# 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 Matt Mackall <mpm@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.

from i18n import _

import errno

import error, util

version = 1

def active(func):

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

        if self.count == 0:

            raise error.Abort(_(

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

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

    return _active

def _playback(journal, report, opener, entries, backupentries, unlink=True):

    for f, o, _ignore in entries:

        if o or not unlink:

            try:

                fp = opener(f, 'a')

                fp.truncate(o)

                fp.close()

            except IOError:

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

                raise

        else:

            try:

                opener.unlink(f)

            except (IOError, OSError), inst:

                if inst.errno != errno.ENOENT:

                    raise

    backupfiles = []

    for f, b in backupentries:

        if b:

            filepath = opener.join(f)

            backuppath = opener.join(b)

            try:

                util.copyfile(backuppath, filepath)

                backupfiles.append(b)

            except IOError:

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

                raise

        else:

            try:

                opener.unlink(f)

            except (IOError, OSError), inst:

                if inst.errno != errno.ENOENT:

                    raise

    opener.unlink(journal)

    backuppath = "%s.backupfiles" % journal

    if opener.exists(backuppath):

        opener.unlink(backuppath)

    for f in backupfiles:

        opener.unlink(f)

class transaction(object):

    def __init__(self, report, opener, journal, after=None, createmode=None,

            onclose=None, onabort=None):

        """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

        * `onclose`: called as the transaction is closing, but before it is

        closed

        * `onabort`: called as the transaction is aborting, but before any files

        have been truncated

        """

        self.count = 1

        self.usages = 1

        self.report = report

        self.opener = opener

        self.after = after

        self.onclose = onclose

        self.onabort = onabort

        self.entries = []

        self.map = {}

        self.journal = journal

        self._queue = []

        # a dict of arguments to be passed to hooks

        self.hookargs = {}

        self.file = opener.open(self.journal, "w")

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

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

        self._backupentries = []

        self._backupmap = {}

        self._backupjournal = "%s.backupfiles" % journal

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

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

        if createmode is not None:

            opener.chmod(self.journal, createmode & 0666)

            opener.chmod(self._backupjournal, createmode & 0666)

        # hold file generations to be performed on commit

        self._filegenerators = {}

        # hold callbalk 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 = {}

        # hold callbalk for post transaction close

        self._postclosecallback = {}

    def __del__(self):

        if self.journal:

            self._abort()

    @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, data in q:

            self._addentry(f, o, data)

    @active

    def add(self, file, offset, data=None):

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

        if file in self.map or file in self._backupmap:

            return

        if self._queue:

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

            return

        self._addentry(file, offset, data)

    def _addentry(self, file, offset, data):

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

        if file in self.map or file in self._backupmap:

            return

        self.entries.append((file, offset, data))

        self.map[file] = len(self.entries) - 1

        # add enough data to the journal to do the truncate

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

        self.file.flush()

    @active

    def addbackup(self, file, hardlink=True, vfs=None):

        """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

        aborting.

        * `file`: the file path, relative to .hg/store

        * `hardlink`: use a hardlink to quickly create the backup

        """

        if self._queue:

            msg = 'cannot use transaction.addbackup inside "group"'

            raise RuntimeError(msg)

        if file in self.map or file in self._backupmap:

            return

        backupfile = "%s.backup.%s" % (self.journal, file)

        if vfs is None:

            vfs = self.opener

        if vfs.exists(file):

            filepath = vfs.join(file)

            backuppath = self.opener.join(backupfile)

            util.copyfiles(filepath, backuppath, hardlink=hardlink)

        else:

            backupfile = ''

        self._backupentries.append((file, backupfile))

        self._backupmap[file] = len(self._backupentries) - 1

        self._backupsfile.write("%s\0%s\n" % (file, backupfile))

        self._backupsfile.flush()

    @active

    def addfilegenerator(self, genid, filenames, genfunc, order=0, vfs=None):

        """add a function to generates some files at transaction commit

        The `genfunc` argument is a function capable of generating proper

        content of each entry in the `filename` tuple.

        At transaction close time, `genfunc` will be called with one file

        object argument per entries in `filenames`.

        The transaction itself is responsible for the backup, creation and

        final write of such file.

        The `genid` argument is used to ensure the same set of file is only

        generated once. Call to `addfilegenerator` for a `genid` already

        present will overwrite the old entry.

