38086-vm/core/views.py

from django.db import models, transaction
from django.utils.translation import gettext_lazy as _
from django.utils import timezone
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.dispatch import receiver
import base64
import os
from django.conf import settings as django_settings
from django.utils.translation import gettext as _, get_language
from django.utils.formats import date_format
from .utils import number_to_words_en, send_whatsapp_document
from django.core.paginator import Paginator
import decimal
from django.contrib.auth.models import User, Group, Permission
from django.urls import reverse
import random
import string
from django.shortcuts import render, get_object_or_404, redirect
from django.db.models import Sum, Count, F, Q
from django.db.models.functions import TruncDate, TruncMonth
from django.http import JsonResponse, HttpResponse
from django.views.decorators.csrf import csrf_exempt
from django.contrib.auth.decorators import login_required
from .models import (
    Expense, ExpenseCategory,
    Product, Sale, Category, Unit, Customer, Supplier, 
    Purchase, PurchaseItem, PurchasePayment, 
    SaleItem, SalePayment, SystemSetting,
    Quotation, QuotationItem,
    SaleReturn, SaleReturnItem, PurchaseReturn, PurchaseReturnItem, PurchaseOrder, PurchaseOrderItem,
    PaymentMethod, HeldSale, LoyaltyTier, LoyaltyTransaction,
    Device, CashierCounterRegistry, CashierSession
)
import json
from datetime import timedelta
from django.utils import timezone
from django.contrib import messages
from django.utils.text import slugify
import openpyxl
import csv

@login_required
def index(request):
    """
    Enhanced Meezan Dashboard View
    """
    total_products = Product.objects.count()
    total_sales_count = Sale.objects.count()
    total_sales_amount = Sale.objects.aggregate(total=Sum('total_amount'))['total'] or 0
    total_customers = Customer.objects.count()
    
    site_settings = SystemSetting.objects.first()

    # --- Charts & Analytics Data ---
    
    # 1. Monthly Sales (Last 6 months)
    today = timezone.now().date()
    six_months_ago = today - timedelta(days=180)
    
    monthly_sales = Sale.objects.filter(created_at__date__gte=six_months_ago)\
        .annotate(month=TruncMonth('created_at'))\
        .values('month')\
        .annotate(total=Sum('total_amount'))\
        .order_by('month')
        
    monthly_labels = []
    monthly_data = []
    
    current_lang = get_language()

    for entry in monthly_sales:
        dt = entry['month']
        # Format: "Jan 2026" or localized equivalent
        monthly_labels.append(date_format(dt, "M Y"))
        monthly_data.append(float(entry['total']))
        
    # 2. Daily Sales (Last 7 days)
    last_week = today - timedelta(days=7)
    daily_sales = Sale.objects.filter(created_at__date__gte=last_week)\
        .annotate(day=TruncDate('created_at'))\
        .values('day')\
        .annotate(total=Sum('total_amount'))\
        .order_by('day')
        
    chart_labels = []
    chart_data = []
    
    # Fill in missing days for a smooth line chart
    days_map = {entry['day']: entry['total'] for entry in daily_sales}
    for i in range(7):
        d = last_week + timedelta(days=i)
        chart_labels.append(date_format(d, "M d")) # "Feb 07"
        chart_data.append(float(days_map.get(d, 0)))

    # 3. Sales by Category
    category_sales = SaleItem.objects.values(
        'product__category__name_en', 
        'product__category__name_ar'
    ).annotate(total=Sum('line_total')).order_by('-total')[:5]
    
    category_labels = []
    category_data = []
    
    for item in category_sales:
        name_en = item['product__category__name_en'] or "Uncategorized"
        name_ar = item['product__category__name_ar'] or name_en
        
        label = name_ar if current_lang == 'ar' else name_en
        category_labels.append(label)
        category_data.append(float(item['total']))
        
    # 4. Top Selling Products
    top_products = SaleItem.objects.values(
        'product__name_en', 
        'product__name_ar'
    ).annotate(
        total_qty=Sum('quantity'),
        total_rev=Sum('line_total')
    ).order_by('-total_qty')[:5]

    # 5. Payment Methods
    payment_stats = SalePayment.objects.values('payment_method_name').annotate(count=Count('id'))
    payment_labels = []
    payment_data = []
    
    for stat in payment_stats:
        method_name = stat['payment_method_name']
        
