"""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.

:stock: use the default strategy of mercurial explaned above

:boxfill: transmit obsolete markers which list any of transmitted changesets as

          a successor (transitively), as well as any kill markers for dead

          nodes descended from any of the precursors of outgoing.missing.

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

"""

import sys

from mercurial import base85

from mercurial import commands

from mercurial import extensions

from mercurial import node

from mercurial import obsolete

from mercurial import exchange

from mercurial import revset

from mercurial.i18n import _

_strategies = {

    'stock': exchange._pushobsolete,

    }

def _strategy(name, default=False):

    def inner(func):

        _strategies[name] = func

        if default:

            _strategies[None] = func

        return func

    return inner

def _pushobsoletewrapper(orig, pushop):

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

    return stratfn(pushop)

extensions.wrapfunction(exchange, '_pushobsolete', _pushobsoletewrapper)

def _precursors(repo, s):

    """Precursor of a changeset"""

    cs = set()

    nm = repo.changelog.nodemap

    markerbysubj = repo.obsstore.precursors

    for r in s:

        for p in markerbysubj.get(repo[r].node(), ()):

            pr = nm.get(p[0])

            if pr is not None:

                cs.add(pr)

    return cs

def _revsetprecursors(repo, subset, x):

    s = revset.getset(repo, revset.baseset(range(len(repo))), x)

    cs = _precursors(repo, s)

    return revset.baseset([r for r in subset if r in cs])

revset.symbols['_fastobs_precursors'] = _revsetprecursors

@_strategy('boxfill', default=True)

def boxfill(pushop):

    """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

    """

    repo = pushop.repo

    remote = pushop.remote

    outgoing = pushop.outgoing

    urepo = pushop.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(_fastobs_precursors(%ln)) or '

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

        outgoing.missing, outgoing.missing)

    transmit = []

    for node in outgoing.missing:

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

    for node in boxedges:

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

    transmit = list(set(transmit))

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

    repo.ui.status(

        'boxpush: about to transmit %d obsolete markers (%d markers total)\n'

        % (xmit, total))

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

    def transmitmarks():

            repo.ui.note(

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

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

            remote.pushkey('obsolete', 'dump-%d' % chunk, '',

                           base85.b85encode(data))

    for marker in transmit:

        enc = obsolete._encodeonemarker(_markertuple(marker))

        parts.append(enc)

        size += len(enc)

        if size > obsolete._maxpayload:

            transmitmarks()

            parts, size = [], 0

            chunk += 1

    if parts:

        transmitmarks()

def _markertuple(marker):

    return marker._data