        The `order` argument may be used to control the order in which multiple

        generator will be executed.

        """

        # For now, we are unable to do proper backup and restore of custom vfs

        # but for bookmarks that are handled outside this mechanism.

        assert vfs is None or filenames == ('bookmarks',)

        self._filegenerators[genid] = (order, filenames, genfunc, vfs)

    def _generatefiles(self):

        # write files registered for generation

        for entry in sorted(self._filegenerators.values()):

            order, filenames, genfunc, vfs = entry

            if vfs is None:

                vfs = self.opener

            files = []

            try:

                for name in filenames:

                    # Some files are already backed up when creating the

                    # localrepo. Until this is properly fixed we disable the

                    # backup for them.

                    if name not in ('phaseroots', 'bookmarks'):

                        self.addbackup(name)

                    files.append(vfs(name, 'w', atomictemp=True))

                genfunc(*files)

            finally:

                for f in files:

                    f.close()

    @active

    def find(self, file):

        if file in self.map:

            return self.entries[self.map[file]]

        if file in self._backupmap:

            return self._backupentries[self._backupmap[file]]

        return None

    @active

    def replace(self, file, offset, data=None):

        '''

        replace can only replace already committed entries

        that are not pending in the queue

        '''

        if file not in self.map:

            raise KeyError(file)

        index = self.map[file]

        self.entries[index] = (file, offset, data)

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

        self.file.flush()

    @active

    def nest(self):

        self.count += 1

        self.usages += 1

        return self

    def release(self):

        if self.count > 0:

            self.usages -= 1

        # if the transaction scopes are left without being closed, fail

        if self.count > 0 and self.usages == 0:

            self._abort()

    def running(self):

        return self.count > 0

    def addpending(self, category, callback):

        """add a callback to be called when the transaction is pending

        Category is a unique identifier to allow overwriting an old callback

        with a newer callback.

        """

        self._pendingcallback[category] = callback

    @active

    def writepending(self):

        '''write pending file to temporary version

        This is used to allow hooks to view a transaction before commit'''

        categories = sorted(self._pendingcallback)

        for cat in categories:

            # remove callback since the data will have been flushed

            self._anypending = self._anypending or any

        return self._anypending

    @active

    def addfinalize(self, category, callback):

        """add a callback to be called when the transaction is closed

        Category is a unique identifier to allow overwriting old callbacks with

        newer callbacks.

        """

        self._finalizecallback[category] = callback

    @active

    def addpostclose(self, category, callback):

        """add a callback to be called after the transaction is closed

        Category is a unique identifier to allow overwriting an old callback

        with a newer callback.

        """

        self._postclosecallback[category] = callback

    @active

    def close(self):

        '''commit the transaction'''

        if self.count == 1 and self.onclose is not None:

            self._generatefiles()

            categories = sorted(self._finalizecallback)

            for cat in categories:

                self._finalizecallback[cat]()

            self.onclose()

        self.count -= 1

        if self.count != 0:

            return

        self.file.close()

        self._backupsfile.close()

        self.entries = []

        if self.after:

            self.after()

        if self.opener.isfile(self.journal):

            self.opener.unlink(self.journal)

        if self.opener.isfile(self._backupjournal):

            self.opener.unlink(self._backupjournal)

            for _f, b in self._backupentries:

                if b:

                    self.opener.unlink(b)

        self._backupentries = []

        self.journal = None

        # run post close action

        categories = sorted(self._postclosecallback)

        for cat in categories:

            self._postclosecallback[cat]()

    @active

    def abort(self):

        '''abort the transaction (generally called on error, or when the

        transaction is not explicitly committed before going out of

        scope)'''

        self._abort()

    def _abort(self):

        self.count = 0

        self.usages = 0

        self.file.close()

        self._backupsfile.close()

        if self.onabort is not None:

            self.onabort()

        try:

            if not self.entries and not self._backupentries:

                if self.journal:

                    self.opener.unlink(self.journal)

                if self._backupjournal:

                    self.opener.unlink(self._backupjournal)

                return

            self.report(_("transaction abort!\n"))

            try:

                _playback(self.journal, self.report, self.opener,

                          self.entries, self._backupentries, False)

                self.report(_("rollback completed\n"))

            except Exception: