<?php

namespace App\Services\Domain;

use App\Jobs\MailProvisioningJob;
use App\Jobs\ProvisionDomainSlaveZoneJob;
use App\Jobs\ProvisionDomainZoneJob;
use App\Jobs\SslProvisioningJob;
use App\Models\Domain;
use App\Models\DomainDkimKey;
use App\Models\DomainDnsRecord;
use App\Models\DomainNsCheck;
use App\Notifications\DomainVerifiedNotification;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\File;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Str;

class DomainVerificationService
{
    public function __construct(
        private readonly DomainDnsBlueprintService $blueprints,
        private readonly \App\Services\Dns\PowerDnsClient $pdns,
    ) {
    }

    public function verify(Domain $domain): bool
    {
        $domain->refresh();
        $statusBefore = (string) $domain->status;
        $stateBefore = (string) ($domain->onboarding_state ?: Domain::STATE_PENDING_NS);

        $domain->update([
            'status' => 'verifying',
            'onboarding_state' => Domain::STATE_VERIFYING_NS,
            'ns_checked_at' => now(),
        ]);

        if ((string) $domain->onboarding_mode === Domain::MODE_MANUAL_DNS) {
            return $this->verifyManualDns($domain->fresh(), $statusBefore, $stateBefore);
        }

        return $this->verifyNameserverTakeover($domain->fresh(), $statusBefore, $stateBefore);
    }

    public function prepareNameserverZone(Domain $domain): void
    {
        $domain = $domain->fresh();
        $this->ensureDkimKeys($domain);
        $this->dispatchProvisioningChain($domain->id);
    }

    public function prepareManualDnsPack(Domain $domain): void
    {
        $domain = $domain->fresh();
        [$selector, $publicKey] = $this->ensureDkimKeys($domain);
        $pack = $this->blueprints->manualDnsPack($domain, $selector, $publicKey);
        $this->syncDnsRecords($domain, $pack, 'required_manual');
    }

    private function verifyNameserverTakeover(Domain $domain, string $statusBefore, string $stateBefore): bool
    {
        $expected = $this->normalizeNameservers((array) ($domain->ns_expected ?? $this->blueprints->expectedNameservers()));
        $observed = $this->lookupNameservers($domain->host);

        $domain->update([
            'ns_expected' => $expected,
            'ns_observed' => $observed,
        ]);

        if (! $this->nameserversMatch($expected, $observed)) {
            $domain->update([
                'status' => 'pending',
                'onboarding_state' => Domain::STATE_PENDING_NS,
            ]);
            $domain = $domain->fresh();
            $this->logCheck($domain, [
                'check_type' => 'ns_takeover',
                'result' => 'pending',
                'expected_nameservers' => $expected,
                'observed_nameservers' => $observed,
                'has_authoritative_answer' => null,
                'status_before' => $statusBefore,
                'status_after' => (string) $domain->status,
                'state_before' => $stateBefore,
                'state_after' => (string) $domain->onboarding_state,
                'notes' => 'Nameservers do not match expected Ladill nameservers yet.',
            ]);

            return false;
        }

        $hasAuthoritativeAnswer = $this->zoneHasAuthoritativeAnswer($domain->host);
        if (! $hasAuthoritativeAnswer) {
            ProvisionDomainZoneJob::dispatch($domain->id);

            $domain->update([
                'status' => 'verifying',
                'onboarding_state' => Domain::STATE_VERIFYING_NS,
            ]);
            $domain = $domain->fresh();
            $this->logCheck($domain, [
                'check_type' => 'ns_takeover',
                'result' => 'pending',
                'expected_nameservers' => $expected,
                'observed_nameservers' => $observed,
                'has_authoritative_answer' => false,
                'status_before' => $statusBefore,
                'status_after' => (string) $domain->status,
                'state_before' => $stateBefore,
                'state_after' => (string) $domain->onboarding_state,
                'notes' => 'Nameservers match, but authoritative zone answer is not ready yet.',
            ]);

            return false;
        }

        return DB::transaction(function () use ($domain, $statusBefore, $stateBefore, $expected, $observed, $hasAuthoritativeAnswer): bool {
            $domain->refresh();
            $domain->update([
                'status' => 'verifying',
                'onboarding_state' => Domain::STATE_CONNECTED,
                'connected_at' => $domain->connected_at ?? now(),
                'dns_mode' => 'managed',
            ]);

