# Copyright 2008-2018 pydicom authors. See LICENSE file for details.
"""Miscellaneous utility routines relating to hex and byte strings"""

from binascii import (a2b_hex, b2a_hex)

from pydicom import compat
from pydicom.compat import in_py2
from pydicom.charset import default_encoding


def hex2bytes(hexstring):
    """Return bytestring for a string of hex bytes separated by whitespace

    This is useful for creating specific byte sequences for testing, using
    python's implied concatenation for strings with comments allowed.
    Example:
        hex_string = (
         "08 00 32 10"     # (0008, 1032) SQ "Procedure Code Sequence"
         " 08 00 00 00"    # length 8
         " fe ff 00 e0"    # (fffe, e000) Item Tag
        )
        byte_string = hex2bytes(hex_string)
    Note in the example that all lines except the first must
    start with a space, alternatively the space could
    end the previous line.
    """

    # This works in both 3.x and 2.x because the first conditional evaluates to
    # true in 2.x so the difference in bytes constructor doesn't matter
    if isinstance(hexstring, bytes):
        return a2b_hex(hexstring.replace(b" ", b""))
    elif isinstance(hexstring, compat.string_types):
        return a2b_hex(bytes(hexstring.replace(" ", ""), default_encoding))
    raise TypeError('argument shall be bytes or string type')


def bytes2hex(byte_string):
    s = b2a_hex(byte_string)
    if not in_py2:
        s = s.decode()
    return " ".join(s[i:i + 2] for i in range(0, len(s), 2))
