Generate a compound success message

success.rb

def create_success_message
  result = @created_events.reduce("Post updated,") do |m, ev|
    case ev.class
    when PostAssignedEvent
      m += " assigned to #{ev.assignee.name},"
    when PostArchivedEvent
      m += " archived,"
    when PostUnassignedEvent
      m += " assigned user cleared,"
    when PostProposedEvent
      m += " proposed,"
    end
    m
  end.chomp(",")

  if result.count(",") > 0
    result[result.rindex(',')...(result.rindex(',') + 1)] = "#{result.count(",") > 1 ? ',' : ''} and"
  end

  result + "."
end

# > Post updated, archived, and assigned user cleared.