import struct

from mercurial import extensions

from mercurial import obsolete

from cStringIO import StringIO

from mercurial import node

_pack = struct.pack

def _encodemarkersstream(fp, markers):

    fp.write(_pack('>B', 0))

    for mark in markers:

        fp.write(obsolete._encodeonemarker(mark))

def _getobsmarkersstream(repo, heads=None, common=None):

    revset = ''

    args = []

    repo = repo.unfiltered()

    if heads is None:

        revset = 'all()'

    elif heads:

        revset += "(::%ln)"

        args.append(heads)

    else:

        assert False, 'pulling no heads?'

    if common:

        revset += ' - (::%ln)'

        args.append(common)

    nodes = [c.node() for c in repo.set(revset, *args)]

    markers = repo.obsstore.relevantmarkers(nodes)

    obsdata = StringIO()

    _encodemarkersstream(obsdata, markers)

    obsdata.seek(0)

    return obsdata

class pruneobsstore(obsolete.obsstore):

    def __init__(self, *args, **kwargs):

        self.prunedchildren = {}

        return super(pruneobsstore, self).__init__(*args, **kwargs)

    def _load(self, markers):

        markers = self._prunedetectingmarkers(markers)

        return super(pruneobsstore, self)._load(markers)

    def _prunedetectingmarkers(self, markers):

        for m in markers:

            if not m[1]: # no successors

                meta = obsolete.decodemeta(m[3])

                if 'p1' in meta:

                    p1 = node.bin(meta['p1'])

                    self.prunedchildren.setdefault(p1, set()).add(m)

                if 'p2' in meta:

                    p2 = node.bin(meta['p2'])

                    self.prunedchildren.setdefault(p2, set()).add(m)

            yield m

def relevantmarkers(self, nodes):

    """return a set of all obsolescence marker relevant to a set of node.

    "relevant" to a set of node mean:

    - marker that use this changeset as successors

    - prune marker of direct children on this changeset.

    - recursive application of the two rules on precursors of these markers

    It  a set so you cannot rely on order"""

    seennodes = set(nodes)

    seenmarkers = set()

    pendingnodes = set(nodes)

    precursorsmarkers = self.precursors

    prunedchildren = self.prunedchildren

    while pendingnodes:

        direct = set()

        for current in pendingnodes:

            direct.update(precursorsmarkers.get(current, ()))

            direct.update(prunedchildren.get(current, ()))

        direct -= seenmarkers

        pendingnodes = set([m[0] for m in direct])

        seenmarkers |= direct

        pendingnodes -= seennodes

        seennodes |= pendingnodes

    return seenmarkers

    obsolete.obsstore = pruneobsstore

    obsolete.obsstore.relevantmarkers = relevantmarkers