# string conversion stuff
def entitize(s):
    """ entitize a string so it can be used in XML content and attrs
    """
    return s.replace('&', '&').replace('"', '"').replace(
                '<', '&lt;').replace('>', '&gt;')

def strconvert(s, charset):
    from templess import nodebase
    if isinstance(s, nodebase):
        return s
    elif isinstance(s, xmlstring):
        return unicode(s)
    elif isinstance(s, str):
        s = unicode(s, charset)
    elif not isinstance(s, unicode):
        s = str(s)
    return entitize(s)

# helper functions
def is_iterable_not_string(v):
    """ determine if something is iterable but not a string
    """
    from templess import elnode
    for t in (str, unicode, xmlstring, objectcontext, elnode):
        if isinstance(v, t):
            return False
    try:
        iter(v)
    except TypeError:
        return False
    else:
        return True


# some helper classes for templess users
class xmlstring(unicode):
    """ wrapper around unicode to mark a string as XML

        when Templess encounters this object, it will not escape entities
    """

def iterwrapper(iterable):
    for i in iterable:
        yield objectcontext(i)


class objectcontext(object):
    """ wrapper around objects to allow Templess to traverse attributes

        this is similar to the nastyness Zope exposes to its users in TAL,
        when Templess retrieves a key from the context, if the context is
        an objectcontext wrapping an object, instead of just doing a 
        __getitem__ the following will be done:

        - first a __getitem__ is tried, then a __getattr_, if the value is
          still not found a KeyError is raised

        - before the value is returned, a check is done whether it's callable,
          and if so it's called (without arguments)
    """
    # XXX do we want to allow arguments in something like "@key,key" form or
    # something scary like that? this is nasty already anyway ;)
    def __init__(self, o):
        self.object = o

    __marker__ = []
    def __getitem__(self, name):
        try:
            ret = self.object[name]
        except (TypeError, KeyError):
            try:
                ret = self.object.__dict__[name]
            except KeyError:
                try:
                    ret = self.object.__class__.__dict__[name]
                except KeyError:
                    raise KeyError, name
        if callable(ret):
            ret = ret()
        return self.wrap(ret)

    def __str__(self):
        return getattr(self.object, '__str__', self.object.__repr__)()

    def __repr__(self):
        return '<objectcontext for "%s">' % (self.object.__class__.__name__,)

    def wrap(self, obj):
        if is_iterable_not_string(obj):
            return iterwrapper(obj)
        return objectcontext(obj)

    def __hasattr__(self, name):
        return hasattr(self.object, name)