From d93a7edb950f4ba4b4d147894fb0baa7bf7eaffa Mon Sep 17 00:00:00 2001
From: Christian Sutter <git@doublesignal.com>
Date: Mon, 11 Dec 2023 12:17:09 +0000
Subject: [PATCH] Refactor expression types into classes

---
 .../all_string_filter_expression.rb           | 11 ++++++++
 .../any_string_filter_expression.rb           |  9 ++++++
 .../string_filter_expression.rb               | 16 +++++++++++
 .../discovery_engine/query/filters.rb         | 28 ++-----------------
 4 files changed, 39 insertions(+), 25 deletions(-)
 create mode 100644 app/services/discovery_engine/query/filter_expressions/all_string_filter_expression.rb
 create mode 100644 app/services/discovery_engine/query/filter_expressions/any_string_filter_expression.rb
 create mode 100644 app/services/discovery_engine/query/filter_expressions/string_filter_expression.rb

diff --git a/app/services/discovery_engine/query/filter_expressions/all_string_filter_expression.rb b/app/services/discovery_engine/query/filter_expressions/all_string_filter_expression.rb
new file mode 100644
index 0000000..f84ce52
--- /dev/null
+++ b/app/services/discovery_engine/query/filter_expressions/all_string_filter_expression.rb
@@ -0,0 +1,11 @@
+module DiscoveryEngine::Query::FilterExpressions
+  class AllStringFilterExpression < StringFilterExpression
+    def expression
+      return if values.empty?
+
+      # There is no `ALL` equivalent for `ANY` in Discovery Engine, so we need to join up multiple
+      # `ANY` expressions to achieve the same effect.
+      values.map { "#{field}: ANY(#{_1})" }.join(" AND ")
+    end
+  end
+end
diff --git a/app/services/discovery_engine/query/filter_expressions/any_string_filter_expression.rb b/app/services/discovery_engine/query/filter_expressions/any_string_filter_expression.rb
new file mode 100644
index 0000000..25306ac
--- /dev/null
+++ b/app/services/discovery_engine/query/filter_expressions/any_string_filter_expression.rb
@@ -0,0 +1,9 @@
+module DiscoveryEngine::Query::FilterExpressions
+  class AnyStringFilterExpression < StringFilterExpression
+    def expression
+      return if values.empty?
+
+      "#{field}: ANY(#{values.join(',')})"
+    end
+  end
+end
diff --git a/app/services/discovery_engine/query/filter_expressions/string_filter_expression.rb b/app/services/discovery_engine/query/filter_expressions/string_filter_expression.rb
new file mode 100644
index 0000000..e12cb71
--- /dev/null
+++ b/app/services/discovery_engine/query/filter_expressions/string_filter_expression.rb
@@ -0,0 +1,16 @@
+module DiscoveryEngine::Query::FilterExpressions
+  class StringFilterExpression
+    def initialize(field, value_or_values)
+      @field = field
+      @values = Array(value_or_values).compact_blank.map { StringValue.new(_1) }
+    end
+
+    def negated_expression
+      "NOT #{expression}"
+    end
+
+  private
+
+    attr_reader :field, :values
+  end
+end
diff --git a/app/services/discovery_engine/query/filters.rb b/app/services/discovery_engine/query/filters.rb
index e6b0bcf..a0390f8 100644
--- a/app/services/discovery_engine/query/filters.rb
+++ b/app/services/discovery_engine/query/filters.rb
@@ -8,9 +8,9 @@ def initialize(query_params)
 
     def filter_expression
       expressions = [
-        *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) },
+        *query_params_of_type(:reject).map { FilterExpressions::AnyStringFilterExpression.new(_1, _2).negated_expression },
+        *query_params_of_type(:filter).map { FilterExpressions::AnyStringFilterExpression.new(_1, _2).expression },
+        *query_params_of_type(:filter_all).map { FilterExpressions::AllStringFilterExpression.new(_1, _2).expression },
       ].compact
 
       expressions
@@ -29,27 +29,5 @@ def query_params_of_type(type)
         .to_h
         .compact_blank
     end
-
-    def reject_filter(field, value_or_values)
-      string_filter_expression(field, value_or_values, negate: true)
-    end
-
-    def all_filter(field, value_or_values)
-      Array(value_or_values)
-        .map { string_filter_expression(field, _1) }
-        .join(" AND ")
-        .presence
-    end
-
-    def any_filter(field, value_or_values)
-      string_filter_expression(field, value_or_values)
-    end
-
-    def string_filter_expression(field, value_or_values, negate: false)
-      values = Array(value_or_values).map { FilterExpressions::StringValue.new(_1) }
-      return if values.blank?
-
-      "#{negate ? 'NOT ' : ''}#{field}: ANY(#{values.join(',')})"
-    end
   end
 end