# docket - code related to revlog "docket"

#

# Copyright 2021 Pierre-Yves David <pierre-yves.david@octobus.net>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

### Revlog docket file

#

# The revlog is stored on disk using multiple files:

#

# * a small docket file, containing metadata and a pointer,

#

# * an index file, containing fixed width information about revisions,

#

# * a data file, containing variable width data for these revisions,

from __future__ import absolute_import

import errno

import os

import random

import struct

from .. import (

    encoding,

    error,

    node,

    pycompat,

    util,

)

from . import (

    constants,

)

def make_uid(id_size=8):

    """return a new unique identifier.

    The identifier is random and composed of ascii characters."""

    # size we "hex" the result we need half the number of bits to have a final

    # uuid of size ID_SIZE

    return node.hex(os.urandom(id_size // 2))

# some special test logic to avoid anoying random output in the test

stable_docket_file = encoding.environ.get(b'HGTEST_UUIDFILE')

if stable_docket_file:

    def make_uid(id_size=8):

        try:

            with open(stable_docket_file, mode='rb') as f:

                seed = f.read().strip()

        except IOError as inst:

            if inst.errno != errno.ENOENT:

                raise

            seed = b'04'  # chosen by a fair dice roll. garanteed to be random

        if pycompat.ispy3:

            iter_seed = iter(seed)

        else:

            iter_seed = (ord(c) for c in seed)

        # some basic circular sum hashing on 64 bits

        int_seed = 0

        low_mask = int('1' * 35, 2)

        for i in iter_seed:

            high_part = int_seed >> 35

            low_part = (int_seed & low_mask) << 28

            int_seed = high_part + low_part + i

        r = random.Random()

        if pycompat.ispy3:

            r.seed(int_seed, version=1)

        else:

            r.seed(int_seed)

        # once we drop python 3.8 support we can simply use r.randbytes

        raw = r.getrandbits(id_size * 4)

        assert id_size == 8

        p = struct.pack('>L', raw)

        new = node.hex(p)

        with open(stable_docket_file, 'wb') as f:

            f.write(new)

        return new

# Docket format

#

# * 4 bytes: revlog version

#          |   This is mandatory as docket must be compatible with the previous

#          |   revlog index header.

# * 1 bytes: size of index uuid

# * 1 bytes: size of data uuid

# * 8 bytes: size of index-data

# * 8 bytes: pending size of index-data

# * 8 bytes: size of data

# * 8 bytes: pending size of data

# * 1 bytes: default compression header

S_HEADER = struct.Struct(constants.INDEX_HEADER.format + 'BBLLLLc')

class RevlogDocket(object):

    """metadata associated with revlog"""

    def __init__(

        self,

        revlog,

        use_pending=False,

        version_header=None,

        index_uuid=None,

        data_uuid=None,

        index_end=0,

        pending_index_end=0,

        data_end=0,

        pending_data_end=0,

        default_compression_header=None,

    ):

        self._version_header = version_header

        self._read_only = bool(use_pending)

        self._dirty = False

        self._radix = revlog.radix

        self._path = revlog._docket_file

        self._opener = revlog.opener

        self._index_uuid = index_uuid

        self._data_uuid = data_uuid

        # thes asserts should be True as long as we have a single index filename

        assert index_end <= pending_index_end

        assert data_end <= pending_data_end

        self._initial_index_end = index_end

        self._pending_index_end = pending_index_end

        self._initial_data_end = data_end

        self._pending_data_end = pending_data_end

        if use_pending:

            self._index_end = self._pending_index_end

            self._data_end = self._pending_data_end

        else:

            self._index_end = self._initial_index_end

            self._data_end = self._initial_data_end

        self.default_compression_header = default_compression_header

    def index_filepath(self):

        """file path to the current index file associated to this docket"""

        # very simplistic version at first

        if self._index_uuid is None:

            self._index_uuid = make_uid()

        return b"%s-%s.idx" % (self._radix, self._index_uuid)

    def data_filepath(self):

        """file path to the current index file associated to this docket"""

        # very simplistic version at first

        if self._data_uuid is None:

            self._data_uuid = make_uid()

        return b"%s-%s.dat" % (self._radix, self._data_uuid)

    @property

    def index_end(self):

        return self._index_end

    @index_end.setter

    def index_end(self, new_size):

        if new_size != self._index_end:

            self._index_end = new_size

            self._dirty = True

    @property

    def data_end(self):

        return self._data_end

    @data_end.setter

    def data_end(self, new_size):

        if new_size != self._data_end:

            self._data_end = new_size

            self._dirty = True

    def write(self, transaction, pending=False, stripping=False):

        """write the modification of disk if any

        This make the new content visible to all process"""

        if not self._dirty:

            return False

        else:

            if self._read_only:

                msg = b'writing read-only docket: %s'

                msg %= self._path

                raise error.ProgrammingError(msg)

            if not stripping:

                # XXX we could, leverage the docket while stripping. However it

                # is not powerfull enough at the time of this comment

                transaction.addbackup(self._path, location=b'store')

            with self._opener(self._path, mode=b'w', atomictemp=True) as f:

                f.write(self._serialize(pending=pending))

            # if pending we still need to the write final data eventually

            self._dirty = pending

            return True

    def _serialize(self, pending=False):

        if pending:

            official_index_end = self._initial_index_end

            official_data_end = self._initial_data_end

        else:

            official_index_end = self._index_end

            official_data_end = self._data_end

        # this assert should be True as long as we have a single index filename

        assert official_data_end <= self._data_end

        data = (

            self._version_header,

            len(self._index_uuid),

            len(self._data_uuid),

            official_index_end,

            self._index_end,

            official_data_end,

            self._data_end,

            self.default_compression_header,

        )

        s = []

        s.append(S_HEADER.pack(*data))

        s.append(self._index_uuid)

        s.append(self._data_uuid)

        return b''.join(s)

def default_docket(revlog, version_header):

    """given a revlog version a new docket object for the given revlog"""

    rl_version = version_header & 0xFFFF

    if rl_version not in (constants.REVLOGV2, constants.CHANGELOGV2):

        return None

    comp = util.compengines[revlog._compengine].revlogheader()

    docket = RevlogDocket(

        revlog,

        version_header=version_header,

        default_compression_header=comp,

    )

    docket._dirty = True

    return docket

def parse_docket(revlog, data, use_pending=False):

    """given some docket data return a docket object for the given revlog"""

    header = S_HEADER.unpack(data[: S_HEADER.size])

    offset = S_HEADER.size

    index_uuid = data[offset : offset + index_uuid_size]

    offset += index_uuid_size

    data_uuid = data[offset : offset + data_uuid_size]

    offset += data_uuid_size

    docket = RevlogDocket(

        revlog,

        use_pending=use_pending,

        version_header=version_header,

        index_uuid=index_uuid,

        data_uuid=data_uuid,

        index_end=index_size,

        pending_index_end=pending_index_size,

        data_end=data_size,

        pending_data_end=pending_data_size,

        default_compression_header=default_compression_header,

    )

    return docket