# This file is part of account_debit_note.
# The COPYRIGHT file at the top level of this repository contains
# the full copyright notices and license terms.
import logging
from decimal import Decimal, ROUND_HALF_UP

from trytond.exceptions import UserError
from trytond.i18n import gettext
from trytond.model import ModelView, fields
from trytond.pool import Pool, PoolMeta
from trytond.pyson import Eval
from trytond.wizard import Button, StateAction, StateView, Wizard

logger = logging.getLogger(__name__)

_DEBIT_MODE = [
    ('full', 'Total (100%)'),
    ('percent', 'Percentage'),
    ('amount', 'Amount'),
]

_DEBIT_AMOUNT_BASIS = [
    ('untaxed', 'Without Taxes'),
    ('total', 'With Taxes'),
]

_ZERO = Decimal('0')
_ONE = Decimal('1')
_ONE_HUNDRED = Decimal('100')


def _decimal(value):
    """Return *value* as Decimal without binary floating-point artifacts."""
    if value is None:
        return _ZERO
    return Decimal(str(value))


def _round_decimal(value, scale):
    quantum = Decimal('1').scaleb(-scale)
    return value.quantize(quantum, rounding=ROUND_HALF_UP)


def _unit_price_scale(line, default=5):
    try:
        digits = line.__class__._fields['unit_price'].digits
        if isinstance(digits, (tuple, list)) and len(digits) == 2:
            return int(digits[1])
    except Exception:
        logger.debug(
            'Could not resolve unit_price digits for invoice line %s',
            getattr(line, 'id', None),
            exc_info=True)
    return int(default)


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

    @classmethod
    def _debit_compute_factor(cls, origin, mode, percent, amount, basis):
        if mode == 'full':
            return _ONE

        if mode == 'percent':
            if percent is None:
                raise UserError(gettext(
                    'account_debit_note.msg_missing_debit_percent'))

            percent = _decimal(percent)
            if percent <= _ZERO:
                raise UserError(gettext(
                    'account_debit_note.msg_invalid_debit_percent'))
            if percent <= _ONE:
                return percent
            if percent <= _ONE_HUNDRED:
                return percent / _ONE_HUNDRED
            raise UserError(gettext(
                'account_debit_note.msg_invalid_debit_percent'))

        if mode == 'amount':
            if amount is None:
                raise UserError(gettext(
                    'account_debit_note.msg_missing_debit_amount'))

            amount = _decimal(amount)
            if amount <= _ZERO:
                raise UserError(gettext(
                    'account_debit_note.msg_invalid_debit_amount'))

            if basis == 'untaxed':
                base = abs(_decimal(origin.untaxed_amount))
            else:
                base = abs(_decimal(origin.total_amount))

            if base <= _ZERO:
                raise UserError(gettext(
                    'account_debit_note.msg_invalid_debit_base'))

            return amount / base

        raise UserError(gettext(
            'account_debit_note.msg_invalid_debit_mode'))

    def _debit(self, **values):
        """
        Return a new invoice that increases the amount of this invoice.

        Tryton core exposes Invoice._credit(), which copies the invoice and
        reverses line signs. Reusing it keeps the same field-copying behavior
        as the core credit flow; the debit note then reverses those signs once
        more to restore the exact signs of the source invoice.
        """
        debit = self._credit(**values)
        self.__class__._debit_force_positive_sign(debit)
        return debit

    @classmethod
    def _debit_force_positive_sign(cls, debit_note):
        """Undo the sign reversal performed by Tryton's core ``_credit``.

        Do not use ``abs`` here: invoices may legitimately contain negative
        adjustment lines or manual taxes.  A debit note must preserve those
        relative signs rather than turn every component positive.
        """
        touched = []
        for line in debit_note.lines:
            if line.type != 'line':
                continue

            quantity = _decimal(line.quantity)
            new_quantity = -quantity

            if quantity != new_quantity:
                line.quantity = new_quantity
                touched.append(line)

        if touched and all(getattr(line, 'id', None) for line in touched):
            Line = Pool().get('account.invoice.line')
            Line.save(touched)

        for tax in getattr(debit_note, 'taxes', None) or []:
            tax.base = -_decimal(tax.base)
            tax.amount = -_decimal(tax.amount)

    @classmethod
    def _debit_apply_factor(cls, origin, debit_note, factor):
        if factor == _ONE:
            return

        lines = [line for line in debit_note.lines if line.type == 'line']
        touched = []

        for line in lines:
            unit_price = _decimal(line.unit_price)
            scale = _unit_price_scale(line)

            line.unit_price = _round_decimal(unit_price * factor, scale)
            touched.append(line)

        if touched and all(getattr(line, 'id', None) for line in touched):
            Line = Pool().get('account.invoice.line')
            Line.save(touched)

        cls._debit_adjust_last_line(origin, touched, factor)

