@php
    $alphabet = range('A', 'Z');
    $lastNameInitials = collect($people ?? [])->map(function($person) {
        $last = collect(explode(' ', $person['title']))->last();
        return strtoupper(substr($last, 0, 1));
    })->unique()->all();
@endphp

<div class="alphabet-filter">
    <ul class="alphabet-filter__list">
        @foreach ($alphabet as $letter)
            <li class="alphabet-filter__item">
                <button type="button" class="alphabet-filter__button" data-letter="{{ $letter }}" aria-label="Filter by {{ $letter }}" {{ in_array($letter, $lastNameInitials) ? '' : 'disabled' }}>
                    {{ $letter }}
                </button>
            </li>
        @endforeach
        <li class="alphabet-filter__item">
            <button type="button" class="alphabet-filter__button alphabet-filter__button--reset" data-letter="all" aria-label="Show all people" disabled>All</button>
        </li>
    </ul>
</div>