stan · September 27, 2012 10:08 · Sep 26, 2011
diff --git a/undo.rb b/undo.rb
@@ -0,0 +1,86 @@
+module Mongoid
+  module Undo
+    extend ActiveSupport::Concern
+
+    included do
+      include Mongoid::Document
+
+      field :version, type: Integer, default: 0
+      before_save :prepare_versioning
+      after_save :create_version
+      before_destroy :version_destroy
+    end
+
+    def versions; ::Version.where(obj_id: id) end
+    def versions_gt(version = self.version); versions.where(:version.gt => version) end
+    def version_at(version = self.version); versions.where(version: version).first end
+    def current_version; version_at end
+    def previous_version; version_at version - 1 end
+
+    def versioned?; version > 0 end
+    def has?(ver)
+      ver.obj_id == id && ver.obj_class == self.class.to_s
+    end
+    def matches?(ver)
+      has?(ver) &&
+          ver.obj_attributes == attributes &&
+          ver.version == version
+    end
+
+    def undo!; rollback_to!(version - 1) end
+
+    def rollback_to!(version)
+      unless persisted?; return false end
+      if version == 0
+        versions.destroy
+        without_versioning :destroy
+        attributes
+      else
+        ver = version_at(version)
+        unless ver; return false end
+
+        ver.rollback_to(self)
+      end
+    end
+
+    def without_versioning(method = nil)
+      @without_versioning = true
+      method ? method.to_proc.call(self) : yield
+    ensure
+      @without_versioning = false
+    end
+
+    private
+    def match_persisted?
+      current_version && attributes == current_version.obj_attributes
+    end
+
+    def prepare_versioning
+      if !@without_versioning
+        if version == 0 && persisted?
+          self.version += 1
+          old_self = self.class.find(id)
+          old_self.version += 1
+          old_self.send(:create_version)
+        end
+        if !match_persisted?; self.version += 1 end
+      end
+    end
+
+    def create_version(destroy = false)
+      if !@without_versioning && (destroy || !match_persisted?)
+        ver = ::Version.new(obj_id: id, obj_class: self.class.to_s, version: version)
+        unless destroy; ver.attributes = ver.attributes.merge({:obj_attributes => attributes}) end
+        ver.save!
+      end
+    end
+
+    def version_destroy
+      if !@without_versioning
+        self.version += 1
+        without_versioning(:save)
+        create_version(true)
+      end
+    end
+  end
+end
diff --git a/version.rb b/version.rb
@@ -0,0 +1,48 @@
+module Mongoid::Undo
+  module Version
+    extend ActiveSupport::Concern
+
+    included do
+      include Mongoid::Document
+      include Mongoid::Timestamps::Created
+
+      field :obj_id
+      field :obj_class
+      field :obj_attributes, type: Hash
+      field :version, type: Integer
+      validates_presence_of(fields.keys - ['_id', '_type', 'created_at', 'obj_attributes'])
+    end
+
+    def obj; obj_class.constantize.find(obj_id) end
+
+    def created?; version == 1 end
+    def deleted?; !obj_attributes end
+    def modified?; !(created? || deleted?) end
+    def latest?(obj = nil)
+      unless obj; obj = self.obj end
+      obj.nil? || version == obj.version
+    end
+
+    def rollback_to(obj = nil)
+      if !deleted?
+        if obj.nil? || obj.id != obj_id; obj = self.obj end
+        if obj.nil?; obj = obj_class.constantize.new end
+
+        obj.versions_gt(version).each {|ver| ver.destroy }
+        rollback(obj)
+      else
+        false
+      end
+    end
+
+    private
+
+    def rollback(obj = nil)
+      old_attributes = obj.attributes
+      obj.attributes = obj_attributes
+      obj.without_versioning :save
+
+      old_attributes
+    end
+  end
+end
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