<?php

namespace App\Services;

use App\Models\Server;
use InvalidArgumentException;
use RuntimeException;
use Throwable;

/**
 * Applies the dashboard server-hardening toggles over SSH (as root). Every item is
 * BIDIRECTIONAL — apply($server, $action, $enable) toggles the underlying feature
 * on/off; package items (fail2ban, unattended-upgrades, UFW) install on demand.
 *
 * apply() runs the exact command built by commandFor() (the single source of truth);
 * title()/description() supply the German confirm-modal copy for each direction.
 * Disabling SSH password auth is GUARDED so the operator can never lock themselves out.
 */
class HardeningService
{
    // 00- so it sorts + wins before distro drop-ins like 50-cloud-init.conf (sshd uses the first value).
    private const SSHD_DROPIN = '/etc/ssh/sshd_config.d/00-clusev.conf';

    // 99zz- so Clusev's apt periodic setting wins (apt uses the LAST value across apt.conf.d/*).
    private const APT_DROPIN = '/etc/apt/apt.conf.d/99zz-clusev';

    public function __construct(private FleetService $fleet, private FirewallService $firewall) {}

    /**
     * Live state of every hardening item, read PRIVILEGED in one shot. SSH uses
     * `sshd -T` (the EFFECTIVE config — honours Include order + Match blocks);
     * UFW uses `ufw status`; unattended uses the apt periodic config.
     *
     * @return array<int, array{key:string, label:string, detail:string, featureOn:bool, secure:bool}>
     */
    public function state(Server $server): array
    {
        $cmd = 'sshd -T 2>/dev/null | grep -iE "^(permitrootlogin|passwordauthentication) "; '
            .'echo "fail2ban $(dpkg -l fail2ban 2>/dev/null | grep -c "^ii") $(systemctl is-active fail2ban 2>/dev/null)"; '
            .'ufw_inst=$(dpkg -l ufw 2>/dev/null | grep -c "^ii"); ufw_act=inactive; '
            .'[ "$ufw_inst" = "1" ] && ufw status 2>/dev/null | grep -qi "Status: active" && ufw_act=active; '
            .'echo "ufw $ufw_inst $ufw_act"; '
            .'ui=$(dpkg -l unattended-upgrades 2>/dev/null | grep -c "^ii"); ua=inactive; '
            // apt-config dump = the EFFECTIVE periodic value across all apt.conf.d files (last wins).
            .'apt-config dump APT::Periodic::Unattended-Upgrade 2>/dev/null | grep -q \'"1"\' && ua=active; '
            .'echo "unattended-upgrades $ui $ua"';

        $res = $this->fleet->runPrivileged($server, $cmd);
        if (! $res['ok']) {
            throw new RuntimeException('Härtungs-Status konnte nicht gelesen werden.');
        }

        return $this->parseState($res['output']);
    }

    /** @return array<int, array{key:string, label:string, detail:string, featureOn:bool, secure:bool}> */
    private function parseState(string $out): array
    {
        $root = 'default';
        $pwauth = 'default';
        $pkg = [];

        foreach (preg_split('/\R/', $out) as $line) {
            $line = trim($line);
            if (preg_match('/^permitrootlogin\s+(\S+)/i', $line, $m)) {
                $root = strtolower($m[1]);
            } elseif (preg_match('/^passwordauthentication\s+(\S+)/i', $line, $m)) {
                $pwauth = strtolower($m[1]);
            } else {
                $p = preg_split('/\s+/', $line);
                if (count($p) === 3 && in_array($p[0], ['fail2ban', 'ufw', 'unattended-upgrades'], true)) {
                    $pkg[$p[0]] = ['installed' => $p[1] === '1', 'active' => $p[2] === 'active'];
                }
            }
        }

        $f2b = $pkg['fail2ban'] ?? ['installed' => false, 'active' => false];
        $ufw = $pkg['ufw'] ?? ['installed' => false, 'active' => false];
        $upg = $pkg['unattended-upgrades'] ?? ['installed' => false, 'active' => false];

