<?php

declare(strict_types=1);

function sortDueWords(array $words): array
{
    $today = date('Y-m-d');

    usort($words, function ($a, $b) use ($today) {

        $aDue = $a['nextReview'] ?? '1970-01-01';
        $bDue = $b['nextReview'] ?? '1970-01-01';

        $aPriority = ($aDue <= $today) ? 0 : 1;
        $bPriority = ($bDue <= $today) ? 0 : 1;

        if ($aPriority !== $bPriority) {
            return $aPriority <=> $bPriority;
        }

        return strcmp($aDue, $bDue);
    });

    return $words;
}