# This file is part of Checkbox.
#
# Copyright 2015 Canonical Ltd.
# Written by:
#   Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
#
# Checkbox is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3,
# as published by the Free Software Foundation.
#
# Checkbox is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Checkbox.  If not, see <http://www.gnu.org/licenses/>.
#
# The enum module was copied from Python trunk, originally written by Ethan
# Furman <ethan@stoneleaf.us>.
#
# The DynamicClassAttribute class was copied from Python trunk, originally
# written by Ethan Furman <ethan@stoneleaf.us>, as committed in git mirror
# commit c621f59146d0f3cd9bd78daa9dbf7784f5f7bcab "Close #19030: improvements
# to inspect and Enum."
#
# The back-ported MappingProxyType was written by
# Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
#
# PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
# --------------------------------------------
#
# 1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"),
#    and the Individual or Organization ("Licensee") accessing and otherwise
#    using this software ("Python") in source or binary form and its associated
#    documentation.
#
# 2. Subject to the terms and conditions of this License Agreement, PSF hereby
#    grants Licensee a nonexclusive, royalty-free, world-wide license to
#    reproduce, analyze, test, perform and/or display publicly, prepare
#    derivative works, distribute, and otherwise use Python alone or in any
#    derivative version, provided, however, that PSF's License Agreement and
#    PSF's notice of copyright, i.e., "Copyright (c) 2001, 2002, 2003, 2004,
#    2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014 Python Software
#    Foundation; All Rights Reserved" are retained in Python alone or in any
#    derivative version prepared by Licensee.
#
# 3. In the event Licensee prepares a derivative work that is based on or
#    incorporates Python or any part thereof, and wants to make the derivative
#    work available to others as provided herein, then Licensee hereby agrees
#    to include in any such work a brief summary of the changes made to Python.
#
# 4. PSF is making Python available to Licensee on an "AS IS" basis.  PSF MAKES
#    NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF EXAMPLE,
#    BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
#    WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT
#    THE USE OF PYTHON WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.
#
# 5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON FOR ANY
#    INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
#    MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON, OR ANY DERIVATIVE
#    THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
#
# 6. This License Agreement will automatically terminate upon a material breach
#    of its terms and conditions.
#
# 7. Nothing in this License Agreement shall be deemed to create any
#    relationship of agency, partnership, or joint venture between PSF and
#    Licensee.  This License Agreement does not grant permission to use PSF
#    trademarks or trade name in a trademark sense to endorse or promote
#    products or services of Licensee, or any third party.
#
# 8. By copying, installing or otherwise using Python, Licensee agrees to be
#    bound by the terms and conditions of this License Agreement.

import sys
from collections import OrderedDict
try:
    from types import MappingProxyType
except ImportError:
    # NOTE: this code is specific to Plainbox
    import ctypes
    PyDictProxy_New = ctypes.pythonapi.PyDictProxy_New
    PyDictProxy_New.argtypes = (ctypes.py_object,)
    PyDictProxy_New.restype = ctypes.py_object

    class MappingProxyType:
        def __new__(cls, dict):
            return PyDictProxy_New(dict)
try:
    from types import DynamicClassAttribute
except ImportError:
    # NOTE: this code is copied from Python trunk
    class DynamicClassAttribute:
        """Route attribute access on a class to __getattr__.

        This is a descriptor, used to define attributes that act differently when
        accessed through an instance and through a class.  Instance access remains
        normal, but access to an attribute through a class will be routed to the
        class's __getattr__ method; this is done by raising AttributeError.

        This allows one to have properties active on an instance, and have virtual
        attributes on the class with the same name (see Enum for an example).

        """
        def __init__(self, fget=None, fset=None, fdel=None, doc=None):
            self.fget = fget
            self.fset = fset
            self.fdel = fdel
            # next two lines make DynamicClassAttribute act the same as property
            self.__doc__ = doc or fget.__doc__
            self.overwrite_doc = doc is None
            # support for abstract methods
            self.__isabstractmethod__ = bool(getattr(fget, '__isabstractmethod__', False))

        def __get__(self, instance, ownerclass=None):
            if instance is None:
                if self.__isabstractmethod__:
                    return self
                raise AttributeError()
            elif self.fget is None:
                raise AttributeError("unreadable attribute")
            return self.fget(instance)

