<?php

namespace App\Services\Link;

use App\Support\LadillLink;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Http;
use Symfony\Component\HttpFoundation\Response;

/**
 * Proxies ladl.link ecosystem paths to the platform QR resolver (/q/* on ladill.com).
 * The browser stays on ladl.link; resolution happens server-side.
 */
class LinkPlatformProxy
{
    public function forward(Request $request, string $slug, ?string $path = null): Response
    {
        $platform = rtrim((string) config('app.platform_url', 'https://ladill.com'), '/');
        $target = $platform.'/q/'.$slug;
        if ($path !== null && $path !== '') {
            $target .= '/'.ltrim($path, '/');
        }
        if ($qs = $request->getQueryString()) {
            $target .= '?'.$qs;
        }

        $method = strtoupper($request->method());
        $followRedirects = $method === 'GET' || $method === 'HEAD';
        $client = Http::withOptions([
            'allow_redirects' => $followRedirects ? ['max' => 5] : false,
        ])->timeout(15);

        $pending = match ($method) {
            'POST' => $client->withHeaders($this->forwardHeaders($request))->asForm()->post($target, $request->post()),
            'PATCH' => $client->withHeaders($this->forwardHeaders($request))->patch($target, $request->all()),
            'DELETE' => $client->withHeaders($this->forwardHeaders($request))->delete($target),
            default => $client->withHeaders($this->forwardHeaders($request))->get($target),
        };

        $upstream = $pending->toPsrResponse();
        $response = new Response(
            (string) $upstream->getBody(),
            $upstream->getStatusCode(),
            $this->sanitizeHeaders($upstream->getHeaders())
        );

        if ($response->isRedirection()) {
            $location = $response->headers->get('Location');
            if (is_string($location)) {
                $response->headers->set('Location', $this->rewriteLocation($location, $slug));
            }
        }

        return $response;
    }

    /** @return array<string, string> */
    private function forwardHeaders(Request $request): array
    {
        $headers = [];
        foreach (['Accept', 'Accept-Language', 'User-Agent', 'Referer'] as $name) {
            $value = $request->header($name);
            if ($value !== null) {
                $headers[$name] = $value;
            }
        }

        return $headers;
    }

    /** @param array<string, array<int, string>> $headers */
    private function sanitizeHeaders(array $headers): array
    {
        $flat = [];
        foreach ($headers as $name => $values) {
            if (strtolower($name) === 'transfer-encoding') {
                continue;
            }
            $flat[$name] = $values[0] ?? '';
        }

        return $flat;
    }

    private function rewriteLocation(string $location, string $slug): string
    {
        $platform = rtrim((string) config('app.platform_url', 'https://ladill.com'), '/');
        $prefix = $platform.'/q/'.$slug;

        if (str_starts_with($location, $prefix)) {
            $suffix = substr($location, strlen($prefix));
            $rewritten = LadillLink::url($slug).$suffix;

            return $rewritten;
        }

        return $location;
    }
}