<?php
declare(strict_types=1);

final class MailboxDirectory
{
    public function __construct(private string $virtualRoot = '/etc/virtual')
    {
    }

    /** @return array<int,array{domain:string,mailbox:string,email:string}> */
    public function mailboxesForUser(string $username): array
    {
        $domains = $this->domainsForUser($username);
        $out = [];
        foreach ($domains as $domain) {
            $passwd = $this->virtualRoot . '/' . $domain . '/passwd';
            if (!is_file($passwd)) {
                continue;
            }
            $lines = file($passwd, FILE_IGNORE_NEW_LINES) ?: [];
            foreach ($lines as $line) {
                $local = trim(strtok($line, ':') ?: '');
                if ($local === '' || !preg_match('/^[A-Za-z0-9._+-]+$/', $local)) {
                    continue;
                }
                $out[] = ['domain' => $domain, 'mailbox' => $local, 'email' => $local . '@' . $domain];
            }
        }
        usort($out, static fn (array $a, array $b): int => strcmp($a['email'], $b['email']));
        return $out;
    }

    /** @return string[] */
    private function domainsForUser(string $username): array
    {
        $path = $this->virtualRoot . '/domainowners';
        if (!is_file($path)) {
            return [];
        }
        $domains = [];
        foreach (file($path, FILE_IGNORE_NEW_LINES) ?: [] as $line) {
            if (!str_contains($line, ':')) {
                continue;
            }
            [$domain, $owner] = array_map('trim', explode(':', $line, 2));
            if ($owner !== $username || !preg_match('/^[A-Za-z0-9.-]+$/', $domain)) {
                continue;
            }
            $domains[] = strtolower($domain);
        }
        sort($domains);
        return $domains;
    }
}