import datetime
import uuid
from typing import (
    Any,
    Callable,
    Dict,
    Optional,
)


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


class Dictifiable:
    """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: str = "collection", value_mapper: Optional[Dict[str, Callable]] = None) -> Dict[str, Any]:
        """
        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:
                assert value_mapper is not None
                if key in value_mapper:
                    return value_mapper[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__(f"dict_{view}_visible_keys")
        except AttributeError:
            raise Exception(f"Unknown Dictifiable view: {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