<?php

namespace App\Services\Hosting\Provisioning;

use App\Enums\IpPoolType;
use App\Exceptions\Hosting\ProvisioningException;
use App\Models\Customer;
use App\Models\IpPool;
use Illuminate\Support\Facades\DB;

class IpAddressAllocator
{
    public function allocateFromPool(?IpPool $pool = null, ?string $preferred = null): string
    {
        $pool ??= $this->defaultPrivatePool();

        return $this->allocate($pool, $preferred);
    }

    public function allocatePublicIp(?IpPool $pool = null, ?string $preferred = null): string
    {
        $pool ??= IpPool::query()
            ->where('type', IpPoolType::Public)
            ->where('is_active', true)
            ->first() ?? $this->bootstrapPublicPool();

        if ($pool->type !== IpPoolType::Public) {
            throw new ProvisioningException('Selected pool is not a public IP pool.', step: 'ip_allocation');
        }

        return $this->allocate($pool, $preferred, 'public_ip');
    }

    public function allocate(IpPool $pool, ?string $preferred = null, string $column = 'ip_address'): string
    {
        return DB::transaction(function () use ($pool, $preferred, $column) {
            IpPool::query()->whereKey($pool->id)->lockForUpdate()->first();

            if ($preferred !== null) {
                if (! $pool->containsIp($preferred)) {
                    throw new ProvisioningException(
                        "IP {$preferred} is outside pool {$pool->name}.",
                        step: 'ip_allocation',
                    );
                }

                if ($this->isIpUsed($preferred, $pool, $column)) {
                    throw new ProvisioningException(
                        "IP address {$preferred} is already in use.",
                        step: 'ip_allocation',
                    );
                }

                return $preferred;
            }

            $start = ip2long($pool->start_ip);
            $end = ip2long($pool->end_ip);

            if ($start === false || $end === false || $start > $end) {
                throw new ProvisioningException('Invalid IP pool range.', step: 'ip_allocation');
            }

            $used = $this->usedIpsInPool($pool, $column);

            for ($long = $start; $long <= $end; $long++) {
                if (! isset($used[$long])) {
                    return long2ip($long);
                }
            }

            throw new ProvisioningException("No free IPs in pool {$pool->name}.", step: 'ip_allocation');
        }, 3);
    }

    private function defaultPrivatePool(): IpPool
    {
        $pool = IpPool::query()
            ->where('type', IpPoolType::Private)
            ->where('is_active', true)
            ->orderBy('id')
            ->first();

        if ($pool) {
            return $pool;
        }

        return $this->bootstrapPoolFromConfig(IpPoolType::Private);
    }

    private function bootstrapPublicPool(): IpPool
    {
        return IpPool::query()->firstOrCreate(
            ['name' => 'Öffentlich 185.45.149.x', 'type' => IpPoolType::Public],
            [
                'start_ip' => config('hosting.public_network.ip_pool_start'),
                'end_ip' => config('hosting.public_network.ip_pool_end'),
                'gateway' => config('hosting.public_network.gateway'),
                'cidr' => config('hosting.public_network.cidr'),
                'is_active' => true,
            ],
        );
    }

    private function bootstrapPoolFromConfig(IpPoolType $type): IpPool
    {
        return IpPool::query()->firstOrCreate(
            ['name' => 'Privat 10.32.0.0/24', 'type' => IpPoolType::Private],
            [
                'start_ip' => config('hosting.network.ip_pool_start'),
                'end_ip' => config('hosting.network.ip_pool_end'),
                'gateway' => config('hosting.network.gateway'),
                'cidr' => config('hosting.network.cidr'),
                'is_active' => true,
            ],
        );
    }

    private function usedIpsInPool(IpPool $pool, string $column): array
    {
        $query = Customer::query()
            ->where('ip_pool_id', $pool->id)
            ->whereIn('status', ['pending', 'active']);

        if ($column === 'public_ip') {
            return $query->whereNotNull('public_ip')
                ->pluck('public_ip')
                ->merge(
                    Customer::query()
                        ->whereIn('status', ['pending', 'active'])
                        ->whereNotNull('public_ip')
                        ->pluck('public_ip')
                )
                ->unique()
                ->map(fn (string $ip) => ip2long($ip))
                ->filter()
                ->flip()
                ->all();
        }

        return $query->whereNotNull('ip_address')
            ->pluck('ip_address')
            ->map(fn (string $ip) => ip2long($ip))
            ->filter()
            ->flip()
            ->all();
    }

    private function isIpUsed(string $ip, IpPool $pool, string $column): bool
    {
        $check = Customer::query()
            ->whereIn('status', ['pending', 'active']);

        if ($column === 'public_ip') {
            return (clone $check)->where('public_ip', $ip)->exists()
                || (clone $check)->where('ip_address', $ip)->exists();
        }

        return (clone $check)->where('ip_address', $ip)->exists()
            || (clone $check)->where('public_ip', $ip)->exists();
    }
}