<?php

namespace App\Services\Admin;

use App\Authorization\Permission as PermissionCatalog;
use App\Models\PressReleaseAttachment;
use App\Models\PressReleaseImage;
use Illuminate\Support\Carbon;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;
use Spatie\Permission\Models\Permission;
use Throwable;

/**
 * Betriebsüberwachung fürs Admin-Backend: Zustand der Queue (kritisch, weil
 * Magic-Link-Login und fristrelevante Bestätigungs-Mails darüber laufen) sowie
 * Deployment-/Konfigurations-Checks (neue Permissions ausgerollt, Debug/Env,
 * ausstehende Medien-Privatisierung).
 */
class AdminSystemHealth
{
    private const StatusOk = 'ok';

    private const StatusWarn = 'warn';

    private const StatusCritical = 'critical';

    /**
     * Sekundenschwellen für den ältesten wartenden Job: darüber gilt der Worker
     * als verzögert (warn) bzw. mutmaßlich gestoppt (critical).
     */
    private const PendingWarnSeconds = 60;

    private const PendingCriticalSeconds = 300;

    /**
     * @return array{
     *     generated_at: Carbon,
     *     overall: string,
     *     queue: array<string, mixed>,
     *     checks: list<array{key: string, label: string, status: string, detail: string}>
     * }
     */
    public function snapshot(): array
    {
        $queue = $this->queueHealth();
        $checks = $this->deploymentChecks($queue);

        $statuses = array_merge(
            [$queue['status']],
            array_map(static fn (array $check): string => $check['status'], $checks),
        );

        return [
            'generated_at' => now(),
            'overall' => $this->worstStatus($statuses),
            'queue' => $queue,
            'checks' => $checks,
        ];
    }

    /**
     * @return array<string, mixed>
     */
    private function queueHealth(): array
    {
        $connection = (string) config('queue.default');
        $usesDatabase = $connection === 'database';

        if (! $usesDatabase || ! Schema::hasTable('jobs')) {
            return [
                'status' => self::StatusWarn,
                'driver' => $connection,
                'supported' => false,
                'pending' => 0,
                'delayed' => 0,
                'reserved' => 0,
                'failed_total' => Schema::hasTable('failed_jobs') ? DB::table('failed_jobs')->count() : 0,
                'failed_recent' => 0,
                'oldest_pending_seconds' => null,
                'worker_running' => null,
                'recent_failures' => [],
            ];
        }

        $now = now()->getTimestamp();

        $pending = DB::table('jobs')->whereNull('reserved_at')->where('available_at', '<=', $now)->count();
        $delayed = DB::table('jobs')->whereNull('reserved_at')->where('available_at', '>', $now)->count();
        $reserved = DB::table('jobs')->whereNotNull('reserved_at')->count();

        $oldestAvailable = DB::table('jobs')
            ->whereNull('reserved_at')
            ->where('available_at', '<=', $now)
            ->min('available_at');

        $oldestPendingSeconds = $oldestAvailable !== null ? max(0, $now - (int) $oldestAvailable) : null;

        $failedTotal = DB::table('failed_jobs')->count();
        $failedRecent = DB::table('failed_jobs')
            ->where('failed_at', '>=', now()->subDay())
            ->count();

        $recentFailures = DB::table('failed_jobs')
            ->orderByDesc('failed_at')
            ->limit(10)
            ->get(['uuid', 'queue', 'payload', 'exception', 'failed_at'])
            ->map(fn ($row): array => [
                'uuid' => $row->uuid,
                'queue' => $row->queue,
                'job' => $this->jobDisplayName($row->payload),
                'error' => $this->firstExceptionLine($row->exception),
                'failed_at' => Carbon::parse($row->failed_at),
            ])
            ->all();

        // Worker gilt als aktiv, wenn kein wartender Job zu lange unbearbeitet
        // liegt. Ein reservierter Job zeigt aktive Verarbeitung an.
        $workerRunning = $oldestPendingSeconds === null || $oldestPendingSeconds < self::PendingCriticalSeconds;

        $status = self::StatusOk;
        if ($oldestPendingSeconds !== null && $oldestPendingSeconds >= self::PendingCriticalSeconds) {
            $status = self::StatusCritical;
        } elseif (($oldestPendingSeconds !== null && $oldestPendingSeconds >= self::PendingWarnSeconds) || $failedRecent > 0) {
            $status = self::StatusWarn;
        }

        return [
            'status' => $status,
            'driver' => $connection,
            'supported' => true,
            'pending' => $pending,
            'delayed' => $delayed,
            'reserved' => $reserved,
            'failed_total' => $failedTotal,
            'failed_recent' => $failedRecent,
            'oldest_pending_seconds' => $oldestPendingSeconds,
            'worker_running' => $workerRunning,
            'recent_failures' => $recentFailures,
        ];
    }

    /**
     * @param  array<string, mixed>  $queue
     * @return list<array{key: string, label: string, status: string, detail: string}>
     */
    private function deploymentChecks(array $queue): array
    {
        $checks = [];

