# discovery.py - protocol changeset discovery functions

#

# Copyright 2010 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 __future__ import absolute_import

import collections

from .i18n import _

from .node import (

    nullid,

    short,

)

from . import (

    error,

)

def findcommonincoming(repo, remote, heads=None, force=False):

    """Return a tuple (common, fetch, heads) used to identify the common

    subset of nodes between repo and remote.

    "common" is a list of (at least) the heads of the common subset.

    "fetch" is a list of roots of the nodes that would be incoming, to be

      supplied to changegroupsubset.

    "heads" is either the supplied heads, or else the remote's heads.

    """

    knownnode = repo.changelog.hasnode

    search = []

    fetch = set()

    seen = set()

    seenbranch = set()

    base = set()

    if not heads:

        heads = remote.heads()

    if repo.changelog.tip() == nullid:

        base.add(nullid)

        if heads != [nullid]:

            return [nullid], [nullid], list(heads)

        return [nullid], [], heads

    # assume we're closer to the tip than the root

    # and start by examining the heads

    repo.ui.status(_("searching for changes\n"))

    unknown = []

    for h in heads:

        if not knownnode(h):

            unknown.append(h)

        else:

            base.add(h)

    if not unknown:

        return list(base), [], list(heads)

    req = set(unknown)

    reqcnt = 0

    # search through remote branches

    # a 'branch' here is a linear segment of history, with four parts:

    # head, root, first parent, second parent

    # (a branch always has two parents (or none) by definition)

    unknown = collections.deque(remote.branches(unknown))

    while unknown:

        r = []

        while unknown:

            n = unknown.popleft()

            if n[0] in seen:

                continue

            repo.ui.debug("examining %s:%s\n"

                          % (short(n[0]), short(n[1])))

            if n[0] == nullid: # found the end of the branch

                pass

            elif n in seenbranch:

                repo.ui.debug("branch already found\n")

                continue

            elif n[1] and knownnode(n[1]): # do we know the base?

                repo.ui.debug("found incomplete branch %s:%s\n"

                              % (short(n[0]), short(n[1])))

                search.append(n[0:2]) # schedule branch range for scanning

                seenbranch.add(n)

            else:

                if n[1] not in seen and n[1] not in fetch:

                    if knownnode(n[2]) and knownnode(n[3]):

                        repo.ui.debug("found new changeset %s\n" %

                                      short(n[1]))

                        fetch.add(n[1]) # earliest unknown

                    for p in n[2:4]:

                        if knownnode(p):

                            base.add(p) # latest known

                for p in n[2:4]:

                    if p not in req and not knownnode(p):

                        r.append(p)

                        req.add(p)

            seen.add(n[0])

        if r:

            reqcnt += 1

            repo.ui.progress(_('searching'), reqcnt, unit=_('queries'))

            repo.ui.debug("request %d: %s\n" %

                        (reqcnt, " ".join(map(short, r))))

            for p in xrange(0, len(r), 10):

                for b in remote.branches(r[p:p + 10]):

                    repo.ui.debug("received %s:%s\n" %

                                  (short(b[0]), short(b[1])))

                    unknown.append(b)

    # do binary search on the branches we found

    while search:

        newsearch = []

        reqcnt += 1

        repo.ui.progress(_('searching'), reqcnt, unit=_('queries'))

        for n, l in zip(search, remote.between(search)):

            l.append(n[1])

            p = n[0]

            f = 1

            for i in l:

                repo.ui.debug("narrowing %d:%d %s\n" % (f, len(l), short(i)))

                if knownnode(i):

                    if f <= 2:

                        repo.ui.debug("found new branch changeset %s\n" %

                                          short(p))

                        fetch.add(p)

                        base.add(i)

                    else:

                        repo.ui.debug("narrowed branch search to %s:%s\n"

                                      % (short(p), short(i)))

                        newsearch.append((p, i))

                    break

                p, f = i, f * 2

            search = newsearch

    # sanity check our fetch list

    for f in fetch:

        if knownnode(f):

            raise error.RepoError(_("already have changeset ")

                                  + short(f[:4]))

    base = list(base)

    if base == [nullid]:

        if force:

            repo.ui.warn(_("warning: repository is unrelated\n"))

        else:

            raise error.Abort(_("repository is unrelated"))

    repo.ui.debug("found new changesets starting at " +

                 " ".join([short(f) for f in fetch]) + "\n")

    repo.ui.progress(_('searching'), None)

    repo.ui.debug("%d total queries\n" % reqcnt)

    return base, list(fetch), heads