<?php

namespace App\Services\Link;

use App\Models\LinkClick;
use App\Models\LinkWallet;
use App\Models\ShortLink;
use App\Models\User;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;
use RuntimeException;

class LinkManagerService
{
    public function __construct(
        private LinkBillingService $billing,
        private LinkClickRecorder $clickRecorder,
    ) {}

    public function create(User $user, array $data): ShortLink
    {
        if (! $this->billing->canCreate($user)) {
            throw new RuntimeException('Insufficient wallet balance. Top up to create links.');
        }

        return DB::transaction(function () use ($user, $data) {
            $slug = $this->resolveSlug($data['custom_slug'] ?? null);
            $wallet = $user->getOrCreateLinkWallet();

            $link = ShortLink::create([
                'user_id' => $user->id,
                'source_app' => 'link',
                'source_kind' => 'redirect',
                'is_managed_here' => true,
                'slug' => $slug,
                'label' => $data['label'] ?? null,
                'destination_url' => $this->normalizeUrl($data['destination_url']),
                'expires_at' => $data['expires_at'] ?? null,
            ]);

            $this->billing->debitForLinkCreation($wallet, $link);

            return $link;
        });
    }

    public function update(ShortLink $link, array $data): ShortLink
    {
        $link->fill([
            'label' => $data['label'] ?? $link->label,
            'destination_url' => isset($data['destination_url'])
                ? $this->normalizeUrl($data['destination_url'])
                : $link->destination_url,
            'is_active' => $data['is_active'] ?? $link->is_active,
            'expires_at' => array_key_exists('expires_at', $data) ? $data['expires_at'] : $link->expires_at,
        ])->save();

        return $link->fresh();
    }

    public function resolve(Request $request, string $slug): ?ShortLink
    {
        $link = ShortLink::query()
            ->where('slug', $slug)
            ->where('is_active', true)
            ->first();

        if ($link === null || $link->isExpired()) {
            return null;
        }

        $this->clickRecorder->record($link, $request);

        return $link;
    }

    private function resolveSlug(?string $custom): string
    {
        if ($custom !== null && $custom !== '') {
            $custom = strtolower(trim($custom));
            if (! preg_match('/^[a-z0-9][a-z0-9-]{1,18}[a-z0-9]$/', $custom)) {
                throw new RuntimeException('Custom slug must be 3–20 characters: lowercase letters, numbers, and hyphens.');
            }
            if (ShortLink::where('slug', $custom)->exists()) {
                throw new RuntimeException('That slug is already taken.');
            }

            return $custom;
        }

        do {
            $slug = Str::lower(Str::random((int) config('link.slug_length', 8)));
        } while (ShortLink::where('slug', $slug)->exists());

        return $slug;
    }

    private function normalizeUrl(string $url): string
    {
        $url = trim($url);
        if ($url === '') {
            throw new RuntimeException('Destination URL is required.');
        }
        if (! preg_match('#^https?://#i', $url)) {
            $url = 'https://'.$url;
        }
        if (! filter_var($url, FILTER_VALIDATE_URL)) {
            throw new RuntimeException('Enter a valid URL.');
        }

        return $url;
    }
}