<?php

namespace App\Helper;

use Carbon\Carbon;
use Modules\Restaurant\Models\Purchase;

class PurchaseHelper
{
    /**
     * Generate a unique purchase invoice number for a restaurant.
     *
     * Format: PUR-{YYYYMMDD}-{RestaurantId}-{AutoIncrement}
     */
    public static function generateInvoiceNumber(int $restaurantId): string
    {
        $today = Carbon::now()->format('Ymd');

        // Get last purchase today for this restaurant
        $lastPurchase = Purchase::where('restaurant_id', $restaurantId)
            ->whereDate('created_at', Carbon::today())
            ->lockForUpdate() // prevent concurrency issues
            ->orderBy('id', 'desc')
            ->first();

        $lastIncrement = 0;

        if ($lastPurchase && preg_match('/PUR-\d{8}-\d+-([\d]+)/', $lastPurchase->invoice_no, $matches)) {
            $lastIncrement = (int) $matches[1];
        }

        $newIncrement = $lastIncrement + 1;

        return "PUR-{$today}-{$restaurantId}-".str_pad($newIncrement, 4, '0', STR_PAD_LEFT);
    }
}