# Original file by Tobias Luetke, found on
#   http://blog.leetsoft.com/2006/5/29/easy-migration-between-databases
#
# set_sequences task by tnb@thenakedbrain.com
#
namespace :db do
  namespace :backup do

    def entity_table?(table_name)
      columns = ActiveRecord::Base.connection.columns(table_name).map { |column| column.name }
      columns.include?('id') || columns.include?('party_id')
    end

    def interesting_tables
      tables = ActiveRecord::Base.connection.tables.sort.reject do |tbl|
        ['schema_info', 'sessions', 'logged_exceptions'].include?(tbl)
      end
      tables.select do |tbl|
        entity_table?(tbl)
      end
    end

    def load_table tbl, loaded_tables
      return if loaded_tables.include? tbl
      loaded_tables << tbl
      klass = tbl.classify.constantize
      klass.foreign_keys.each do |f_key|
        load_table f_key.references_table_name, loaded_tables
      end
      ActiveRecord::Base.transaction do
        puts "Loading #{tbl}..."
        if ActiveRecord::Base.connection.adapter_name.downcase == 'postgresql'
          ActiveRecord::Base.connection.execute "ALTER TABLE #{tbl} DISABLE TRIGGER ALL"
        elsif ActiveRecord::Base.connection.adapter_name.downcase == 'mysql'
          ActiveRecord::Base.connection.execute "SET FOREIGN_KEY_CHECKS=0"
        end
        YAML.load_file("#{tbl}.yml").each do |fixture|
          entity    = klass.new(fixture)
          entity.id = fixture['id']
          entity.save_without_validation!
          if fixture.keys.include?('position') && entity.position != fixture['position'].to_i
            puts "Adjusting position #{entity.position} => #{fixture['position']}"
            entity.position = fixture['position']
            entity.save_without_validation!
          end
          klass.find(fixture['id'])
        end
        if ActiveRecord::Base.connection.adapter_name.downcase == "postgresql"
          ActiveRecord::Base.connection.execute "ALTER TABLE #{tbl} ENABLE TRIGGER ALL"
        elsif ActiveRecord::Base.connection.adapter_name.downcase == 'mysql'
          ActiveRecord::Base.connection.execute "SET FOREIGN_KEY_CHECKS=1"
        end
      end
    end

    desc "Dump entire db."
    task :write => :environment do
      dir = Rails.root + "/db/backup"
      FileUtils.mkdir_p(dir)
      FileUtils.chdir(dir)

      interesting_tables.each do |tbl|
        klass = tbl.classify.constantize
        puts "Writing #{tbl}..."
        entities = klass.find(:all)
        if klass.column_names.include? 'type'
          entities = entities.select { |e| e.type == klass }
        end
        File.open("#{tbl}.yml", 'w+') { |f| YAML.dump entities.collect(&:attributes), f }
      end
    end

    task :read => [:environment, 'db:schema:load'] do
      dir = Rails.root + '/db/backup'
      FileUtils.mkdir_p(dir)
      FileUtils.chdir(dir)

      loaded_tables = []

      interesting_tables.each do |tbl|
        load_table(tbl, loaded_tables)
      end
    end

    desc "Set postgresql sequence currval to highest id for each table"
    task :set_sequences => :environment do
      if ActiveRecord::Base.connection.adapter_name.downcase == "postgresql"
        interesting_tables.each do |tbl|
          if ActiveRecord::Base.connection.columns(tbl).map { |column| column.name }.include?('id')
            puts "Setting sequence's currval to highest id for #{tbl}"
            ActiveRecord::Base.connection.execute "select setval('#{tbl}_id_seq', (select max(id) from #{tbl}));"
          end
        end
      else
        puts "This operation only works for postgresql databases."
      end
    end

  end
end