        # Simple translation/mapping for known methods
        if method_name:
            if method_name.lower() == 'cash':
                label = _('Cash')
            elif method_name.lower() == 'card':
                label = _('Card')
            else:
                label = method_name
        else:
            label = _('Unknown')
            
        payment_labels.append(str(label))
        payment_data.append(stat['count'])

    # --- Inventory Alerts ---
    low_stock_threshold = 10
    low_stock_products = Product.objects.filter(stock_quantity__lte=F('min_stock_level')).select_related('category')[:5]
    low_stock_count = Product.objects.filter(stock_quantity__lte=F('min_stock_level')).count()
    
    expired_count = Product.objects.filter(expiry_date__lt=today).count()

    # --- Recent Transactions ---
    recent_sales = Sale.objects.select_related('customer', 'created_by').order_by('-created_at')[:5]

    context = {
        'total_products': total_products,
        'total_sales_count': total_sales_count,
        'total_sales_amount': total_sales_amount,
        'total_customers': total_customers,
        'site_settings': site_settings,
        'monthly_labels': json.dumps(monthly_labels),
        'monthly_data': json.dumps(monthly_data),
        'chart_labels': json.dumps(chart_labels),
        'chart_data': json.dumps(chart_data),
        'category_labels': json.dumps(category_labels),
        'category_data': json.dumps(category_data),
        'top_products': top_products,
        'payment_labels': json.dumps(payment_labels),
        'payment_data': json.dumps(payment_data),
        'low_stock_products': low_stock_products,
        'low_stock_count': low_stock_count,
        'expired_count': expired_count,
        'recent_sales': recent_sales,
    }
    return render(request, 'core/index.html', context)

@login_required
def inventory(request):
    products = Product.objects.all().order_by('-id')
    categories = Category.objects.all()
    units = Unit.objects.all()
    
    # Filter by Category
    category_id = request.GET.get('category')
    if category_id:
        products = products.filter(category_id=category_id)

    # Filter by Search
    search_query = request.GET.get('search')
    if search_query:
        products = products.filter(
            Q(name_en__icontains=search_query) | 
            Q(name_ar__icontains=search_query) |
            Q(sku__icontains=search_query)
        )
        
    paginator = Paginator(products, 25)
    page_number = request.GET.get('page')
    page_obj = paginator.get_page(page_number)
    
    context = {
        'products': page_obj,
        'categories': categories,
        'units': units,
    }
    return render(request, 'core/inventory.html', context)

@login_required
def customers(request):
    customers = Customer.objects.all().order_by('-id')
    paginator = Paginator(customers, 25)
    return render(request, 'core/customers.html', {'customers': paginator.get_page(request.GET.get('page'))})

@login_required
def suppliers(request):
    suppliers = Supplier.objects.all().order_by('-id')
    paginator = Paginator(suppliers, 25)
    return render(request, 'core/suppliers.html', {'suppliers': paginator.get_page(request.GET.get('page'))})

@login_required
def purchases(request):
    purchases = Purchase.objects.all().order_by('-created_at')
    paginator = Paginator(purchases, 25)
    return render(request, 'core/purchases.html', {'purchases': paginator.get_page(request.GET.get('page'))})

@login_required
def purchase_detail(request, pk):
    purchase = get_object_or_404(Purchase, pk=pk)
    return render(request, 'core/purchase_detail.html', {'purchase': purchase, 'settings': SystemSetting.objects.first()})

@login_required
def purchase_create(request):
    # Stub for purchase creation - redirects to list for now
    return redirect('purchases')

@login_required
def add_product(request):
    if request.method == 'POST':
        # Quick add logic for simplified form
        name_en = request.POST.get('name_en')
        sku = request.POST.get('sku')
        price = request.POST.get('price')
        cost_price = request.POST.get('cost_price')
        stock = request.POST.get('stock_quantity')
        category_id = request.POST.get('category')
        
        try:
            Product.objects.create(
                name_en=name_en, sku=sku, price=price, cost_price=cost_price,
                stock_quantity=stock, category_id=category_id,
                created_by=request.user
            )
            messages.success(request, 'Product added successfully.')
        except Exception as e:
            messages.error(request, str(e))
            
    return redirect('inventory')

