<?php

declare(strict_types=1);

namespace TFGraphics\SmartImport\Knowledge;

final class KnowledgePolicy
{
    public const FRESH = 'Fresh';
    public const EXPIRED = 'Expired';
    public const STALE = 'Stale';
    public const INVALID = 'Invalid';
    public const MERGED = 'Merged';

    private int $staleTtl;

    public function __construct(int $staleTtl = 86400)
    {
        $this->staleTtl = max(0, $staleTtl);
    }

    public function getStatus(KnowledgeEntry $entry, \DateTimeImmutable $at): string
    {
        if (! $entry->isValid()) {
            return self::INVALID;
        }

        if ($entry->isMerged()) {
            return self::MERGED;
        }

        if ($at <= $entry->getExpiresAt()) {
            return self::FRESH;
        }

        $staleUntil = $entry->getExpiresAt()->modify('+' . $this->staleTtl . ' seconds');

        return $at <= $staleUntil ? self::STALE : self::EXPIRED;
    }

    public function isReusable(KnowledgeEntry $entry, \DateTimeImmutable $at, bool $allowStale = true): bool
    {
        $status = $this->getStatus($entry, $at);

        return $status === self::FRESH || ($allowStale && in_array($status, [self::STALE, self::MERGED], true));
    }

    public function getStaleTtl(): int
    {
        return $this->staleTtl;
    }
}