        $detail = fn (string $name, array $st): string => $name.' · '
            .(! $st['installed'] ? 'nicht installiert' : ($st['active'] ? 'aktiv' : 'inaktiv'));
        // A package feature is only effectively ON when the package is installed AND active —
        // stale config (e.g. apt periodic = 1 after removal) must not read as secure.
        $on = fn (array $st): bool => $st['installed'] && $st['active'];

        // `featureOn` drives the button (Aktivieren/Deaktivieren); `secure` drives the OK/Offen pill.
        return [
            ['key' => 'ssh_root', 'label' => 'SSH-Root-Login', 'detail' => 'PermitRootLogin '.$root,
                'featureOn' => $root !== 'no', 'secure' => $root === 'no'],
            ['key' => 'ssh_password', 'label' => 'SSH-Passwort-Login', 'detail' => 'PasswordAuthentication '.$pwauth,
                'featureOn' => $pwauth !== 'no', 'secure' => $pwauth === 'no'],
            ['key' => 'fail2ban', 'label' => 'fail2ban', 'detail' => $detail('fail2ban.service', $f2b),
                'featureOn' => $on($f2b), 'secure' => $on($f2b)],
            ['key' => 'firewall', 'label' => 'Firewall (UFW)', 'detail' => $detail('ufw', $ufw),
                'featureOn' => $on($ufw), 'secure' => $on($ufw)],
            ['key' => 'unattended', 'label' => 'Automatische Updates', 'detail' => $detail('unattended-upgrades', $upg),
                'featureOn' => $on($upg), 'secure' => $on($upg)],
        ];
    }

    /** Modal title, reflecting the toggle direction. */
    public function title(string $action, bool $enable): string
    {
        return match ($action) {
            'ssh_root' => $enable ? 'SSH-Root-Login erlauben' : 'SSH-Root-Login deaktivieren',
            'ssh_password' => $enable ? 'SSH-Passwort-Login erlauben' : 'SSH-Passwort-Login deaktivieren',
            'fail2ban' => $enable ? 'fail2ban aktivieren' : 'fail2ban deaktivieren',
            'firewall' => $enable ? 'Firewall (UFW) aktivieren' : 'Firewall (UFW) deaktivieren',
            'unattended' => $enable ? 'Automatische Updates aktivieren' : 'Automatische Updates deaktivieren',
            default => throw new InvalidArgumentException("Unbekannte Härtung: {$action}"),
        };
    }

    public function description(string $action, bool $enable): string
    {
        return match ($action) {
            'ssh_root' => $enable
                ? 'Erlaubt direkten Root-Login über SSH wieder (PermitRootLogin yes) und lädt den SSH-Dienst neu.'
                : 'Unterbindet direkten Root-Login über SSH (PermitRootLogin no) und lädt den SSH-Dienst neu.',
            'ssh_password' => $enable
                ? 'Erlaubt die Anmeldung per Passwort wieder (PasswordAuthentication yes).'
                : 'Anmeldung nur noch per SSH-Key (PasswordAuthentication no). Nur möglich, wenn ein Key hinterlegt ist.',
            'fail2ban' => $enable
                ? 'Installiert fail2ban (falls nötig) und startet den Dienst. Wiederholte Fehl-Logins werden gesperrt.'
                : 'Stoppt fail2ban und deaktiviert den Autostart.',
            'firewall' => $enable
                ? 'Installiert UFW (falls nötig), gibt SSH + 80/443 frei und aktiviert die Firewall.'
                : 'Deaktiviert die UFW-Firewall (ufw disable).',
            'unattended' => $enable
                ? 'Installiert unattended-upgrades (falls nötig) und aktiviert die automatische Update-Periodik + Timer.'
                : 'Schaltet die automatische Update-Periodik ab.',
            default => throw new InvalidArgumentException("Unbekannte Härtung: {$action}"),
        };
    }

