<?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 array{owner:string,domain:string,mailbox:string,email:string}|null */
    public function resolveRecipient(string $email): ?array
    {
        $email = strtolower(trim($email));
        if (!preg_match('/^([A-Za-z0-9._+-]+)@([A-Za-z0-9.-]+)$/', $email, $m)) {
            return null;
        }
        $local = $m[1];
        $domain = $m[2];
        $owners = $this->domainOwners();
        $owner = $owners[$domain] ?? null;
        if ($owner === null) {
            return null;
        }
        $passwd = $this->virtualRoot . '/' . $domain . '/passwd';
        if (!is_file($passwd)) {
            return null;
        }
        foreach (file($passwd, FILE_IGNORE_NEW_LINES) ?: [] as $line) {
            $mailbox = strtolower(trim(strtok($line, ':') ?: ''));
            if ($mailbox === $local) {
                return ['owner' => $owner, 'domain' => $domain, 'mailbox' => $local, 'email' => $local . '@' . $domain];
            }
        }
        return null;
    }

    /** @return string[] */
    public function domainsForUser(string $username): array
    {
        $domains = [];
        foreach ($this->domainOwners() as $domain => $owner) {
            if ($owner === $username) {
                $domains[] = $domain;
            }
        }
        sort($domains);
        return $domains;
    }

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