# obsutil.py - utility functions for obsolescence

#

# Copyright 2017 Boris Feld <boris.feld@octobus.net>

#

# 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

class marker(object):

    """Wrap obsolete marker raw data"""

    def __init__(self, repo, data):

        # the repo argument will be used to create changectx in later version

        self._repo = repo

        self._data = data

        self._decodedmeta = None

    def __hash__(self):

        return hash(self._data)

    def __eq__(self, other):

        if type(other) != type(self):

            return False

        return self._data == other._data

    def precnode(self):

        """Precursor changeset node identifier"""

        return self._data[0]

    def succnodes(self):

        """List of successor changesets node identifiers"""

        return self._data[1]

    def parentnodes(self):

        """Parents of the precursors (None if not recorded)"""

        return self._data[5]

    def metadata(self):

        """Decoded metadata dictionary"""

        return dict(self._data[3])

    def date(self):

        """Creation date as (unixtime, offset)"""

        return self._data[4]

    def flags(self):

        """The flags field of the marker"""

        return self._data[2]

def getmarkers(repo, nodes=None, exclusive=False):

    """returns markers known in a repository

    If <nodes> is specified, only markers "relevant" to those nodes are are

    returned"""

    if nodes is None:

        rawmarkers = repo.obsstore

    elif exclusive:

        rawmarkers = exclusivemarkers(repo, nodes)

    else:

        rawmarkers = repo.obsstore.relevantmarkers(nodes)

    for markerdata in rawmarkers:

        yield marker(repo, markerdata)

def closestpredecessors(repo, nodeid):

    """yield the list of next predecessors pointing on visible changectx nodes

    This function respect the repoview filtering, filtered revision will be

    considered missing.

    """

    precursors = repo.obsstore.precursors

    stack = [nodeid]

    seen = set(stack)

    while stack:

        current = stack.pop()

        currentpreccs = precursors.get(current, ())

        for prec in currentpreccs:

            precnodeid = prec[0]

            # Basic cycle protection

            if precnodeid in seen:

                continue

            seen.add(precnodeid)

            if precnodeid in repo:

                yield precnodeid

            else:

                stack.append(precnodeid)

def allprecursors(obsstore, nodes, ignoreflags=0):

    """Yield node for every precursors of <nodes>.

    Some precursors may be unknown locally.

    This is a linear yield unsuited to detecting folded changesets. It includes

    initial nodes too."""

    remaining = set(nodes)

    seen = set(remaining)

    while remaining:

        current = remaining.pop()

        yield current

        for mark in obsstore.precursors.get(current, ()):

            # ignore marker flagged with specified flag

            if mark[2] & ignoreflags:

                continue

            suc = mark[0]

            if suc not in seen:

                seen.add(suc)

                remaining.add(suc)

def allsuccessors(obsstore, nodes, ignoreflags=0):

    """Yield node for every successor of <nodes>.

    Some successors may be unknown locally.

    This is a linear yield unsuited to detecting split changesets. It includes

    initial nodes too."""

    remaining = set(nodes)

    seen = set(remaining)

    while remaining:

        current = remaining.pop()

        yield current

        for mark in obsstore.successors.get(current, ()):

            # ignore marker flagged with specified flag

            if mark[2] & ignoreflags:

                continue

            for suc in mark[1]:

                if suc not in seen:

                    seen.add(suc)

                    remaining.add(suc)

def _filterprunes(markers):

    """return a set with no prune markers"""

    return set(m for m in markers if m[1])

def exclusivemarkers(repo, nodes):

    """set of markers relevant to "nodes" but no other locally-known nodes

    This function compute the set of markers "exclusive" to a locally-known

    node. This means we walk the markers starting from <nodes> until we reach a

    locally-known precursors outside of <nodes>. Element of <nodes> with

    locally-known successors outside of <nodes> are ignored (since their

    precursors markers are also relevant to these successors).

