"""Balance-only corrections, deliberately unrelated to payroll input lines."""

import uuid
from decimal import Decimal

from django.conf import settings
from django.core.exceptions import ValidationError
from django.core.validators import MinValueValidator
from django.db import models

from finance.enums import PayrollCarryoverDirection


class PayrollBalanceAdjustment(models.Model):
    employee = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.PROTECT,
        related_name="payroll_balance_adjustments",
    )
    effective_period = models.ForeignKey(
        "finance.PayrollPeriod",
        on_delete=models.PROTECT,
        related_name="balance_adjustments",
    )
    source_period = models.ForeignKey(
        "finance.PayrollPeriod",
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name="referenced_balance_adjustments",
    )
    direction = models.CharField(
        max_length=20, choices=PayrollCarryoverDirection.choices
    )
    amount = models.DecimalField(
        max_digits=19,
        decimal_places=2,
        validators=[MinValueValidator(Decimal("0.01"))],
    )
    reason = models.CharField(max_length=1000, blank=True)
    request_id = models.UUIDField(default=uuid.uuid4, unique=True, editable=False)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.PROTECT,
        related_name="payroll_balance_adjustments_created",
    )
    created_at = models.DateTimeField(auto_now_add=True)
    voided_at = models.DateTimeField(null=True, blank=True)
    voided_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name="payroll_balance_adjustments_voided",
    )
    void_reason = models.CharField(max_length=1000, blank=True)

    class Meta:
        ordering = ["-effective_period__date_from", "-created_at", "-pk"]
        verbose_name = "Ручная корректировка остатка"
        verbose_name_plural = "Ручные корректировки остатков"
        constraints = [
            models.CheckConstraint(
                condition=models.Q(amount__gt=0),
                name="balance_adjustment_positive",
            ),
            models.CheckConstraint(
                condition=models.Q(direction__in=["company_owes", "employee_owes"]),
                name="balance_adjustment_direction",
            ),
            models.CheckConstraint(
                condition=(
                    models.Q(
                        voided_at__isnull=True, voided_by__isnull=True, void_reason=""
                    )
                    | models.Q(voided_at__isnull=False, voided_by__isnull=False)
                ),
                name="balance_adjustment_void_consistent",
            ),
        ]

    @property
    def contribution(self):
        return self.amount if self.direction == "company_owes" else -self.amount

    def clean(self):
        super().clean()
        if self.source_period_id and self.effective_period_id:
            if self.source_period.currency != self.effective_period.currency:
                raise ValidationError(
                    {"source_period": "Валюты периодов должны совпадать."}
                )
            if self.source_period.date_to >= self.effective_period.date_from:
                raise ValidationError(
                    {"source_period": "Выберите более ранний период."}
                )