#
# This file is part of pretix (Community Edition).
#
# Copyright (C) 2014-2020  Raphael Michel and contributors
# Copyright (C) 2020-today pretix GmbH and contributors
#
# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
# Public License as published by the Free Software Foundation in version 3 of the License.
#
# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
# this file, see <https://pretix.eu/about/en/license>.
#
# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
# <https://www.gnu.org/licenses/>.
#
import copy
from decimal import Decimal

from django.core.files import File
from django.db import models
from django.db.models.fields import DecimalField


class Thumbnail(models.Model):
    source = models.CharField(max_length=255)
    size = models.CharField(max_length=255)
    thumb = models.FileField(upload_to='pub/thumbs/', max_length=255)
    created = models.DateTimeField(auto_now_add=True, null=True)

    class Meta:
        unique_together = (('source', 'size'),)


def modelcopy(obj: models.Model, **kwargs):
    n = obj.__class__(**kwargs)
    for f in obj._meta.fields:
        val = getattr(obj, f.name)
        if isinstance(val, (models.Model, File)):
            setattr(n, f.name, copy.copy(val))
        else:
            setattr(n, f.name, copy.deepcopy(val))
    return n


# django 5 contains this in django.utils.choices.flatten_choices
def flatten_choices(choices):
    """Flatten choices by removing nested values."""
    for value_or_group, label_or_nested in choices or ():
        if isinstance(label_or_nested, (list, tuple)):
            yield from label_or_nested
        else:
            yield value_or_group, label_or_nested


def _normalize_decimal(d: Decimal) -> Decimal:
    """
    Strips trailing zeros, e.g.

    20.000 → 20
    20.010 → 20.01
    20.100 → 20.1

    But unlike of Decimal.normalize(), 20.000 will not become 2e+1
    """
    normalized = d.normalize()
    sign, digit, exponent = normalized.as_tuple()
    return normalized if exponent <= 0 else normalized.quantize(1)


class NormalizedDecimalField(DecimalField):
    """
    Variant of DecimalField that never outputs the trailing zeros, so we always have normalized decimals internally.
    Use this only for fields where the trailing zeros are pointless (e.g. percentages), not for monetary amounts.
    """

    def from_db_value(self, value, expression, connection):
        if value is not None:
            value = _normalize_decimal(value)
        return value