        def __set__(self, instance, value):
            if self.fset is None:
                raise AttributeError("can't set attribute")
            self.fset(instance, value)

        def __delete__(self, instance):
            if self.fdel is None:
                raise AttributeError("can't delete attribute")
            self.fdel(instance)

        def getter(self, fget):
            fdoc = fget.__doc__ if self.overwrite_doc else None
            result = type(self)(fget, self.fset, self.fdel, fdoc or self.__doc__)
            result.overwrite_doc = self.overwrite_doc
            return result

        def setter(self, fset):
            result = type(self)(self.fget, fset, self.fdel, self.__doc__)
            result.overwrite_doc = self.overwrite_doc
            return result

        def deleter(self, fdel):
            result = type(self)(self.fget, self.fset, fdel, self.__doc__)
            result.overwrite_doc = self.overwrite_doc
            return result

__all__ = ['Enum', 'IntEnum', 'unique']


def _is_descriptor(obj):
    """Returns True if obj is a descriptor, False otherwise."""
    return (
            hasattr(obj, '__get__') or
            hasattr(obj, '__set__') or
            hasattr(obj, '__delete__'))


def _is_dunder(name):
    """Returns True if a __dunder__ name, False otherwise."""
    return (name[:2] == name[-2:] == '__' and
            name[2:3] != '_' and
            name[-3:-2] != '_' and
            len(name) > 4)


def _is_sunder(name):
    """Returns True if a _sunder_ name, False otherwise."""
    return (name[0] == name[-1] == '_' and
            name[1:2] != '_' and
            name[-2:-1] != '_' and
            len(name) > 2)


def _make_class_unpicklable(cls):
    """Make the given class un-picklable."""
    def _break_on_call_reduce(self, proto):
        raise TypeError('%r cannot be pickled' % self)
    cls.__reduce_ex__ = _break_on_call_reduce
    cls.__module__ = '<unknown>'


class _EnumDict(dict):
    """Track enum member order and ensure member names are not reused.

    EnumMeta will use the names found in self._member_names as the
    enumeration member names.

    """
    def __init__(self):
        super().__init__()
        self._member_names = []

    def __setitem__(self, key, value):
        """Changes anything not dundered or not a descriptor.

        If an enum member name is used twice, an error is raised; duplicate
        values are not checked for.

        Single underscore (sunder) names are reserved.

        """
        if _is_sunder(key):
            raise ValueError('_names_ are reserved for future Enum use')
        elif _is_dunder(key):
            pass
        elif key in self._member_names:
            # descriptor overwriting an enum?
            raise TypeError('Attempted to reuse key: %r' % key)
        elif not _is_descriptor(value):
            if key in self:
                # enum overwriting a descriptor?
                raise TypeError('Key already defined as: %r' % self[key])
            self._member_names.append(key)
        super().__setitem__(key, value)



# Dummy value for Enum as EnumMeta explicitly checks for it, but of course
# until EnumMeta finishes running the first time the Enum class doesn't exist.
# This is also why there are checks in EnumMeta like `if Enum is not None`
Enum = None


class EnumMeta(type):
    """Metaclass for Enum"""
    @classmethod
    def __prepare__(metacls, cls, bases):
        return _EnumDict()

    def __new__(metacls, cls, bases, classdict):
        # an Enum class is final once enumeration items have been defined; it
        # cannot be mixed with other types (int, float, etc.) if it has an
        # inherited __new__ unless a new __new__ is defined (or the resulting
        # class will fail).
        member_type, first_enum = metacls._get_mixins_(bases)
        __new__, save_new, use_args = metacls._find_new_(classdict, member_type,
                                                        first_enum)

        # save enum items into separate mapping so they don't get baked into
        # the new class
        members = {k: classdict[k] for k in classdict._member_names}
        for name in classdict._member_names:
            del classdict[name]

        # check for illegal enum names (any others?)
        invalid_names = set(members) & {'mro', }
        if invalid_names:
            raise ValueError('Invalid enum member name: {0}'.format(
                ','.join(invalid_names)))

        # create our new Enum type
        enum_class = super().__new__(metacls, cls, bases, classdict)
        enum_class._member_names_ = []               # names in definition order
        enum_class._member_map_ = OrderedDict()      # name->value map
        enum_class._member_type_ = member_type

