Limit number of audits stored

lib/audited/audit.rb

@@ -105,6 +105,12 @@ def undo
       end
     end
 
+    def merge!(other)
+      raise ArgumentError, "#{other.inspect} should belong to the same auditable" \
+        if other.auditable_type != auditable_type || other.auditable_id != auditable_id
+      update_column(:audited_changes, other.audited_changes.merge(audited_changes))
+    end
+
     # Allows user to be set to either a string or an ActiveRecord object
     # @private
     def user_as_string=(user)

lib/audited/auditor.rb

@@ -43,12 +43,14 @@ def audited(options = {})
 
         class_attribute :audit_associated_with,   instance_writer: false
         class_attribute :audited_options,       instance_writer: false
+        class_attribute :keep_audits,             instance_writer: false
         attr_accessor :version, :audit_comment
 
         self.audited_options = options
         normalize_audited_options
 
         self.audit_associated_with = audited_options[:associated_with]
+        self.keep_audits = audited_options[:keep_audits]
 
         if audited_options[:comment_required]
           validates_presence_of :audit_comment, if: :auditing_enabled
@@ -204,7 +206,13 @@ def audit_create
       def audit_update
         unless (changes = audited_changes).empty? && audit_comment.blank?
           write_audit(action: 'update', audited_changes: changes,
-                      comment: audit_comment)
+                      comment: audit_comment) do
+            if keep_audits && audits.count > keep_audits.to_i
+              first_audit, second_audit = audits.limit(2)
+              second_audit.merge!(first_audit)
+              first_audit.destroy!
+            end
+          end
         end
       end
 
@@ -216,7 +224,14 @@ def audit_destroy
       def write_audit(attrs)
         attrs[:associated] = send(audit_associated_with) unless audit_associated_with.nil?
         self.audit_comment = nil
-        run_callbacks(:audit)  { audits.create(attrs) } if auditing_enabled
+
+        if auditing_enabled
+          run_callbacks(:audit) {
+            audit = audits.create(attrs)
+            yield if block_given?
+            audit
+          }
+        end
       end
 
       def require_comment

spec/audited/audit_spec.rb

@@ -200,6 +200,31 @@ class Models::ActiveRecord::CustomUserSubclass < Models::ActiveRecord::CustomUse
     end
   end
 
+  describe "merge!" do
+    it "should merge two audits" do
+      user = Models::ActiveRecord::User.create!(name: "John")
+      user.update(username: "john")
+      user.update(name: "John Doe")
+      expect(user.audits.count).to eq(3)
+
+      second, third = user.audits.offset(1)
+      third_created_at = third.created_at
+      third.merge!(second)
+      expect(third.reload.audited_changes).to eq({ "name" => ["John", "John Doe"], "username" => [nil, "john"] })
+      expect(third.created_at).to eq(third_created_at)
+      expect(user.audits.count).to eq(3)
+    end
+
+    it "should raise when audit belongs to other auditable" do
+      audit = Audited::Audit.new(auditable_type: "User", auditable_id: 1)
+      for_other = Audited::Audit.new(auditable_type: "User", auditable_id: 2)
+
+      assert_raises(ArgumentError) do
+        audit.merge!(for_other)
+      end
+    end
+  end
+
   describe "as_user" do
     it "should record user objects" do
       Audited::Audit.as_user(user) do

spec/audited/auditor_spec.rb

@@ -329,6 +329,36 @@ def non_column_attr=(val)
     end
   end
 
+  describe "keep_audits" do
+    it "should be nil by default" do
+      expect(Models::ActiveRecord::User.keep_audits).to be_nil
+    end
+
+    it "should delete old audits when keeped amount exceeded" do
+      previous_keep_audits = Models::ActiveRecord::User.keep_audits
+      begin
+        Models::ActiveRecord::User.keep_audits = 2
+        user = create_versions(2)
+        user.update(name: "John")
+        expect(user.audits.pluck(:version)).to eq([2, 3])
+      ensure
+        Models::ActiveRecord::User.keep_audits = previous_keep_audits
+      end
+    end
+
+    it "should not delete old audits when keeped amount not exceeded" do
+      previous_keep_audits = Models::ActiveRecord::User.keep_audits
+      begin
+        Models::ActiveRecord::User.keep_audits = 3
+        user = create_versions(2)
+        user.update(name: "John")
+        expect(user.audits.pluck(:version)).to eq([1, 2, 3])
+      ensure
+        Models::ActiveRecord::User.keep_audits = previous_keep_audits
+      end
+    end
+  end
+
   describe "revisions" do
     let( :user ) { create_versions }