<?php

declare(strict_types=1);

namespace Mod\Proxy\Services;

use Illuminate\Support\Facades\Cache;
use Mod\Chain\Services\DaemonRpc;

/**
 * Selects a gateway node matching the requested service type.
 *
 *   $selector = app(NodeSelector::class);
 *   $node = $selector->selectNode('mobile');  // returns gateway with cap=mobile
 *   $node = $selector->selectNode('proxy');   // returns gateway with cap=proxy
 *   $nodes = $selector->availableNodes('vpn'); // all VPN-capable gateways
 */
class NodeSelector
{
    public function __construct(
        private readonly DaemonRpc $rpc,
    ) {}

    /**
     * Get all nodes with a given capability.
     *
     *   $nodes = $selector->availableNodes('proxy');
     */
    public function availableNodes(string $capability = ''): array
    {
        $aliases = Cache::remember('proxy.nodes', 60, function () {
            $result = $this->rpc->getAllAliases();
            $aliases = $result['aliases'] ?? [];

            return array_values(array_filter($aliases, function ($alias) {
                $comment = $alias['comment'] ?? '';

                return str_contains($comment, 'type=gateway') || str_contains($comment, 'type=exit');
            }));
        });

        if (empty($capability)) {
            return array_values($aliases);
        }

        return array_values(array_filter($aliases, function ($alias) use ($capability) {
            return str_contains($alias['comment'] ?? '', $capability);
        }));
    }

    /**
     * Select a single node matching capability. Round-robin via cache counter.
     *
     *   $node = $selector->selectNode('proxy');
     */
    public function selectNode(string $capability): ?array
    {
        $nodes = $this->availableNodes($capability);

        if (empty($nodes)) {
            return null;
        }

        // Round-robin selection
        $counterKey = "proxy.rr:{$capability}";
        $index = (int) Cache::get($counterKey, 0);
        $node = $nodes[$index % count($nodes)];
        Cache::put($counterKey, $index + 1, 3600);

        return $node;
    }
}