<?php

declare(strict_types=1);

namespace Domovoy\Services\Discovery;

class ArpTableReader
{
    /**
     * Read ARP table from system.
     * Returns array keyed by IP => ['mac' => '...', 'vendor' => '...']
     */
    public function read(): array
    {
        $entries = [];

        // Try ip neigh first (modern Linux)
        $output = [];
        $exitCode = 0;
        exec('ip neigh show 2>/dev/null', $output, $exitCode);
        if ($exitCode === 0) {
            foreach ($output as $line) {
                if (preg_match('/^(\d+\.\d+\.\d+\.\d+)\s+.*lladdr\s+([0-9a-f:]+)/i', $line, $m)) {
                    $entries[$m[1]] = ['mac' => strtolower($m[2]), 'vendor' => null];
                }
            }
        }

        // Fallback: arp -a
        if (empty($entries)) {
            exec('arp -a 2>/dev/null', $output, $exitCode);
            if ($exitCode === 0) {
                foreach ($output as $line) {
                    if (preg_match('/\((\d+\.\d+\.\d+\.\d+)\)\s+at\s+([0-9a-f:]+)/i', $line, $m)) {
                        $entries[$m[1]] = ['mac' => strtolower($m[2]), 'vendor' => null];
                    }
                }
            }
        }

        return $entries;
    }
}