STOP keyword opt-out handling for inbound SMS

<?php

namespace App\Messaging;

use Illuminate\Support\Facades\DB;

final class KeywordConsent
{
    private const OUT = ['STOP', 'STOPALL', 'UNSUBSCRIBE', 'CANCEL', 'END', 'QUIT'];

    private const IN = ['START', 'YES', 'UNSTOP'];

    /** Returns 'opted_out', 'opted_in' or null. The whole body must be the keyword. */
    public static function interpret(string $body): ?string
    {
        $word = strtoupper(trim(preg_replace('/[^\p{L}\p{N}\s]/u', '', $body)));

        return match (true) {
            in_array($word, self::OUT, true) => 'opted_out',
            in_array($word, self::IN, true) => 'opted_in',
            default => null,
        };
    }

    /** Applies the change and returns the confirmation to send back, or null for ordinary messages. */
    public static function apply(string $phone, string $body): ?string
    {
        $status = self::interpret($body);

        if ($status === null) {
            return null;
        }

        DB::table('consents')->upsert(
            [['phone' => $phone, 'status' => $status, 'keyword' => strtoupper(trim($body)), 'changed_at' => now()]],
            ['phone'],
            ['status', 'keyword', 'changed_at'],
        );

        return $status === 'opted_out'
            ? 'You have been unsubscribed and will receive no more messages. Reply START to rejoin.'
            : 'You are subscribed again. Reply STOP at any time to opt out.';
    }
}

<?php

namespace App\Http\Controllers;

use App\Messaging\KeywordConsent;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;

class InboundSmsController extends Controller
{
    public function __invoke(Request $request): JsonResponse
    {
        $phone = '+'.preg_replace('/\D+/', '', (string) $request->input('From'));
        $reply = KeywordConsent::apply($phone, (string) $request->input('Body'));

        // Keywords are answered in the same response; everything else goes to the inbox.
        if ($reply === null) {
            // InboxService::store($phone, $request->input('Body')); // your normal handling
            return response()->json(['handled' => false]);
        }

        return response()->json(['handled' => true, 'reply' => $reply]);
    }
}