            [$selector, $publicKey] = $this->ensureDkimKeys($domain);
            $records = $this->blueprints->managedRecords($domain, $selector, $publicKey);
            $this->syncDnsRecords($domain, $records, 'managed');

            $domain->update([
                'onboarding_state' => Domain::STATE_MAIL_READY,
                'mail_ready_at' => $domain->mail_ready_at ?? now(),
            ]);

            $domain->update([
                'status' => 'verified',
                'verified_at' => $domain->verified_at ?? now(),
                'onboarding_state' => Domain::STATE_ACTIVE,
                'active_at' => $domain->active_at ?? now(),
            ]);
            $domain->refresh();
            $this->logCheck($domain, [
                'check_type' => 'ns_takeover',
                'result' => 'success',
                'expected_nameservers' => $expected,
                'observed_nameservers' => $observed,
                'has_authoritative_answer' => $hasAuthoritativeAnswer,
                'status_before' => $statusBefore,
                'status_after' => (string) $domain->status,
                'state_before' => $stateBefore,
                'state_after' => (string) $domain->onboarding_state,
                'notes' => 'Nameserver takeover complete. Managed DNS and mail records are provisioned.',
            ]);
            $this->dispatchProvisioningChain($domain->id);

            // Notify user that domain is verified
            $user = $domain->website?->user;
            if ($user) {
                $user->notify(new DomainVerifiedNotification($domain));
            }

            return true;
        });
    }

    private function verifyManualDns(Domain $domain, string $statusBefore, string $stateBefore): bool
    {
        $this->prepareManualDnsPack($domain);
        $domain = $domain->fresh('dnsRecords');

        $records = $domain->dnsRecords
            ->where('source', 'required_manual')
            ->values();

        if ($records->isEmpty()) {
            $domain->update([
                'status' => 'failed',
                'onboarding_state' => Domain::STATE_FAILED,
            ]);
            $domain = $domain->fresh();
            $this->logCheck($domain, [
                'check_type' => 'manual_dns',
                'result' => 'failed',
                'manual_records_total' => 0,
                'manual_records_verified' => 0,
                'status_before' => $statusBefore,
                'status_after' => (string) $domain->status,
                'state_before' => $stateBefore,
                'state_after' => (string) $domain->onboarding_state,
                'notes' => 'Manual DNS pack is empty; cannot verify domain.',
            ]);

            return false;
        }

        $allVerified = true;

        foreach ($records as $record) {
            $matched = $this->recordExistsInPublicDns($domain->host, $record);

            $record->update([
                'status' => $matched ? 'verified' : 'pending',
                'last_checked_at' => now(),
            ]);

            if (! $matched) {
                $allVerified = false;
            }
        }

        if (! $allVerified) {
            $domain->update([
                'status' => 'pending',
                'onboarding_state' => Domain::STATE_VERIFYING_NS,
                'ns_checked_at' => now(),
            ]);
            $domain = $domain->fresh();
            $this->logCheck($domain, [
                'check_type' => 'manual_dns',
                'result' => 'pending',
                'manual_records_total' => $records->count(),
                'manual_records_verified' => $records->where('status', 'verified')->count(),
                'status_before' => $statusBefore,
                'status_after' => (string) $domain->status,
                'state_before' => $stateBefore,
                'state_after' => (string) $domain->onboarding_state,
                'notes' => 'Manual DNS records are not fully propagated yet.',
            ]);

            return false;
        }

        $domain->update([
            'status' => 'verified',
            'verified_at' => $domain->verified_at ?? now(),
            'onboarding_state' => Domain::STATE_ACTIVE,
            'dns_mode' => 'manual',
            'manual_dns_verified_at' => $domain->manual_dns_verified_at ?? now(),
            'connected_at' => $domain->connected_at ?? now(),
            'mail_ready_at' => $domain->mail_ready_at ?? now(),
            'active_at' => $domain->active_at ?? now(),
            'ns_checked_at' => now(),
        ]);
        $domain = $domain->fresh();
        $this->logCheck($domain, [
            'check_type' => 'manual_dns',
            'result' => 'success',
            'manual_records_total' => $records->count(),
            'manual_records_verified' => $records->where('status', 'verified')->count(),
            'status_before' => $statusBefore,
            'status_after' => (string) $domain->status,
            'state_before' => $stateBefore,
            'state_after' => (string) $domain->onboarding_state,
            'notes' => 'All required manual DNS records are verified.',
        ]);
        $this->dispatchProvisioningChain($domain->id);

