# branchmap.py - logic to computes, maintain and stores branchmap for local repo

#

# Copyright 2005-2007 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 struct

from .node import (

    bin,

    hex,

    nullid,

    nullrev,

)

from . import (

    encoding,

    error,

    scmutil,

    util,

)

calcsize = struct.calcsize

pack_into = struct.pack_into

unpack_from = struct.unpack_from

def _filename(repo):

    """name of a branchcache file for a given repo or repoview"""

    filename = "branch2"

    if repo.filtername:

        filename = '%s-%s' % (filename, repo.filtername)

    return filename

def read(repo):

    try:

        f = repo.cachevfs(_filename(repo))

        lines = f.read().split('\n')

        f.close()

    except (IOError, OSError):

        return None

    try:

        cachekey = lines.pop(0).split(" ", 2)

        last, lrev = cachekey[:2]

        last, lrev = bin(last), int(lrev)

        filteredhash = None

        if len(cachekey) > 2:

            filteredhash = bin(cachekey[2])

        partial = branchcache(tipnode=last, tiprev=lrev,

                              filteredhash=filteredhash)

        if not partial.validfor(repo):

            # invalidate the cache

            raise ValueError('tip differs')

        cl = repo.changelog

        for l in lines:

            if not l:

                continue

            node, state, label = l.split(" ", 2)

            if state not in 'oc':

                raise ValueError('invalid branch state')

            label = encoding.tolocal(label.strip())

            node = bin(node)

            if not cl.hasnode(node):

                raise ValueError('node %s does not exist' % hex(node))

            partial.setdefault(label, []).append(node)

            if state == 'c':

                partial._closednodes.add(node)

    except Exception as inst:

        if repo.ui.debugflag:

            msg = 'invalid branchheads cache'

            if repo.filtername is not None:

                msg += ' (%s)' % repo.filtername

            msg += ': %s\n'

            repo.ui.debug(msg % inst)

        partial = None

    return partial

### Nearest subset relation

# Nearest subset of filter X is a filter Y so that:

# * Y is included in X,

# * X - Y is as small as possible.

# This create and ordering used for branchmap purpose.

# the ordering may be partial

subsettable = {None: 'visible',

               'visible': 'served',

               'served': 'immutable',

               'immutable': 'base'}

def updatecache(repo):

    cl = repo.changelog

    filtername = repo.filtername

    partial = repo._branchcaches.get(filtername)

    revs = []

    if partial is None or not partial.validfor(repo):

        partial = read(repo)

        if partial is None:

            subsetname = subsettable.get(filtername)

            if subsetname is None:

                partial = branchcache()

            else:

                subset = repo.filtered(subsetname)

                partial = subset.branchmap().copy()

                extrarevs = subset.changelog.filteredrevs - cl.filteredrevs

                revs.extend(r for  r in extrarevs if r <= partial.tiprev)

    revs.extend(cl.revs(start=partial.tiprev + 1))

    if revs:

        partial.update(repo, revs)

        partial.write(repo)

    assert partial.validfor(repo), filtername

    repo._branchcaches[repo.filtername] = partial

def replacecache(repo, bm):

    """Replace the branchmap cache for a repo with a branch mapping.

    This is likely only called during clone with a branch map from a remote.

    """

    rbheads = []

    closed = []

    for bheads in bm.itervalues():

        rbheads.extend(bheads)

        for h in bheads:

            r = repo.changelog.rev(h)

            b, c = repo.changelog.branchinfo(r)

            if c:

                closed.append(h)

    if rbheads:

        rtiprev = max((int(repo.changelog.rev(node))

                for node in rbheads))

        cache = branchcache(bm,

                            repo[rtiprev].node(),

                            rtiprev,

                            closednodes=closed)

        # Try to stick it as low as possible

        # filter above served are unlikely to be fetch from a clone

        for candidate in ('base', 'immutable', 'served'):

            rview = repo.filtered(candidate)

            if cache.validfor(rview):

                repo._branchcaches[candidate] = cache

                cache.write(rview)

                break

class branchcache(dict):

    """A dict like object that hold branches heads cache.

    This cache is used to avoid costly computations to determine all the

    branch heads of a repo.

