<?php

namespace App\RequiredTeamerCheck;

use Carbon\CarbonImmutable;

/**
 * A set of yearly recurring dates after which something must be confirmed again.
 *
 * Belongs to the individual check that composes it, never to the application as a
 * whole: a deadline expresses "this particular confirmation has expired", not
 * "portal access has expired".
 */
final class RecurringDeadlines
{
    /**
     * @param string[] $deadlines dates as MM-DD, e.g. ['04-01', '10-01']; an empty
     *                            list is never due
     */
    public function __construct(private readonly array $deadlines)
    {
    }

    /**
     * Whether a confirmation is outstanding: never confirmed, or last confirmed
     * before the most recent deadline that has passed.
     */
    public function isDue(?\DateTimeInterface $confirmedAt, ?\DateTimeInterface $registeredAt, CarbonImmutable $now): bool
    {
        $deadline = $this->getCurrentDeadline($now);

        if (null === $deadline) {
            return false;
        }

        if (true === $this->isRegisteredAfterAnyDeadline($registeredAt, $now)) {
            return false;
        }

        if (null === $confirmedAt) {
            return true;
        }

        return CarbonImmutable::instance($confirmedAt) < $deadline;
    }

    /**
     * The most recent deadline that has already passed, or null when none has.
     */
    public function getCurrentDeadline(CarbonImmutable $now): ?CarbonImmutable
    {
        $deadlines = $this->getDeadlinesForYear($now);
        rsort($deadlines);

        foreach ($deadlines as $deadline) {
            if ($deadline <= $now) {
                return $deadline;
            }
        }

        return null;
    }

    /**
     * Someone who registered after a deadline has effectively confirmed their data
     * by registering, so they are exempt until the next one.
     */
    private function isRegisteredAfterAnyDeadline(?\DateTimeInterface $registeredAt, CarbonImmutable $now): bool
    {
        if (null === $registeredAt) {
            return false;
        }

        $registeredAt = CarbonImmutable::instance($registeredAt)->startOfDay();

        foreach ($this->getDeadlinesForYear($now) as $deadline) {
            if ($registeredAt > $deadline) {
                return true;
            }
        }

        return false;
    }

    /**
     * @return CarbonImmutable[]
     */
    private function getDeadlinesForYear(CarbonImmutable $now): array
    {
        $deadlines = [];

        foreach (array_filter(array_map('trim', $this->deadlines)) as $date) {
            $deadline = CarbonImmutable::createFromFormat('Y-m-d', sprintf('%s-%s', $now->format('Y'), $date));

            if (false === $deadline instanceof CarbonImmutable) {
                continue;
            }

            $deadlines[] = $deadline->startOfDay();
        }

        return $deadlines;
    }
}