        // Notify user that domain is verified
        $user = $domain->website?->user;
        if ($user) {
            $user->notify(new DomainVerifiedNotification($domain));
        }

        return true;
    }

    public function reprovision(Domain $domain): void
    {
        $domain = $domain->fresh() ?? $domain;
        $this->ensureDkimKeys($domain);

        // Create the authoritative zone immediately when possible. Async-only
        // provisioning left Ladill NS delegated with REFUSED answers (SERVFAIL
        // for Let's Encrypt) whenever the queue lagged or failed.
        try {
            $this->pdns->ensureZone($domain->fresh());
            ProvisionDomainSlaveZoneJob::dispatch($domain->id);
        } catch (\Throwable $e) {
            Log::warning('Immediate PDNS ensureZone failed; queueing retry', [
                'domain_id' => $domain->id,
                'host' => $domain->host,
                'error' => $e->getMessage(),
            ]);
            ProvisionDomainZoneJob::dispatch($domain->id);
        }

        MailProvisioningJob::dispatch($domain->id);
        SslProvisioningJob::dispatch($domain->id);
    }

    private function dispatchProvisioningChain(int $domainId): void
    {
        ProvisionDomainZoneJob::withChain([
            new MailProvisioningJob($domainId),
            new SslProvisioningJob($domainId),
        ])->dispatch($domainId);
    }

    private function ensureDkimKeys(Domain $domain): array
    {
        $existing = DomainDkimKey::query()
            ->where('domain_id', $domain->id)
            ->where('status', 'active')
            ->latest('id')
            ->first();

        if ($existing) {
            return [$existing->selector, $existing->public_key_txt];
        }

        $prefix = (string) config('mailinfra.dkim_selector_prefix', 'ladill');
        $selector = Str::lower(trim($prefix)) ?: 'ladill';
        $selector .= '1';

        $publicKey = '';
        $privateKey = null;

        if (function_exists('openssl_pkey_new')) {
            $resource = openssl_pkey_new([
                'private_key_bits' => 2048,
                'private_key_type' => OPENSSL_KEYTYPE_RSA,
            ]);

            if ($resource !== false) {
                openssl_pkey_export($resource, $privateOut);
                $details = openssl_pkey_get_details($resource);
                $publicPem = (string) ($details['key'] ?? '');
                $publicKey = preg_replace('/-----BEGIN PUBLIC KEY-----|-----END PUBLIC KEY-----|\s+/', '', $publicPem) ?: '';
                $privateKey = $privateOut ?: null;
            }
        }

        if ($publicKey === '') {
            $publicKey = Str::upper(Str::random(360));
        }

        $privatePath = null;
        if (is_string($privateKey) && trim($privateKey) !== '') {
            $safeHost = Str::slug($domain->host, '_');
            $directory = storage_path('app/mail/dkim');
            File::ensureDirectoryExists($directory);
            $privatePath = $directory.'/'.$safeHost.'_'.$selector.'.key';
            File::put($privatePath, $privateKey);
        }

        $key = DomainDkimKey::query()->create([
            'domain_id' => $domain->id,
            'selector' => $selector,
            'public_key_txt' => $publicKey,
            'private_key_path' => $privatePath,
            'status' => 'active',
            'generated_at' => now(),
        ]);

        return [$key->selector, $key->public_key_txt];
    }

    private function syncDnsRecords(Domain $domain, array $records, string $source): void
    {
        $keepSignatures = [];

        foreach ($records as $record) {
            if (! is_array($record)) {
                continue;
            }

            $name = (string) ($record['name'] ?? '@');
            $type = strtoupper((string) ($record['type'] ?? 'TXT'));
            $value = (string) ($record['value'] ?? '');
            $keepSignatures[] = strtolower($name.'|'.$type.'|'.$value);

            DomainDnsRecord::query()->updateOrCreate(
                [
                    'domain_id' => $domain->id,
                    'name' => $name,
                    'type' => $type,
                    'value' => $value,
                ],
                [
                    'ttl' => (int) ($record['ttl'] ?? 3600),
                    'priority' => isset($record['priority']) ? (int) $record['priority'] : null,
                    'source' => $source,
                    'status' => (string) ($record['status'] ?? 'pending'),
                    'notes' => $record['notes'] ?? null,
                    'last_checked_at' => now(),
                ]
            );
        }

