# 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 node import bin, hex, nullid, nullrev

import encoding

import util

import time

from array import array

from struct import calcsize, pack, unpack

def _filename(repo):

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

    filename = "cache/branch2"

    if repo.filtername:

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

    return filename

def read(repo):

    try:

        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')

        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())

            if not node in repo:

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

            node = bin(node)

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

            if state == 'c':

                partial._closednodes.add(node)

    except KeyboardInterrupt:

        raise

    except Exception, 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

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

        self._revbranchcache = None

    def _hashfiltered(self, repo):

        """build hash of revision filtered in the current cache

        Tracking tipnode and tiprev is not enough to ensure validity of the

        cache as they do not help to distinct cache that ignored various

        revision bellow tiprev.

        To detect such difference, we build a cache of all ignored revisions.

        """

        cl = repo.changelog

        if not cl.filteredrevs:

            return None

        key = None

        revs = sorted(r for r in cl.filteredrevs if r <= self.tiprev)

        if revs:

            s = util.sha1()

            for rev in revs:

                s.update('%s;' % rev)

            key = s.digest()

        return key

    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 == self._hashfiltered(repo)))

        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:

            cachekey = [hex(self.tipnode), str(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, util.Abort), inst:

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

            # Abort may be raise by read only opener

            pass

        if self._revbranchcache:

            self._revbranchcache.write(repo.unfiltered())

            self._revbranchcache = None

    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 = time.time()

        cl = repo.changelog

        # collect new branch entries

        newbranches = {}

        urepo = repo.unfiltered()

        self._revbranchcache = revbranchcache(urepo)

        getbranchinfo = self._revbranchcache.branchinfo

        ucl = urepo.changelog

        for r in revgen:

            branch, closesbranch = getbranchinfo(ucl, 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 = self._hashfiltered(repo)

        duration = time.time() - starttime

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

                    repo.filtername, duration)

# Revision branch info cache

_rbcversion = '-v1'

_rbcnames = 'cache/rbc-names' + _rbcversion

_rbcrevs = 'cache/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):

        assert repo.filtername is None

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

        self._rbcrevs = array('c') # structs of type _rbcrecfmt

        self._rbcsnameslen = 0

        try:

            bndata = repo.vfs.read(_rbcnames)

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

            self._names = [encoding.tolocal(bn) for bn in bndata.split('\0')]

        except (IOError, OSError), inst:

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

                          inst)

        if self._names:

            try:

                data = repo.vfs.read(_rbcrevs)

                self._rbcrevs.fromstring(data)

            except (IOError, OSError), 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,

                               len(repo.changelog))

        if self._rbcrevslen == 0:

            self._names = []

        self._rbcnamescount = len(self._names) # number of good names on disk

        self._namesreverse = dict((b, r) for r, b in enumerate(self._names))

    def branchinfo(self, changelog, rev):

        """Return branch name and close flag for rev, using and updating

        persistent cache."""

        rbcrevidx = rev * _rbcrecsize

        # if requested rev is missing, add and populate all missing revs

        if len(self._rbcrevs) < rbcrevidx + _rbcrecsize:

            first = len(self._rbcrevs) // _rbcrecsize

            self._rbcrevs.extend('\0' * (len(changelog) * _rbcrecsize -

                                         len(self._rbcrevs)))

            for r in xrange(first, len(changelog)):

                self._branchinfo(changelog, r)

        # fast path: extract data from cache, use it if node is matching

        reponode = changelog.node(rev)[:_rbcnodelen]