        # Reverse value->name map for hashable values.
        enum_class._value2member_map_ = {}

        # If a custom type is mixed into the Enum, and it does not know how
        # to pickle itself, pickle.dumps will succeed but pickle.loads will
        # fail.  Rather than have the error show up later and possibly far
        # from the source, sabotage the pickle protocol for this class so
        # that pickle.dumps also fails.
        #
        # However, if the new class implements its own __reduce_ex__, do not
        # sabotage -- it's on them to make sure it works correctly.  We use
        # __reduce_ex__ instead of any of the others as it is preferred by
        # pickle over __reduce__, and it handles all pickle protocols.
        if '__reduce_ex__' not in classdict:
            if member_type is not object:
                methods = ('__getnewargs_ex__', '__getnewargs__',
                        '__reduce_ex__', '__reduce__')
                if not any(m in member_type.__dict__ for m in methods):
                    _make_class_unpicklable(enum_class)

        # instantiate them, checking for duplicates as we go
        # we instantiate first instead of checking for duplicates first in case
        # a custom __new__ is doing something funky with the values -- such as
        # auto-numbering ;)
        for member_name in classdict._member_names:
            value = members[member_name]
            if not isinstance(value, tuple):
                args = (value, )
            else:
                args = value
            if member_type is tuple:   # special case for tuple enums
                args = (args, )     # wrap it one more time
            if not use_args:
                enum_member = __new__(enum_class)
                if not hasattr(enum_member, '_value_'):
                    enum_member._value_ = value
            else:
                enum_member = __new__(enum_class, *args)
                if not hasattr(enum_member, '_value_'):
                    enum_member._value_ = member_type(*args)
            value = enum_member._value_
            enum_member._name_ = member_name
            enum_member.__objclass__ = enum_class
            enum_member.__init__(*args)
            # If another member with the same value was already defined, the
            # new member becomes an alias to the existing one.
            for name, canonical_member in enum_class._member_map_.items():
                if canonical_member._value_ == enum_member._value_:
                    enum_member = canonical_member
                    break
            else:
                # Aliases don't appear in member names (only in __members__).
                enum_class._member_names_.append(member_name)
            enum_class._member_map_[member_name] = enum_member
            try:
                # This may fail if value is not hashable. We can't add the value
                # to the map, and by-value lookups for this value will be
                # linear.
                enum_class._value2member_map_[value] = enum_member
            except TypeError:
                pass

        # double check that repr and friends are not the mixin's or various
        # things break (such as pickle)
        for name in ('__repr__', '__str__', '__format__', '__reduce_ex__'):
            class_method = getattr(enum_class, name)
            obj_method = getattr(member_type, name, None)
            enum_method = getattr(first_enum, name, None)
            if obj_method is not None and obj_method is class_method:
                setattr(enum_class, name, enum_method)

        # replace any other __new__ with our own (as long as Enum is not None,
        # anyway) -- again, this is to support pickle
        if Enum is not None:
            # if the user defined their own __new__, save it before it gets
            # clobbered in case they subclass later
            if save_new:
                enum_class.__new_member__ = __new__
            enum_class.__new__ = Enum.__new__
        return enum_class

    def __call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1):
        """Either returns an existing member, or creates a new enum class.

        This method is used both when an enum class is given a value to match
        to an enumeration member (i.e. Color(3)) and for the functional API
        (i.e. Color = Enum('Color', names='red green blue')).

        When used for the functional API:

        `value` will be the name of the new class.

        `names` should be either a string of white-space/comma delimited names
        (values will start at `start`), or an iterator/mapping of name, value pairs.

        `module` should be set to the module this class is being created in;
        if it is not set, an attempt to find that module will be made, but if
        it fails the class will not be picklable.

        `qualname` should be set to the actual location this class can be found
        at in its module; by default it is set to the global scope.  If this is
        not correct, unpickling will fail in some circumstances.

        `type`, if set, will be mixed in as the first base class.

        """
        if names is None:  # simple value lookup
            return cls.__new__(cls, value)
        # otherwise, functional API: we're creating a new Enum type
        return cls._create_(value, names, module=module, qualname=qualname, type=type, start=start)

    def __contains__(cls, member):
        return isinstance(member, cls) and member._name_ in cls._member_map_

    def __delattr__(cls, attr):
        # nicer error message when someone tries to delete an attribute
        # (see issue19025).
        if attr in cls._member_map_:
            raise AttributeError(
                    "%s: cannot delete Enum member." % cls.__name__)
        super().__delattr__(attr)

    def __dir__(self):
        return (['__class__', '__doc__', '__members__', '__module__'] +
                self._member_names_)

    def __getattr__(cls, name):
        """Return the enum member matching `name`

        We use __getattr__ instead of descriptors or inserting into the enum
        class' __dict__ in order to support `name` and `value` being both
        properties for enum members (which live in the class' __dict__) and
        enum members themselves.

