Data provenance with Neo4j.rb

auditable.rb

module Auditable
  def audit model_name: :audits, method_name: :audit
    define_method method_name do |info={}|
      from = changed_attributes.to_h
      to = from.each_key.each_with_object({}) do |key, hash|
        hash[key] = self[key]
      end

      @__current_audit = {
        from: from,
        to: to,
        # Allow multiple audit calls to just merge the info
        info: (@__current_audit || { info: {} })[:info].merge(info),
        model: self,
      }
    end

    before_update method_name

    after_update_commit do
      Entry.create @__current_audit if @__current_audit
      @__current_audit = nil
    end

    has_many :in, model_name, type: :AUDITS, model_class: 'Auditable::Entry'
  end

  class Entry
    include Neo4j::ActiveNode

    property :from
    property :to
    property :info
    property :created_at

    serialize :from
    serialize :to
    serialize :info

    has_one :out, :model, type: :AUDITS, model_class: false
  end
end

user.rb

class User
  include Neo4j::ActiveNode
  extend Auditable
  
  audit model_name: :audits, method_name: :audit

  property :email, type: String
  property :name, type: String
end

me = User.create!(email: '[email protected]', name: 'Me')
me.audit reason: 'Oops, wrong name'
me.update! name: 'Myself'