@login_required
def edit_product(request, pk):
    product = get_object_or_404(Product, pk=pk)
    if request.method == 'POST':
        product.name_en = request.POST.get('name_en')
        product.name_ar = request.POST.get('name_ar')
        product.sku = request.POST.get('sku')
        product.price = request.POST.get('price')
        product.cost_price = request.POST.get('cost_price')
        product.stock_quantity = request.POST.get('stock_quantity')
        product.min_stock_level = request.POST.get('min_stock_level') or 0
        product.category_id = request.POST.get('category')
        product.save()
        messages.success(request, 'Product updated.')
        return redirect('inventory')
    
    # Render edit form if needed, but for now redirecting
    return redirect('inventory')

@login_required
def delete_product(request, pk):
    product = get_object_or_404(Product, pk=pk)
    product.delete()
    messages.success(request, 'Product deleted.')
    return redirect('inventory')

@login_required
def barcode_labels(request):
    # Logic to print barcodes
    return render(request, 'core/barcode_labels.html')

@login_required
def import_products(request):
    # Logic to import from Excel
    return redirect('inventory')

@login_required
def pos(request):
    # Ensure a session is active for this user/device
    # Check if this user has an open session
    # For now, we'll just show the POS
    
    products = Product.objects.filter(is_active=True).select_related('category')
    categories = Category.objects.all()
    customers = Customer.objects.all()
    payment_methods = PaymentMethod.objects.filter(is_active=True)
    settings = SystemSetting.objects.first()
    
    context = {
        'products': products,
        'categories': categories,
        'customers': customers,
        'payment_methods': payment_methods,
        'settings': settings,
    }
    return render(request, 'core/pos.html', context)

@login_required
def customer_display(request):
    return render(request, 'core/customer_display.html')

# --- Reports ---
@login_required
def reports(request):
    return render(request, 'core/reports.html')

@login_required
def customer_statement(request):
    customers = Customer.objects.all()
    selected_customer = None
    transactions = []
    
    if request.GET.get('customer'):
        selected_customer = get_object_or_404(Customer, pk=request.GET.get('customer'))
        # Gather sales, payments, etc.
        sales = Sale.objects.filter(customer=selected_customer).annotate(type=models.Value('Sale', output_field=models.CharField()))
        payments = SalePayment.objects.filter(sale__customer=selected_customer).annotate(type=models.Value('Payment', output_field=models.CharField()))
        # Merge and sort by date... (Simplified)
        transactions = list(sales) + list(payments)
        transactions.sort(key=lambda x: x.created_at, reverse=True)

    return render(request, 'core/customer_statement.html', {'customers': customers, 'selected_customer': selected_customer, 'transactions': transactions})

@login_required
def supplier_statement(request):
    suppliers = Supplier.objects.all()
    return render(request, 'core/supplier_statement.html', {'suppliers': suppliers})

@login_required
def cashflow_report(request):
    sales = Sale.objects.all()
    expenses = Expense.objects.all()
    purchases = Purchase.objects.all()
    if request.GET.get('start_date'):
        sales = sales.filter(created_at__date__gte=request.GET.get('start_date'))
        expenses = expenses.filter(date__gte=request.GET.get('start_date'))
        purchases = purchases.filter(created_at__date__gte=request.GET.get('start_date'))
    if request.GET.get('end_date'):
        sales = sales.filter(created_at__date__lte=request.GET.get('end_date'))
        expenses = expenses.filter(date__lte=request.GET.get('end_date'))
        purchases = purchases.filter(created_at__date__lte=request.GET.get('end_date'))
    total_sales = sales.aggregate(total=Sum('total_amount'))['total'] or 0
    total_expenses = expenses.aggregate(total=Sum('amount'))['total'] or 0
    total_purchases = purchases.aggregate(total=Sum('total_amount'))['total'] or 0
    return render(request, 'core/cashflow_report.html', {'total_sales': total_sales, 'total_expenses': total_expenses, 'total_purchases': total_purchases, 'net_profit': total_sales - total_expenses - total_purchases})

@login_required
def invoice_list(request):
    sales = Sale.objects.all().order_by('-created_at')
    
    # Filter by date range
    start_date = request.GET.get('start_date')
    end_date = request.GET.get('end_date')
    if start_date:
        sales = sales.filter(created_at__date__gte=start_date)
    if end_date:
        sales = sales.filter(created_at__date__lte=end_date)
        
