from mercurial import branchmap

def _filename(repo):

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

    filename = "cache/topicmap"

    if repo.filtername:

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

    return filename

oldbranchcache = branchmap.branchcache

class topiccache(oldbranchcache):

    def __init__(self, *args, **kwargs):

        otherbranchcache = branchmap.branchcache

        try:

            # super() call may fail otherwise

            branchmap.branchcache = oldbranchcache

            return super(topiccache, self).__init__(*args, **kwargs)

        finally:

            branchmap.branchcache = otherbranchcache

    def branchtip(self, branch, topic=''):

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

        tipmost closed head on branch.

        Raise KeyError for unknown branch.'''

        if topic:

            branch = '%s:%s' % (branch, topic)

        return super(topiccache, self).branchtip(branch)

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

        if topic:

            branch = '%s:%s' % (branch, topic)

        return super(topiccache, self).branchheads(branch, closed=closed)

    def write(self, repo):

        # The cache key needs to take phase root in account because change to

        # what is public affect topics. We can't write on disk until we have this.

        return

    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.

        """

        oldgetbranchinfo = repo.revbranchcache().branchinfo

        try:

            def branchinfo(r):

                info = oldgetbranchinfo(r)

                topic = ''

                ctx = repo[r]

                if ctx.mutable():

                    topic = ctx.topic()

                branch = info[0]

                if topic:

                    branch = '%s:%s' % (branch, topic)

                return (branch, info[1])

            repo.revbranchcache().branchinfo = branchinfo

            return super(topiccache, self).update(repo, revgen)

        finally:

            repo.revbranchcache().branchinfo = oldgetbranchinfo