from django.db import models
from django.conf import settings
from django.urls import reverse
from django.utils import timezone
from django.core.validators import MinValueValidator, MaxValueValidator


class Service(models.Model):
    """Services that can be booked as appointments"""
    name = models.CharField(max_length=100)
    description = models.TextField(blank=True)
    duration = models.DurationField(help_text="Duration in minutes")
    price = models.DecimalField(max_digits=10, decimal_places=2)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(default=timezone.now)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        ordering = ['name']
    
    def __str__(self):
        return self.name


class StaffMember(models.Model):
    """Staff members who can be assigned to appointments"""
    user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    services = models.ManyToManyField(Service, related_name='staff_members')
    bio = models.TextField(blank=True)
    is_active = models.BooleanField(default=True)
    
    def __str__(self):
        return self.user.get_full_name() or self.user.username


class Appointment(models.Model):
    """Appointment model for scheduling services"""
    STATUS_CHOICES = [
        ('pending', 'Pending'),
        ('confirmed', 'Confirmed'),
        ('in_progress', 'In Progress'),
        ('completed', 'Completed'),
        ('cancelled', 'Cancelled'),
        ('no_show', 'No Show'),
    ]
    
    client = models.ForeignKey(
        settings.AUTH_USER_MODEL, 
        on_delete=models.CASCADE, 
        related_name='appointments'
    )
    service = models.ForeignKey(
        Service, 
        on_delete=models.PROTECT,
        related_name='appointments'
    )
    staff_member = models.ForeignKey(
        StaffMember,
        on_delete=models.PROTECT,
        related_name='appointments',
        null=True,
        blank=True
    )
    start_time = models.DateTimeField()
    end_time = models.DateTimeField()
    status = models.CharField(
        max_length=20, 
        choices=STATUS_CHOICES, 
        default='pending'
    )
    notes = models.TextField(blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        ordering = ['start_time']
        indexes = [
            models.Index(fields=['start_time', 'end_time']),
            models.Index(fields=['status']),
        ]
    
    def __str__(self):
        return f"{self.client.email} - {self.service.name} at {self.start_time}"
    
    def get_absolute_url(self):
        return reverse('appointments:appointment-detail', kwargs={'pk': self.pk})
    
    def save(self, *args, **kwargs):
        # Calculate end_time based on service duration if not set
        if not self.end_time and self.service:
            self.end_time = self.start_time + self.service.duration
        super().save(*args, **kwargs)


class AppointmentNote(models.Model):
    """Notes related to an appointment"""
    appointment = models.ForeignKey(
        Appointment, 
        on_delete=models.CASCADE, 
        related_name='notes_history'
    )
    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    
    class Meta:
        ordering = ['-created_at']
    
    def __str__(self):
        return f"Note by {self.author.username} for {self.appointment}"


class BusinessHours(models.Model):
    """Business hours configuration"""
    DAYS_OF_WEEK = [
        (0, 'Monday'),
        (1, 'Tuesday'),
        (2, 'Wednesday'),
        (3, 'Thursday'),
        (4, 'Friday'),
        (5, 'Saturday'),
        (6, 'Sunday'),
    ]
    
    day_of_week = models.IntegerField(choices=DAYS_OF_WEEK, unique=True)
    open_time = models.TimeField()
    close_time = models.TimeField()
    is_closed = models.BooleanField(default=False)
    
    class Meta:
        verbose_name_plural = 'Business Hours'
        ordering = ['day_of_week']
    
    def __str__(self):
        return f"{self.get_day_of_week_display()}: {'Closed' if self.is_closed else f'{self.open_time} - {self.close_time}'}"