<?php namespace App\Services;

use App\Models\Sale;
use App\Models\SaleDetail;
use App\Models\Inventory;
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) {
            // 1. Crear la venta principal
            $sale = Sale::create([
                'user_id' => $data['user_id'],
                'invoice_number' => $data['invoice_number'] ?? $this->generateInvoiceNumber(),
                'subtotal' => $data['subtotal'],
                'tax' => $data['tax'],
                'total' => $data['total'],
                'payment_method' => $data['payment_method'],
                'status' => $data['status'] ?? 'completed',
            ]);

            // 2. Crear los detalles de la venta y actualizar stock
            foreach ($data['items'] as $item) {
                // Crear detalle de venta
                SaleDetail::create([
                    'sale_id' => $sale->id,
                    'inventory_id' => $item['inventory_id'],
                    'product_name' => $item['product_name'],
                    'quantity' => $item['quantity'],
                    'unit_price' => $item['unit_price'],
                    'subtotal' => $item['subtotal'],
                ]);

                // Descontar del stock
                $inventory = Inventory::find($item['inventory_id']);
                if ($inventory) {
                    $inventory->decrement('stock', $item['quantity']);
                }
            }

            // 3. Retornar la venta con sus relaciones cargadas
            return $sale->load(['details.inventory', '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 stock de cada producto
            foreach ($sale->details as $detail) {
                $inventory = Inventory::find($detail->inventory_id);
                if ($inventory) {
                    $inventory->increment('stock', $detail->quantity);
                }
            }

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

            return $sale->fresh(['details.inventory', '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);
    }
}