    # Filter by customer
    customer_id = request.GET.get('customer')
    if customer_id:
        sales = sales.filter(customer_id=customer_id)
        
    # Filter by status
    status = request.GET.get('status')
    if status:
        sales = sales.filter(status=status)

    paginator = Paginator(sales, 25)
    
    context = {
        'sales': paginator.get_page(request.GET.get('page')),
        'customers': Customer.objects.all(),
        'payment_methods': PaymentMethod.objects.filter(is_active=True),
        'site_settings': SystemSetting.objects.first(),
    }
    return render(request, 'core/invoices.html', context)

@login_required
def invoice_detail(request, pk):
    return render(request, 'core/invoice_detail.html', {'sale': get_object_or_404(Sale, pk=pk), 'settings': SystemSetting.objects.first()})

@login_required
def invoice_create(request):
    customers = Customer.objects.all()
    products = Product.objects.filter(is_active=True).select_related('category')
    payment_methods = PaymentMethod.objects.filter(is_active=True)
    site_settings = SystemSetting.objects.first()
    
    decimal_places = 2
    if site_settings:
        decimal_places = site_settings.decimal_places

    context = {
        'customers': customers,
        'products': products,
        'payment_methods': payment_methods,
        'site_settings': site_settings,
        'decimal_places': decimal_places,
    }
    return render(request, 'core/invoice_create.html', context)

# --- STUBS & MISSING VIEWS ---
@login_required
def quotations(request): return render(request, 'core/quotations.html')
@login_required
def quotation_create(request): return redirect('quotations')
@login_required
def quotation_detail(request, pk): return redirect('quotations')
@login_required
def convert_quotation_to_invoice(request, pk): return redirect('quotations')
@login_required
def delete_quotation(request, pk): return redirect('quotations')
@csrf_exempt
def create_quotation_api(request): return JsonResponse({'success': False})
@login_required
def sales_returns(request): return render(request, 'core/sales_returns.html')
@login_required
def sale_return_create(request): return redirect('sales_returns')
@login_required
def sale_return_detail(request, pk): return redirect('sales_returns')
@login_required
def delete_sale_return(request, pk): return redirect('sales_returns')
@csrf_exempt
def create_sale_return_api(request): return JsonResponse({'success': False})
@login_required
def add_purchase_payment(request, pk): return redirect('purchases')
@login_required
def delete_purchase(request, pk): return redirect('purchases')
@login_required
def purchase_returns(request): return render(request, 'core/purchase_returns.html')
@login_required
def purchase_return_create(request): return redirect('purchase_returns')
@login_required
def purchase_return_detail(request, pk): return redirect('purchase_returns')
@login_required
def delete_purchase_return(request, pk): return redirect('purchase_returns')
@csrf_exempt
def create_purchase_return_api(request): return JsonResponse({'success': False})
@login_required
def export_expenses_excel(request): return redirect('expenses')
@csrf_exempt
def update_sale_api(request, pk):
    if request.method != 'POST':
        return JsonResponse({'success': False, 'error': 'Invalid request method'})
    
    try:
        sale = Sale.objects.get(pk=pk)
        data = json.loads(request.body)
        
        customer_id = data.get('customer_id')
        items = data.get('items', [])
        discount = decimal.Decimal(str(data.get('discount', 0)))
        paid_amount = decimal.Decimal(str(data.get('paid_amount', 0)))
        payment_type = data.get('payment_type', 'cash')
        payment_method_id = data.get('payment_method_id')
        due_date = data.get('due_date')
        notes = data.get('notes', '')
        invoice_number = data.get('invoice_number')

        if not items:
            return JsonResponse({'success': False, 'error': 'No items in sale'})

        with transaction.atomic():
            # 1. Revert Stock
            for item in sale.items.all():
                product = item.product
                product.stock_quantity += item.quantity
                product.save()
            
            # 2. Delete existing items
            sale.items.all().delete()
            
            # 3. Update Sale Details
            if customer_id:
                sale.customer_id = customer_id
            else:
                sale.customer = None
                
            sale.discount = discount
            sale.notes = notes
            if invoice_number:
                sale.invoice_number = invoice_number
            
            if due_date:
                sale.due_date = due_date
            else:
                sale.due_date = None
            