        """
        if _is_dunder(name):
            raise AttributeError(name)
        try:
            return cls._member_map_[name]
        except KeyError:
            # NOTE: patched on python 3.2
            raise AttributeError(name)

    def __getitem__(cls, name):
        return cls._member_map_[name]

    def __iter__(cls):
        return (cls._member_map_[name] for name in cls._member_names_)

    def __len__(cls):
        return len(cls._member_names_)

    @property
    def __members__(cls):
        """Returns a mapping of member name->value.

        This mapping lists all enum members, including aliases. Note that this
        is a read-only view of the internal mapping.

        """
        return MappingProxyType(cls._member_map_)

    def __repr__(cls):
        return "<enum %r>" % cls.__name__

    def __reversed__(cls):
        return (cls._member_map_[name] for name in reversed(cls._member_names_))

    def __setattr__(cls, name, value):
        """Block attempts to reassign Enum members.

        A simple assignment to the class namespace only changes one of the
        several possible ways to get an Enum member from the Enum class,
        resulting in an inconsistent Enumeration.

        """
        member_map = cls.__dict__.get('_member_map_', {})
        if name in member_map:
            raise AttributeError('Cannot reassign members.')
        super().__setattr__(name, value)

    def _create_(cls, class_name, names=None, *, module=None, qualname=None, type=None, start=1):
        """Convenience method to create a new Enum class.

        `names` can be:

        * A string containing member names, separated either with spaces or
          commas.  Values are incremented by 1 from `start`.
        * An iterable of member names.  Values are incremented by 1 from `start`.
        * An iterable of (member name, value) pairs.
        * A mapping of member name -> value pairs.

        """
        metacls = cls.__class__
        bases = (cls, ) if type is None else (type, cls)
        classdict = metacls.__prepare__(class_name, bases)

        # special processing needed for names?
        if isinstance(names, str):
            names = names.replace(',', ' ').split()
        if isinstance(names, (tuple, list)) and isinstance(names[0], str):
            names = [(e, i) for (i, e) in enumerate(names, start)]

        # Here, names is either an iterable of (name, value) or a mapping.
        for item in names:
            if isinstance(item, str):
                member_name, member_value = item, names[item]
            else:
                member_name, member_value = item
            classdict[member_name] = member_value
        enum_class = metacls.__new__(metacls, class_name, bases, classdict)

        # TODO: replace the frame hack if a blessed way to know the calling
        # module is ever developed
        if module is None:
            try:
                module = sys._getframe(2).f_globals['__name__']
            except (AttributeError, ValueError) as exc:
                pass
        if module is None:
            _make_class_unpicklable(enum_class)
        else:
            enum_class.__module__ = module
        if qualname is not None:
            enum_class.__qualname__ = qualname

        return enum_class

    @staticmethod
    def _get_mixins_(bases):
        """Returns the type for creating enum members, and the first inherited
        enum class.

        bases: the tuple of bases that was given to __new__

        """
        if not bases:
            return object, Enum

        # double check that we are not subclassing a class with existing
        # enumeration members; while we're at it, see if any other data
        # type has been mixed in so we can use the correct __new__
        member_type = first_enum = None
        for base in bases:
            if  (base is not Enum and
                    issubclass(base, Enum) and
                    base._member_names_):
                raise TypeError("Cannot extend enumerations")
        # base is now the last base in bases
        if not issubclass(base, Enum):
            raise TypeError("new enumerations must be created as "
                    "`ClassName([mixin_type,] enum_type)`")

