<?php

namespace App\Services;

use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;

class ShopifyService
{
    private string $baseUrl;
    private string $token;

    public function __construct()
    {
        $domain = config('services.shopify.domain');
        $version = config('services.shopify.api_version');
        $this->baseUrl = "https://{$domain}/admin/api/{$version}";
        $this->token   = config('services.shopify.access_token');
    }

    /**
     * Returns all product variants from Shopify.
     * Each entry: ['id', 'sku', 'inventory_quantity', 'product_title']
     */
    public function getAllVariants(): array
    {
        $variants = [];
        $url = "{$this->baseUrl}/products.json?limit=250&fields=id,title,variants";

        while ($url) {
            $response = Http::withHeader('X-Shopify-Access-Token', $this->token)->get($url);

            if ($response->failed()) {
                $status = $response->status();
                $hint   = match (true) {
                    $status === 401 => 'Access Token ungültig oder fehlt',
                    $status === 403 => 'IP-Whitelist: VPS-IP ist in Shopify nicht freigeschalten',
                    $status === 429 => 'Rate Limit überschritten',
                    $status >= 500  => 'Shopify-seitiger Fehler',
                    default         => 'Unbekannter Fehler',
                };
                Log::error("Shopify Sync fehlgeschlagen: {$hint}", [
                    'status' => $status,
                    'url'    => $url,
                    'body'   => $response->body(),
                ]);
                break;
            }

            foreach ($response->json('products', []) as $product) {
                foreach ($product['variants'] as $variant) {
                    $variants[] = [
                        'id'                => (string) $variant['id'],
                        'sku'               => $variant['sku'] ?? '',
                        'inventory_quantity' => (int) ($variant['inventory_quantity'] ?? 0),
                        'product_title'     => $product['title'],
                    ];
                }
            }

            // Follow Shopify's Link header pagination
            $url = $this->nextPageUrl($response->header('Link'));

            if ($url) {
                usleep(500_000); // 0.5s — stay well within 2 req/s limit
            }
        }

        return $variants;
    }

    private function nextPageUrl(?string $linkHeader): ?string
    {
        if (!$linkHeader) {
            return null;
        }

        // Link: <https://...?page_info=abc>; rel="next"
        if (preg_match('/<([^>]+)>;\s*rel="next"/', $linkHeader, $m)) {
            return $m[1];
        }

        return null;
    }
}