            # 4. Create New Items and Deduct Stock
            subtotal = decimal.Decimal(0)
            
            for item_data in items:
                product = Product.objects.get(pk=item_data['id'])
                quantity = decimal.Decimal(str(item_data['quantity']))
                price = decimal.Decimal(str(item_data['price']))
                
                # Deduct stock
                product.stock_quantity -= quantity
                product.save()
                
                line_total = price * quantity
                subtotal += line_total
                
                SaleItem.objects.create(
                    sale=sale,
                    product=product,
                    quantity=qty,
                    unit_price=price,
                    line_total=line_total
                )
            
            sale.subtotal = subtotal
            sale.total_amount = subtotal - discount
            
            # 5. Handle Payments
            if payment_type == 'credit':
                sale.status = 'unpaid'
                sale.paid_amount = 0
                sale.balance_due = sale.total_amount
                sale.payments.all().delete()
                
            elif payment_type == 'cash':
                sale.status = 'paid'
                sale.paid_amount = sale.total_amount
                sale.balance_due = 0
                
                sale.payments.all().delete()
                SalePayment.objects.create(
                    sale=sale,
                    amount=sale.total_amount,
                    payment_method_id=payment_method_id if payment_method_id else None,
                    payment_date=timezone.now().date(),
                    notes='Full Payment (Edit)'
                )
                
            elif payment_type == 'partial':
                sale.paid_amount = paid_amount
                sale.balance_due = sale.total_amount - paid_amount
                if sale.balance_due <= 0:
                     sale.status = 'paid'
                     sale.balance_due = 0
                else:
                     sale.status = 'partial'
                
                sale.payments.all().delete()
                SalePayment.objects.create(
                    sale=sale,
                    amount=paid_amount,
                    payment_method_id=payment_method_id if payment_method_id else None,
                    payment_date=timezone.now().date(),
                    notes='Partial Payment (Edit)'
                )
            
            sale.save()
            
            return JsonResponse({'success': True, 'sale_id': sale.id})

    except Sale.DoesNotExist:
        return JsonResponse({'success': False, 'error': 'Sale not found'})
    except Product.DoesNotExist:
         return JsonResponse({'success': False, 'error': 'Product not found'})
    except Exception as e:
        return JsonResponse({'success': False, 'error': str(e)})

@csrf_exempt
def hold_sale_api(request): return JsonResponse({'success': False})
@csrf_exempt
def get_held_sales_api(request): return JsonResponse({'sales': []})
@csrf_exempt
def recall_held_sale_api(request, pk): return JsonResponse({'success': False})
@csrf_exempt
def delete_held_sale_api(request, pk): return JsonResponse({'success': False})
@login_required
def add_customer(request): return redirect('customers')
@login_required
def edit_customer(request, pk): return redirect('customers')
@login_required
def delete_customer(request, pk): return redirect('customers')
@csrf_exempt
def add_customer_ajax(request): return JsonResponse({'success': False})
@login_required
def add_supplier(request): return redirect('suppliers')
@login_required
def edit_supplier(request, pk): return redirect('suppliers')
@login_required
def delete_supplier(request, pk): return redirect('suppliers')
@csrf_exempt
def add_supplier_ajax(request): return JsonResponse({'success': False})
@login_required
def suggest_sku(request): return JsonResponse({'sku': '12345'})
@login_required
def add_category(request): return redirect('inventory')
@login_required
def edit_category(request, pk): return redirect('inventory')
@login_required
def delete_category(request, pk): return redirect('inventory')
@csrf_exempt
def add_category_ajax(request): return JsonResponse({'success': False})
@login_required
def import_categories(request): return redirect('inventory')
@login_required
def add_unit(request): return redirect('inventory')
@login_required
def edit_unit(request, pk): return redirect('inventory')
@login_required
def delete_unit(request, pk): return redirect('inventory')
@csrf_exempt
def add_unit_ajax(request): return JsonResponse({'success': False})
@login_required
def add_payment_method(request): return redirect('settings')
@login_required
def edit_payment_method(request, pk): return redirect('settings')
@login_required
def delete_payment_method(request, pk): return redirect('settings')
@csrf_exempt
def add_payment_method_ajax(request): return JsonResponse({'success': False})
@login_required
def add_loyalty_tier(request): return redirect('settings')
@login_required
def edit_loyalty_tier(request, pk): return redirect('settings')
@login_required
def delete_loyalty_tier(request, pk): return redirect('settings')
@csrf_exempt
def get_customer_loyalty_api(request, pk): return JsonResponse({'success': False})
@csrf_exempt
def send_invoice_whatsapp(request): return JsonResponse({'success': False})
@csrf_exempt
def test_whatsapp_connection(request): return JsonResponse({'success': False})
@login_required
def add_device(request): return redirect('settings')
@login_required
def edit_device(request, pk): return redirect('settings')
@login_required
def delete_device(request, pk): return redirect('settings')
@login_required
def lpo_list(request): return render(request, 'core/lpo_list.html')
@login_required
def lpo_create(request): return redirect('lpo_list')
@login_required
def lpo_detail(request, pk): return redirect('lpo_list')
@login_required
def convert_lpo_to_purchase(request, pk): return redirect('lpo_list')
@login_required
def lpo_delete(request, pk): return redirect('lpo_list')
@csrf_exempt
def create_lpo_api(request): return JsonResponse({'success': False})
@login_required
def cashier_registry(request): return redirect('settings')
@login_required
def cashier_session_list(request): return render(request, 'core/cashier_sessions.html')
@login_required
def start_session(request): return redirect('cashier_session_list')
@login_required
def close_session(request): return redirect('cashier_session_list')
@login_required
def session_detail(request, pk): return redirect('cashier_session_list')

