#!/usr/bin/python

import argparse
import logging
import os
import os.path
import subprocess
import sys
import tempfile
import uuid


log_name = __name__
if log_name == '__main__':
    log_name = os.path.basename(sys.argv[0])
log = logging.getLogger(log_name)


class PrepareError(Exception):
    """
    OSD preparation error
    """

    def __str__(self):
        doc = self.__doc__.strip()
        return ': '.join([doc] + [str(a) for a in self.args])


class MountError(PrepareError):
    """
    Mounting filesystem failed
    """


class UnmountError(PrepareError):
    """
    Unmounting filesystem failed
    """


def write_one_line(parent, name, text):
    """
    Write a file whose sole contents are a single line.

    Adds a newline.
    """
    path = os.path.join(parent, name)
    tmp = '{path}.{pid}.tmp'.format(path=path, pid=os.getpid())
    with file(tmp, 'wb') as f:
        f.write(text + '\n')
        os.fsync(f.fileno())
    os.rename(tmp, path)


CEPH_OSD_ONDISK_MAGIC = 'ceph osd volume v026'

JOURNAL_UUID = '45b0969e-9b03-4f30-b4c6-b4b80ceff106'


# TODO depend on python2.7
def _check_output(*args, **kwargs):
    process = subprocess.Popen(
        stdout=subprocess.PIPE,
        *args, **kwargs)
    out, _ = process.communicate()
    ret = process.wait()
    if ret:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = args[0]
        raise subprocess.CalledProcessError(ret, cmd, output=out)
    return out


def get_conf(cluster, variable):
    try:
        p = subprocess.Popen(
            args=[
                'ceph-conf',
                '--cluster={cluster}'.format(
                    cluster=cluster,
                    ),
                '--name=osd.',
                '--lookup',
                variable,
                ],
            stdout=subprocess.PIPE,
            close_fds=True,
            )
    except OSError as e:
        raise PrepareError('error executing ceph-conf', e)
    (out, _err) = p.communicate()
    ret = p.wait()
    if ret == 1:
        # config entry not found
        return None
    elif ret != 0:
        raise PrepareError('getting variable from configuration failed')
    value = out.split('\n', 1)[0]
    # don't differentiate between "var=" and no var set
    if not value:
        return None
    return value


def get_conf_with_default(cluster, variable):
    """
    Get a config value that is known to the C++ code.

    This will fail if called on variables that are not defined in
    common config options.
    """
    try:
        out = _check_output(
            args=[
                'ceph-osd',
                '--cluster={cluster}'.format(
                    cluster=cluster,
                    ),
                '--show-config-value={variable}'.format(
                    variable=variable,
                    ),
                ],
            close_fds=True,
            )
    except subprocess.CalledProcessError as e:
        raise PrepareError(
            'getting variable from configuration failed',
            e,
            )

    value = out.split('\n', 1)[0]
    return value


def get_fsid(cluster):
    fsid = get_conf(cluster=cluster, variable='fsid')
    if fsid is None:
        raise PrepareError('getting cluster uuid from configuration failed')
    return fsid


DEFAULT_FS_TYPE = 'xfs'

MOUNT_OPTIONS = dict(
    btrfs='noatime,user_subvol_rm_allowed',
    ext4='noatime,user_xattr',
    xfs='noatime',
    )

MKFS_ARGS = dict(
    btrfs=[
        '-m', 'single',
        '-l', '32768',
        '-n', '32768',
        ],
    xfs=[
        # xfs insists on not overwriting previous fs; even if we wipe
        # partition table, we often recreate it exactly the same way,
        # so we'll see ghosts of filesystems past
        '-f',
        '-i', 'size=2048',
        ],
    )


def mount(
    dev,
    fstype,
    options,
    ):
    # pick best-of-breed mount options based on fs type
    if options is None:
        options = MOUNT_OPTIONS.get(fstype, '')

