from django.db import models
from django.utils.translation import gettext_lazy as _
from django.utils import timezone

class Category(models.Model):
    name_en = models.CharField(_("Name (English)"), max_length=100)
    name_ar = models.CharField(_("Name (Arabic)"), max_length=100)
    slug = models.SlugField(unique=True)

    class Meta:
        verbose_name_plural = _("Categories")

    def __str__(self):
        return f"{self.name_en} / {self.name_ar}"

class Unit(models.Model):
    name_en = models.CharField(_("Name (English)"), max_length=50)
    name_ar = models.CharField(_("Name (Arabic)"), max_length=50)
    short_name = models.CharField(_("Short Name"), max_length=10)

    def __str__(self):
        return f"{self.name_en} / {self.name_ar}"

class Product(models.Model):
    category = models.ForeignKey(Category, on_delete=models.CASCADE, related_name="products")
    unit = models.ForeignKey(Unit, on_delete=models.SET_NULL, null=True, blank=True, related_name="products")
    supplier = models.ForeignKey('Supplier', on_delete=models.SET_NULL, null=True, blank=True, related_name="products")
    name_en = models.CharField(_("Name (English)"), max_length=200)
    name_ar = models.CharField(_("Name (Arabic)"), max_length=200)
    sku = models.CharField(_("Barcode/SKU"), max_length=50, unique=True)
    description = models.TextField(_("Description"), blank=True)
    cost_price = models.DecimalField(_("Cost Price"), max_digits=12, decimal_places=3, default=0)
    price = models.DecimalField(_("Sale Price"), max_digits=12, decimal_places=3)
    vat = models.DecimalField(_("VAT (%)"), max_digits=5, decimal_places=2, default=0)
    opening_stock = models.PositiveIntegerField(_("Opening Stock"), default=0)
    stock_quantity = models.PositiveIntegerField(_("In Stock"), default=0)
    image = models.ImageField(_("Product Image"), upload_to="product_images/", blank=True, null=True)
    is_active = models.BooleanField(_("Active"), default=True)
    created_at = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f"{self.name_en} ({self.sku})"

class Customer(models.Model):
    name = models.CharField(_("Name"), max_length=200)
    phone = models.CharField(_("Phone"), max_length=20, blank=True)
    email = models.EmailField(_("Email"), blank=True)
    address = models.TextField(_("Address"), blank=True)

    def __str__(self):
        return self.name

class Supplier(models.Model):
    name = models.CharField(_("Name"), max_length=200)
    contact_person = models.CharField(_("Contact Person"), max_length=200, blank=True)
    phone = models.CharField(_("Phone"), max_length=20, blank=True)

    def __str__(self):
        return self.name

class Sale(models.Model):
    PAYMENT_TYPE_CHOICES = [
        ('cash', _('Cash')),
        ('credit', _('Credit')),
        ('partial', _('Partial')),
    ]
    STATUS_CHOICES = [
        ('paid', _('Paid')),
        ('partial', _('Partial')),
        ('unpaid', _('Unpaid')),
    ]
    
    customer = models.ForeignKey(Customer, on_delete=models.SET_NULL, null=True, blank=True, related_name="sales")
    invoice_number = models.CharField(_("Invoice Number"), max_length=50, blank=True)
    total_amount = models.DecimalField(_("Total Amount"), max_digits=15, decimal_places=3)
    paid_amount = models.DecimalField(_("Paid Amount"), max_digits=15, decimal_places=3, default=0)
    balance_due = models.DecimalField(_("Balance Due"), max_digits=15, decimal_places=3, default=0)
    discount = models.DecimalField(_("Discount"), max_digits=15, decimal_places=3, default=0)
    payment_type = models.CharField(_("Payment Type"), max_length=20, choices=PAYMENT_TYPE_CHOICES, default='cash')
    status = models.CharField(_("Status"), max_length=20, choices=STATUS_CHOICES, default='paid')
    due_date = models.DateField(_("Due Date"), null=True, blank=True)
    notes = models.TextField(_("Notes"), blank=True)
    created_at = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f"Sale #{self.id} - {self.customer.name if self.customer else 'Guest'}"

    def update_balance(self):
        payments_total = self.payments.aggregate(total=models.Sum('amount'))['total'] or 0
        self.paid_amount = payments_total
        self.balance_due = self.total_amount - self.paid_amount
        if self.balance_due <= 0:
            self.status = 'paid'
        elif self.paid_amount > 0:
            self.status = 'partial'
        else:
            self.status = 'unpaid'
        self.save()