    /** @return array{ok: bool, output: string} */
    public function apply(Server $server, string $action, bool $enable): array
    {
        if ($action === 'firewall') {
            $res = $enable ? $this->firewall->enable($server) : $this->firewall->disable($server);

            return ['ok' => $res['ok'], 'output' => $res['output']];
        }

        // Lock-out guard: never disable password auth without a usable key path.
        if ($action === 'ssh_password' && ! $enable) {
            if ($server->credential?->auth_type === 'password') {
                return ['ok' => false, 'output' => 'Clusev verbindet sich selbst per Passwort — Passwort-Login kann nicht deaktiviert werden, sonst verliert Clusev den Zugang. Hinterlege zuerst einen SSH-Key-Zugang.'];
            }
            if (! $this->hasAuthorizedKey($server)) {
                return ['ok' => false, 'output' => 'Kein SSH-Key hinterlegt — Passwort-Login kann nicht deaktiviert werden (Aussperrgefahr).'];
            }
        }

        // apt operations need a long timeout; the 12s default would abort the install.
        $timeout = $enable && in_array($action, ['fail2ban', 'unattended'], true) ? 600 : 60;
        $res = $this->fleet->runPrivileged($server, $this->commandFor($action, $enable), $timeout);

        return ['ok' => $res['ok'], 'output' => $res['output']];
    }

    /** Single source of truth for the shell command of a (non-firewall) toggle. */
    private function commandFor(string $action, bool $enable): string
    {
        return match ($action) {
            'ssh_root' => $this->sshDropInScript('PermitRootLogin '.($enable ? 'yes' : 'no')),
            'ssh_password' => $this->sshDropInScript('PasswordAuthentication '.($enable ? 'yes' : 'no')),
            'fail2ban' => $enable
                ? '(dpkg -l fail2ban 2>/dev/null | grep -q "^ii" || DEBIAN_FRONTEND=noninteractive apt-get install -y fail2ban) && systemctl enable --now fail2ban'
                : 'systemctl disable --now fail2ban',
            'unattended' => $enable
                ? '(dpkg -l unattended-upgrades 2>/dev/null | grep -q "^ii" || DEBIAN_FRONTEND=noninteractive apt-get install -y unattended-upgrades)'
                    .' && printf \'%s\n%s\n\' \'APT::Periodic::Update-Package-Lists "1";\' \'APT::Periodic::Unattended-Upgrade "1";\' > '.self::APT_DROPIN
                    .' && systemctl enable --now unattended-upgrades apt-daily-upgrade.timer apt-daily.timer'
                : 'printf \'%s\n%s\n\' \'APT::Periodic::Update-Package-Lists "0";\' \'APT::Periodic::Unattended-Upgrade "0";\' > '.self::APT_DROPIN
                    .' && (systemctl disable --now unattended-upgrades 2>/dev/null || true)',
            default => throw new InvalidArgumentException("Unbekannte Härtung: {$action}"),
        };
    }

    /** True if the SSH user has at least one authorized key. */
    private function hasAuthorizedKey(Server $server): bool
    {
        try {
            if (count($this->fleet->sshKeys($server)) > 0) {
                return true;
            }
        } catch (Throwable) {
            // fall through to the raw check
        }

        $res = $this->fleet->runPlain($server, 'grep -cE "^(ssh-|ecdsa-|sk-)" ~/.ssh/authorized_keys 2>/dev/null || echo 0');

        return $res['ok'] && (int) trim($res['output']) > 0;
    }

    /**
     * Install one sshd directive into the Clusev drop-in (replacing any prior value
     * of the same key), then reload whichever ssh unit exists.
     */
    private function sshDropInScript(string $directive): string
    {
        $key = strtok($directive, ' ');

        return 'mkdir -p /etc/ssh/sshd_config.d'
            .' && touch '.self::SSHD_DROPIN
            .' && grep -viE "^[[:space:]]*'.$key.'[[:space:]]" '.self::SSHD_DROPIN.' > '.self::SSHD_DROPIN.'.tmp 2>/dev/null; '
            .'mv '.self::SSHD_DROPIN.'.tmp '.self::SSHD_DROPIN.' 2>/dev/null; '
            .'echo "'.$directive.'" >> '.self::SSHD_DROPIN
            .' && (systemctl reload ssh || systemctl reload sshd)';
    }
}