from decimal import Decimal

from django.conf import settings
from django.utils.safestring import mark_safe


def format(number, decimal_sep, decimal_pos=None, grouping=0, thousand_sep='',
           force_grouping=False):
    """
    Gets a number (as a number or string), and returns it as a string,
    using formats defined as arguments:

    * decimal_sep: Decimal separator symbol (for example ".")
    * decimal_pos: Number of decimal positions
    * grouping: Number of digits in every group limited by thousand separator.
        For non-uniform digit grouping, it can be a sequence with the number
        of digit group sizes following the format used by the Python locale
        module in locale.localeconv() LC_NUMERIC grouping (e.g. (3, 2, 0)).
    * thousand_sep: Thousand separator symbol (for example ",")
    """
    use_grouping = settings.USE_L10N and settings.USE_THOUSAND_SEPARATOR
    use_grouping = use_grouping or force_grouping
    use_grouping = use_grouping and grouping != 0
    # Make the common case fast
    if isinstance(number, int) and not use_grouping and not decimal_pos:
        return mark_safe(str(number))
    # sign
    sign = ''
    if isinstance(number, Decimal):
        str_number = '{:f}'.format(number)
    else:
        str_number = str(number)
    if str_number[0] == '-':
        sign = '-'
        str_number = str_number[1:]
    # decimal part
    if '.' in str_number:
        int_part, dec_part = str_number.split('.')
        if decimal_pos is not None:
            dec_part = dec_part[:decimal_pos]
    else:
        int_part, dec_part = str_number, ''
    if decimal_pos is not None:
        dec_part = dec_part + ('0' * (decimal_pos - len(dec_part)))
    if dec_part:
        dec_part = decimal_sep + dec_part
    # grouping
    if use_grouping:
        try:
            # if grouping is a sequence
            intervals = list(grouping)
        except TypeError:
            # grouping is a single value
            intervals = [grouping, 0]
        active_interval = intervals.pop(0)
        int_part_gd = ''
        cnt = 0
        for digit in int_part[::-1]:
            if cnt and cnt == active_interval:
                if intervals:
                    active_interval = intervals.pop(0) or active_interval
                int_part_gd += thousand_sep[::-1]
                cnt = 0
            int_part_gd += digit
            cnt += 1
        int_part = int_part_gd[::-1]
    return sign + int_part + dec_part