<?php

declare(strict_types=1);

namespace App\Services\WorkingDays;

use App\Services\Utils\DurationConvertor;

/**
 * Solves the duration of a given period based on working days and return new end date.
 */
class DurationSolver
{
    protected const int MAX_ITERATIONS = 100;

    public function __construct(
        protected readonly WorkingDayDeterminerInterface $workingDayDeterminer,
        protected readonly DurationConvertor $durationConvertor,
    ) {
    }

    /**
     * Calculate the duration of a given period based on working days.
     * @param \DateTimeImmutable $startDate
     * @param \DateTimeImmutable $endDate
     * @return \DateTimeImmutable
     * @throws \Exception
     */
    public function calculateDuration(
        \DateTimeImmutable $startDate,
        \DateTimeImmutable $endDate,
    ): \DateTimeImmutable {
        $loopId = 0;
        $requiredWorkingDaysCount = (int) ($startDate->setTime(0, 0)->diff($endDate->setTime(0, 0))->format('%a')) + 1;

        do {
            $workingDaysCount = (int) ($startDate->setTime(0, 0)->diff($endDate->setTime(0, 0))->format('%a')) + 1;
            $workingDaysCountInInterval = $this->workingDayDeterminer->getWorkingDaysCount($startDate, $workingDaysCount);

            if ($workingDaysCountInInterval >= $requiredWorkingDaysCount) {
                // there is no weekends or holidays in the given interval
                break;
            } else {
                $endDate = $endDate->add(new \DateInterval(sprintf('P%dD', $requiredWorkingDaysCount - $workingDaysCountInInterval)));
                if ($loopId > static::MAX_ITERATIONS) {
                    throw new \InvalidArgumentException('No working days found in the given interval');
                }
            }

            $loopId++;
        } while ($workingDaysCount != $workingDaysCountInInterval);

        return $endDate;
    }
}