module Neo4j
  module Migrations


    # By including this mixing on a node class one can add migrations to it.
    # Each class has a unique db version.
    #
    # ==== Example
    #
    #  class Person
    #    include Neo4j::NodeMixin
    #    include Neo4j::Migrations::NodeMixin
    #    rule :all  # adding the method all to make it possible to find all nodes of this class
    #  end
    #
    #  Person.migration 1, :split_property do
    #    up do
    #      all.each_raw do |node|
    #          node[:given_name] = node[:name].split[0]
    #          node[:surname]    = node[:name].split[1]
    #          node[:name]       = nil
    #        end
    #    end
    #
    #    down do
    #      all.each_raw do |node|
    #       node[:name]       = "#{node[:given_name]} #{node[:surname]}"
    #       node[:surename]   = nil
    #       node[:given_name] = nil
    #      end
    #    end
    #  end
    #
    # Notice that the up and down methods are evaluated in the context of the class (where the all method is defined
    # if using the rule :all).
    #
    module NodeMixin
      extend ActiveSupport::Concern

      included do
        extend Neo4j::Migrations::ClassMethods
      end

      module ClassMethods
        def migrate!(version=nil)
          _migrate!(self, migration_meta_node, version)
        end

        # The node that holds the db version property
        def migration_meta_node
          Neo4j::Rule::Rule.rule_node_for(self).rule_node
        end

        # Remote all migration and set migrate_to = nil and set the current version to nil
        def reset_migrations!
          @migrations = nil
          @migrate_to = nil
          Neo4j::Transaction.run do
            migration_meta_node[:_db_version] = nil
          end
        end

        # sets the migration db version for this class on a 'meta' node.
        def db_version=(version)
          Neo4j::Transaction.run do
            migration_meta_node[:_db_version] = version
          end
        end

        # returns the current version of the database for this class.
        def db_version
          migration_meta_node[:_db_version]
        end
      end

    end


  end
end