# transaction.py - simple journaling scheme for mercurial

#

# This transaction scheme is intended to gracefully handle program

# errors and interruptions. More serious failures like system crashes

# can be recovered with an fsck-like tool. As the whole repository is

# effectively log-structured, this should amount to simply truncating

# anything that isn't referenced in the changelog.

#

# Copyright 2005, 2006 Olivia Mackall <olivia@selenic.com>

#

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

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

import errno

import os

from .i18n import _

from . import (

    error,

    pycompat,

    util,

)

from .utils import stringutil

version = 2

GEN_GROUP_ALL = b'all'

GEN_GROUP_PRE_FINALIZE = b'prefinalize'

GEN_GROUP_POST_FINALIZE = b'postfinalize'

def active(func):

    def _active(self, *args, **kwds):

        if self._count == 0:

            raise error.ProgrammingError(

                b'cannot use transaction when it is already committed/aborted'

            )

        return func(self, *args, **kwds)

    return _active

UNDO_BACKUP = b'%s.backupfiles'

UNDO_FILES_MAY_NEED_CLEANUP = [

    # legacy entries that might exists on disk from previous version:

    (b'store', b'%s.narrowspec'),

    (b'plain', b'%s.narrowspec.dirstate'),

    (b'plain', b'%s.branch'),

    (b'plain', b'%s.bookmarks'),

    (b'store', b'%s.phaseroots'),

    (b'plain', b'%s.dirstate'),

    # files actually in uses today:

    (b'plain', b'%s.desc'),

    # Always delete undo last to make sure we detect that a clean up is needed if

    # the process is interrupted.

    (b'store', b'%s'),

]

def cleanup_undo_files(report, vfsmap, undo_prefix=b'undo'):

    """remove "undo" files used by the rollback logic

    This is useful to prevent rollback running in situation were it does not

    make sense. For example after a strip.

    """

    backup_listing = UNDO_BACKUP % undo_prefix

    backup_entries = []

    undo_files = []

    svfs = vfsmap[b'store']

    try:

        with svfs(backup_listing) as f:

            backup_entries = read_backup_files(report, f)

    except OSError as e:

        if e.errno != errno.ENOENT:

            msg = _(b'could not read %s: %s\n')

            msg %= (svfs.join(backup_listing), stringutil.forcebytestr(e))

            report(msg)

    for location, f, backup_path, c in backup_entries:

        if location in vfsmap and backup_path:

            undo_files.append((vfsmap[location], backup_path))

    undo_files.append((svfs, backup_listing))

    for location, undo_path in UNDO_FILES_MAY_NEED_CLEANUP:

        undo_files.append((vfsmap[location], undo_path % undo_prefix))

    for undovfs, undofile in undo_files:

        try:

            undovfs.unlink(undofile)

        except OSError as e:

            if e.errno != errno.ENOENT:

                msg = _(b'error removing %s: %s\n')

                msg %= (undovfs.join(undofile), stringutil.forcebytestr(e))

                report(msg)

def _playback(

    journal,

    report,

    opener,

    vfsmap,

    entries,

    backupentries,

    unlink=True,

    checkambigfiles=None,

):

    """rollback a transaction :

    - truncate files that have been appended to

    - restore file backups

    - delete temporary files

    """

    backupfiles = []

    def restore_one_backup(vfs, f, b, checkambig):

        filepath = vfs.join(f)

        backuppath = vfs.join(b)

        try:

            util.copyfile(backuppath, filepath, checkambig=checkambig)

            backupfiles.append((vfs, b))

        except IOError as exc:

            e_msg = stringutil.forcebytestr(exc)

            report(_(b"failed to recover %s (%s)\n") % (f, e_msg))

            raise

    # gather all backup files that impact the store

    # (we need this to detect files that are both backed up and truncated)

    store_backup = {}

    for entry in backupentries:

        location, file_path, backup_path, cache = entry

        vfs = vfsmap[location]

        is_store = vfs.join(b'') == opener.join(b'')

        if is_store and file_path and backup_path:

            store_backup[file_path] = entry

    copy_done = set()

    # truncate all file `f` to offset `o`

    for f, o in sorted(dict(entries).items()):

        # if we have a backup for `f`, we should restore it first and truncate

        # the restored file

        bck_entry = store_backup.get(f)

        if bck_entry is not None:

            location, file_path, backup_path, cache = bck_entry

            checkambig = False

            if checkambigfiles:

                checkambig = (file_path, location) in checkambigfiles

            restore_one_backup(opener, file_path, backup_path, checkambig)

            copy_done.add(bck_entry)

        # truncate the file to its pre-transaction size

        if o or not unlink:

            checkambig = checkambigfiles and (f, b'') in checkambigfiles

            try:

                fp = opener(f, b'a', checkambig=checkambig)

                if fp.tell() < o:

                    raise error.Abort(

                        _(

                            b"attempted to truncate %s to %d bytes, but it was "

                            b"already %d bytes\n"

                        )

                        % (f, o, fp.tell())

                    )

                fp.truncate(o)

                fp.close()

            except IOError:

                report(_(b"failed to truncate %s\n") % f)

                raise

        else:

            # delete empty file

            try:

                opener.unlink(f)

            except FileNotFoundError:

                pass

    # restore backed up files and clean up temporary files

    for entry in backupentries:

        if entry in copy_done:

            continue

        l, f, b, c = entry

        if l not in vfsmap and c:

            report(b"couldn't handle %s: unknown cache location %s\n" % (b, l))

        vfs = vfsmap[l]

        try:

            checkambig = checkambigfiles and (f, l) in checkambigfiles

            if f and b:

                restore_one_backup(vfs, f, b, checkambig)

            else:

                target = f or b

                try:

                    vfs.unlink(target)

                except FileNotFoundError:

