import datetime
import uuid


def dict_for(obj, **kwds):
    # Create dict to represent item.
    return dict(
        model_class=obj.__class__.__name__,
        **kwds
    )


class Dictifiable(object):
    """ Mixin that enables objects to be converted to dictionaries. This is useful
        when for sharing objects across boundaries, such as the API, tool scripts,
        and JavaScript code. """

    def to_dict(self, view='collection', value_mapper=None):
        """
        Return item dictionary.
        """

        if not value_mapper:
            value_mapper = {}

        def get_value(key, item):
            """
            Recursive helper function to get item values.
            """
            # FIXME: why use exception here? Why not look for key in value_mapper
            # first and then default to to_dict?
            try:
                return item.to_dict(view=view, value_mapper=value_mapper)
            except Exception:
                if key in value_mapper:
                    return value_mapper.get(key)(item)
                if type(item) == datetime.datetime:
                    return item.isoformat()
                elif type(item) == uuid.UUID:
                    return str(item)
                # Leaving this for future reference, though we may want a more
                # generic way to handle special type mappings going forward.
                # If the item is of a class that needs to be 'stringified' before being put into a JSON data structure
                # elif type(item) in []:
                #    return str(item)
                return item

        # Create dict to represent item.
        rval = dict_for(self)

        # Fill item dict with visible keys.
        try:
            visible_keys = self.__getattribute__('dict_' + view + '_visible_keys')
        except AttributeError:
            raise Exception('Unknown Dictifiable view: %s' % view)
        for key in visible_keys:
            try:
                item = self.__getattribute__(key)
                if isinstance(item, list):
                    rval[key] = []
                    for i in item:
                        rval[key].append(get_value(key, i))
                else:
                    rval[key] = get_value(key, item)
            except AttributeError:
                rval[key] = None

        return rval