    The cache is serialized on disk in the following format:

    <tip hex node> <tip rev number> [optional filtered repo hex hash]

    <branch head hex node> <open/closed state> <branch name>

    <branch head hex node> <open/closed state> <branch name>

    ...

    The first line is used to check if the cache is still valid. If the

    branch cache is for a filtered repo view, an optional third hash is

    included that hashes the hashes of all filtered revisions.

    The open/closed state is represented by a single letter 'o' or 'c'.

    This field can be used to avoid changelog reads when determining if a

    branch head closes a branch or not.

    """

    def __init__(self, entries=(), tipnode=nullid, tiprev=nullrev,

                 filteredhash=None, closednodes=None):

        super(branchcache, self).__init__(entries)

        self.tipnode = tipnode

        self.tiprev = tiprev

        self.filteredhash = filteredhash

        # closednodes is a set of nodes that close their branch. If the branch

        # cache has been updated, it may contain nodes that are no longer

        # heads.

        if closednodes is None:

            self._closednodes = set()

        else:

            self._closednodes = closednodes

    def validfor(self, repo):

        """Is the cache content valid regarding a repo

        - False when cached tipnode is unknown or if we detect a strip.

        - True when cache is up to date or a subset of current repo."""

        try:

            return ((self.tipnode == repo.changelog.node(self.tiprev))

                    and (self.filteredhash == \

                         scmutil.filteredhash(repo, self.tiprev)))

        except IndexError:

            return False

    def _branchtip(self, heads):

        '''Return tuple with last open head in heads and false,

        otherwise return last closed head and true.'''

        tip = heads[-1]

        closed = True

        for h in reversed(heads):

            if h not in self._closednodes:

                tip = h

                closed = False

                break

        return tip, closed

    def branchtip(self, branch):

        '''Return the tipmost open head on branch head, otherwise return the

        tipmost closed head on branch.

        Raise KeyError for unknown branch.'''

        return self._branchtip(self[branch])[0]

    def branchheads(self, branch, closed=False):

        heads = self[branch]

        if not closed:

            heads = [h for h in heads if h not in self._closednodes]

        return heads

    def iterbranches(self):

        for bn, heads in self.iteritems():

            yield (bn, heads) + self._branchtip(heads)

    def copy(self):

        """return an deep copy of the branchcache object"""

        return branchcache(self, self.tipnode, self.tiprev, self.filteredhash,

                           self._closednodes)

    def write(self, repo):

        try:

            f = repo.cachevfs(_filename(repo), "w", atomictemp=True)

            cachekey = [hex(self.tipnode), '%d' % self.tiprev]

            if self.filteredhash is not None:

                cachekey.append(hex(self.filteredhash))

            f.write(" ".join(cachekey) + '\n')

            nodecount = 0

            for label, nodes in sorted(self.iteritems()):

                for node in nodes:

                    nodecount += 1

                    if node in self._closednodes:

                        state = 'c'

                    else:

                        state = 'o'

                    f.write("%s %s %s\n" % (hex(node), state,

                                            encoding.fromlocal(label)))

            f.close()

            repo.ui.log('branchcache',

                        'wrote %s branch cache with %d labels and %d nodes\n',

                        repo.filtername, len(self), nodecount)

        except (IOError, OSError, error.Abort) as inst:

            repo.ui.debug("couldn't write branch cache: %s\n" % inst)

            # Abort may be raise by read only opener

            pass

    def update(self, repo, revgen):

        """Given a branchhead cache, self, that may have extra nodes or be

        missing heads, and a generator of nodes that are strictly a superset of

        heads missing, this function updates self to be correct.

