#     Copyright 2019, Kay Hayen, mailto:kay.hayen@gmail.com
#
#     Part of "Nuitka", an optimizing Python compiler that is compatible and
#     integrates with CPython, but also works on its own.
#
#     Licensed under the Apache License, Version 2.0 (the "License");
#     you may not use this file except in compliance with the License.
#     You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#     Unless required by applicable law or agreed to in writing, software
#     distributed under the License is distributed on an "AS IS" BASIS,
#     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#     See the License for the specific language governing permissions and
#     limitations under the License.
#
""" Specification record for future flags.

A source reference also implies a specific set of future flags in use by the
parser at that location. Can be different inside a module due to e.g. the
in-lining of "exec" statements with their own future imports, or in-lining of
code from other modules.
"""

from nuitka.PythonVersions import python_version
from nuitka.utils.InstanceCounters import counted_del, counted_init

# These defaults have changed with Python versions.
_future_division_default = python_version >= 300
_future_absolute_import_default = python_version >= 300
_future_generator_stop_default = python_version >= 370
_future_annotations_default = python_version >= 400


class FutureSpec(object):
    __slots__ = (
        "future_division",
        "unicode_literals",
        "absolute_import",
        "future_print",
        "barry_bdfl",
        "generator_stop",
        "future_annotations",
    )

    @counted_init
    def __init__(self):
        self.future_division = _future_division_default
        self.unicode_literals = False
        self.absolute_import = _future_absolute_import_default
        self.future_print = False
        self.barry_bdfl = False
        self.generator_stop = _future_generator_stop_default
        self.future_annotations = _future_annotations_default

    __del__ = counted_del()

    def __repr__(self):
        return "<FutureSpec %s>" % ",".join(self.asFlags())

    def clone(self):
        result = FutureSpec()

        result.future_division = self.future_division
        result.unicode_literals = self.unicode_literals
        result.absolute_import = self.absolute_import
        result.future_print = self.future_print
        result.barry_bdfl = self.barry_bdfl
        result.generator_stop = self.generator_stop
        result.future_annotations = result.future_annotations

        return result

    def isFutureDivision(self):
        return self.future_division

    def enableFutureDivision(self):
        self.future_division = True

    def isFuturePrint(self):
        return self.future_print

    def enableFuturePrint(self):
        self.future_print = True

    def enableUnicodeLiterals(self):
        self.unicode_literals = True

    def enableAbsoluteImport(self):
        self.absolute_import = True

    def enableBarry(self):
        self.barry_bdfl = True

    def enableGeneratorStop(self):
        self.generator_stop = True

    def isAbsoluteImport(self):
        return self.absolute_import

    def isGeneratorStop(self):
        return self.generator_stop

    def enableFutureAnnotations(self):
        self.future_annotations = True

    def isFutureAnnotations(self):
        return self.future_annotations

    def asFlags(self):
        """ Create a list of C identifiers to represent the flag values.

            This is for use in code generation and to restore from
            saved modules.
        """

        result = []

        if python_version < 300 and self.future_division:
            result.append("CO_FUTURE_DIVISION")

        if self.unicode_literals:
            result.append("CO_FUTURE_UNICODE_LITERALS")

        if python_version < 300 and self.absolute_import:
            result.append("CO_FUTURE_ABSOLUTE_IMPORT")

        if python_version < 300 and self.future_print:
            result.append("CO_FUTURE_PRINT_FUNCTION")

        if python_version >= 300 and self.barry_bdfl:
            result.append("CO_FUTURE_BARRY_AS_BDFL")

        if 350 <= python_version < 370 and self.generator_stop:
            result.append("CO_FUTURE_GENERATOR_STOP")

        if python_version >= 370 and self.future_annotations:
            result.append("CO_FUTURE_ANNOTATIONS")

        return tuple(result)


def fromFlags(flags):
    flags = flags.split(",")
    if "" in flags:
        flags.remove("")

    result = FutureSpec()

    if "CO_FUTURE_DIVISION" in flags:
        result.enableFutureDivision()

    if "CO_FUTURE_UNICODE_LITERALS" in flags:
        result.enableUnicodeLiterals()

    if "CO_FUTURE_ABSOLUTE_IMPORT" in flags:
        result.enableAbsoluteImport()

    if "CO_FUTURE_PRINT_FUNCTION" in flags:
        result.enableFuturePrint()

    if "CO_FUTURE_BARRY_AS_BDFL" in flags:
        result.enableBarry()

    if "CO_FUTURE_GENERATOR_STOP" in flags:
        result.enableGeneratorStop()

    # Check if we are going to give similar results than what we got.
    assert tuple(result.asFlags()) == tuple(flags), (result, result.asFlags(), flags)

    return result
