# upgradegeneraldelta.py
#
# Copyright 2014 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''upgrade manifests to generaldelta in-place

Performs an upgrade of this repo's manifest to generaldelta on pull, without
needing to reclone. This tries to be as safe as possible but is inherently not a
completely safe operation.

Filelogs are not touched -- the manifest is often the revlog that benefits the
most from generaldelta. New filelogs will be generaldelta, though.

The following configuration options are available:

:upgradegeneraldelta.upgrade: Set to True to actually perform the
    upgrade. Default is False.

:upgradegeneraldelta.dryrun: Write out the generaldelta manifest, but do not
    move it into place. This will cause the generaldelta manifest to be
    rewritten every single time a Mercurial command is run. Default is False.

:upgradegeneraldelta.backup: Set to False to disable backing up the old manifest
    as 00manifestold.{i,d}. Default is True.

'''

from mercurial.i18n import _
from mercurial import commands, extensions, revlog, util
import os, struct, weakref

def wrappull(orig, ui, repo, *args, **kwargs):
    _upgrade(ui, repo)
    orig(ui, repo, *args, **kwargs)

def _upgrade(ui, repo):
    if not util.safehasattr(repo, 'svfs'):
        return
    if not ui.configbool('upgradegeneraldelta', 'upgrade'):
        return

    f = repo.svfs('00manifest.i')
    i = f.read(4)
    f.close()
    if len(i) < 4:
        # empty manifest
        return

    # probably only works with revlogng -- it became the default years ago so
    # that's fine
    v = struct.unpack(revlog.versionformat, i)[0]
    isgeneraldelta = v & revlog.REVLOGGENERALDELTA
    if isgeneraldelta:
        return

    # write out a new revlog, this time with generaldelta
    oldopts = repo.svfs.options
    lock = repo.lock()
    tr = repo.transaction('upgradegeneraldelta')
    try:
        ui.warn(_('upgrading repository to generaldelta\n'))
        trp = weakref.proxy(tr)

        newopts = oldopts.copy()
        newopts['generaldelta'] = 1
        repo.svfs.options = newopts
        # remove 00manifestgd.i if present
        repo.svfs.unlinkpath('00manifestgd.i', ignoremissing=True)
        newmf = revlog.revlog(repo.svfs, '00manifestgd.i')
        oldmf = repo.manifest
        i = oldmf.index
        chunk = oldmf._chunk

        for rev in oldmf:
            ui.progress(_('upgrading'), rev, total=len(oldmf))
            e = i[rev]
            # if the delta base is the rev, this rev is a fulltext
            isdelta = (rev != e[3])
            revchunk = chunk(rev)
            if isdelta:
                newmf.addrevision(None, trp, e[4], i[e[5]][7], i[e[6]][7],
                                  cachedelta=(rev - 1, revchunk),
                                  node=e[7])
            else:
                newmf.addrevision(revchunk, trp, e[4], i[e[5]][7], i[e[6]][7],
                                  node=e[7])
        tr.close()
        if not ui.configbool('upgradegeneraldelta', 'dryrun', default=False):
            manifesti = repo.sjoin('00manifest.i')
            manifestd = repo.sjoin('00manifest.d')
            manifestgdi = repo.sjoin('00manifestgd.i')
            manifestgdd = repo.sjoin('00manifestgd.d')
            manifestoldi = repo.sjoin('00manifestold.i')
            manifestoldd = repo.sjoin('00manifestold.d')
            # move the newly created manifests over
            if ui.configbool('upgradegeneraldelta', 'backup', default=True):
                os.rename(manifesti, manifestoldi)
                if os.path.exists(manifestd):
                    os.rename(manifestd, manifestoldd)
            os.rename(manifestgdi, manifesti)
            if os.path.exists(manifestgdd):
                os.rename(manifestgdd, manifestd)
            with repo.opener('requires', 'a+') as f:
                f.write('generaldelta\n')
        repo.invalidate()
    finally:
        ui.progress(_('upgrading'), None)
        if tr:
            tr.release()
        lock.release()
        repo.svfs.options = oldopts

def extsetup(ui):
    extensions.wrapcommand(commands.table, 'pull', wrappull)