        """

        starttime = util.timer()

        cl = repo.changelog

        # collect new branch entries

        newbranches = {}

        getbranchinfo = repo.revbranchcache().branchinfo

        for r in revgen:

            branch, closesbranch = getbranchinfo(r)

            newbranches.setdefault(branch, []).append(r)

            if closesbranch:

                self._closednodes.add(cl.node(r))

        # fetch current topological heads to speed up filtering

        topoheads = set(cl.headrevs())

        # if older branchheads are reachable from new ones, they aren't

        # really branchheads. Note checking parents is insufficient:

        # 1 (branch a) -> 2 (branch b) -> 3 (branch a)

        for branch, newheadrevs in newbranches.iteritems():

            bheads = self.setdefault(branch, [])

            bheadset = set(cl.rev(node) for node in bheads)

            # This have been tested True on all internal usage of this function.

            # run it again in case of doubt

            # assert not (set(bheadrevs) & set(newheadrevs))

            newheadrevs.sort()

            bheadset.update(newheadrevs)

            # This prunes out two kinds of heads - heads that are superseded by

            # a head in newheadrevs, and newheadrevs that are not heads because

            # an existing head is their descendant.

            uncertain = bheadset - topoheads

            if uncertain:

                floorrev = min(uncertain)

                ancestors = set(cl.ancestors(newheadrevs, floorrev))

                bheadset -= ancestors

            bheadrevs = sorted(bheadset)

            self[branch] = [cl.node(rev) for rev in bheadrevs]

            tiprev = bheadrevs[-1]

            if tiprev > self.tiprev:

                self.tipnode = cl.node(tiprev)

                self.tiprev = tiprev

        if not self.validfor(repo):

            # cache key are not valid anymore

            self.tipnode = nullid

            self.tiprev = nullrev

            for heads in self.values():

                tiprev = max(cl.rev(node) for node in heads)

                if tiprev > self.tiprev:

                    self.tipnode = cl.node(tiprev)

                    self.tiprev = tiprev

        self.filteredhash = scmutil.filteredhash(repo, self.tiprev)

        duration = util.timer() - starttime

        repo.ui.log('branchcache', 'updated %s branch cache in %.4f seconds\n',

                    repo.filtername, duration)

# Revision branch info cache

_rbcversion = '-v1'

_rbcnames = 'rbc-names' + _rbcversion

_rbcrevs = 'rbc-revs' + _rbcversion

# [4 byte hash prefix][4 byte branch name number with sign bit indicating open]

_rbcrecfmt = '>4sI'

_rbcrecsize = calcsize(_rbcrecfmt)

_rbcnodelen = 4

_rbcbranchidxmask = 0x7fffffff

_rbccloseflag = 0x80000000

class revbranchcache(object):

    """Persistent cache, mapping from revision number to branch name and close.

    This is a low level cache, independent of filtering.

    Branch names are stored in rbc-names in internal encoding separated by 0.

    rbc-names is append-only, and each branch name is only stored once and will

    thus have a unique index.

    The branch info for each revision is stored in rbc-revs as constant size

    records. The whole file is read into memory, but it is only 'parsed' on

    demand. The file is usually append-only but will be truncated if repo

    modification is detected.

    The record for each revision contains the first 4 bytes of the

    corresponding node hash, and the record is only used if it still matches.

    Even a completely trashed rbc-revs fill thus still give the right result

    while converging towards full recovery ... assuming no incorrectly matching

    node hashes.

    The record also contains 4 bytes where 31 bits contains the index of the

    branch and the last bit indicate that it is a branch close commit.

    The usage pattern for rbc-revs is thus somewhat similar to 00changelog.i

    and will grow with it but be 1/8th of its size.

    """

    def __init__(self, repo, readonly=True):

        assert repo.filtername is None

        self._repo = repo

        self._names = [] # branch names in local encoding with static index

        self._rbcrevs = bytearray()

        self._rbcsnameslen = 0 # length of names read at _rbcsnameslen

        try:

            bndata = repo.cachevfs.read(_rbcnames)

            self._rbcsnameslen = len(bndata) # for verification before writing

            if bndata:

                self._names = [encoding.tolocal(bn)

                               for bn in bndata.split('\0')]

        except (IOError, OSError):

            if readonly:

                # don't try to use cache - fall back to the slow path

                self.branchinfo = self._branchinfo

        if self._names:

            try:

                data = repo.cachevfs.read(_rbcrevs)

                self._rbcrevs[:] = data

            except (IOError, OSError) as inst:

                repo.ui.debug("couldn't read revision branch cache: %s\n" %

                              inst)

        # remember number of good records on disk

        self._rbcrevslen = min(len(self._rbcrevs) // _rbcrecsize,