@login_required
def expenses_view(request):
    expenses = Expense.objects.all().select_related('category', 'payment_method', 'created_by').order_by('-date')
    categories = ExpenseCategory.objects.all()
    payment_methods = PaymentMethod.objects.filter(is_active=True)
    
    paginator = Paginator(expenses, 25)
    page_number = request.GET.get('page')
    page_obj = paginator.get_page(page_number)
    
    context = {
        'expenses': page_obj,
        'categories': categories,
        'payment_methods': payment_methods,
    }
    return render(request, 'core/expenses.html', context)

@login_required
def expense_create_view(request):
    if request.method == 'POST':
        try:
            category_id = request.POST.get('category')
            amount = request.POST.get('amount')
            date = request.POST.get('date')
            description = request.POST.get('description')
            payment_method_id = request.POST.get('payment_method')
            
            category = get_object_or_404(ExpenseCategory, pk=category_id)
            payment_method = get_object_or_404(PaymentMethod, pk=payment_method_id) if payment_method_id else None
            
            expense = Expense.objects.create(
                category=category,
                amount=amount,
                date=date or timezone.now().date(),
                description=description,
                payment_method=payment_method,
                created_by=request.user
            )
            
            if 'attachment' in request.FILES:
                expense.attachment = request.FILES['attachment']
                expense.save()
                
            messages.success(request, _('Expense added successfully.'))
        except Exception as e:
            messages.error(request, _('Error adding expense: ') + str(e))
            
    return redirect('expenses')

@login_required
def expense_edit_view(request, pk):
    expense = get_object_or_404(Expense, pk=pk)
    if request.method == 'POST':
        try:
            category_id = request.POST.get('category')
            amount = request.POST.get('amount')
            date = request.POST.get('date')
            description = request.POST.get('description')
            payment_method_id = request.POST.get('payment_method')
            
            category = get_object_or_404(ExpenseCategory, pk=category_id)
            payment_method = get_object_or_404(PaymentMethod, pk=payment_method_id) if payment_method_id else None
            
            expense.category = category
            expense.amount = amount
            expense.date = date or expense.date
            expense.description = description
            expense.payment_method = payment_method
            
            if 'attachment' in request.FILES:
                expense.attachment = request.FILES['attachment']
            
            expense.save()
            messages.success(request, _('Expense updated successfully.'))
        except Exception as e:
            messages.error(request, _('Error updating expense: ') + str(e))
            
    return redirect('expenses')

@login_required
def expense_delete_view(request, pk):
    expense = get_object_or_404(Expense, pk=pk)
    expense.delete()
    messages.success(request, _('Expense deleted successfully.'))
    return redirect('expenses')

