MONGOID-4906 Implement $mod (#4922)

lib/mongoid/matcher.rb

@@ -116,6 +116,7 @@ module Matcher
 require 'mongoid/matcher/in'
 require 'mongoid/matcher/lt'
 require 'mongoid/matcher/lte'
+require 'mongoid/matcher/mod'
 require 'mongoid/matcher/ne'
 require 'mongoid/matcher/nin'
 require 'mongoid/matcher/nor'

lib/mongoid/matcher/field_operator.rb

@@ -13,6 +13,7 @@ module FieldOperator
         '$in' => In,
         '$lt' => Lt,
         '$lte' => Lte,
+        '$mod' => Mod,
         '$nin' => Nin,
         '$ne' => Ne,
         '$not' => Not,

lib/mongoid/matcher/mod.rb

@@ -0,0 +1,17 @@
+module Mongoid
+  module Matcher
+
+    # @api private
+    module Mod
+      module_function def matches?(exists, value, condition)
+        unless Array === condition
+          raise Errors::InvalidQuery, "Unknown $mod argument #{condition}"
+        end
+        if condition.length != 2
+          raise Errors::InvalidQuery, "Malformed $mod argument #{condition}, should have 2 elements"
+        end
+        condition[1] == value%condition[0]
+      end
+    end
+  end
+end

spec/integration/matcher_operator_data/mod.yml

@@ -0,0 +1,55 @@
+- name: existing field - matches
+  document:
+    pi: 8
+  query:
+    pi:
+      $mod: [5, 3]
+  matches: true
+
+- name: existing field - does not match
+  document:
+    pi: 9
+  query:
+    pi:
+      $mod: [5, 3]
+  matches: false
+
+- name: invalid condition
+  document:
+    pi: 9
+  query:
+    pi:
+      $mod: 5
+  error: true
+
+- name: invalid field
+  document:
+    pi: [1, 2]
+  query:
+    pi:
+      $mod: 5
+  error: true
+
+- name: array too short
+  document:
+    pi: 3
+  query:
+    pi:
+      $mod: [5]
+  error: true
+
+- name: empty array
+  document:
+    pi: 3
+  query:
+    pi:
+      $mod: []
+  error: true
+
+- name: array too long
+  document:
+    pi: 3
+  query:
+    pi:
+      $mod: [1, 2, 3]
+  error: true