        # get correct mix-in type (either mix-in type of Enum subclass, or
        # first base if last base is Enum)
        if not issubclass(bases[0], Enum):
            member_type = bases[0]     # first data type
            first_enum = bases[-1]  # enum type
        else:
            for base in bases[0].__mro__:
                # most common: (IntEnum, int, Enum, object)
                # possible:    (<Enum 'AutoIntEnum'>, <Enum 'IntEnum'>,
                #               <class 'int'>, <Enum 'Enum'>,
                #               <class 'object'>)
                if issubclass(base, Enum):
                    if first_enum is None:
                        first_enum = base
                else:
                    if member_type is None:
                        member_type = base

        return member_type, first_enum

    @staticmethod
    def _find_new_(classdict, member_type, first_enum):
        """Returns the __new__ to be used for creating the enum members.

        classdict: the class dictionary given to __new__
        member_type: the data type whose __new__ will be used by default
        first_enum: enumeration to check for an overriding __new__

        """
        # now find the correct __new__, checking to see of one was defined
        # by the user; also check earlier enum classes in case a __new__ was
        # saved as __new_member__
        __new__ = classdict.get('__new__', None)

        # should __new__ be saved as __new_member__ later?
        save_new = __new__ is not None

        if __new__ is None:
            # check all possibles for __new_member__ before falling back to
            # __new__
            for method in ('__new_member__', '__new__'):
                for possible in (member_type, first_enum):
                    target = getattr(possible, method, None)
                    if target not in {
                            None,
                            None.__new__,
                            object.__new__,
                            Enum.__new__,
                            }:
                        __new__ = target
                        break
                if __new__ is not None:
                    break
            else:
                __new__ = object.__new__

        # if a non-object.__new__ is used then whatever value/tuple was
        # assigned to the enum member name will be passed to __new__ and to the
        # new enum member's __init__
        if __new__ is object.__new__:
            use_args = False
        else:
            use_args = True

        return __new__, save_new, use_args


class Enum(metaclass=EnumMeta):
    """Generic enumeration.

    Derive from this class to define new enumerations.

    """
    def __new__(cls, value):
        # all enum instances are actually created during class construction
        # without calling this method; this method is called by the metaclass'
        # __call__ (i.e. Color(3) ), and by pickle
        if type(value) is cls:
            # For lookups like Color(Color.red)
            return value
        # by-value search for a matching enum member
        # see if it's in the reverse mapping (for hashable values)
        try:
            if value in cls._value2member_map_:
                return cls._value2member_map_[value]
        except TypeError:
            # not there, now do long search -- O(n) behavior
            for member in cls._member_map_.values():
                if member._value_ == value:
                    return member
        raise ValueError("%r is not a valid %s" % (value, cls.__name__))

    def __repr__(self):
        return "<%s.%s: %r>" % (
                self.__class__.__name__, self._name_, self._value_)

    def __str__(self):
        return "%s.%s" % (self.__class__.__name__, self._name_)

    def __dir__(self):
        added_behavior = [
                m
                for cls in self.__class__.mro()
                for m in cls.__dict__
                if m[0] != '_'
                ]
        return (['__class__', '__doc__', '__module__'] + added_behavior)

    def __format__(self, format_spec):
        # mixed-in Enums should use the mixed-in type's __format__, otherwise
        # we can get strange results with the Enum name showing up instead of
        # the value

        # pure Enum branch
        if self._member_type_ is object:
            cls = str
            val = str(self)
        # mix-in branch
        else:
            cls = self._member_type_
            val = self._value_
        return cls.__format__(val, format_spec)

    def __hash__(self):
        return hash(self._name_)

    def __reduce_ex__(self, proto):
        return self.__class__, (self._value_, )

    # DynamicClassAttribute is used to provide access to the `name` and
    # `value` properties of enum members while keeping some measure of
    # protection from modification, while still allowing for an enumeration
    # to have members named `name` and `value`.  This works because enumeration
    # members are not set directly on the enum class -- __getattr__ is
    # used to look them up.

    @DynamicClassAttribute
    def name(self):
        """The name of the Enum member."""
        return self._name_

    @DynamicClassAttribute
    def value(self):
        """The value of the Enum member."""
        return self._value_


class IntEnum(int, Enum):
    """Enum where members are also (and must be) ints"""


def unique(enumeration):
    """Class decorator for enumerations ensuring unique member values."""
    duplicates = []
    for name, member in enumeration.__members__.items():
        if name != member.name:
            duplicates.append((name, member.name))
    if duplicates:
        alias_details = ', '.join(
                ["%s -> %s" % (alias, name) for (alias, name) in duplicates])
        raise ValueError('duplicate values found in %r: %s' %
                (enumeration, alias_details))
    return enumeration
