# The basic idea is that we take the existing data via ActiveRecord
# and create new documents in MongoDB using MongoMapper.
# This method is necessary as we want to keep all the associations of existing dataset
# and by the way, clean up empty columns
# We rely on models still being ActiveRecord::Base, I bet you can figure out how the look like.
# And have the newer MongoDB ones here in a module, painful as we have to set the collection_name
# Don't put a +timestamps!+ into your MongoMapper models yet because this would change the updated_at if existing

module MongoStream
  class Photo
    @collection_name = 'photos'
    include MongoMapper::Document
  end
  class Source
    include MongoMapper::EmbeddedDocument
  end
  class Album
    include MongoMapper::EmbeddedDocument
    has_many :photos, :class_name => "MongoStream::Photo"
  end
  class Page
    include MongoMapper::EmbeddedDocument
    has_many :photos, :class_name => "MongoStream::Photo"
  end
  class User
    @collection_name = 'users'
    include MongoMapper::Document
    has_many :sources, :class_name => "MongoStream::Source"
    has_many :websites, :class_name => "MongoStream::Website"
  end
  class Website
    @collection_name = 'websites'
    include MongoMapper::Document
    has_many :pages, :class_name => "MongoStream::Page"
    has_many :users, :class_name => "MongoStream::User"
    has_many :photos, :class_name => "MongoStream::Photo"
    has_many :albums, :class_name => "MongoStream::Album"
  end
end

class MigrateToMongodb < ActiveRecord::Migration
  require 'mongo_mapper'
  def self.clean_attrs(attributes)
    attributes.reject{|k,v|k=="id" || v.nil?}
  end
  def self.up
    %w(MongoStream::User MongoStream::Website MongoStream::Photo).map{|klass| instance_eval("#{klass}.delete_all") rescue nil }
    ::User.all.each do |user|
      m_user = MongoStream::User.create!(clean_attrs(user.attributes))
      user.sources.all.each do |source|
        m_source = MongoStream::Source.new(clean_attrs(source.attributes))
        source.photos.each do |photo|
          p = MongoStream::Photo.create!(clean_attrs(photo.attributes))
          p[:tags] = photo.tag_list.to_a
          p[:source_id] = m_source.id
          p.save
        end
        m_source.save
        m_user.sources << m_source
      end
      m_user.save
    end
  end

  def self.down
  end
end