# ancestor.py - generic DAG ancestor algorithm for mercurial

#

# Copyright 2006 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.

import heapq, util

from node import nullrev

def ancestors(pfunc, *orignodes):

    """

    Returns the common ancestors of a and b that are furthest from a

    root (as measured by longest path).

    pfunc must return a list of parent vertices for a given vertex.

    """

    if not isinstance(orignodes, set):

        orignodes = set(orignodes)

    if nullrev in orignodes:

        return set()

    if len(orignodes) <= 1:

        return orignodes

    def candidates(nodes):

        allseen = (1 << len(nodes)) - 1

        seen = [0] * (max(nodes) + 1)

        for i, n in enumerate(nodes):

            seen[n] = 1 << i

        poison = 1 << (i + 1)

        gca = set()

        interesting = left = len(nodes)

        nv = len(seen) - 1

        while nv >= 0 and interesting:

            v = nv

            nv -= 1

            if not seen[v]:

                continue

            sv = seen[v]

            if sv < poison:

                interesting -= 1

                if sv == allseen:

                    gca.add(v)

                    sv |= poison

                    if v in nodes:

                        left -= 1

                        if left <= 1:

                            # history is linear

                            return set([v])

            if sv < poison:

                for p in pfunc(v):

                    sp = seen[p]

                    if p == nullrev:

                        continue

                    if sp == 0:

                        seen[p] = sv

                        interesting += 1

                    elif sp != sv:

                        seen[p] |= sv

            else:

                for p in pfunc(v):

                    if p == nullrev:

                        continue

                    sp = seen[p]

                    if sp and sp < poison:

                        interesting -= 1

                    seen[p] = sv

        return gca

    def deepest(nodes):

        interesting = {}

        count = max(nodes) + 1

        depth = [0] * count

        seen = [0] * count

        mapping = []

        for (i, n) in enumerate(sorted(nodes)):

            depth[n] = 1

            b = 1 << i

            seen[n] = b

            interesting[b] = 1

            mapping.append((b, n))

        nv = count - 1

        while nv >= 0 and len(interesting) > 1:

            v = nv

            nv -= 1

            dv = depth[v]

            if dv == 0:

                continue

            sv = seen[v]

            for p in pfunc(v):

                if p == nullrev:

                    continue

                dp = depth[p]

                nsp = sp = seen[p]

                if dp <= dv:

                    depth[p] = dv + 1

                    if sp != sv:

                        interesting[sv] += 1

                        nsp = seen[p] = sv

                        if sp:

                            interesting[sp] -= 1

                            if interesting[sp] == 0:

                                del interesting[sp]

                elif dv == dp - 1:

                    nsp = sp | sv

                    if nsp == sp:

                        continue

                    seen[p] = nsp

                    interesting.setdefault(nsp, 0)

                    interesting[nsp] += 1

                    interesting[sp] -= 1

                    if interesting[sp] == 0:

                        del interesting[sp]

            interesting[sv] -= 1

            if interesting[sv] == 0:

                del interesting[sv]

        if len(interesting) != 1:

            return []

        k = 0

        for i in interesting:

            k |= i

        return set(n for (i, n) in mapping if k & i)

    gca = candidates(orignodes)

    if len(gca) <= 1:

        return gca

    return deepest(gca)

def genericancestor(a, b, pfunc):

    """

    Returns the common ancestor of a and b that is furthest from a

    root (as measured by longest path) or None if no ancestor is

    found. If there are multiple common ancestors at the same

    distance, the first one found is returned.

    pfunc must return a list of parent vertices for a given vertex

    """

    if a == b:

        return a

    a, b = sorted([a, b])

    # find depth from root of all ancestors

    # depth is stored as a negative for heapq

    parentcache = {}

    visit = [a, b]

    depth = {}

    while visit:

        vertex = visit[-1]

        pl = [p for p in pfunc(vertex) if p != nullrev]

        parentcache[vertex] = pl

        if not pl:

            depth[vertex] = 0

            visit.pop()

        else:

            for p in pl:

                if p == a or p == b: # did we find a or b as a parent?

                    return p # we're done

                if p not in depth:

                    visit.append(p)

            if visit[-1] == vertex:

                # -(maximum distance of parents + 1)

                depth[vertex] = min([depth[p] for p in pl]) - 1

                visit.pop()

    # traverse ancestors in order of decreasing distance from root

    def ancestors(vertex):

        h = [(depth[vertex], vertex)]

        seen = set()

        while h:

            d, n = heapq.heappop(h)

            if n not in seen:

                seen.add(n)

                yield (d, n)

                for p in parentcache[n]:

                    heapq.heappush(h, (depth[p], p))

    def generations(vertex):

        sg, s = None, set()

        for g, v in ancestors(vertex):

            if g != sg:

                if sg:

                    yield sg, s

                sg, s = g, set((v,))

            else:

                s.add(v)

        yield sg, s

    x = generations(a)

    y = generations(b)

    gx = x.next()

    gy = y.next()

    # increment each ancestor list until it is closer to root than

    # the other, or they match

    try:

        while True:

            if gx[0] == gy[0]:

                for v in gx[1]:

                    if v in gy[1]:

                        return v

                gy = y.next()

                gx = x.next()

            elif gx[0] > gy[0]:

                gy = y.next()

            else:

                gx = x.next()

    except StopIteration:

        return None

def missingancestors(revs, bases, pfunc):

    """Return all the ancestors of revs that are not ancestors of bases.

