# tags.py - read tag info from local repository

#

# Copyright 2009 Matt Mackall <mpm@selenic.com>

# Copyright 2009 Greg Ward <greg@gerg.ca>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

# Currently this module only deals with reading and caching tags.

# Eventually, it could take care of updating (adding/removing/moving)

# tags too.

from __future__ import absolute_import

import array

import errno

import time

from .node import (

    bin,

    hex,

    nullid,

    short,

)

from . import (

    encoding,

    error,

    util,

)

array = array.array

# Tags computation can be expensive and caches exist to make it fast in

# the common case.

#

# The "hgtagsfnodes1" cache file caches the .hgtags filenode values for

# each revision in the repository. The file is effectively an array of

# fixed length records. Read the docs for "hgtagsfnodescache" for technical

# details.

#

# The .hgtags filenode cache grows in proportion to the length of the

# changelog. The file is truncated when the # changelog is stripped.

#

# The purpose of the filenode cache is to avoid the most expensive part

# of finding global tags, which is looking up the .hgtags filenode in the

# manifest for each head. This can take dozens or over 100ms for

# repositories with very large manifests. Multiplied by dozens or even

# hundreds of heads and there is a significant performance concern.

#

# There also exist a separate cache file for each repository filter.

# These "tags-*" files store information about the history of tags.

#

# The tags cache files consists of a cache validation line followed by

# a history of tags.

#

# The cache validation line has the format:

#

#   <tiprev> <tipnode> [<filteredhash>]

#

# <tiprev> is an integer revision and <tipnode> is a 40 character hex

# node for that changeset. These redundantly identify the repository

# tip from the time the cache was written. In addition, <filteredhash>,

# if present, is a 40 character hex hash of the contents of the filtered

# revisions for this filter. If the set of filtered revs changes, the

# hash will change and invalidate the cache.

#

# The history part of the tags cache consists of lines of the form:

#

#   <node> <tag>

#

# (This format is identical to that of .hgtags files.)

#

# <tag> is the tag name and <node> is the 40 character hex changeset

# the tag is associated with.

#

# Tags are written sorted by tag name.

#

# Tags associated with multiple changesets have an entry for each changeset.

# The most recent changeset (in terms of revlog ordering for the head

# setting it) for each tag is last.

def findglobaltags(ui, repo, alltags, tagtypes):

    '''Find global tags in a repo.

    "alltags" maps tag name to (node, hist) 2-tuples.

    "tagtypes" maps tag name to tag type. Global tags always have the

    "global" tag type.

    The "alltags" and "tagtypes" dicts are updated in place. Empty dicts

    should be passed in.

    The tags cache is read and updated as a side-effect of calling.

    '''

    # This is so we can be lazy and assume alltags contains only global

    # tags when we pass it to _writetagcache().

    assert len(alltags) == len(tagtypes) == 0, \

           "findglobaltags() should be called first"

    (heads, tagfnode, valid, cachetags, shouldwrite) = _readtagcache(ui, repo)

    if cachetags is not None:

        assert not shouldwrite

        # XXX is this really 100% correct?  are there oddball special

        # cases where a global tag should outrank a local tag but won't,

        # because cachetags does not contain rank info?

        _updatetags(cachetags, 'global', alltags, tagtypes)

        return

    seen = set()  # set of fnode

    fctx = None

    for head in reversed(heads):  # oldest to newest

        assert head in repo.changelog.nodemap, \

               "tag cache returned bogus head %s" % short(head)

        fnode = tagfnode.get(head)

        if fnode and fnode not in seen:

            seen.add(fnode)

            if not fctx:

                fctx = repo.filectx('.hgtags', fileid=fnode)

            else:

                fctx = fctx.filectx(fnode)

            filetags = _readtags(ui, repo, fctx.data().splitlines(), fctx)

            _updatetags(filetags, 'global', alltags, tagtypes)

    # and update the cache (if necessary)

    if shouldwrite:

        _writetagcache(ui, repo, valid, alltags)

def readlocaltags(ui, repo, alltags, tagtypes):

    '''Read local tags in repo. Update alltags and tagtypes.'''

    try:

        data = repo.vfs.read("localtags")

    except IOError as inst:

        if inst.errno != errno.ENOENT:

            raise

        return

    # localtags is in the local encoding; re-encode to UTF-8 on

    # input for consistency with the rest of this module.

    filetags = _readtags(

        ui, repo, data.splitlines(), "localtags",

        recode=encoding.fromlocal)

    # remove tags pointing to invalid nodes

    cl = repo.changelog

    for t in filetags.keys():

        try:

            cl.rev(filetags[t][0])

        except (LookupError, ValueError):

            del filetags[t]

    _updatetags(filetags, "local", alltags, tagtypes)

def _readtaghist(ui, repo, lines, fn, recode=None, calcnodelines=False):

    '''Read tag definitions from a file (or any source of lines).

