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