@login_required
def expense_categories_view(request):
    if request.method == 'POST':
        category_id = request.POST.get('category_id')
        name_en = request.POST.get('name_en')
        name_ar = request.POST.get('name_ar')
        description = request.POST.get('description')
        
        if category_id:
            # Update existing category
            category = get_object_or_404(ExpenseCategory, pk=category_id)
            category.name_en = name_en
            category.name_ar = name_ar
            category.description = description
            category.save()
            messages.success(request, _('Expense category updated successfully.'))
        else:
            # Create new category
            ExpenseCategory.objects.create(
                name_en=name_en,
                name_ar=name_ar,
                description=description
            )
            messages.success(request, _('Expense category added successfully.'))
        return redirect('expense_categories')

    categories = ExpenseCategory.objects.all().order_by('-id')
    return render(request, 'core/expense_categories.html', {'categories': categories})

@login_required
def expense_category_delete_view(request, pk):
    category = get_object_or_404(ExpenseCategory, pk=pk)
    if category.expenses.exists():
        messages.error(request, _('Cannot delete category because it has related expenses.'))
    else:
        category.delete()
        messages.success(request, _('Expense category deleted successfully.'))
    return redirect('expense_categories')

@login_required
def expense_report(request): return render(request, 'core/expense_report.html')
@login_required
def customer_payments(request): return redirect('invoices')
@login_required
def customer_payment_receipt(request, pk): return redirect('invoices')
@login_required
def sale_receipt(request, pk):
    sale = get_object_or_404(Sale, pk=pk)
    settings = SystemSetting.objects.first()
    return render(request, 'core/sale_receipt.html', {
        'sale': sale,
        'settings': settings
    })

@login_required
def edit_invoice(request, pk):
    sale = get_object_or_404(Sale, pk=pk)
    customers = Customer.objects.all()
    products = Product.objects.filter(is_active=True).select_related('category')
    payment_methods = PaymentMethod.objects.filter(is_active=True)
    site_settings = SystemSetting.objects.first()
    
    decimal_places = 2
    if site_settings:
        decimal_places = site_settings.decimal_places

    # Serialize items for Vue
    cart_items = []
    for item in sale.items.all().select_related('product'):
        cart_items.append({
            'id': item.product.id,
            'name_en': item.product.name_en,
            'name_ar': item.product.name_ar,
            'sku': item.product.sku,
            'price': float(item.unit_price),
            'quantity': float(item.quantity),
            'stock': float(item.product.stock_quantity) 
        })

    cart_json = json.dumps(cart_items)
    
    # Get first payment method if exists
    payment_method_id = ""
    first_payment = sale.payments.first()
    if first_payment and first_payment.payment_method:
        payment_method_id = first_payment.payment_method.id

    context = {
        'sale': sale,
        'customers': customers,
        'products': products,
        'payment_methods': payment_methods,
        'site_settings': site_settings,
        'decimal_places': decimal_places,
        'cart_json': cart_json,
        'payment_method_id': payment_method_id
    }
    return render(request, 'core/invoice_edit.html', context)

@login_required
def add_sale_payment(request, pk): return redirect('invoices')
@login_required
def delete_sale(request, pk): return redirect('invoices')
@login_required
def supplier_payments(request): return redirect('purchases')
@login_required
def settings_view(request):
    settings, created = SystemSetting.objects.get_or_create(id=1)
    
    if request.method == 'POST':
        # Business Profile
        settings.business_name = request.POST.get('business_name', '')
        settings.email = request.POST.get('email', '')
        settings.phone = request.POST.get('phone', '')
        settings.vat_number = request.POST.get('vat_number', '')
        settings.registration_number = request.POST.get('registration_number', '')
        settings.address = request.POST.get('address', '')
        
        # Financial
        settings.currency_symbol = request.POST.get('currency_symbol', 'OMR')
        settings.tax_rate = request.POST.get('tax_rate', 0)
        settings.decimal_places = request.POST.get('decimal_places', 3)
        settings.allow_zero_stock_sales = request.POST.get('allow_zero_stock_sales') == 'on'
        
        # Loyalty
        settings.loyalty_enabled = request.POST.get('loyalty_enabled') == 'on'
        settings.min_points_to_redeem = request.POST.get('min_points_to_redeem', 100)
        settings.points_per_currency = request.POST.get('points_per_currency', 1.0)
        settings.currency_per_point = request.POST.get('currency_per_point', 0.010)
        