    This function returns two sortdicts with similar information:

    - the first dict, bintaghist, contains the tag information as expected by

      the _readtags function, i.e. a mapping from tag name to (node, hist):

        - node is the node id from the last line read for that name,

        - hist is the list of node ids previously associated with it (in file

          order). All node ids are binary, not hex.

    - the second dict, hextaglines, is a mapping from tag name to a list of

      [hexnode, line number] pairs, ordered from the oldest to the newest node.

    When calcnodelines is False the hextaglines dict is not calculated (an

    empty dict is returned). This is done to improve this function's

    performance in cases where the line numbers are not needed.

    '''

    bintaghist = util.sortdict()

    hextaglines = util.sortdict()

    count = 0

    def dbg(msg):

        ui.debug("%s, line %s: %s\n" % (fn, count, msg))

    for nline, line in enumerate(lines):

        count += 1

        if not line:

            continue

        try:

            (nodehex, name) = line.split(" ", 1)

        except ValueError:

            dbg("cannot parse entry")

            continue

        name = name.strip()

        if recode:

            name = recode(name)

        try:

            nodebin = bin(nodehex)

        except TypeError:

            dbg("node '%s' is not well formed" % nodehex)

            continue

        # update filetags

        if calcnodelines:

            # map tag name to a list of line numbers

            if name not in hextaglines:

                hextaglines[name] = []

            hextaglines[name].append([nodehex, nline])

            continue

        # map tag name to (node, hist)

        if name not in bintaghist:

            bintaghist[name] = []

        bintaghist[name].append(nodebin)

    return bintaghist, hextaglines

def _readtags(ui, repo, lines, fn, recode=None, calcnodelines=False):

    '''Read tag definitions from a file (or any source of lines).

    Returns a mapping from tag name to (node, hist).

    "node" is the node id from the last line read for that name. "hist"

    is the list of node ids previously associated with it (in file order).

    All node ids are binary, not hex.

    '''

    filetags, nodelines = _readtaghist(ui, repo, lines, fn, recode=recode,

                                       calcnodelines=calcnodelines)

    # util.sortdict().__setitem__ is much slower at replacing then inserting

    # new entries. The difference can matter if there are thousands of tags.

    # Create a new sortdict to avoid the performance penalty.

    newtags = util.sortdict()

    for tag, taghist in filetags.items():

        newtags[tag] = (taghist[-1], taghist[:-1])

    return newtags

def _updatetags(filetags, tagtype, alltags, tagtypes):

    '''Incorporate the tag info read from one file into the two

    dictionaries, alltags and tagtypes, that contain all tag

    info (global across all heads plus local).'''

    for name, nodehist in filetags.iteritems():

        if name not in alltags:

            alltags[name] = nodehist

            tagtypes[name] = tagtype

            continue

        # we prefer alltags[name] if:

        #  it supersedes us OR

        #  mutual supersedes and it has a higher rank

        # otherwise we win because we're tip-most

        anode, ahist = nodehist

        bnode, bhist = alltags[name]

        if (bnode != anode and anode in bhist and

            (bnode not in ahist or len(bhist) > len(ahist))):

            anode = bnode

        else:

            tagtypes[name] = tagtype

        ahist.extend([n for n in bhist if n not in ahist])

        alltags[name] = anode, ahist

def _filename(repo):

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

    filename = 'cache/tags2'

    if repo.filtername:

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

    return filename

def _readtagcache(ui, repo):

    '''Read the tag cache.

    Returns a tuple (heads, fnodes, validinfo, cachetags, shouldwrite).

    If the cache is completely up-to-date, "cachetags" is a dict of the

    form returned by _readtags() and "heads", "fnodes", and "validinfo" are

    None and "shouldwrite" is False.

    If the cache is not up to date, "cachetags" is None. "heads" is a list

    of all heads currently in the repository, ordered from tip to oldest.

    "validinfo" is a tuple describing cache validation info. This is used

    when writing the tags cache. "fnodes" is a mapping from head to .hgtags

    filenode. "shouldwrite" is True.

