from i18n import _

from mercurial import util

def tolist(val):

    """

    a convenience method to return an empty list instead of None

    """

    if val is None:

        return []

    else:

        return [val]

class namespaces(object):

    """

    provides an interface to register a generic many-to-many mapping between

    some (namespaced) names and nodes. The goal here is to control the

    pollution of jamming things into tags or bookmarks (in extension-land) and

    to simplify internal bits of mercurial: log output, tab completion, etc.

    More precisely, we define a list of names (the namespace) and  a mapping of

    names to nodes. This name mapping returns a list of nodes.

    Furthermore, each name mapping will be passed a name to lookup which might

    not be in its domain. In this case, each method should return an empty list

    and not raise an error.

    We'll have a dictionary '_names' where each key is a namespace and

    its value is a dictionary of functions:

      'templatename': name to use for templating (usually the singular form

                      of the plural namespace name)

      'namemap': function that takes a name and returns a list of nodes

    """

    _names_version = 0

    def __init__(self):

        self._names = util.sortdict()

        addns = self.addnamespace

        # we need current mercurial named objects (bookmarks, tags, and

        # branches) to be initialized somewhere, so that place is here

        addns("bookmarks", "bookmark",

              lambda repo, name: tolist(repo._bookmarks.get(name)))

        addns("tags", "tag",

              lambda repo, name: tolist(repo._tagscache.tags.get(name)))

        addns("branches", "branch",

              lambda repo, name: tolist(repo.branchtip(name)))

    def addnamespace(self, namespace, templatename, namemap, order=None):

        """

        register a namespace

        namespace: the name to be registered (in plural form)

        templatename: the name to use for templating

        namemap: function that inputs a node, output name(s)

        order: optional argument to specify the order of namespaces

               (e.g. 'branches' should be listed before 'bookmarks')

        """

        val = {'templatename': templatename,

               'namemap': namemap}

        if order is not None:

            self._names.insert(order, namespace, val)

        else:

            self._names[namespace] = val

    def singlenode(self, repo, name):

        """

        Return the 'best' node for the given name. Best means the first node

        in the first nonempty list returned by a name-to-nodes mapping function

        in the defined precedence order.

        Raises a KeyError if there is no such node.

        """

        for ns, v in self._names.iteritems():

            n = v['namemap'](repo, name)

            if n:

                # return max revision number

                if len(n) > 1:

                    cl = repo.changelog

                    maxrev = max(cl.rev(node) for node in n)

                    return cl.node(maxrev)

                return n[0]

        raise KeyError(_('no such name: %s') % name)