"""Dominican invoice tax rounding policy.

Tryton's generic taxable mixin compensates the aggregate currency-rounding
remainder on the first non-zero tax.  That keeps the rounded aggregate equal
to the aggregate of the unrounded taxes, but it can change the reported value
of a specific Dominican tax (ITBIS, ISC or CDT).

Dominican fiscal documents state every tax in currency precision.  Each tax
must therefore retain its own rounded result; no residual is redistributed
between different tax liabilities or tax credits.
"""

from trytond.model import fields
from trytond.pool import PoolMeta


def round_taxes_independently(currency, taxes):
    """Round every tax amount without reallocating the aggregate residual."""
    if not currency:
        return
    for taxline in taxes.values():
        taxline.amount = currency.round(taxline.amount)


class IndependentTaxRoundingMixin:

    __slots__ = ()

    @fields.depends('currency')
    def _round_taxes(self, taxes):
        round_taxes_independently(self.currency, taxes)


class Invoice(IndependentTaxRoundingMixin, metaclass=PoolMeta):
    __name__ = 'account.invoice'


class InvoiceLine(IndependentTaxRoundingMixin, metaclass=PoolMeta):
    __name__ = 'account.invoice.line'