Komando

require "komando/command"
require "komando/active_record"

class AdUpdateCommand
  include Komando::Command

  def initialize(*args)
    @initiated_at = Time.now.utc

    # If you must override #initialize, NEVER forget to call super
    super

    # Forgetting to call super will result in NoMethodError and such
    # being raised from your code.
  end

  # Lets exceptions through -- nothing is rescued -- callers will have
  # to handle exceptions themselves. The command's success/failure state
  # is determined by the fact that no exceptions are raised. The block's
  # return value is ignored.
  #
  # All #mandatory_steps are run within a single database transaction.
  mandatory_steps do
    @ad.update_attributes!(@params)
    @ad.campaign.update_attribute(:active_ad_units_count, @ad.campaign.ad_units.active.count)
  end

  # The #transaction block can be used to root your transaction differently.
  # The default #transaction block simply yields - no transactions will be
  # processed. The komando-active_record gem will root your transactions
  # against ActiveRecord::Base#transaction.
  #
  # This method is important if you have more than one database connection,
  # where each model might open transactions against different databases.
  transaction do
    AdUnit.transaction do
      yield
    end
  end
end

class PlacementEventLoggerCommand
  include Komando::Command

  mandatory_steps do
    Event.create!(:event_type => "placement:created", :actor => @actor, :subject => @subject)
  end
end

class PlacementCreationCommand
  include Komando::Command

  mandatory_steps do
    @placement = Placement.create!(@params)

    @placement.campaign.increment!(:active_placements_count, 1)    if @placement.active?
    @placement.campaign.increment!(:scheduled_placements_count, 1) if @placement.scheduled?
  end

  # Call #best_effort_step multiple times to declare each individual step
  # that will be attempted. If a block fails, logging will ensue, and
  # other blocks will be attempted.
  #
  # #best_effort_step can document what it's supposed to do, enabling
  # better logging. Either pass a String or Symbol, the latter of which will
  # be #humanized.
  best_effort_step(:event_generation) do

    # Note the availability of a class-level method named #run, which simply does the obvious
    # instantiation and call the instance-level #run.
    PlacementEventLoggerCommand.run(:actor => @placement.created_by, :subject => @placement)

  end
end

# Usage from Rails
class AdsController < ApplicationController

  def update
    @ad = Ad.find(params[:id])

    # Commands accept any number of parameters, as a Hash. Parameters are translated
    # to instance variables within the Command object itself.
    command = AdUpdateCommand.new(:ad     => @ad,
                                  :params => params[:ad])
    if command.run then
      flash[:notice] = "Ad updated"
      redirect_to @ad
    else
      flash.new[:error] = "Ad failed to save"
      render :action => :edit
    end
  end

end