# (C) Copyright 2020-2021 by Rocky Bernstein
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program 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 this program; if not, write to the Free Software
#  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

import types
from copy import deepcopy

from xdis.codetype.code20 import Code2, Code2FieldTypes
from xdis.version_info import PYTHON_VERSION_TRIPLE, version_tuple_to_str

# Below, in the Python 2.4 branch "bytes" is "str" since there may not be a "bytes" type.
Code3FieldTypes = deepcopy(Code2FieldTypes)
Code3FieldTypes.update(
    {
        "co_kwonlyargcount": int,
    }
)


class Code3(Code2):
    """Class for a Python3 code object used when a Python interpreter less than 3 is
    working on Python3 bytecode. It also functions as an object that can be used
    to build or write a Python3 code object, since we allow mutable structures.
    When done mutating, call method freeze().

    For convenience in generating code objects, fields like
    `co_consts`, co_names which are (immutable) tuples in the end-result can be stored
    instead as (mutable) lists. Likewise the line number table `co_lnotab`
    can be stored as a simple list of offset, line_number tuples.
    """

    def __init__(
        self,
        co_argcount,
        co_kwonlyargcount,
        co_nlocals,
        co_stacksize,
        co_flags,
        co_code,
        co_consts,
        co_names,
        co_varnames,
        co_filename,
        co_name,
        co_firstlineno,
        co_lnotab,
        co_freevars,
        co_cellvars,
    ):
        super(Code3, self).__init__(
            co_argcount,
            co_nlocals,
            co_stacksize,
            co_flags,
            co_code,
            co_consts,
            co_names,
            co_varnames,
            co_filename,
            co_name,
            co_firstlineno,
            co_lnotab,
            co_freevars,
            co_cellvars,
        )
        self.co_kwonlyargcount = co_kwonlyargcount
        self.fieldtypes = Code3FieldTypes

        if type(self) == Code3:
            self.check()
        return

    def encode_lineno_tab(self):
        co_lnotab = b""

        prev_line_number = self.co_firstlineno
        prev_offset = 0
        for offset, line_number in self.co_lnotab:
            offset_diff = offset - prev_offset
            line_diff = line_number - prev_line_number
            prev_offset = offset
            prev_line_number = line_number
            while offset_diff >= 256:
                co_lnotab += bytearray([255, 0])
                offset_diff -= 255
            while line_diff >= 256:
                co_lnotab += bytearray([0, 255])
                line_diff -= 255
            if 0 <= line_diff <= 256:
                # FIXME: should warn bout dropping off a line number
                co_lnotab += bytearray([offset_diff, line_diff])

        self.co_lnotab = co_lnotab

    def freeze(self):
        for field in "co_consts co_names co_varnames co_freevars co_cellvars".split():
            val = getattr(self, field)
            if isinstance(val, list):
                setattr(self, field, tuple(val))

        # for field, typename in self.fieldtypes:
        #     pass

        if isinstance(self.co_lnotab, dict):
            d = self.co_lnotab
            self.co_lnotab = sorted(zip(d.keys(), d.values()), key=lambda tup: tup[0])
        if isinstance(self.co_lnotab, list):
            # We assume we have a list of tuples:
            # (offset, linenumber) which we convert
            # into the encoded format
            self.encode_lineno_tab()

        if isinstance(self.co_code, str) and PYTHON_VERSION_TRIPLE >= (3, 0):
            self.co_code = self.co_code.encode()

        if isinstance(self.co_lnotab, str):
            self.co_lnotab = self.co_lnotab.encode()

        return self

    def to_native(self):
        if not (3, 0) <= PYTHON_VERSION_TRIPLE < (3, 8):
            raise TypeError(
                "Python Interpreter needs to be in range 3.0..3.7; is %s"
                % version_tuple_to_str()
            )

        code = deepcopy(self)
        code.freeze()
        try:
            code.check()
        except AssertionError as e:
            raise TypeError(e)

        return types.CodeType(
            code.co_argcount,
            code.co_kwonlyargcount,
            code.co_nlocals,
            code.co_stacksize,
            code.co_flags,
            code.co_code,
            code.co_consts,
            code.co_names,
            code.co_varnames,
            code.co_filename,
            code.co_name,
            code.co_firstlineno,
            code.co_lnotab,
            code.co_freevars,
            code.co_cellvars,
        )
