geekq/workflow-activerecord

require 'rubygems'
require 'workflow'
require 'workflow/specification'

module WorkflowActiverecord
  def self.included(klass)
    klass.send :include, ::Workflow
    klass.send :include, InstanceMethods
    klass.send :extend, Scopes
    klass.before_validation :write_initial_state
  end

  module InstanceMethods
    def load_workflow_state
      read_attribute(self.class.workflow_column)
    end

    # On transition the new workflow state is immediately saved in the
    # database.
    def persist_workflow_state(new_value)
      # Rails 3.1 or newer
      update_column self.class.workflow_column, new_value
    end

    private

    # Motivation: even if NULL is stored in the workflow_state database column,
    # the current_state is correctly recognized in the Ruby code. The problem
    # arises when you want to SELECT records filtering by the value of initial
    # state. That's why it is important to save the string with the name of the
    # initial state in all the new records.
    def write_initial_state
      write_attribute self.class.workflow_column, current_state.to_s
    end
  end

  # This module will automatically generate ActiveRecord scopes based on workflow states.
  # The name of each generated scope will be something like `with_<state_name>_state`
  #
  # Examples:
  #
  # Article.with_pending_state # => ActiveRecord::Relation
  # Payment.without_refunded_state # => ActiveRecord::Relation
  #`
  # Example above just adds `where(:state_column_name => 'pending')` or
  # `where.not(:state_column_name => 'pending')` to AR query and returns
  # ActiveRecord::Relation.
  module Scopes
    def self.extended(object)
      class << object
        alias_method :workflow_without_scopes, :workflow unless method_defined?(:workflow_without_scopes)
        alias_method :workflow, :workflow_with_scopes
      end
    end

    def workflow_with_scopes(&specification)
      workflow_without_scopes(&specification)
      states = workflow_spec.states.values

      states.each do |state|
        define_singleton_method("with_#{state}_state") do
          where("#{table_name}.#{self.workflow_column.to_sym} = ?", state.to_s)
        end

        define_singleton_method("without_#{state}_state") do
          where.not("#{table_name}.#{self.workflow_column.to_sym} = ?", state.to_s)
        end
      end
    end

  end
end