        DomainDnsRecord::query()
            ->where('domain_id', $domain->id)
            ->where('source', $source)
            ->get()
            ->each(function (DomainDnsRecord $record) use ($keepSignatures): void {
                $signature = strtolower($record->name.'|'.$record->type.'|'.$record->value);
                if (! in_array($signature, $keepSignatures, true)) {
                    $record->delete();
                }
            });
    }

    private function lookupNameservers(string $host): array
    {
        if (! function_exists('dns_get_record')) {
            return [];
        }

        $records = @dns_get_record($host, DNS_NS);
        if (! is_array($records)) {
            return [];
        }

        return collect($records)
            ->map(fn ($record) => strtolower(trim((string) ($record['target'] ?? ''), ". \t\n\r\0\x0B")))
            ->filter()
            ->unique()
            ->values()
            ->all();
    }

    private function normalizeNameservers(array $nameservers): array
    {
        return collect($nameservers)
            ->map(fn ($record) => strtolower(trim((string) $record, ". \t\n\r\0\x0B")))
            ->filter()
            ->unique()
            ->values()
            ->all();
    }

    private function nameserversMatch(array $expected, array $observed): bool
    {
        $expected = $this->normalizeNameservers($expected);
        $observed = $this->normalizeNameservers($observed);

        if ($expected === [] || $observed === []) {
            return false;
        }

        return collect($expected)->diff($observed)->isEmpty();
    }

    private function recordExistsInPublicDns(string $zoneHost, DomainDnsRecord $record): bool
    {
        if (! function_exists('dns_get_record')) {
            return false;
        }

        $name = trim((string) $record->name);
        $fqdn = $name === '@' ? $zoneHost : $name.'.'.$zoneHost;
        $type = strtoupper(trim((string) $record->type));
        $expectedValue = strtolower(trim((string) $record->value, ". \t\n\r\0\x0B\""));

        $flag = match ($type) {
            'MX' => DNS_MX,
            'CNAME' => DNS_CNAME,
            'A' => DNS_A,
            default => DNS_TXT,
        };

        $records = @dns_get_record($fqdn, $flag);
        if (! is_array($records) || $records === []) {
            return false;
        }

        foreach ($records as $item) {
            if ($type === 'MX') {
                $value = strtolower(trim((string) ($item['target'] ?? ''), ". \t\n\r\0\x0B"));
                $priority = (int) ($item['pri'] ?? 0);
                $expectedPriority = (int) ($record->priority ?? 0);
                if ($value === $expectedValue && $priority === $expectedPriority) {
                    return true;
                }
                continue;
            }

            if ($type === 'TXT') {
                $value = strtolower(trim((string) ($item['txt'] ?? ''), "\" \t\n\r\0\x0B"));
                if ($value === $expectedValue) {
                    return true;
                }
                continue;
            }

            if ($type === 'CNAME') {
                $value = strtolower(trim((string) ($item['target'] ?? ''), ". \t\n\r\0\x0B"));
                if ($value === $expectedValue) {
                    return true;
                }
                continue;
            }

            if ($type === 'A') {
                $value = strtolower(trim((string) ($item['ip'] ?? ''), ". \t\n\r\0\x0B"));
                if ($value === $expectedValue) {
                    return true;
                }
            }
        }

        return false;
    }

    private function zoneHasAuthoritativeAnswer(string $host): bool
    {
        if (! function_exists('dns_get_record')) {
            return false;
        }

        $soa = @dns_get_record($host, DNS_SOA);
        if (is_array($soa) && $soa !== []) {
            return true;
        }

        $ns = @dns_get_record($host, DNS_NS);

        return is_array($ns) && $ns !== [];
    }

    private function logCheck(Domain $domain, array $payload): void
    {
        DomainNsCheck::query()->create([
            'domain_id' => $domain->id,
            'check_type' => (string) ($payload['check_type'] ?? 'onboarding'),
            'result' => (string) ($payload['result'] ?? 'pending'),
            'expected_nameservers' => $payload['expected_nameservers'] ?? null,
            'observed_nameservers' => $payload['observed_nameservers'] ?? null,
            'has_authoritative_answer' => $payload['has_authoritative_answer'] ?? null,
            'manual_records_total' => (int) ($payload['manual_records_total'] ?? 0),
            'manual_records_verified' => (int) ($payload['manual_records_verified'] ?? 0),
            'status_before' => $payload['status_before'] ?? null,
            'status_after' => $payload['status_after'] ?? null,
            'state_before' => $payload['state_before'] ?? null,
            'state_after' => $payload['state_after'] ?? null,
            'notes' => $payload['notes'] ?? null,
            'checked_at' => now(),
        ]);
    }
}