    For example:

        # (A0 rewritten as A1)

        #

        # A0 <-1- A1 # Marker "1" is exclusive to A1

        or

        # (A0 rewritten as AX; AX rewritten as A1; AX is unkown locally)

        #

        # <-1- A0 <-2- AX <-3- A1 # Marker "2,3" are exclusive to A1

        or

        # (A0 has unknown precursors, A0 rewritten as A1 and A2 (divergence))

        #

        #          <-2- A1 # Marker "2" is exclusive to A0,A1

        #        /

        # <-1- A0

        #        \

        #         <-3- A2 # Marker "3" is exclusive to A0,A2

        #

        # in addition:

        #

        #  Markers "2,3" are exclusive to A1,A2

        #  Markers "1,2,3" are exclusive to A0,A1,A2

        See test/test-obsolete-bundle-strip.t for more examples.

    An example usage is strip. When stripping a changeset, we also want to

    strip the markers exclusive to this changeset. Otherwise we would have

    "dangling"" obsolescence markers from its precursors: Obsolescence markers

    marking a node as obsolete without any successors available locally.

    As for relevant markers, the prune markers for children will be followed.

    Of course, they will only be followed if the pruned children is

    locally-known. Since the prune markers are relevant to the pruned node.

    However, while prune markers are considered relevant to the parent of the

    pruned changesets, prune markers for locally-known changeset (with no

    successors) are considered exclusive to the pruned nodes. This allows

    to strip the prune markers (with the rest of the exclusive chain) alongside

    the pruned changesets.

    """

    # running on a filtered repository would be dangerous as markers could be

    # reported as exclusive when they are relevant for other filtered nodes.

    unfi = repo.unfiltered()

    # shortcut to various useful item

    nm = unfi.changelog.nodemap

    precursorsmarkers = unfi.obsstore.precursors

    successormarkers = unfi.obsstore.successors

    childrenmarkers = unfi.obsstore.children

    # exclusive markers (return of the function)

    exclmarkers = set()

    # we need fast membership testing

    nodes = set(nodes)

    # looking for head in the obshistory

    #

    # XXX we are ignoring all issues in regard with cycle for now.

    stack = [n for n in nodes if not _filterprunes(successormarkers.get(n, ()))]

    stack.sort()

    # nodes already stacked

    seennodes = set(stack)

    while stack:

        current = stack.pop()

        # fetch precursors markers

        markers = list(precursorsmarkers.get(current, ()))

        # extend the list with prune markers

        for mark in successormarkers.get(current, ()):

            if not mark[1]:

                markers.append(mark)

        # and markers from children (looking for prune)

        for mark in childrenmarkers.get(current, ()):

            if not mark[1]:

                markers.append(mark)

        # traverse the markers

        for mark in markers:

            if mark in exclmarkers:

                # markers already selected

                continue

            # If the markers is about the current node, select it

            #

            # (this delay the addition of markers from children)

            if mark[1] or mark[0] == current:

                exclmarkers.add(mark)

            # should we keep traversing through the precursors?

            prec = mark[0]

            # nodes in the stack or already processed

            if prec in seennodes:

                continue

            # is this a locally known node ?

            known = prec in nm

            # if locally-known and not in the <nodes> set the traversal

            # stop here.

            if known and prec not in nodes:

                continue

            # do not keep going if there are unselected markers pointing to this

            # nodes. If we end up traversing these unselected markers later the

            # node will be taken care of at that point.

            precmarkers = _filterprunes(successormarkers.get(prec))

            if precmarkers.issubset(exclmarkers):

                seennodes.add(prec)

                stack.append(prec)

    return exclmarkers

def foreground(repo, nodes):

    """return all nodes in the "foreground" of other node

    The foreground of a revision is anything reachable using parent -> children

    or precursor -> successor relation. It is very similar to "descendant" but

    augmented with obsolescence information.

    Beware that possible obsolescence cycle may result if complex situation.