class SaleItem(models.Model):
    sale = models.ForeignKey(Sale, on_delete=models.CASCADE, related_name="items")
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField(_("Quantity"))
    unit_price = models.DecimalField(_("Unit Price"), max_digits=12, decimal_places=3)
    line_total = models.DecimalField(_("Line Total"), max_digits=15, decimal_places=3)

    def __str__(self):
        return f"{self.product.name_en} x {self.quantity}"

class SalePayment(models.Model):
    sale = models.ForeignKey(Sale, on_delete=models.CASCADE, related_name="payments")
    amount = models.DecimalField(_("Amount"), max_digits=15, decimal_places=3)
    payment_date = models.DateField(_("Payment Date"), default=timezone.now)
    payment_method = models.CharField(_("Payment Method"), max_length=50, default="Cash")
    notes = models.TextField(_("Notes"), blank=True)

    def __str__(self):
        return f"Payment of {self.amount} for Sale #{self.sale.id}"

class Purchase(models.Model):
    PAYMENT_TYPE_CHOICES = [
        ('cash', _('Cash')),
        ('credit', _('Credit')),
        ('partial', _('Partial')),
    ]
    STATUS_CHOICES = [
        ('paid', _('Paid')),
        ('partial', _('Partial')),
        ('unpaid', _('Unpaid')),
    ]
    
    supplier = models.ForeignKey(Supplier, on_delete=models.SET_NULL, null=True, related_name="purchases")
    invoice_number = models.CharField(_("Invoice Number"), max_length=50, blank=True)
    total_amount = models.DecimalField(_("Total Amount"), max_digits=15, decimal_places=3)
    paid_amount = models.DecimalField(_("Paid Amount"), max_digits=15, decimal_places=3, default=0)
    balance_due = models.DecimalField(_("Balance Due"), max_digits=15, decimal_places=3, default=0)
    payment_type = models.CharField(_("Payment Type"), max_length=20, choices=PAYMENT_TYPE_CHOICES, default='cash')
    status = models.CharField(_("Status"), max_length=20, choices=STATUS_CHOICES, default='paid')
    due_date = models.DateField(_("Due Date"), null=True, blank=True)
    notes = models.TextField(_("Notes"), blank=True)
    created_at = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f"Purchase #{self.id} - {self.supplier.name if self.supplier else 'N/A'}"

    def update_balance(self):
        payments_total = self.payments.aggregate(total=models.Sum('amount'))['total'] or 0
        self.paid_amount = payments_total
        self.balance_due = self.total_amount - self.paid_amount
        if self.balance_due <= 0:
            self.status = 'paid'
        elif self.paid_amount > 0:
            self.status = 'partial'
        else:
            self.status = 'unpaid'
        self.save()

class PurchaseItem(models.Model):
    purchase = models.ForeignKey(Purchase, on_delete=models.CASCADE, related_name="items")
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField(_("Quantity"))
    cost_price = models.DecimalField(_("Cost Price"), max_digits=12, decimal_places=3)
    line_total = models.DecimalField(_("Line Total"), max_digits=15, decimal_places=3)

    def __str__(self):
        return f"{self.product.name_en} x {self.quantity}"

class PurchasePayment(models.Model):
    purchase = models.ForeignKey(Purchase, on_delete=models.CASCADE, related_name="payments")
    amount = models.DecimalField(_("Amount"), max_digits=15, decimal_places=3)
    payment_date = models.DateField(_("Payment Date"), default=timezone.now)
    payment_method = models.CharField(_("Payment Method"), max_length=50, default="Cash")
    notes = models.TextField(_("Notes"), blank=True)

    def __str__(self):
        return f"Payment of {self.amount} for Purchase #{self.purchase.id}"

class SystemSetting(models.Model):
    business_name = models.CharField(_("Business Name"), max_length=200, default="Meezan Accounting")
    address = models.TextField(_("Address"), blank=True)
    phone = models.CharField(_("Phone"), max_length=20, blank=True)
    email = models.EmailField(_("Email"), blank=True)
    currency_symbol = models.CharField(_("Currency Symbol"), max_length=10, default="OMR")
    tax_rate = models.DecimalField(_("Tax Rate (%)"), max_digits=5, decimal_places=2, default=0)
    logo = models.ImageField(_("Logo"), upload_to="business_logos/", blank=True, null=True)
    vat_number = models.CharField(_("VAT Number"), max_length=50, blank=True)
    registration_number = models.CharField(_("Registration Number"), max_length=50, blank=True)

    def __str__(self):
        return self.business_name