<?php
declare(strict_types=1);
namespace App\Repository\Pdo;

use App\Repository\RateLimiterRepository;
use PDO;

/**
 * Atomic upsert via MySQL's INSERT ... ON DUPLICATE KEY UPDATE against the
 * unique (rate_key, window_start) primary key (see schema.sql) -- no
 * read-modify-write race between reading the current count and writing the
 * incremented value back.
 */
final class PdoRateLimiterRepository implements RateLimiterRepository
{
    public function __construct(private PDO $pdo) {}

    public function hit(string $key, int $windowStart): int
    {
        $upsert = $this->pdo->prepare(
            'INSERT INTO rate_limits (rate_key, window_start, count) VALUES (?, ?, 1)
             ON DUPLICATE KEY UPDATE count = count + 1'
        );
        $upsert->execute([$key, $windowStart]);

        $select = $this->pdo->prepare(
            'SELECT count FROM rate_limits WHERE rate_key = ? AND window_start = ?'
        );
        $select->execute([$key, $windowStart]);
        return (int)$select->fetchColumn();
    }
}