    If the cache is not up to date, the caller is responsible for reading tag

    info from each returned head. (See findglobaltags().)

    '''

    from . import scmutil  # avoid cycle

    try:

        cachefile = repo.vfs(_filename(repo), 'r')

        # force reading the file for static-http

        cachelines = iter(cachefile)

    except IOError:

        cachefile = None

    cacherev = None

    cachenode = None

    cachehash = None

    if cachefile:

        try:

            validline = cachelines.next()

            validline = validline.split()

            cacherev = int(validline[0])

            cachenode = bin(validline[1])

            if len(validline) > 2:

                cachehash = bin(validline[2])

        except Exception:

            # corruption of the cache, just recompute it.

            pass

    tipnode = repo.changelog.tip()

    tiprev = len(repo.changelog) - 1

    # Case 1 (common): tip is the same, so nothing has changed.

    # (Unchanged tip trivially means no changesets have been added.

    # But, thanks to localrepository.destroyed(), it also means none

    # have been destroyed by strip or rollback.)

    if (cacherev == tiprev

            and cachenode == tipnode

            and cachehash == scmutil.filteredhash(repo, tiprev)):

        tags = _readtags(ui, repo, cachelines, cachefile.name)

        cachefile.close()

        return (None, None, None, tags, False)

    if cachefile:

        cachefile.close()               # ignore rest of file

    valid = (tiprev, tipnode, scmutil.filteredhash(repo, tiprev))

    repoheads = repo.heads()

    # Case 2 (uncommon): empty repo; get out quickly and don't bother

    # writing an empty cache.

    if repoheads == [nullid]:

        return ([], {}, valid, {}, False)

    # Case 3 (uncommon): cache file missing or empty.

    # Case 4 (uncommon): tip rev decreased.  This should only happen

    # when we're called from localrepository.destroyed().  Refresh the

    # cache so future invocations will not see disappeared heads in the

    # cache.

    # Case 5 (common): tip has changed, so we've added/replaced heads.

    # As it happens, the code to handle cases 3, 4, 5 is the same.

    # N.B. in case 4 (nodes destroyed), "new head" really means "newly

    # exposed".

    if not len(repo.file('.hgtags')):

        # No tags have ever been committed, so we can avoid a

        # potentially expensive search.

        return ([], {}, valid, None, True)

    starttime = time.time()

    # Now we have to lookup the .hgtags filenode for every new head.

    # This is the most expensive part of finding tags, so performance

    # depends primarily on the size of newheads.  Worst case: no cache

    # file, so newheads == repoheads.

    fnodescache = hgtagsfnodescache(repo.unfiltered())

    cachefnode = {}

    for head in reversed(repoheads):

        fnode = fnodescache.getfnode(head)

        if fnode != nullid:

            cachefnode[head] = fnode

    fnodescache.write()

    duration = time.time() - starttime

    ui.log('tagscache',

           '%d/%d cache hits/lookups in %0.4f '

           'seconds\n',

           fnodescache.hitcount, fnodescache.lookupcount, duration)

    # Caller has to iterate over all heads, but can use the filenodes in

    # cachefnode to get to each .hgtags revision quickly.

    return (repoheads, cachefnode, valid, None, True)

def _writetagcache(ui, repo, valid, cachetags):

    filename = _filename(repo)

    try:

        cachefile = repo.vfs(filename, 'w', atomictemp=True)

    except (OSError, IOError):

        return

    ui.log('tagscache', 'writing .hg/%s with %d tags\n',

           filename, len(cachetags))

    if valid[2]:

        cachefile.write('%d %s %s\n' % (valid[0], hex(valid[1]), hex(valid[2])))

    else:

        cachefile.write('%d %s\n' % (valid[0], hex(valid[1])))

    # Tag names in the cache are in UTF-8 -- which is the whole reason

    # we keep them in UTF-8 throughout this module.  If we converted

    # them local encoding on input, we would lose info writing them to

    # the cache.

    for (name, (node, hist)) in sorted(cachetags.iteritems()):

        for n in hist:

            cachefile.write("%s %s\n" % (hex(n), name))

        cachefile.write("%s %s\n" % (hex(node), name))

    try:

        cachefile.close()

    except (OSError, IOError):

        pass

_fnodescachefile = 'cache/hgtagsfnodes1'

_fnodesrecsize = 4 + 20 # changeset fragment + filenode