Attainly/backend/app/Schedule/UseCases/CreateSchedule/CreateSchedule.php

<?php

namespace App\Schedule\UseCases\CreateSchedule;

use App\Element\Element;
use App\Element\ElementRepository;
use App\Exceptions\BadRequestException;
use App\Exceptions\NotFoundException;
use App\Schedule\CreateScheduleAssignmentDto;
use App\Schedule\CreateScheduleDto;
use App\Schedule\Schedule;
use App\Schedule\ScheduleRepository;
use App\Set\Set;
use App\Set\SetRepository;
use DateTimeImmutable;
use DateTimeZone;

class CreateSchedule
{
    public function __construct(
        private SetRepository $setRepository,
        private ElementRepository $elementRepository,
        private ScheduleRepository $scheduleRepository,
    ) {}

    /**
     * @throws BadRequestException
     * @throws NotFoundException
     */
    public function execute(CreateScheduleRequest $request): Schedule
    {
        if ($request->setId === null || $request->setId < 1) {
            throw new BadRequestException('setId is required');
        }

        $set = $this->setRepository->find($request->setId);
        if ($set === null) {
            throw new NotFoundException('set not found');
        }

        if ($request->elementKind === null || $request->elementKind === '') {
            throw new BadRequestException('elementKind is required');
        }

        $startDate = $this->parseDate($request->startDate, 'startDate');
        $targetDate = $this->parseDate($request->targetDate, 'targetDate');
        if ($targetDate < $startDate) {
            throw new BadRequestException(
                'targetDate must not be before startDate',
            );
        }

        $elements = array_values(array_filter(
            $this->orderedElements($set),
            function (Element $element) use ($request): bool {
                return $element->getKind() === $request->elementKind;
            },
        ));
        if ($elements === []) {
            throw new BadRequestException(
                'elementKind is not available for set',
            );
        }

        $assignments = $this->assignments(
            elements: $elements,
            startDate: $startDate,
            targetDate: $targetDate,
        );

        return $this->scheduleRepository->create(new CreateScheduleDto(
            user: $request->user,
            set: $set,
            elementKind: $request->elementKind,
            startDate: $startDate,
            targetDate: $targetDate,
            assignments: $assignments,
        ));
    }

    /**
     * @return list<Element>
     */
    private function orderedElements(Set $set): array
    {
        $childrenByParentId = [];

        foreach ($this->elementRepository->findBySet($set) as $element) {
            $parentId = $element->getParentElement()?->getId() ?? 0;
            $childrenByParentId[$parentId][] = $element;
        }

        foreach ($childrenByParentId as &$children) {
            usort($children, function (Element $first, Element $second): int {
                $positionComparison = $first->getPosition()
                    <=> $second->getPosition();
                if ($positionComparison !== 0) {
                    return $positionComparison;
                }

                return $first->getId() <=> $second->getId();
            });
        }
        unset($children);

        $orderedElements = [];
        $this->appendChildren(
            parentId: 0,
            childrenByParentId: $childrenByParentId,
            orderedElements: $orderedElements,
        );

        return $orderedElements;
    }

    /**
     * @param array<int, list<Element>> $childrenByParentId
     * @param list<Element> $orderedElements
     */
    private function appendChildren(
        int $parentId,
        array $childrenByParentId,
        array &$orderedElements,
    ): void {
        foreach ($childrenByParentId[$parentId] ?? [] as $element) {
            $orderedElements[] = $element;
            $this->appendChildren(
                parentId: $element->getId(),
                childrenByParentId: $childrenByParentId,
                orderedElements: $orderedElements,
            );
        }
    }

    /**
     * @param list<Element> $elements
     * @return list<CreateScheduleAssignmentDto>
     */
    private function assignments(
        array $elements,
        DateTimeImmutable $startDate,
        DateTimeImmutable $targetDate,
    ): array {
        $differenceInDays = $startDate->diff($targetDate)->days;
        $dayCount = $differenceInDays + 1;
        $elementCount = count($elements);
        $assignments = [];

        foreach ($elements as $index => $element) {
            $dayIndex = $this->dayIndex(
                elementIndex: $index,
                elementCount: $elementCount,
                dayCount: $dayCount,
            );
            $assignments[] = new CreateScheduleAssignmentDto(
                element: $element,
                scheduledDate: $startDate->modify("+{$dayIndex} days"),
                position: $index + 1,
            );
        }

        return $assignments;
    }

    private function dayIndex(
        int $elementIndex,
        int $elementCount,
        int $dayCount,
    ): int {
        if ($elementCount === 1 || $dayCount === 1) {
            return 0;
        }

        if ($elementCount < $dayCount) {
            $scaledIndex = $elementIndex * ($dayCount - 1)
                / ($elementCount - 1);

            return (int) floor($scaledIndex + 0.5);
        }

        return intdiv($elementIndex * $dayCount, $elementCount);
    }

    /**
     * @throws BadRequestException
     */
    private function parseDate(?string $value, string $field): DateTimeImmutable
    {
        if ($value === null || $value === '') {
            throw new BadRequestException("{$field} is required");
        }

        $date = DateTimeImmutable::createFromFormat(
            '!Y-m-d',
            $value,
            new DateTimeZone('UTC'),
        );
        $errors = DateTimeImmutable::getLastErrors();
        if (
            $date === false
            || $date->format('Y-m-d') !== $value
            || ($errors !== false
                && ($errors['warning_count'] > 0 || $errors['error_count'] > 0))
        ) {
            throw new BadRequestException(
                "{$field} must be a valid date in YYYY-MM-DD format",
            );
        }

        return $date;
    }
}