module EY
  module Backup
    class MysqlEngine < Engine
      register 'mysql'

      def dump(database_name, basename)
        file = basename + '.sql'

        command = "mysqldump #{username_option} #{host_option} #{single_transaction_option(database_name)} #{routines_option} #{master_data_option} #{databases_option(database_name)} 2> /tmp/eybackup.$$.dumperr"

        if gpg?
          command << " | " << GPGEncryptor.command_for(key_id)
          file << GPGEncryptor.extension
        else
          command << " | " << GZipper.gzip
          file << GZipper.extension
        end

        command << " > #{file}"

        run(command, database_name)

        file
      end

      def load(database_name, file)
        cycle_database(database_name)
        command = "cat #{file}"

        if gpg?
          raise "Cannot load a GPG backup"
        else
          command << " | " << GZipper.gunzip
        end

        command << " | mysql #{username_option} #{host_option} #{database_name}"

        run(command)
      end
      
      def check_if_replica
        err_msg="ERROR: Target host: '#{host}' is currently: "
        err_msg=err_msg + "a replica based on 'show slave status', " if db_replicating?
        err_msg=err_msg + "in read_only mode, " if read_only_on?
        err_msg=err_msg + "restores should be processed against the master."
        
        EY::Backup.logger.fatal(%Q{#{err_msg}}) if db_replicating? or read_only_on?
      end

      def routines_option
        "--routines"
      end
      
      def master_data_option
        "--master-data=2" if log_bin_on?
      end
      
      def databases_option(db)
        "--add-drop-database --databases #{db}"
      end

      def host_option
        "-h#{host}"
      end

      def username_option
        "-u#{username}"
      end

      def single_transaction_option(database_name)
        '--single-transaction' unless db_has_myisam?(database_name)
      end

      def db_has_myisam?(database_name)
        query, stdout = "SELECT 1 FROM information_schema.tables WHERE table_schema='#{database_name}' AND engine='MyISAM' LIMIT 1;", StringIO.new
        spawn(%Q{mysql #{username_option} #{host_option} -N -e"#{query}"}, stdout)
        stdout.string.strip == '1'
      end
      
      def db_replicating?
        stdout = StringIO.new
        spawn(%Q{mysql #{username_option} #{host_option} -BN -e"show slave status"|wc -l}, stdout)
        stdout.string.to_i > 0
      end
      
      def read_only_on?
        stdout = StringIO.new
        spawn(%Q{mysql #{username_option} #{host_option} -BN -e"select @@global.read_only"}, stdout)
        stdout.string.to_i == 1
      end
      
      def log_bin_on?
        stdout = StringIO.new
        spawn(%Q{mysql #{username_option} #{host_option} -BN -e"select @@global.log_bin"}, stdout)
        stdout.string.to_i == 1
      end
      
      def cycle_database(database_name)
        query = "show create database #{database_name} \\G"
        create_cmd = %x(mysql #{username_option} #{host_option} -NB -e "#{query}"|tail -n 1)
        create_cmd="Create database #{database_name}" if create_cmd==""
        
        %x(mysql #{username_option} #{host_option} -e 'DROP DATABASE IF EXISTS #{database_name}')
        %x(mysql #{username_option} #{host_option} -e '#{create_cmd}')
        
      end

      def suffix
        /sql\.(gz|gpz)$/
      end
    end
  end
end