"""Extension to try and speed up transfer of obsolete markers.

Mercurial 2.6 transfers obsolete markers in the dumbest way possible:

it simply transfers all of them to the server on every

operation. While this /works/, it's not ideal because it's a large

amount of extra data for users to pull down (1.9M for the 17k obsolete

markers in hg-crew as of this writing in late July 2013). It's also

frustrating because this transfer takes a nontrivial amount of time.

You can specify a strategy with the config knob

obsolete.syncstrategy. Current strategies are "stock" and

"boxfill". Default strategy is presently boxfill.

TODO(durin42): consider better names for sync strategies.

"""

import sys

from mercurial import commands

from mercurial import extensions

from mercurial import obsolete

from mercurial import node

from mercurial.i18n import _

_strategies = {

    'stock': obsolete.syncpush,

    }

def _strategy(name, default=False):

    def inner(func):

        _strategies[name] = func

        if default:

            _strategies[None] = func

        return func

    return inner

def syncpushwrapper(orig, repo, remote):

    stratfn = _strategies[repo.ui.config('obsolete', 'syncstrategy')]

    return stratfn(repo, remote)

extensions.wrapfunction(obsolete, 'syncpush', syncpushwrapper)

def pushmarkerwrapper(orig, repo, *args):

    if repo.ui.config('obsolete', 'syncstrategy') == 'stock':

        return orig(repo, *args)

    # We shouldn't need to do this, since we transmit markers

    # effectively during push in localrepo. Just return success.

    return 1

def _getoutgoing():

    f = sys._getframe(4)

    return f.f_locals['outgoing']

@_strategy('boxfill', default=True)

def boxfill(repo, remote):

    """The "fill in the box" strategy from the 2.6 sprint.

    See the notes[0] from the 2.6 sprint for what "fill in the box"

    means here. It's a fairly subtle algorithm, which may have

    surprising behavior at times, but was the least-bad option

    proposed at the sprint.

    [0]: https://bitbucket.org/durin42/2.6sprint-notes/src/tip/mercurial26-obsstore-rev.1398.txt

    """

    outgoing = _getoutgoing()

    urepo = repo.unfiltered()

    # need to collect obsolete markers which list any of

    # outgoing.missing as a successor (transitively), as well as any

    # kill markers for dead nodes descended from any of the precursors

    # of outgoing.missing.

    boxedges = urepo.revs(

        '(descendants(precursors(%ln)) or descendants(%ln)) and hidden()',

        outgoing.missing, outgoing.missing)

    transmit = []

    for node in boxedges:

        transmit.extend(obsolete.successormarkers(urepo[node]))

    xmit, total = len(transmit), len(repo.obsstore._all)

    repo.ui.status('about to transmit %d obsolete markers (%d markers total)\n'

                   % (xmit, total))

    parts, size, chunk = [], 0, 0

    for marker in transmit:

        enc = obsolete._encodeonemarker(_markertuple(marker))

        parts.append(enc)

        size += len(enc)

        if size > obsolete._maxpayload:

            repo.ui.note(

                'obsolete boxpush: sending a chunk of obsolete markers\n')

            data = ''.join([obsolete._pack('>B', _fmversion)], parts)

            remote.pushkey('obsolete', 'dump%d' % chunk, base85.b85encode(data))

            parts, size = [], 0

            chunk += 1

def _markertuple(marker):

    return marker._data