# 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 os

import errno

import error, util

version = 2

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, vfsmap, 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 l, f, b, c in backupentries:

        if l not in vfsmap and c:

            report("couldn't handle %s: unknown cache location %s\n"

                        % (b, l))

        vfs = vfsmap[l]

        try:

            if f and b:

                filepath = vfs.join(f)

                backuppath = vfs.join(b)

                try:

                    util.copyfile(backuppath, filepath)

                    backupfiles.append(b)

                except IOError:

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

            else:

                target = f or b

                try:

                    vfs.unlink(target)

                except (IOError, OSError), inst:

                    if inst.errno != errno.ENOENT:

                        raise

        except (IOError, OSError, util.Abort), inst:

            if not c:

                raise

    opener.unlink(journal)

    backuppath = "%s.backupfiles" % journal

    if opener.exists(backuppath):

        opener.unlink(backuppath)

    try:

        for f in backupfiles:

            if opener.exists(f):

                opener.unlink(f)

    except (IOError, OSError, util.Abort), inst:

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

        pass

class transaction(object):

    def __init__(self, report, opener, vfsmap, 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

        # a vfs to the store content

        self.opener = opener

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

        vfsmap = vfsmap.copy()

        vfsmap[''] = opener  # set default value

        self._vfsmap = vfsmap

        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 ('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 = "%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, location=''):

        """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

        dirname, filename = os.path.split(file)

        backupfilename = "%s.backup.%s" % (self.journal, filename)

        backupfile = os.path.join(dirname, backupfilename)

        vfs = self._vfsmap[location]

        if vfs.exists(file):

            filepath = vfs.join(file)

            backuppath = vfs.join(backupfile)

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

        else:

            backupfile = ''

        self._addbackupentry((location, file, backupfile, False))

    def _addbackupentry(self, entry):

        """register a new backup entry and write it to disk"""

        self._backupentries.append(entry)

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

        self._backupsfile.write("%s\0%s\0%s\0%d\n" % entry)

        self._backupsfile.flush()

    @active

    def registertmp(self, tmpfile, location=''):

        """register a temporary transaction file

        Such files will be deleted when the transaction exits (on both

        failure and success).

        """

        self._addbackupentry((location, '', tmpfile, False))

    @active

    def addfilegenerator(self, genid, filenames, genfunc, order=0,

                         location=''):

        """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.

        The `location` arguments may be used to indicate the files are located

        outside of the the standard directory for transaction. It should match

        one of the key of the `transaction.vfsmap` dictionnary.

        """

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

        # but for bookmarks that are handled outside this mechanism.

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

    def _generatefiles(self, suffix=''):

        # write files registered for generation

        any = False

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

            any = True

            order, filenames, genfunc, location = entry

            vfs = self._vfsmap[location]

            files = []

            try:

                for name in filenames:

                    name += suffix

                    if suffix:

                        self.registertmp(name, location=location)

                    else:

                        self.addbackup(name, location=location)

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

                genfunc(*files)

            finally:

                for f in files:

                    f.close()

        return any

    @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

        The transaction will be given as callback's first argument.

        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

            any = self._pendingcallback.pop(cat)(self)

            self._anypending = self._anypending or any

        self._anypending |= self._generatefiles(suffix='.pending')

        return self._anypending

    @active

    def addfinalize(self, category, callback):

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

        The transaction will be given as callback's first argument.

        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

        The transaction will be given as callback's first argument.

        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:

            self._generatefiles()

            categories = sorted(self._finalizecallback)

            for cat in categories:

                self._finalizecallback[cat](self)

            if self.onclose is not None:

                self.onclose()

        self.count -= 1

        if self.count != 0:

            return

        self.file.close()

        self._backupsfile.close()