    @classmethod
    def _debit_adjust_last_line(cls, origin, lines, factor):
        if not lines:
            return

        target_untaxed = _decimal(origin.untaxed_amount) * factor
        current_untaxed = sum(
            (_decimal(cls._debit_line_amount(line)) for line in lines),
            _ZERO)
        difference = target_untaxed - current_untaxed
        if abs(difference) < Decimal('0.0001'):
            return

        last = lines[-1]
        quantity = _decimal(last.quantity)
        if quantity == _ZERO:
            return

        new_unit_price = _decimal(last.unit_price) + difference / quantity
        last.unit_price = _round_decimal(
            new_unit_price, _unit_price_scale(last))
        if getattr(last, 'id', None):
            Line = Pool().get('account.invoice.line')
            Line.save([last])

    @classmethod
    def _debit_line_amount(cls, line):
        on_change_with_amount = getattr(line, 'on_change_with_amount', None)
        if on_change_with_amount:
            return on_change_with_amount()
        return _decimal(line.quantity) * _decimal(line.unit_price)

    @classmethod
    def _debit_recompute_taxes(cls, debit_note):
        if hasattr(debit_note, 'on_change_lines'):
            debit_note.on_change_lines()
        elif hasattr(debit_note, '_get_taxes'):
            InvoiceTax = Pool().get('account.invoice.tax')
            debit_note.taxes = [
                InvoiceTax(**values)
                for values in debit_note._get_taxes().values()
            ]

    @classmethod
    def _debit_prepare_note_from_origin(cls, origin, debit_note, values):
        """
        Extension hook for localization/fiscal modules.

        The base account_debit_note module only creates the accounting debit
        note. Fiscal and electronic fields must be provided by their owning
        modules.
        """
        return None

    @classmethod
    def debit(cls, invoices, **values):
        debit_mode = values.pop('debit_mode', None) or 'full'
        debit_percent = values.pop('debit_percent', None)
        debit_amount = values.pop('debit_amount', None)
        debit_amount_basis = values.pop('debit_amount_basis', None) or 'total'

        if debit_mode == 'amount' and len(invoices) != 1:
            raise UserError(gettext(
                'account_debit_note.msg_amount_multiple_invoices'))

        factors = [
            cls._debit_compute_factor(
                origin, debit_mode, debit_percent, debit_amount,
                debit_amount_basis)
            for origin in invoices
        ]

        new_invoices = [
            origin._debit(invoice_date=values.get('invoice_date'))
            for origin in invoices
        ]

        for origin, debit_note, factor in zip(invoices, new_invoices, factors):
            cls._debit_apply_factor(origin, debit_note, factor)
            cls._debit_recompute_taxes(debit_note)
            cls._debit_prepare_note_from_origin(origin, debit_note, values)

        cls.save(new_invoices)
        return new_invoices


class DebitInvoiceStart(ModelView):
    'Debit Invoice'
    __name__ = 'account.invoice.debit.start'

    invoice_date = fields.Date('Invoice Date')
    debit_mode = fields.Selection(
        _DEBIT_MODE, 'Debit Type', required=True)
    debit_percent = fields.Numeric(
        'Debit Percentage', digits=(16, 4),
        states={
            'invisible': Eval('debit_mode') != 'percent',
            'required': Eval('debit_mode') == 'percent',
        },
        depends=['debit_mode'])
    debit_amount = fields.Numeric(
        'Debit Amount', digits=(16, 2),
        states={
            'invisible': Eval('debit_mode') != 'amount',
            'required': Eval('debit_mode') == 'amount',
        },
        depends=['debit_mode'])
    debit_amount_basis = fields.Selection(
        _DEBIT_AMOUNT_BASIS, 'Amount Basis',
        states={
            'invisible': Eval('debit_mode') != 'amount',
            'required': Eval('debit_mode') == 'amount',
        },
        depends=['debit_mode'])
    @staticmethod
    def default_debit_mode():
        return 'full'

    @staticmethod
    def default_debit_amount_basis():
        return 'total'


class DebitInvoice(Wizard):
    'Debit Invoice'
    __name__ = 'account.invoice.debit'

    start = StateView('account.invoice.debit.start',
        'account_debit_note.debit_start_view_form', [
            Button('Cancel', 'end', 'tryton-cancel'),
            Button('Debit', 'debit', 'tryton-ok', default=True),
            ])
    debit = StateAction('account_invoice.act_invoice_form')

    def default_start(self, fields_):
        default = {
            'debit_mode': 'full',
            'debit_percent': None,
            'debit_amount': None,
            'debit_amount_basis': 'total',
            }

        return default

    @property
    def _debit_options(self):
        return {
            'invoice_date': self.start.invoice_date,
            'debit_mode': self.start.debit_mode,
            'debit_percent': self.start.debit_percent,
            'debit_amount': self.start.debit_amount,
            'debit_amount_basis': self.start.debit_amount_basis,
            }

    def do_debit(self, action):
        debit_invoices = self.model.debit(
            self.records, **self._debit_options)

        data = {'res_id': [i.id for i in debit_invoices]}
        if len(debit_invoices) == 1:
            action['views'].reverse()
        return action, data