        // Queue-Worker als expliziter Check (spiegelt den Queue-Block).
        $checks[] = [
            'key' => 'queue_worker',
            'label' => 'Queue-Worker',
            'status' => $queue['status'],
            'detail' => $this->queueWorkerDetail($queue),
        ];

        // Neue Permissions ausgerollt?
        $expected = PermissionCatalog::adminOnly();
        $existing = Permission::query()->whereIn('name', $expected)->pluck('name')->all();
        $missing = array_values(array_diff($expected, $existing));
        $checks[] = [
            'key' => 'permissions',
            'label' => 'Berechtigungen ausgerollt',
            'status' => $missing === [] ? self::StatusOk : self::StatusCritical,
            'detail' => $missing === []
                ? 'Alle erwarteten Rollen-Permissions sind vorhanden.'
                : 'Fehlende Permissions (Seeder ausführen): '.implode(', ', $missing),
        ];

        // APP_DEBUG in nicht-lokalen Umgebungen.
        $isLocal = app()->environment('local');
        $debug = (bool) config('app.debug');
        $checks[] = [
            'key' => 'app_debug',
            'label' => 'Debug-Modus',
            'status' => ($debug && ! $isLocal) ? self::StatusCritical : self::StatusOk,
            'detail' => $debug
                ? ('APP_DEBUG ist aktiv'.($isLocal ? ' (lokal ok).' : ' — im Produktivbetrieb deaktivieren!'))
                : 'APP_DEBUG ist deaktiviert.',
        ];

        // Secure Session Cookie außerhalb lokaler Umgebung.
        $secureCookie = (bool) config('session.secure');
        $checks[] = [
            'key' => 'session_secure_cookie',
            'label' => 'Session Secure-Cookie',
            'status' => (! $secureCookie && ! $isLocal) ? self::StatusWarn : self::StatusOk,
            'detail' => $secureCookie
                ? 'Session-Cookie wird nur über HTTPS gesetzt.'
                : 'SESSION_SECURE_COOKIE ist aus'.($isLocal ? ' (lokal ok).' : ' — in https-Umgebungen aktivieren.'),
        ];

        // Ausstehende Medien-Privatisierung.
        $publicImages = PressReleaseImage::query()->withTrashed()->where('disk', 'public')->count();
        $publicAttachments = PressReleaseAttachment::query()->withTrashed()->where('disk', 'public')->count();
        $publicMedia = $publicImages + $publicAttachments;
        $checks[] = [
            'key' => 'media_privatization',
            'label' => 'Medien-Privatisierung',
            'status' => $publicMedia > 0 ? self::StatusWarn : self::StatusOk,
            'detail' => $publicMedia > 0
                ? "Noch {$publicMedia} PM-Medien auf der public-Disk — `press-releases:privatize-media` ausführen."
                : 'Alle PM-Medien liegen auf der privaten Disk.',
        ];

        return $checks;
    }

    /**
     * @param  array<string, mixed>  $queue
     */
    private function queueWorkerDetail(array $queue): string
    {
        if (! $queue['supported']) {
            return "Queue-Treiber „{$queue['driver']}\" — Job-Metriken hier nicht verfügbar.";
        }

        if ($queue['oldest_pending_seconds'] === null) {
            return 'Keine wartenden Jobs. Worker im Leerlauf oder aktiv.';
        }

        $age = $this->humanizeSeconds((int) $queue['oldest_pending_seconds']);

        if ($queue['status'] === self::StatusCritical) {
            return "Ältester wartender Job seit {$age} unbearbeitet — Worker vermutlich gestoppt.";
        }

        return "Ältester wartender Job seit {$age} in der Warteschlange.";
    }

    private function jobDisplayName(string $payload): string
    {
        try {
            $data = json_decode($payload, true, flags: JSON_THROW_ON_ERROR);
        } catch (Throwable) {
            return 'Unbekannter Job';
        }

        if (is_array($data) && is_string($data['displayName'] ?? null)) {
            return $data['displayName'];
        }

        return 'Unbekannter Job';
    }

    private function firstExceptionLine(string $exception): string
    {
        $line = trim(strtok($exception, "\n") ?: '');

        return $line === '' ? 'Unbekannter Fehler' : mb_strimwidth($line, 0, 240, '…');
    }

    private function humanizeSeconds(int $seconds): string
    {
        if ($seconds < 60) {
            return "{$seconds}s";
        }

        if ($seconds < 3600) {
            return floor($seconds / 60).'min';
        }

        return floor($seconds / 3600).'h';
    }

    /**
     * @param  list<string>  $statuses
     */
    private function worstStatus(array $statuses): string
    {
        if (in_array(self::StatusCritical, $statuses, true)) {
            return self::StatusCritical;
        }

        if (in_array(self::StatusWarn, $statuses, true)) {
            return self::StatusWarn;
        }

        return self::StatusOk;
    }
}