                    # This is fine because

                    #

                    # either we are trying to delete the main file, and it is

                    # already deleted.

                    #

                    # or we are trying to delete a temporary file and it is

                    # already deleted.

                    #

                    # in both case, our target result (delete the file) is

                    # already achieved.

                    pass

        except (IOError, OSError, error.Abort):

            if not c:

                raise

    # cleanup transaction state file and the backups file

    backuppath = b"%s.backupfiles" % journal

    if opener.exists(backuppath):

        opener.unlink(backuppath)

    opener.unlink(journal)

    try:

        for vfs, f in backupfiles:

            if vfs.exists(f):

                vfs.unlink(f)

    except (IOError, OSError, error.Abort):

        # only pure backup file remains, it is sage to ignore any error

        pass

class transaction(util.transactional):

    def __init__(

        self,

        report,

        opener,

        vfsmap,

        journalname,

        undoname=None,

        after=None,

        createmode=None,

        validator=None,

        releasefn=None,

        checkambigfiles=None,

        name='<unnamed>',

    ):

        """Begin a new transaction

        Begins a new transaction that allows rolling back writes in the event of

        an exception.

        * `after`: called after the transaction has been committed

        * `createmode`: the mode of the journal file that will be created

        * `releasefn`: called after releasing (with transaction and result)

        `checkambigfiles` is a set of (path, vfs-location) tuples,

        which determine whether file stat ambiguity should be avoided

        for corresponded files.

        """

        self._count = 1

        self._usages = 1

        self._report = report

        # a vfs to the store content

        self._opener = opener

        # a map to access file in various {location -> vfs}

        vfsmap = vfsmap.copy()

        vfsmap[b''] = opener  # set default value

        self._vfsmap = vfsmap

        self._after = after

        self._offsetmap = {}

        self._newfiles = set()

        self._journal = journalname

        self._journal_files = []

        self._undoname = undoname

        self._queue = []

        # A callback to do something just after releasing transaction.

        if releasefn is None:

            releasefn = lambda tr, success: None

        self._releasefn = releasefn

        self._checkambigfiles = set()

        if checkambigfiles:

            self._checkambigfiles.update(checkambigfiles)

        self._names = [name]

        # A dict dedicated to precisely tracking the changes introduced in the

        # transaction.

        self.changes = {}

        # a dict of arguments to be passed to hooks

        self.hookargs = {}

        self._file = opener.open(self._journal, b"w+")

        # a list of ('location', 'path', 'backuppath', cache) entries.

        # - if 'backuppath' is empty, no file existed at backup time

        # - if 'path' is empty, this is a temporary transaction file

        # - if 'location' is not empty, the path is outside main opener reach.

        #   use 'location' value as a key in a vfsmap to find the right 'vfs'

        # (cache is currently unused)

        self._backupentries = []

        self._backupmap = {}

        self._backupjournal = b"%s.backupfiles" % self._journal

        self._backupsfile = opener.open(self._backupjournal, b'w')

        self._backupsfile.write(b'%d\n' % version)

        if createmode is not None:

            opener.chmod(self._journal, createmode & 0o666)

            opener.chmod(self._backupjournal, createmode & 0o666)

        # hold file generations to be performed on commit

        self._filegenerators = {}

        # hold callback to write pending data for hooks

        self._pendingcallback = {}

        # True is any pending data have been written ever

        self._anypending = False

        # holds callback to call when writing the transaction

        self._finalizecallback = {}

        # holds callback to call when validating the transaction

        # should raise exception if anything is wrong

        self._validatecallback = {}

        if validator is not None:

            self._validatecallback[b'001-userhooks'] = validator

        # hold callback for post transaction close

        self._postclosecallback = {}

        # holds callbacks to call during abort

        self._abortcallback = {}

    def __repr__(self):

        name = '/'.join(self._names)

        return '<transaction name=%s, count=%d, usages=%d>' % (

            name,

            self._count,

            self._usages,

        )

    def __del__(self):

        if self._journal:

            self._abort()

    @property

    def finalized(self):

        return self._finalizecallback is None

    @active

    def startgroup(self):

        """delay registration of file entry

        This is used by strip to delay vision of strip offset. The transaction

        sees either none or all of the strip actions to be done."""

        self._queue.append([])

    @active

    def endgroup(self):

        """apply delayed registration of file entry.

        This is used by strip to delay vision of strip offset. The transaction

        sees either none or all of the strip actions to be done."""

        q = self._queue.pop()

        for f, o in q:

            self._addentry(f, o)

    @active

    def add(self, file, offset):

        """record the state of an append-only file before update"""

        if (

            file in self._newfiles

            or file in self._offsetmap

            or file in self._backupmap

        ):

            return

        if self._queue:

            self._queue[-1].append((file, offset))

            return

        self._addentry(file, offset)

    def _addentry(self, file, offset):

        """add a append-only entry to memory and on-disk state"""

        if (

            file in self._newfiles

            or file in self._offsetmap

            or file in self._backupmap

        ):

            return

        if offset:

            self._offsetmap[file] = offset

        else:

            self._newfiles.add(file)

        # add enough data to the journal to do the truncate

        self._file.write(b"%s\0%d\n" % (file, offset))

        self._file.flush()

    @active

    def addbackup(self, file, hardlink=True, location=b'', for_offset=False):

        """Adds a backup of the file to the transaction

        Calling addbackup() creates a hardlink backup of the specified file

        that is used to recover the file in the event of the transaction