_all_part_of_taxonomy_tree: "cafe-1234" } }
+
+        it { is_expected.to eq('(part_of_taxonomy_tree: ANY("cafe-1234"))') }
+      end
+
+      context "with several parameters" do
+        let(:query_params) do
+          { q: "garden centres", filter_all_part_of_taxonomy_tree: %w[cafe-1234 face-5678] }
+        end
+
+        it { is_expected.to eq('(part_of_taxonomy_tree: ANY("cafe-1234") AND part_of_taxonomy_tree: ANY("face-5678"))') }
+      end
+    end
+
     context "with several filters specified" do
-      let(:query_params) { { q: "garden centres", reject_link: "/foo", filter_content_purpose_supergroup: "services" } }
+      let(:query_params) do
+        {
+          q: "garden centres",
+          reject_link: "/foo",
+          filter_content_purpose_supergroup: "services",
+          filter_all_part_of_taxonomy_tree: %w[cafe-1234 face-5678],
+        }
+      end
 
-      it { is_expected.to eq('(NOT link: ANY("/foo")) AND (content_purpose_supergroup: ANY("services"))') }
+      it { is_expected.to eq('(NOT link: ANY("/foo")) AND (content_purpose_supergroup: ANY("services")) AND (part_of_taxonomy_tree: ANY("cafe-1234") AND part_of_taxonomy_tree: ANY("face-5678"))') }
     end
 
     context "with filters containing escapable characters" do