Get a group of dates and group them by X minutes (timetables)

TimeService.php

<?php

namespace App\Services;

use ArrayIterator;
use Carbon\Carbon;
use Illuminate\Support\Collection;

class TimeService
{
    /** @var int */
    public const GROUP_BY_MINUTES = 30;

    /** @var array */
    protected $timesArray = [];

    /** @var */
    protected $times;

    /** @var string */
    protected $dateFormat = 'N';

    /**
     * @param  \Illuminate\Support\Collection  $times
     * @param  string  $format
     * @return array
     */
    public function groupTimes(Collection $times, string $format = 'H:i'): array
    {
        $groups = $times->groupBy(function (Carbon $obj, $key) {
            return $obj->format($this->dateFormat);
        });

        /** @var \Illuminate\Support\Collection $groupTimes */
        foreach ($groups as $groupTimes) {
            $groupTimes = $groupTimes->sortBy(function (Carbon $obj, $key) {
                return Carbon::parse($obj->getTimestamp())->timestamp;
            });

            $this->times = $groupTimes;

            $iterator = $groupTimes->getIterator();

            $i = 0;

            while ($this->times->count() > 0) {
                $time = $iterator->current();
                $date = $time->format($this->dateFormat);
                $newTime = $time->format($format);
                $this->timesArray[$date][$i][] = $newTime;
                $this->times->forget($iterator->key());

                $this->nextTime($iterator, $i, $format);
            }
        }

        return $this->timesArray;
    }

    /**
     * @param  \ArrayIterator  $iterator
     * @param  int  $i
     * @param  string  $format
     */
    public function nextTime(ArrayIterator $iterator, int $i, string $format): void
    {
        $time = $iterator->current();
        $iterator->next();
        $nextTime = $iterator->current();
        $date = $time->format($this->dateFormat);

        // Create new group
        if (!now()->parse($time)->addMinutes(self::GROUP_BY_MINUTES)->eq($nextTime)) {
            $i++;
        }

        $newTime = $nextTime->format($format);
        $this->timesArray[$date][$i][] = $newTime;
        $this->times->forget($iterator->key());

        while ($this->times->count() > 0 && $iterator->valid()) {
            $this->nextTime($iterator, $i, $format);
            $i++;
        }
    }
}

TimeServiceTest.php

<?php

namespace Tests\Unit;

use App\Services\TimeService;
use Tests\TestCase;

class TimeServiceTest extends TestCase
{
    /** @test */
    public function make_time_range(): void
    {
        $times = collect([
            now()->parse(now()->format('Y-m-d') . '14:30'),
            now()->parse(now()->format('Y-m-d') . '09:00'),
            now()->parse(now()->format('Y-m-d') . '09:30'),
            now()->parse(now()->format('Y-m-d') . '10:00'),
            now()->parse(now()->format('Y-m-d') . '12:00'),
            now()->parse(now()->format('Y-m-d') . '13:00'),
            now()->parse(now()->format('Y-m-d') . '13:30'),
            now()->parse(now()->format('Y-m-d') . '15:00'),
            now()->parse(now()->format('Y-m-d') . '15:30'),
            now()->parse(now()->format('Y-m-d') . '16:00'),
        ]);

        /** @var \App\Services\TimeService $timeService */
        $timeService = app(TimeService::class);
        $this->assertEquals($timeService->groupTimes($times), [
            0 => [
                0 => '09:00',
                1 => '09:30',
                2 => '10:00',
            ],
            1 => [
                0 => '12:00',
            ],
            2 => [
                0 => '13:00',
                1 => '13:30',
            ],
            3 => [
                0 => '14:30',
                1 => '15:00',
                2 => '15:30',
                3 => '16:00',
            ],
        ]);
    }
}