import datetime
from django.core.exceptions import ValidationError
from django.db import models
from django.db.models import Q
from core.models.base import BaseModel
from core.models.account import AccountAddress


class Schedule(BaseModel):
    """
    Service schedules for accounts.
    """
    name = models.CharField(max_length=255, blank=True, null=True, verbose_name="Name")
    account_address = models.ForeignKey(AccountAddress, on_delete=models.PROTECT, related_name='schedules',
                                        verbose_name="Account Service Address", null=True)
    monday_service = models.BooleanField(default=False, verbose_name="Monday Service")
    tuesday_service = models.BooleanField(default=False, verbose_name="Tuesday Service")
    wednesday_service = models.BooleanField(default=False, verbose_name="Wednesday Service")
    thursday_service = models.BooleanField(default=False, verbose_name="Thursday Service")
    friday_service = models.BooleanField(default=False, verbose_name="Friday Service")
    saturday_service = models.BooleanField(default=False, verbose_name="Saturday Service")
    sunday_service = models.BooleanField(default=False, verbose_name="Sunday Service")
    weekend_service = models.BooleanField(default=False, verbose_name="Weekend Service",
                                          help_text=(
                                              "When enabled, represents a single service visit on Friday that can be performed "
                                              "any time between Friday-Sunday and verified by Monday morning. "
                                              "Individual Fri/Sat/Sun service flags must be disabled when this is enabled."))
    schedule_exception = models.TextField(blank=True, null=True, verbose_name="Schedule Exceptions",
                                          help_text=(
                                              "Notes about any exceptions or special requirements for this schedule"))
    start_date = models.DateField(verbose_name="Start Date", help_text="Date when this schedule becomes active")
    end_date = models.DateField(blank=True, null=True, verbose_name="End Date",
                                help_text="Optional date when this schedule expires")

    class Meta:
        ordering = ['-start_date']
        verbose_name = "Schedule"
        verbose_name_plural = "Schedules"
        indexes = [
            models.Index(fields=['account_address', 'start_date']),
            models.Index(fields=['weekend_service']),
        ]

    def __str__(self):
        return f"Schedule for {self.account_address.account.name} - {self.account_address.name if self.account_address.name else 'Primary Service Address'}"

    def clean(self):
        """Validate schedule configuration"""
        super().clean()

        if self.end_date and self.start_date > self.end_date:
            raise ValidationError({
                'end_date': "End date must be after start date"
            })

        start = self.start_date
        end = self.end_date or datetime.date.max

        qs = Schedule.objects.filter(account_address=self.account_address)
        if self.pk:
            qs = qs.exclude(pk=self.pk)

        overlaps = qs.filter(
            Q(end_date__isnull=True, start_date__lte=end) |
            Q(end_date__isnull=False, start_date__lte=end, end_date__gte=start)
        )

        if overlaps.exists():
            raise ValidationError("Schedule dates overlap with an existing schedule for this address.")

        # Validate weekend service configuration
        if self.weekend_service:
            weekend_days = [
                self.friday_service,
                self.saturday_service,
                self.sunday_service
            ]
            if any(weekend_days):
                raise ValidationError({
                    'weekend_service': "When weekend service is enabled, Friday, Saturday, "
                                       "and Sunday service flags must be disabled"
                })

        has_regular_service = any([
            self.monday_service,
            self.tuesday_service,
            self.wednesday_service,
            self.thursday_service,
            self.friday_service,
            self.saturday_service,
            self.sunday_service
        ])
        if not has_regular_service and not self.weekend_service:
            raise ValidationError(
                "At least one service day or weekend service must be selected"
            )