import re
import commands

class DeviceMap:
    device_map = "/boot/grub/device.map"
    host_os = "linux"

    class Error( Exception):
        pass

    def convert_linux(self, os_device):
        """ Convert an OS device to the corresponding Linux GRUB drive. """
        found = re.match( "([sh]d[a-z])([0-9]*)$", os_device)
        if found:
            return found.group(1), found.group(2)
        found = re.match( "(d[0-9]*)p([0-9]*)$", os_device)
        if found:
            return found.group(1), found.group(3)
        found = re.match( "(fd[0-9]*)$", os_device)
        if found:
            return found.group(1), ""
        found = re.match( "(/disk|/part([0-9]*))$", os_device)
        if found:
            return "/disc", found.group(2)
        found = re.match( "(c[0-7]d[0-9]*)(p*)(.*)", os_device)
        if found:
            return found.group(1), found.group(3)
        return os_device, ""
    def convert_drivemap(self, diskpart):
        """ Get the drive name """
        tmp_drive= commands.getoutput(
            r"grep -v '^#' '"+self.device_map+"'"+
            r"| grep '"+diskpart+" *$'"+
            r"| sed 's%.*\(([hf]d[0-9][a-g0-9,]*)\).*%\1%'")
        # If not found, print an error message and exit.
        if not tmp_drive:
            raise DeviceMap.Error(
                "%s does not have any corresponding BIOS drive."%( diskpart))
        return tmp_drive[0].strip()
        
    def convert(self, os_device):
        """ Convert an OS device to the corresponding GRUB drive.
            This part is OS-specific. """
        if "linux" in self.host_os:
            tmp_disk, tmp_part = self.convert_linux( os_device)
        tmp_drive= self.convert_drivemap( tmp_disk)
        if not tmp_part:
           # If no partition is specified, just print the drive name.
           return tmp_drive
        # If a partition is specified, we need to translate it into the
        # GRUB's syntax.
        if "linux" in self.host_os:
            return tmp_drive.replace( ")", ",%i)"%( int(tmp_part) -1))