"""String parser."""

import hashlib
import re
import zlib


def process_string(original_string, variables):
    """Pattern replacement helper.

    Args:
        original_string (str): The original string
        variables (dict): Replacement variables

    Returns:
        str: Parsed string
    """
    md5 = False
    crc = False
    crc_pos = False

    if original_string[:5] == '[MD5]':
        md5 = True
        original_string = original_string[5:]
    elif original_string[:5] == '[CRC]':
        crc = True
        original_string = original_string[5:]
    elif original_string[:6] == '[CRC+]':
        crc_pos = True
        original_string = original_string[6:]

    breakdown = _split_string(original_string)
    return_string = _parse_vars(breakdown, variables)

    if md5:
        return_string = hashlib.md5(return_string.encode('utf-8')).hexdigest()
    elif crc:
        return_string = _get_signed_int(
            zlib.crc32(return_string.encode('utf-8')))
    elif crc_pos:
        return_string = zlib.crc32(return_string.encode('utf-8'))

    return return_string


def _split_string(original_string):
    """Splits string by specail characters.

    Args:
        original_string (str): The original string

    Returns:
        list: A list of the split string
    """
    pattern = '({(?:[^{}]+(?:"[^"]*"|\'[^\']*\')?)+})'
    return re.split(pattern, original_string)


def _parse_vars(breakdown, variables):
    """Replace variables with actual values.

    Args:
        breakdown (list): List of string chunks
        variables (dict): List of values for variable replacement

    Returns:
        str: Parsed string with actual values
    """
    return_string = ''

    for tmp_str in breakdown:
        if re.search('{.*}$', tmp_str):
            tmp_str = tmp_str.lstrip('{').rstrip('}')
            len_vars = ''

            if '(' in tmp_str:
                var_name, len_vars, *remainders = tmp_str.split('(')
            else:
                var_name = tmp_str

            var_value = variables[var_name]

            if len_vars:
                len_vars_arr = len_vars.strip(')').split(',')

                if len(len_vars_arr) == 1:
                    return_string = ''.join([
                        return_string,
                        '{:0{}d}'.format(
                            int(var_value), int(len_vars_arr[0]))])
                else:
                    first_pos = int(len_vars_arr[0])
                    second_pos = int(len_vars_arr[1]) + first_pos

                    return_string = ''.join([
                        return_string,
                        str(var_value)[first_pos:second_pos]])
            else:
                return_string = ''.join([return_string, str(var_value)])
        else:
            return_string = ''.join([return_string, tmp_str])

    return return_string


def _get_signed_int(input_int):
    """Returns a signed integer.

    Args:
        input_int (int): Unsinged int

    Returns:
        int: Signed int
    """
    sign_bit = (1 << 31)

    if input_int & sign_bit:
        invert = input_int ^ (2 ** 32 - 1)
        return -1 * (invert + 1)

    return input_int