#!/usr/bin/python
# -- Content-Encoding: utf-8 --
"""
Provides utility methods used by the core implementation of javaobj.

Namely: logging methods, bytes/str/unicode converters

:authors: Thomas Calmant
:license: Apache License 2.0
:version: 0.4.3
:status: Alpha

..

    Copyright 2021 Thomas Calmant

    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.
"""

from __future__ import absolute_import

# Standard library
from typing import IO, Tuple  # noqa: F401
import gzip
import logging
import os
import struct
import sys

# Modified UTF-8 parser
from .modifiedutf8 import byte_to_int, decode_modified_utf8

# ------------------------------------------------------------------------------

# Module version
__version_info__ = (0, 4, 3)
__version__ = ".".join(str(x) for x in __version_info__)

# Documentation strings format
__docformat__ = "restructuredtext en"

# ------------------------------------------------------------------------------

# Setup the logger
_log = logging.getLogger("javaobj")


def log_debug(message, ident=0):
    """
    Logs a message at debug level

    :param message: Message to log
    :param ident: Number of indentation spaces
    """
    _log.debug("%s%s", " " * (ident * 2), message)


def log_error(message, ident=0):
    """
    Logs a message at error level

    :param message: Message to log
    :param ident: Number of indentation spaces
    """
    _log.error("%s%s", " " * (ident * 2), message)


# ------------------------------------------------------------------------------


def read_struct(data, fmt_str):
    # type: (bytes, str) -> Tuple
    """
    Reads input bytes and extract the given structure. Returns both the read
    elements and the remaining data

    :param data: Data as bytes
    :param fmt_str: Struct unpack format string
    :return: A tuple (results as tuple, remaining data)
    """
    size = struct.calcsize(fmt_str)
    return struct.unpack(fmt_str, data[:size]), data[size:]


def read_string(data, length_fmt="H"):
    # type: (bytes, str) -> Tuple[UNICODE_TYPE, bytes]
    """
    Reads a serialized string

    :param data: Bytes where to read the string from
    :param length_fmt: Structure format of the string length (H or Q)
    :return: The deserialized string
    """
    (length,), data = read_struct(data, ">{0}".format(length_fmt))
    ba, data = data[:length], data[length:]
    return to_unicode(ba), data


# ------------------------------------------------------------------------------


def java_data_fd(original_df):
    # type: (IO[bytes]) -> IO[bytes]
    """
    Ensures that the input file descriptor contains a Java serialized content.
    Automatically uncompresses GZipped data

    :param original_df: Input file descriptor
    :return: Input file descriptor or a fake one to access uncompressed data
    :raise IOError: Error reading input file
    """
    # Read the first bytes
    start_idx = original_df.tell()
    magic_header = [byte_to_int(x) for x in original_df.read(2)]  # type: ignore
    original_df.seek(start_idx, os.SEEK_SET)

    if magic_header[0] == 0xAC:
        # Consider we have a raw seralized stream: use it
        original_df.seek(start_idx, os.SEEK_SET)
        return original_df
    elif magic_header[0] == 0x1F and magic_header[1] == 0x8B:
        # Open the GZip file
        return gzip.GzipFile(fileobj=original_df, mode="rb")  # type: ignore
    else:
        # Let the parser raise the error
        return original_df


# ------------------------------------------------------------------------------


def hexdump(src, start_offset=0, length=16):
    # type: (str, int, int) -> str
    """
    Prepares an hexadecimal dump string

    :param src: A string containing binary data
    :param start_offset: The start offset of the source
    :param length: Length of a dump line
    :return: A dump string
    """
    hex_filter = "".join(
        (len(repr(chr(x))) == 3) and chr(x) or "." for x in range(256)
    )
    pattern = "{{0:04X}}   {{1:<{0}}}  {{2}}\n".format(length * 3)

    # Convert raw data to str (Python 3 compatibility)
    src = to_str(src, "latin-1")

    result = []
    for i in range(0, len(src), length):
        s = src[i : i + length]
        hexa = " ".join("{0:02X}".format(ord(x)) for x in s)
        printable = s.translate(hex_filter)
        result.append(pattern.format(i + start_offset, hexa, printable))

    return "".join(result)


# ------------------------------------------------------------------------------


if sys.version_info[0] >= 3:
    BYTES_TYPE = bytes  # pylint:disable=C0103
    UNICODE_TYPE = str  # pylint:disable=C0103
    unicode_char = chr  # pylint:disable=C0103

    def bytes_char(c):
        """
        Converts the given character to a bytes string
        """
        return bytes((c,))

    # Python 3 interpreter : bytes & str
    def to_bytes(data, encoding="UTF-8"):
        """
        Converts the given string to an array of bytes.
        Returns the first parameter if it is already an array of bytes.

        :param data: A unicode string
        :param encoding: The encoding of data
        :return: The corresponding array of bytes
        """
        if type(data) is bytes:  # pylint:disable=C0123
            # Nothing to do
            return data
        return data.encode(encoding)

    def to_str(data, encoding="UTF-8"):
        """
        Converts the given parameter to a string.
        Returns the first parameter if it is already an instance of ``str``.

        :param data: A string
        :param encoding: The encoding of data
        :return: The corresponding string
        """
        if type(data) is str:  # pylint:disable=C0123
            # Nothing to do
            return data
        try:
            return str(data, encoding)
        except UnicodeDecodeError:
            return decode_modified_utf8(data)[0]

    # Same operation
    to_unicode = to_str  # pylint:disable=C0103

    def read_to_str(data):
        """
        Concats all bytes into a string
        """
        return "".join(chr(char) for char in data)


else:
    BYTES_TYPE = str  # pylint:disable=C0103
    UNICODE_TYPE = (
        unicode  # pylint:disable=C0103,undefined-variable  # noqa: F821
    )
    unicode_char = (
        unichr  # pylint:disable=C0103,undefined-variable  # noqa: F821
    )
    bytes_char = chr  # pylint:disable=C0103

    # Python 2 interpreter : str & unicode
    def to_str(data, encoding="UTF-8"):
        """
        Converts the given parameter to a string.
        Returns the first parameter if it is already an instance of ``str``.

        :param data: A string
        :param encoding: The encoding of data
        :return: The corresponding string
        """
        if type(data) is str:  # pylint:disable=C0123
            # Nothing to do
            return data
        return data.encode(encoding)

    # Same operation
    to_bytes = to_str  # pylint:disable=C0103

    # Python 2 interpreter : str & unicode
    def to_unicode(data, encoding="UTF-8"):
        """
        Converts the given parameter to a string.
        Returns the first parameter if it is already an instance of ``str``.

        :param data: A string
        :param encoding: The encoding of data
        :return: The corresponding string
        """
        if type(data) is UNICODE_TYPE:  # pylint:disable=C0123
            # Nothing to do
            return data
        try:
            return data.decode(encoding)
        except UnicodeDecodeError:
            return decode_modified_utf8(data)[0]

    def read_to_str(data):
        """
        Nothing to do in Python 2
        """
        return data