    # mount
    path = tempfile.mkdtemp(
        prefix='mnt.',
        dir='/var/lib/ceph/tmp',
        )
    try:
        subprocess.check_call(
            args=[
                'mount',
                '-o', options,
                '--',
                dev,
                path,
                ],
            )
    except subprocess.CalledProcessError as e:
        try:
            os.rmdir(path)
        except (OSError, IOError):
            pass
        raise MountError(e)

    return path


def unmount(
    path,
    ):
    try:
        subprocess.check_call(
            args=[
                'umount',
                '--',
                path,
                ],
            )
    except subprocess.CalledProcessError as e:
        raise UnmountError(e)

    os.rmdir(path)


def get_free_partition_index(dev):
    try:
        lines = _check_output(
            args=[
                'parted',
                '--machine',
                '--',
                dev,
                'print',
                ],
            )
    except subprocess.CalledProcessError as e:
        print 'cannot read partition index; assume it isn\'t present\n'
        return 1

    if not lines:
        raise PrepareError('parted failed to output anything')
    lines = lines.splitlines(True)

    if lines[0] not in ['CHS;\n', 'CYL;\n', 'BYT;\n']:
        raise PrepareError('weird parted units', lines[0])
    del lines[0]

    if not lines[0].startswith('/dev/'):
        raise PrepareError('weird parted disk entry', lines[0])
    del lines[0]

    seen = set()
    for line in lines:
        idx, _ = line.split(':', 1)
        idx = int(idx)
        seen.add(idx)

    num = 1
    while num in seen:
        num += 1
    return num


def prepare(
    disk,
    journal,
    journal_size,
    fstype,
    mkfs_args,
    mount_options,
    cluster_uuid,
    ):
    """
    Prepare a disk to be used as an OSD data disk.

    The ``magic`` file is written last, so it's presence is a reliable
    indicator of the whole sequence having completed.

    WARNING: This will unconditionally overwrite anything given to
    it.
    """

    try:
        # this kills the crab
        subprocess.check_call(
            args=[
                'sgdisk',
                '--zap-all',
                '--clear',
                '--mbrtogpt',
                '--',
                disk,
                ],
            )
    except subprocess.CalledProcessError as e:
        raise PrepareError(e)

    osd_uuid = str(uuid.uuid4())

    # store the partition uuid iff using external journal
    journal_uuid = None

    if journal is not None:
        journal_uuid = str(uuid.uuid4())

        if journal == disk:
            # we're sharing the disk between osd data and journal;
            # make journal be partition number 2, so it's pretty; put
            # journal at end of free space so partitioning tools don't
            # reorder them suddenly
            num = 2
            journal_part = '{num}:-{size}M:0'.format(
                num=num,
                size=journal_size,
                )
        else:
            # sgdisk has no way for me to say "whatever is the next
            # free index number" when setting type guids etc, so we
            # need to awkwardly look up the next free number, and then
            # fix that in the call -- and hope nobody races with us;
            # then again nothing guards the partition table from races
            # anyway
            num = get_free_partition_index(dev=journal)
            journal_part = '{num}:0:+{size}M'.format(
                num=num,
                size=journal_size,
                )

        try:
            subprocess.check_call(
                args=[
                    'sgdisk',
                    '--new={part}'.format(part=journal_part),
                    '--change-name={num}:ceph journal'.format(num=num),
                    '--partition-guid={num}:{journal_uuid}'.format(
                        num=num,
                        journal_uuid=journal_uuid,
                        ),
                    '--typecode={num}:{uuid}'.format(
                        num=num,
                        uuid=JOURNAL_UUID,
                        ),
                    '--',
                    journal,
                    ],
                )
            subprocess.check_call(
                args=[
                    # also make sure the kernel refreshes the new table
                    'partprobe',
                    journal,
                    ],
                )
        except subprocess.CalledProcessError as e:
            raise PrepareError(e)

    try:
        subprocess.check_call(
            args=[
                'sgdisk',
                '--largest-new=1',
                '--change-name=1:ceph data',
                '--partition-guid=1:{osd_uuid}'.format(
                    osd_uuid=osd_uuid,
                    ),
                '--typecode=1:89c57f98-2fe5-4dc0-89c1-f3ad0ceff2be',
                '--',
                disk,
                ],
            )
        subprocess.check_call(
            args=[
                # also make sure the kernel refreshes the new table
                'partprobe',
                disk,
                ],
            )
    except subprocess.CalledProcessError as e:
        raise PrepareError(e)