    This may include elements from revs.

    Equivalent to the revset (::revs - ::bases). Revs are returned in

    revision number order, which is a topological order.

    revs and bases should both be iterables. pfunc must return a list of

    parent revs for a given revs.

    """

    revsvisit = set(revs)

    basesvisit = set(bases)

    if not revsvisit:

        return []

    if not basesvisit:

        basesvisit.add(nullrev)

    start = max(max(revsvisit), max(basesvisit))

    bothvisit = revsvisit.intersection(basesvisit)

    revsvisit.difference_update(bothvisit)

    basesvisit.difference_update(bothvisit)

    # At this point, we hold the invariants that:

    # - revsvisit is the set of nodes we know are an ancestor of at least one

    #   of the nodes in revs

    # - basesvisit is the same for bases

    # - bothvisit is the set of nodes we know are ancestors of at least one of

    #   the nodes in revs and one of the nodes in bases

    # - a node may be in none or one, but not more, of revsvisit, basesvisit

    #   and bothvisit at any given time

    # Now we walk down in reverse topo order, adding parents of nodes already

    # visited to the sets while maintaining the invariants. When a node is

    # found in both revsvisit and basesvisit, it is removed from them and

    # added to bothvisit instead. When revsvisit becomes empty, there are no

    # more ancestors of revs that aren't also ancestors of bases, so exit.

    missing = []

    for curr in xrange(start, nullrev, -1):

        if not revsvisit:

            break

        if curr in bothvisit:

            bothvisit.remove(curr)

            # curr's parents might have made it into revsvisit or basesvisit

            # through another path

            for p in pfunc(curr):

                revsvisit.discard(p)

                basesvisit.discard(p)

                bothvisit.add(p)

            continue

        # curr will never be in both revsvisit and basesvisit, since if it

        # were it'd have been pushed to bothvisit

        if curr in revsvisit:

            missing.append(curr)

            thisvisit = revsvisit

            othervisit = basesvisit

        elif curr in basesvisit:

            thisvisit = basesvisit

            othervisit = revsvisit

        else:

            # not an ancestor of revs or bases: ignore

            continue

        thisvisit.remove(curr)

        for p in pfunc(curr):

            if p == nullrev:

                pass

            elif p in othervisit or p in bothvisit:

                # p is implicitly in thisvisit. This means p is or should be

                # in bothvisit

                revsvisit.discard(p)

                basesvisit.discard(p)

                bothvisit.add(p)

            else:

                # visit later

                thisvisit.add(p)

    missing.reverse()

    return missing

class lazyancestors(object):

    def __init__(self, cl, revs, stoprev=0, inclusive=False):

        """Create a new object generating ancestors for the given revs. Does

        not generate revs lower than stoprev.

        This is computed lazily starting from revs. The object supports

        iteration and membership.

        cl should be a changelog and revs should be an iterable. inclusive is

        a boolean that indicates whether revs should be included. Revs lower

        than stoprev will not be generated.

        Result does not include the null revision."""

        self._parentrevs = cl.parentrevs

        self._initrevs = revs

        self._stoprev = stoprev

        self._inclusive = inclusive

        # Initialize data structures for __contains__.

        # For __contains__, we use a heap rather than a deque because

        # (a) it minimizes the number of parentrevs calls made

        # (b) it makes the loop termination condition obvious

        # Python's heap is a min-heap. Multiply all values by -1 to convert it

        # into a max-heap.

        self._containsvisit = [-rev for rev in revs]

        heapq.heapify(self._containsvisit)

        if inclusive:

            self._containsseen = set(revs)

        else:

            self._containsseen = set()

    def __iter__(self):

        """Generate the ancestors of _initrevs in reverse topological order.

        If inclusive is False, yield a sequence of revision numbers starting

        with the parents of each revision in revs, i.e., each revision is *not*

        considered an ancestor of itself.  Results are in breadth-first order:

        parents of each rev in revs, then parents of those, etc.

        If inclusive is True, yield all the revs first (ignoring stoprev),

        then yield all the ancestors of revs as when inclusive is False.

        If an element in revs is an ancestor of a different rev it is not

        yielded again."""

        seen = set()

        revs = self._initrevs

        if self._inclusive:

            for rev in revs:

                yield rev

            seen.update(revs)

        parentrevs = self._parentrevs

        stoprev = self._stoprev

        visit = util.deque(revs)

        while visit:

            for parent in parentrevs(visit.popleft()):

                if parent >= stoprev and parent not in seen:

                    visit.append(parent)

                    seen.add(parent)

                    yield parent

    def __contains__(self, target):

        """Test whether target is an ancestor of self._initrevs."""

        # Trying to do both __iter__ and __contains__ using the same visit

        # heap and seen set is complex enough that it slows down both. Keep

        # them separate.

        seen = self._containsseen

        if target in seen:

            return True

        parentrevs = self._parentrevs

        visit = self._containsvisit

        stoprev = self._stoprev

        heappop = heapq.heappop

        heappush = heapq.heappush

        targetseen = False

        while visit and -visit[0] > target and not targetseen:

            for parent in parentrevs(-heappop(visit)):

                if parent < stoprev or parent in seen:

                    continue

                # We need to make sure we push all parents into the heap so

                # that we leave it in a consistent state for future calls.

                heappush(visit, -parent)

                seen.add(parent)

                if parent == target:

                    targetseen = True

        return targetseen