# -*- test-case-name: mv3d.test.util.test_enum -*-
# Copyright (C) 2012 Mortal Coil Games
# See LICENSE for details.
"""
Simple base enum utils!

@author:  mike
"""
class MetaEnum(type):
    """
    Turns a class into an enum by assigning numbers to attributes that are
    set to None. See the Enum class for example usage.
    """
    def __new__(cls, name, bases, attrs):
        start = 0
        unnumbered = []
        valueToName = {}
        nameToValue = {}
        for item, value in attrs.items():
            if isinstance(value, classmethod):
                continue
            if item.startswith("_"):
                continue
            if value is None:
                unnumbered.append(item)
                continue
            elif value >= start:
                start = value + 1
            valueToName[value] = item
            nameToValue[item] = value

        for value, item in enumerate(sorted(unnumbered)):
            attrs[item] = value + start
            valueToName[value + start] = item
            nameToValue[item] = value + start

        attrs["_valueToName"] = valueToName
        attrs["_nameToValue"] = nameToValue
        return type.__new__(cls, name, bases, attrs)


    def __len__(self):
        """
        Return the number of enum items.
        """
        return len(self._valueToName)


    def __getitem__(self, index):
        """
        Returns the string representation for an index.
        """
        if index < 0:
            return sorted(self._valueToName.items())[index][1]
        return self._valueToName[index]



class Enum(object):
    """
    Subclass to define a basic enum class. Assing values to enum items or
    assign them to None for auto-numbering. Note that numbering occurs in
    alphabetical order. Example:

    >>> class Weapon(Enum):
    ...    shortSword = None
    ...    dagger = 2
    ...    mace = 43
    ...    bow = None
    ...
    >>> Weapon.shortSword
    45
    >>> Weapon.mace
    43
    >>> Weapon.bow
    44
    
    See the unit tests for more examples.
    """
    __metaclass__ = MetaEnum
    _valueToName = None
    _nameToValue = None


    @classmethod
    def values(self):
        """
        Returns all the enum values.
        """
        return self._nameToValue.values()


    @classmethod
    def keys(self):
        """
        Returns all the enum names.
        """
        return self._nameToValue.keys()


    @classmethod
    def items(self):
        """
        Returns tuples of (name, value) for each enum entry.
        """
        return self._nameToValue.items()