# 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 node import nullid, bin, hex, short

from i18n import _

import encoding

import error

import errno

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

    '''Find global tags in repo by reading .hgtags from every head that

    has a distinct version of it, using a cache to avoid excess work.

    Updates the dicts alltags, tagtypes in place: alltags maps tag name

    to (node, hist) pair (see _readtags() below), and tagtypes maps tag

    name to tag type ("global" in this case).'''

    # 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, 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, heads, tagfnode, alltags)

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

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

    try:

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

    except IOError, 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)

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

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

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

    Return a mapping from tag name to (node, hist): node is the node id

    from the last line read for that name, and hist is the list of node

    ids previously associated with it (in file order).  All node ids are

    binary, not hex.'''

    filetags = {}               # map tag name to (node, hist)

    count = 0

    def warn(msg):

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

    for line in lines:

        count += 1

        if not line:

            continue

        try:

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

        except ValueError:

            warn(_("cannot parse entry"))

            continue

        name = name.strip()

        if recode:

            name = recode(name)

        try:

            nodebin = bin(nodehex)

        except TypeError:

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

            continue

        # update filetags

        hist = []

        if name in filetags:

            n, hist = filetags[name]

            hist.append(n)

        filetags[name] = (nodebin, hist)

    return filetags

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

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

        alltags[name] = anode, ahist

        tagtypes[name] = tagtype

# The tag cache only stores info about heads, not the tag contents

# from each head.  I.e. it doesn't try to squeeze out the maximum

# performance, but is simpler has a better chance of actually

# working correctly.  And this gives the biggest performance win: it

# avoids looking up .hgtags in the manifest for every head, and it

# can avoid calling heads() at all if there have been no changes to

# the repo.

def _readtagcache(ui, repo):

    '''Read the tag cache and return a tuple (heads, fnodes, cachetags,

    shouldwrite).  If the cache is completely up-to-date, cachetags is a

    dict of the form returned by _readtags(); otherwise, it is None and

    heads and fnodes are set.  In that case, heads is the list of all

    heads currently in the repository (ordered from tip to oldest) and

    fnodes is a mapping from head to .hgtags filenode.  If those two are

    set, caller is responsible for reading tag info from each head.'''

    try:

        cachefile = repo.opener('cache/tags', 'r')

        # force reading the file for static-http

        cachelines = iter(cachefile)

    except IOError:

        cachefile = None

    # The cache file consists of lines like

    #   <headrev> <headnode> [<tagnode>]

    # where <headrev> and <headnode> redundantly identify a repository

    # head from the time the cache was written, and <tagnode> is the

    # filenode of .hgtags on that head.  Heads with no .hgtags file will

    # have no <tagnode>.  The cache is ordered from tip to oldest (which

    # is part of why <headrev> is there: a quick visual check is all

    # that's required to ensure correct order).

    #

    # This information is enough to let us avoid the most expensive part

    # of finding global tags, which is looking up <tagnode> in the

    # manifest for each head.

    cacherevs = []                      # list of headrev

    cacheheads = []                     # list of headnode

    cachefnode = {}                     # map headnode to filenode

    if cachefile:

        try:

            for line in cachelines:

                if line == "\n":

                    break

                line = line.split()

                cacherevs.append(int(line[0]))

                headnode = bin(line[1])

                cacheheads.append(headnode)

                if len(line) == 3:

                    fnode = bin(line[2])

                    cachefnode[headnode] = fnode

        except Exception:

            # corruption of the tags cache, just recompute it

            ui.warn(_('.hg/cache/tags is corrupt, rebuilding it\n'))

            cacheheads = []

            cacherevs = []

            cachefnode = {}

    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 cacheheads and cacheheads[0] == tipnode and cacherevs[0] == tiprev:

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

        cachefile.close()

        return (None, None, tags, False)

    if cachefile:

        cachefile.close()               # ignore rest of file

    repoheads = repo.heads()

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

    # writing an empty cache.

    if repoheads == [nullid]:

        return ([], {}, {}, 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 (repoheads, cachefnode, None, True)

    newheads = [head

                for head in repoheads

                if head not in set(cacheheads)]

    # 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.

    for head in reversed(newheads):

        cctx = repo[head]

        try:

            fnode = cctx.filenode('.hgtags')

            cachefnode[head] = fnode

        except error.LookupError:

            # no .hgtags file on this head

            pass

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

    # cachefnode to get to each .hgtags revision quickly.

    return (repoheads, cachefnode, None, True)

def _writetagcache(ui, repo, heads, tagfnode, cachetags):

    try:

        cachefile = repo.opener('cache/tags', 'w', atomictemp=True)

    except (OSError, IOError):

        return

    realheads = repo.heads()            # for sanity checks below

    for head in heads:

        # temporary sanity checks; these can probably be removed

        # once this code has been in crew for a few weeks

        assert head in repo.changelog.nodemap, \

               'trying to write non-existent node %s to tag cache' % short(head)

        assert head in realheads, \

               'trying to write non-head %s to tag cache' % short(head)

        assert head != nullid, \

               'trying to write nullid to tag cache'

        # This can't fail because of the first assert above.  When/if we

        # remove that assert, we might want to catch LookupError here

        # and downgrade it to a warning.

        rev = repo.changelog.rev(head)

        fnode = tagfnode.get(head)

        if fnode:

            cachefile.write('%d %s %s\n' % (rev, hex(head), hex(fnode)))

        else:

            cachefile.write('%d %s\n' % (rev, hex(head)))

    # 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.

    cachefile.write('\n')

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

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

    try:

        cachefile.close()

    except (OSError, IOError):

        pass