Better strategy for handling decrement

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    statisfy (0.0.3)
+    statisfy (0.0.4)
 
 GEM
   remote: https://rubygems.org/

lib/statisfy/counter.rb

@@ -39,7 +39,7 @@ def count(args = {})
       # but the `count` DSL defines them automatically based on the options provided
       #
       def apply_default_counter_options(args)
-        define_method(:identifier, args[:uniq_by] || -> { params["id"] })
+        define_method(:identifier, args[:uniq_by] || -> { nil })
         define_method(:scopes, args[:scopes] || Statisfy.configuration.default_scopes || -> { [] })
         define_method(:if_async, args[:if_async] || -> { true })
         define_method(:decrement?, args[:decrement_if] || -> { false })
@@ -66,10 +66,18 @@ def value(scope: nil, month: nil)
         if const_get(:COUNTER_TYPE) == :aggregate
           average(scope:, month:)
         else
-          elements_in(scope:, month:).uniq.size
+          size(scope:, month:)
         end
       end
 
+      def size(scope: nil, month: nil)
+        redis_client.scard(key_for(scope:, month:))
+      end
+
+      def members(scope: nil, month: nil)
+        redis_client.smembers(key_for(scope:, month:))
+      end
+
       #
       # Returns the list of elements in the set (in case you use .append and not .increment)
       #
@@ -102,12 +110,13 @@ def average(scope: nil, month: nil)
       #
       # This is the name of the Redis key that will be used to store the counter
       #
-      def key_for(scope:, month: nil)
+      def key_for(scope:, month: nil, key_value: nil)
         {
           counter: name.demodulize.underscore,
           month:,
           scope_type: scope&.class&.name,
-          scope_id: scope&.id
+          scope_id: scope&.id,
+          key_value:
         }.to_json
       end
 
@@ -171,11 +180,15 @@ def process_event
       return if destroy_event_handled?
       return unless if_async
 
-      decrement? ? decrement : increment
+      if value.present?
+        append(value:)
+      else
+        decrement? ? decrement : increment
+      end
     end
 
     def destroy_event_handled?
-      return false unless params[:statisfy_trigger] == :destroy
+      return false unless params[:statisfy_trigger] == :destroy && value.blank?
 
       if decrement_on_destroy?
         decrement
@@ -188,6 +201,14 @@ def destroy_event_handled?
       false
     end
 
+    def key_value
+      value || identifier || params["id"]
+    end
+
+    def custom_key_value?
+      identifier.present? || value.present?
+    end
+
     #
     # This allows to iterate over all the counters that need to be updated
     # (in general the Department(s) and Organisation(s) for both the current month and the global counter)
@@ -202,15 +223,36 @@ def all_counters
 
     def increment
       all_counters do |key|
-        self.class.redis_client.rpush(key, value || identifier)
+        self.class.redis_client.sadd?(key, key_value)
+        self.class.redis_client.sadd?(uniq_by_ids(key), params["id"]) if custom_key_value?
       end
     end
 
+    #
+    # To be used to store a list of values instead of a basic counter
+    #
+    def append(value:)
+      all_counters do |key|
+        self.class.redis_client.rpush(key, value)
+      end
+    end
+
+    # rubocop:disable Metrics/AbcSize
     def decrement
       all_counters do |key|
-        self.class.redis_client.lrem(key, 1, value || identifier)
+        if custom_key_value?
+          self.class.redis_client.srem?(uniq_by_ids(key), params["id"])
+          self.class.redis_client.srem?(key, key_value) if self.class.redis_client.scard(uniq_by_ids(key)).zero?
+        else
+          self.class.redis_client.srem?(key, key_value)
+        end
       end
     end
+    # rubocop:enable Metrics/AbcSize
+
+    def uniq_by_ids(key)
+      "#{key};#{key_value}"
+    end
   end
 end
 

statisfy.gemspec

@@ -2,7 +2,7 @@
 
 Gem::Specification.new do |s|
   s.name        = "statisfy"
-  s.version     = "0.0.3"
+  s.version     = "0.0.4"
   s.required_ruby_version = ">= 3.2.0"
   s.date        = "2023-12-07"
   s.summary     = "A performant and flexible counter solution"

test/statisfy_test.rb

@@ -229,4 +229,22 @@ class UserCounter
     User.last.destroy
     assert_equal UserCounter.value, 0
   end
+
+  test "decrement_on_destroy works with custom uniq uniq_by" do
+    class OrganisationsWithUsersCounter
+      include Statisfy::Counter
+
+      count every: :user_created, decrement_on_destroy: true, uniq_by: -> { user.organisation_id }
+    end
+
+    User.create!(organisation_id: 8)
+    User.create!(organisation_id: 8)
+    User.create!(organisation_id: 2)
+
+    assert_equal OrganisationsWithUsersCounter.value, 2
+    User.where(organisation_id: 8).first.destroy
+    assert_equal OrganisationsWithUsersCounter.value, 2
+    User.where(organisation_id: 8).last.destroy
+    assert_equal OrganisationsWithUsersCounter.value, 1
+  end
 end