eatvio-infra/app/Http/Controllers/ChatController.php

<?php

namespace App\Http\Controllers;

use App\Models\Chat;
use App\Models\User;
use Illuminate\Contracts\View\Factory as ViewFactory;
use Illuminate\Contracts\View\View;

class ChatController extends Controller
{
    public function index(): View|ViewFactory
    {
        // $_ = "from_user_id to_user_id";
        $curUserId = Auth()->user()->id;
        $lastChatUsers = Chat::select(['from_user_id', 'to_user_id'])
            ->where('from_user_id', $curUserId)
            ->orWhere('to_user_id', $curUserId)
            ->get()
            ->map(fn ($e) => [$e['from_user_id'], $e['to_user_id']])
            ->flatten()
            ->unique()
            ->filter(fn ($e) => $e !== $curUserId)
            ->values()
            ->map(fn ($id) => User::find($id));

        $lastChatMessage = Chat::withLastUserMessage($curUserId);

        $lastChatRecipientUserId = $lastChatMessage->count() ? $lastChatMessage['from_user_id'] : null;

        if (! is_null($lastChatRecipientUserId) && $lastChatMessage['from_user_id'] === $curUserId) {
            $lastChatRecipientUserId = $lastChatMessage['to_user_id'];
        }

        return view(
            'chat.index',
            [
                'lastChatRecipientUserId' => $lastChatRecipientUserId,
                'lastChatUsers' => $lastChatUsers,
                'curUserId' => $curUserId,
                'chanId' => $this->makeChanName($curUserId, $lastChatRecipientUserId),
            ]
        );
    }

    public function show(int $lastChatUser): View|ViewFactory
    {
        $lastChatUser = User::find($lastChatUser);
        // $_ = "from_user_id to_user_id";
        $curUserId = Auth()->user()->id;

        $lastChatUsers = Chat::select(['from_user_id', 'to_user_id'])
            ->where('from_user_id', $curUserId)
            ->orWhere('to_user_id', $curUserId)
            ->get()
            ->map(fn ($e) => [$e['from_user_id'], $e['to_user_id']])
            ->flatten()
            ->unique()
            ->filter(fn ($e) => $e !== $curUserId)
            ->values()
            ->map(fn ($id) => User::find($id));

        return view(
            'chat.index',
            [
                'lastChatRecipientUserId' => $lastChatUser->id,
                'lastChatUsers' => $lastChatUsers,
                'curUserId' => $curUserId,
                'chanId' => $this->makeChanName($curUserId, $lastChatUser->id),
            ]
        );
    }

    private function makeChanName(?int $from = null, ?int $to = null): string
    {
        return (int) $from < (int) $to
            ? $from.'_'.$to
            : $to.'_'.$from;
    }
}