pdv.backend/app/Services/SaleService.php

<?php namespace App\Services;

use App\Models\CashRegister;
use App\Models\CatalogItem;
use App\Models\Sale;
use App\Models\SaleDetail;
use App\Models\InventorySerial;
use Illuminate\Support\Facades\DB;

class SaleService
{
    /**
     * Crear una nueva venta con sus detalles
     *
     */
    public function createSale(array $data)
    {
        return DB::transaction(function () use ($data) {
            // Calcular el cambio si es pago en efectivo
            $cashReceived = null;
            $change = null;

            if ($data['payment_method'] === 'cash' && isset($data['cash_received'])) {
                $cashReceived = $data['cash_received'];
                $change = $cashReceived - $data['total'];
            }

            // 1. Crear la venta principal
            $sale = Sale::create([
                'user_id' => $data['user_id'],
                'cash_register_id' => $data['cash_register_id'] ?? $this->getCurrentCashRegister($data['user_id']),
                'invoice_number' => $data['invoice_number'] ?? $this->generateInvoiceNumber(),
                'subtotal' => $data['subtotal'],
                'tax' => $data['tax'],
                'total' => $data['total'],
                'cash_received' => $cashReceived,
                'change' => $change,
                'payment_method' => $data['payment_method'],
                'status' => $data['status'] ?? 'completed',
            ]);

            // 2. Crear los detalles de la venta y asignar seriales
            foreach ($data['items'] as $item) {
                // Crear detalle de venta
                $saleDetail = SaleDetail::create([
                    'sale_id' => $sale->id,
                    'catalog_item_id' => $item['catalog_item_id'],
                    'product_name' => $item['product_name'],
                    'quantity' => $item['quantity'],
                    'unit_price' => $item['unit_price'],
                    'subtotal' => $item['subtotal'],
                    'serial_numbers' => $item['serial_numbers'] ?? null, // Si vienen del frontend
                ]);

                // Obtener el inventario
                $catalogItem = CatalogItem::find($item['catalog_item']);

                if ($catalogItem && $catalogItem->is_stockable) {
                    // Si se proporcionaron números de serie específicos
                    if (isset($item['serial_numbers']) && is_array($item['serial_numbers'])) {
                        foreach ($item['serial_numbers'] as $serialNumber) {
                            $serial = InventorySerial::where('catalog_item_id', $catalogItem->id)
                                ->where('serial_number', $serialNumber)
                                ->where('status', 'disponible')
                                ->first();

                            if ($serial) {
                                $serial->markAsSold($saleDetail->id);
                            } else {
                                throw new \Exception("Serial {$serialNumber} no disponible");
                            }
                        }
                    } else {
                        // Asignar automáticamente los primeros N seriales disponibles
                        $serials = InventorySerial::where('catalog_item_id', $catalogItem->id)
                            ->where('status', 'disponible')
                            ->limit($item['quantity'])
                            ->get();

                        if ($serials->count() < $item['quantity']) {
                            throw new \Exception("Stock insuficiente de seriales para {$item['product_name']}");
                        }

                        foreach ($serials as $serial) {
                            $serial->markAsSold($saleDetail->id);
                        }
                    }

                    // Sincronizar el stock
                    $catalogItem->syncStock();
                }
            }

            // 3. Retornar la venta con sus relaciones cargadas
            return $sale->load(['details.catalogItem', 'details.serials', 'user']);
        });
    }

    /**
     * Cancelar una venta y restaurar el stock
     *
     */
    public function cancelSale(Sale $sale)
    {
        return DB::transaction(function () use ($sale) {
            // Verificar que la venta esté completada
            if ($sale->status !== 'completed') {
                throw new \Exception('Solo se pueden cancelar ventas completadas.');
            }

            // Restaurar seriales a disponible
            foreach ($sale->details as $detail) {
                $serials = InventorySerial::where('sale_detail_id', $detail->id)->get();

                foreach ($serials as $serial) {
                    $serial->markAsAvailable();
                }

                // Sincronizar stock
                $detail->catalogItem->syncStock();
            }

            // Marcar venta como cancelada
            $sale->update(['status' => 'cancelled']);

            return $sale->fresh(['details.catalogItem', 'details.serials', 'user']);
        });
    }

    /**
     * Generar número de factura único
     * Formato: INV-YYYYMMDD-0001
     */
    private function generateInvoiceNumber(): string
    {
        $prefix = 'INV-';
        $date = now()->format('Ymd');

        // Obtener la última venta del día
        $lastSale = Sale::whereDate('created_at', today())
            ->orderBy('id', 'desc')
            ->first();

        // Incrementar secuencial
        $sequential = $lastSale ? (intval(substr($lastSale->invoice_number, -4)) + 1) : 1;

        return $prefix . $date . '-' . str_pad($sequential, 4, '0', STR_PAD_LEFT);
    }

    private function getCurrentCashRegister($userId)
    {
        $register = CashRegister::where('user_id', $userId)
            ->where('status', 'open')
            ->first();

        return $register ? $register->id : null;
    }
}