from django.db import models
from django.utils.text import slugify
from django.urls import reverse


class Brand(models.Model):
    name = models.CharField(max_length=100, unique=True)
    slug = models.SlugField(max_length=100, unique=True, blank=True)
    logo = models.ImageField(upload_to='brands/', blank=True, null=True)
    description = models.TextField(blank=True)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ['name']

    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.name)
        super().save(*args, **kwargs)

    def __str__(self):
        return self.name


class Category(models.Model):
    name = models.CharField(max_length=100)
    slug = models.SlugField(max_length=100, unique=True, blank=True)
    image = models.ImageField(upload_to='categories/', blank=True, null=True)
    description = models.TextField(blank=True)
    parent = models.ForeignKey(
        'self', 
        on_delete=models.CASCADE, 
        null=True, 
        blank=True, 
        related_name='children'
    )
    order = models.PositiveIntegerField(default=0, help_text="Display order (lower numbers appear first)")
    is_active = models.BooleanField(default=True)
    show_in_menu = models.BooleanField(
        default=False, 
        help_text="Show this subcategory in the parent category's dropdown menu (max 10)"
    )
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        verbose_name = 'Category'
        verbose_name_plural = 'Categories'
        ordering = ['order', 'name']
    
    
class Product(models.Model):
    class Status(models.TextChoices):
        DRAFT = 'draft', 'Draft'
        ACTIVE = 'active', 'Active'
        OUT_OF_STOCK = 'out_of_stock', 'Out of Stock'
        DISCONTINUED = 'discontinued', 'Discontinued'

    name = models.CharField(max_length=255)
    slug = models.SlugField(max_length=255, unique=True, blank=True)
    sku = models.CharField(max_length=50, unique=True, help_text="Stock Keeping Unit")
    part_number = models.CharField(max_length=100, blank=True, help_text="OEM Part Number")
    is_top_rated = models.BooleanField(default=False, help_text="Show in Top Rated Products section on landing page (max 3)")
    
    short_description = models.TextField(max_length=500, blank=True)
    description = models.TextField(blank=True)
    
    category = models.ForeignKey(
        Category, 
        on_delete=models.SET_NULL, 
        null=True, 
        related_name='products'
    )
    brand = models.ForeignKey(
        Brand, 
        on_delete=models.SET_NULL, 
        null=True, 
        blank=True,
        related_name='products'
    )
    
    price = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
    sale_price = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)

    stock_quantity = models.PositiveIntegerField(default=0, blank=True, null=True)
    low_stock_threshold = models.PositiveIntegerField(default=10, blank=True, null=True)
    
    main_image = models.ImageField(upload_to='products/%Y/%m/', blank=True, null=True)
    
    compatible_vehicles = models.TextField(
        blank=True, 
        help_text="List compatible vehicle makes/models/years"
    )
    
    status = models.CharField(max_length=20, choices=Status.choices, default=Status.DRAFT)
    is_featured = models.BooleanField(default=False)
    
    meta_title = models.CharField(max_length=255, blank=True)
    meta_description = models.TextField(max_length=160, blank=True)
    
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['slug']),
            models.Index(fields=['sku']),
            models.Index(fields=['-created_at']),
        ]

    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.name)
        super().save(*args, **kwargs)

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('products:product_detail', kwargs={'slug': self.slug})

    @property
    def is_on_sale(self):
        return self.sale_price is not None and self.price is not None and self.sale_price < self.price

    @property
    def current_price(self):
        if self.is_on_sale:
            return self.sale_price
        return self.price

    @property
    def discount_percentage(self):
        if self.is_on_sale and self.price:
            return int(((self.price - self.sale_price) / self.price) * 100)
        return 0

    @property
    def is_in_stock(self):
        if self.stock_quantity is None:
            return True 
        return self.stock_quantity > 0

    @property
    def is_low_stock(self):
        if self.stock_quantity is None or self.low_stock_threshold is None:
            return False
        return self.stock_quantity <= self.low_stock_threshold


class ProductImage(models.Model):
    product = models.ForeignKey(
        Product, 
        on_delete=models.CASCADE, 
        related_name='images'
    )
    image = models.ImageField(upload_to='products/%Y/%m/')
    alt_text = models.CharField(max_length=255, blank=True)
    is_primary = models.BooleanField(default=False)
    order = models.PositiveIntegerField(default=0)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ['order', 'created_at']

    def __str__(self):
        return f"{self.product.name} - Image {self.order}"