    dev = '{disk}1'.format(disk=disk)
    args = [
        'mkfs',
        '--type={fstype}'.format(fstype=fstype),
        ]
    args.extend(MKFS_ARGS.get(fstype, []))
    if mkfs_args is not None:
        args.extend(mkfs_args.split())
    args.extend
    args.extend([
            '--',
            dev,
            ])
    try:
        subprocess.check_call(args=args)
    except subprocess.CalledProcessError as e:
        raise PrepareError(e)

    path = mount(dev=dev, fstype=fstype, options=mount_options)
    try:
        if journal_uuid is not None:
            # we're using an external journal; point to it here
            os.symlink(
                '/dev/disk/by-partuuid/{journal_uuid}'.format(
                    journal_uuid=journal_uuid,
                    ),
                os.path.join(path, 'journal'),
                )
        write_one_line(path, 'ceph_fsid', cluster_uuid)
        write_one_line(path, 'fsid', osd_uuid)
        write_one_line(path, 'magic', CEPH_OSD_ONDISK_MAGIC)
    finally:
        unmount(path)

    try:
        subprocess.check_call(
            args=[
                'sgdisk',
               '--typecode=1:4fbd7e29-9d25-41b8-afd0-062c0ceff05d',
                '--',
                disk,
                ],
            )
    except subprocess.CalledProcessError as e:
        raise PrepareError(e)


def parse_args():
    parser = argparse.ArgumentParser(
        description='Prepare a disk for a Ceph OSD',
        )
    parser.add_argument(
        '-v', '--verbose',
        action='store_true', default=None,
        help='be more verbose',
        )
    parser.add_argument(
        '--cluster',
        metavar='NAME',
        help='cluster name to assign this disk to',
        )
    parser.add_argument(
        '--cluster-uuid',
        metavar='UUID',
        help='cluster uuid to assign this disk to',
        )
    parser.add_argument(
        '--fs-type',
        help='file system type to use (e.g. "ext4")',
        )
    parser.add_argument(
        'disk',
        metavar='DISK',
        help='path to OSD data disk block device',
        )
    parser.add_argument(
        'journal',
        metavar='JOURNAL',
        nargs='?',
        help=('path to OSD journal disk block device;'
              + ' leave out to store journal in file'),
        )
    parser.set_defaults(
        # we want to hold on to this, for later
        prog=parser.prog,
        cluster='ceph',
        )
    args = parser.parse_args()
    return args


def main():
    args = parse_args()

    loglevel = logging.INFO
    if args.verbose:
        loglevel = logging.DEBUG

    logging.basicConfig(
        level=loglevel,
        )

    try:
        if args.cluster_uuid is None:
            args.cluster_uuid = get_fsid(cluster=args.cluster)
            if args.cluster_uuid is None:
                raise PrepareError(
                    'must have fsid in config or pass --cluster--uuid=',
                    )

        if args.fs_type is None:
            args.fs_type = get_conf(
                cluster=args.cluster,
                variable='osd_fs_type',
                )
            if args.fs_type is None:
                args.fs_type = DEFAULT_FS_TYPE

        mkfs_args = get_conf(
            cluster=args.cluster,
            variable='osd_fs_mkfs_arguments_{fstype}'.format(
                fstype=args.fs_type,
                ),
            )

        mount_options = get_conf(
            cluster=args.cluster,
            variable='osd_fs_mount_options_{fstype}'.format(
                fstype=args.fs_type,
                ),
            )

        journal_size = get_conf_with_default(
            cluster=args.cluster,
            variable='osd_journal_size',
            )
        journal_size = int(journal_size)

        prepare(
            disk=args.disk,
            journal=args.journal,
            journal_size=journal_size,
            fstype=args.fs_type,
            mkfs_args=mkfs_args,
            mount_options=mount_options,
            cluster_uuid=args.cluster_uuid,
            )
    except PrepareError as e:
        print >>sys.stderr, '{prog}: {msg}'.format(
            prog=args.prog,
            msg=e,
            )
        sys.exit(1)

if __name__ == '__main__':
    main()