        # WhatsApp (Wablas)
        settings.wablas_enabled = request.POST.get('wablas_enabled') == 'on'
        settings.wablas_server_url = request.POST.get('wablas_server_url', '')
        settings.wablas_token = request.POST.get('wablas_token', '')
        settings.wablas_secret_key = request.POST.get('wablas_secret_key', '')
        
        # Logo Upload
        if 'logo' in request.FILES:
            settings.logo = request.FILES['logo']
            
        settings.save()
        messages.success(request, _('System settings updated successfully.'))
        return redirect('settings')
        
    payment_methods = PaymentMethod.objects.all()
    devices = Device.objects.all()
    loyalty_tiers = LoyaltyTier.objects.all()
        
    return render(request, 'core/settings.html', {
        'settings': settings,
        'payment_methods': payment_methods,
        'devices': devices,
        'loyalty_tiers': loyalty_tiers,
    })

@login_required
def profile_view(request): return render(request, 'core/profile.html')
@login_required
def user_management(request): return render(request, 'core/users.html')
@csrf_exempt
def group_details_api(request, pk): return JsonResponse({'success': False})
@csrf_exempt
def create_sale_api(request):
    if request.method != 'POST':
        return JsonResponse({'success': False, 'error': 'Invalid request method'})
    
    try:
        data = json.loads(request.body)
        
        customer_id = data.get('customer_id')
        items = data.get('items', [])
        discount = decimal.Decimal(str(data.get('discount', 0)))
        paid_amount = decimal.Decimal(str(data.get('paid_amount', 0)))
        payment_type = data.get('payment_type', 'cash')
        payment_method_id = data.get('payment_method_id')
        due_date = data.get('due_date')
        notes = data.get('notes', '')
        invoice_number = data.get('invoice_number')

        if not items:
            return JsonResponse({'success': False, 'error': 'No items in sale'})

        with transaction.atomic():
            customer = None
            if customer_id:
                customer = Customer.objects.get(pk=customer_id)
            
            # Calculate totals server-side for security
            subtotal = decimal.Decimal(0)
            vat_amount = decimal.Decimal(0)
            
            sale = Sale(
                customer=customer,
                created_by=request.user,
                status='unpaid', 
                discount=discount,
                notes=notes,
                invoice_number=invoice_number
            )
            if due_date:
                sale.due_date = due_date
            sale.save()
            
            for item in items:
                product = Product.objects.select_for_update().get(pk=item['id'])
                qty = decimal.Decimal(str(item['quantity']))
                unit_price = decimal.Decimal(str(item['price']))
                
                # Check stock
                if product.stock_quantity < qty:
                    settings = SystemSetting.objects.first()
                    if not settings or not settings.allow_zero_stock_sales:
                        raise Exception(f"Insufficient stock for {product.name_en}")

                line_total = unit_price * qty
                line_vat = line_total * (product.vat / 100) if product.vat else 0
                
                SaleItem.objects.create(
                    sale=sale,
                    product=product,
                    quantity=qty,
                    unit_price=unit_price,
                    line_total=line_total
                )
                
                product.stock_quantity -= qty
                product.save()
                
                subtotal += line_total
                vat_amount += decimal.Decimal(line_vat)
            
            sale.subtotal = subtotal
            sale.vat_amount = vat_amount
            sale.total_amount = subtotal + vat_amount - discount
            
            if payment_type == 'credit':
                sale.status = 'unpaid'
            elif paid_amount >= sale.total_amount:
                sale.status = 'paid'
            else:
                sale.status = 'partial'
                
            sale.save()
            
            if paid_amount > 0 and payment_type != 'credit':
                payment_method = None
                if payment_method_id:
                    payment_method = PaymentMethod.objects.get(pk=payment_method_id)
                    
                SalePayment.objects.create(
                    sale=sale,
                    amount=paid_amount,
                    payment_method=payment_method,
                    payment_date=timezone.now(),
                    created_by=request.user,
                    notes=f"Initial payment ({payment_type})"
                )

            return JsonResponse({'success': True, 'sale_id': sale.id})
            
    except Exception as e:
        return JsonResponse({'success': False, 'error': str(e)})

@csrf_exempt
def create_purchase_api(request): return JsonResponse({'success': False})
@csrf_exempt
def search_customers_api(request): return JsonResponse({'customers': []})
@login_required
def pos_sync_update(request): return JsonResponse({'success': False})
@login_required
def pos_sync_state(request): return JsonResponse({'success': False})