applicant-site/app/Http/Controllers/Api/CalculatorController.php

<?php

namespace App\Http\Controllers\Api;

use App\Http\Controllers\Controller;
use App\Models\Department;
use App\Models\Direction;
use App\Models\EntranceExamination;
use App\Models\Faculty;
use Illuminate\Http\Request;

class CalculatorController extends Controller
{
    public function findDirectionFromSubjects(Request $request)
    {
        $getJSON = $request->input()['predmets'];
        $getsSubjects = json_decode($getJSON);
        $countUserSubjects = count($getsSubjects);

        $filteredDirectionIds = EntranceExamination::all()
            ->select("direction_id", "subject_id")
            ->groupBy('direction_id')
            ->map(function ($direction) {
                return $direction->map(fn($item) => $item['subject_id']);
            })
            ->filter(fn($direction) => count($direction) <= $countUserSubjects)
            ->keys();

        $directions = Direction::whereIn('id', $filteredDirectionIds)->get();


        $generateHtml = function ($acc, $direction) {
            $department = Department::find($direction->department_id);
            $faculty = Faculty::find($department->faculty_id);

            return "{$acc} <tr class=\"\">
<td id=\"faculty\"> {$faculty->name} </td>
<td> {$direction->name} </td>
<td class=\"text-end\"> {$direction->period} </td>
</tr>";
        };

        $html = $directions->reduce($generateHtml, '');

        return response()->json(['html' => $html]);
    }
}