    """

    repo = repo.unfiltered()

    foreground = set(repo.set('%ln::', nodes))

    if repo.obsstore:

        # We only need this complicated logic if there is obsolescence

        # XXX will probably deserve an optimised revset.

        nm = repo.changelog.nodemap

        plen = -1

        # compute the whole set of successors or descendants

        while len(foreground) != plen:

            plen = len(foreground)

            succs = set(c.node() for c in foreground)

            mutable = [c.node() for c in foreground if c.mutable()]

            succs.update(allsuccessors(repo.obsstore, mutable))

            known = (n for n in succs if n in nm)

            foreground = set(repo.set('%ln::', known))

    return set(c.node() for c in foreground)

def successorssets(repo, initialnode, cache=None):

    """Return set of all latest successors of initial nodes

    The successors set of a changeset A are the group of revisions that succeed

    A. It succeeds A as a consistent whole, each revision being only a partial

    replacement. The successors set contains non-obsolete changesets only.

    This function returns the full list of successor sets which is why it

    returns a list of tuples and not just a single tuple. Each tuple is a valid

    successors set. Note that (A,) may be a valid successors set for changeset A

    (see below).

    In most cases, a changeset A will have a single element (e.g. the changeset

    A is replaced by A') in its successors set. Though, it is also common for a

    changeset A to have no elements in its successor set (e.g. the changeset

    has been pruned). Therefore, the returned list of successors sets will be

    [(A',)] or [], respectively.

    When a changeset A is split into A' and B', however, it will result in a

    successors set containing more than a single element, i.e. [(A',B')].

    Divergent changesets will result in multiple successors sets, i.e. [(A',),

    (A'')].

    If a changeset A is not obsolete, then it will conceptually have no

    successors set. To distinguish this from a pruned changeset, the successor

    set will contain itself only, i.e. [(A,)].

    Finally, successors unknown locally are considered to be pruned (obsoleted

    without any successors).

    The optional `cache` parameter is a dictionary that may contain precomputed

    successors sets. It is meant to reuse the computation of a previous call to

    `successorssets` when multiple calls are made at the same time. The cache

    dictionary is updated in place. The caller is responsible for its life

    span. Code that makes multiple calls to `successorssets` *must* use this

    cache mechanism or suffer terrible performance.

    """

    succmarkers = repo.obsstore.successors

    # Stack of nodes we search successors sets for

    toproceed = [initialnode]

    # set version of above list for fast loop detection

    # element added to "toproceed" must be added here

    stackedset = set(toproceed)

    if cache is None:

        cache = {}

    # This while loop is the flattened version of a recursive search for

    # successors sets

    #

    # def successorssets(x):

    #    successors = directsuccessors(x)

    #    ss = [[]]

    #    for succ in directsuccessors(x):

    #        # product as in itertools cartesian product

    #        ss = product(ss, successorssets(succ))

    #    return ss

    #

    # But we can not use plain recursive calls here:

    # - that would blow the python call stack

    # - obsolescence markers may have cycles, we need to handle them.

    #

    # The `toproceed` list act as our call stack. Every node we search

    # successors set for are stacked there.

    #

    # The `stackedset` is set version of this stack used to check if a node is

    # already stacked. This check is used to detect cycles and prevent infinite

    # loop.

    #

    # successors set of all nodes are stored in the `cache` dictionary.

    #

    # After this while loop ends we use the cache to return the successors sets

    # for the node requested by the caller.

    while toproceed:

        # Every iteration tries to compute the successors sets of the topmost

        # node of the stack: CURRENT.

        #

        # There are four possible outcomes:

        #

        # 1) We already know the successors sets of CURRENT:

        #    -> mission accomplished, pop it from the stack.

        # 2) Node is not obsolete:

        #    -> the node is its own successors sets. Add it to the cache.

        # 3) We do not know successors set of direct successors of CURRENT:

        #    -> We add those successors to the stack.

        # 4) We know successors sets of all direct successors of CURRENT:

        #    -> We can compute CURRENT successors set and add it to the

        #       cache.

        #

        current = toproceed[-1]

        if current in cache:

            # case (1): We already know the successors sets

            stackedset.remove(toproceed.pop())

        elif current not in succmarkers:

            # case (2): The node is not obsolete.

            if current in repo:

                # We have a valid last successors.

                cache[current] = [(current,)]

            else:

                # Final obsolete version is unknown locally.

                # Do not count that as a valid successors

                cache[current] = []

        else:

            # cases (3) and (4)

            #