# 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.

from __future__ import absolute_import

import collections

import heapq

from .node import nullrev

def commonancestorsheads(pfunc, *nodes):

    """Returns a set with the heads of all common ancestors of all nodes,

    heads(::nodes[0] and ::nodes[1] and ...) .

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

    """

    if not isinstance(nodes, set):

        nodes = set(nodes)

    if nullrev in nodes:

        return set()

    if len(nodes) <= 1:

        return 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 = 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:

                    # 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 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.

    """

    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 = commonancestorsheads(pfunc, *orignodes)

    if len(gca) <= 1:

        return gca

    return deepest(gca)

class incrementalmissingancestors(object):

    '''persistent state used to calculate missing ancestors incrementally

    Although similar in spirit to lazyancestors below, this is a separate class

    because trying to support contains and missingancestors operations with the

    same internal data structures adds needless complexity.'''

    def __init__(self, pfunc, bases):

        self.bases = set(bases)

        if not self.bases:

            self.bases.add(nullrev)

        self.pfunc = pfunc

    def hasbases(self):

        '''whether the common set has any non-trivial bases'''

        return self.bases and self.bases != set([nullrev])

    def addbases(self, newbases):

        '''grow the ancestor set by adding new bases'''

        self.bases.update(newbases)

    def removeancestorsfrom(self, revs):

        '''remove all ancestors of bases from the set revs (in place)'''

        bases = self.bases

        pfunc = self.pfunc

        revs.difference_update(bases)

        # nullrev is always an ancestor

        revs.discard(nullrev)

        if not revs:

            return

        # anything in revs > start is definitely not an ancestor of bases

        # revs <= start needs to be investigated

        start = max(bases)

        keepcount = sum(1 for r in revs if r > start)

        if len(revs) == keepcount:

            # no revs to consider

            return

        for curr in xrange(start, min(revs) - 1, -1):

            if curr not in bases:

                continue

            revs.discard(curr)

            bases.update(pfunc(curr))

            if len(revs) == keepcount:

                # no more potential revs to discard

                break

    def missingancestors(self, revs):

        '''return all the ancestors of revs that are not ancestors of self.bases

        This may include elements from revs.

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

        revision number order, which is a topological order.'''

        revsvisit = set(revs)

        basesvisit = self.bases

        pfunc = self.pfunc

        bothvisit = revsvisit.intersection(basesvisit)

        revsvisit.difference_update(bothvisit)

        if not revsvisit:

            return []

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

        # 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. bothvisit and

        #   revsvisit are mutually exclusive, but bothvisit is a subset of

        #   basesvisit.

        # 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

        # revsvisit and added to bothvisit. 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 through

                # another path

                for p in pfunc(curr):

                    revsvisit.discard(p)

                    basesvisit.add(p)

                    bothvisit.add(p)

                continue

            if curr in revsvisit:

                missing.append(curr)

                revsvisit.remove(curr)

                thisvisit = revsvisit

                othervisit = basesvisit

            elif curr in basesvisit:

                thisvisit = basesvisit

                othervisit = revsvisit

            else:

                # not an ancestor of revs or bases: ignore

                continue

            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.add(p)

                    bothvisit.add(p)

                else:

                    # visit later

                    thisvisit.add(p)

        missing.reverse()

        return missing

class lazyancestors(object):

    def __init__(self, pfunc, 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 = pfunc

        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 __nonzero__(self):

        """False if the set is empty, True otherwise."""

        try:

            next(iter(self))

            return True

        except StopIteration:

            return False

    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 = collections.deque(revs)

        see = seen.add

        schedule = visit.append

        while visit:

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

                if parent >= stoprev and parent not in seen:

                    schedule(parent)

                    see(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

        see = seen.add

        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)

                see(parent)

                if parent == target:

                    targetseen = True

        return targetseen