<?php
declare(strict_types=1);

/** Fixed-window rate limiter backed by the database (works on shared hosting without Redis). */
final class RateLimit
{
    /**
     * @return array{allowed:bool, retryAfter:int}
     */
    public static function hit(string $bucket, int $limit, int $windowSeconds): array
    {
        $pdo = Db::pdo();
        $now = time();
        $pdo->beginTransaction();
        try {
            $st = $pdo->prepare('SELECT hits, window_start FROM rate_limits WHERE bucket = ?');
            $st->execute([$bucket]);
            $row = $st->fetch();
            if (!$row || ($now - (int)$row['window_start']) >= $windowSeconds) {
                if (Db::isSqlite()) {
                    $pdo->prepare('INSERT OR REPLACE INTO rate_limits (bucket, hits, window_start) VALUES (?, 1, ?)')->execute([$bucket, $now]);
                } else {
                    $pdo->prepare('REPLACE INTO rate_limits (bucket, hits, window_start) VALUES (?, 1, ?)')->execute([$bucket, $now]);
                }
                $pdo->commit();
                return ['allowed' => true, 'retryAfter' => 0];
            }
            $hits = (int)$row['hits'] + 1;
            $pdo->prepare('UPDATE rate_limits SET hits = ? WHERE bucket = ?')->execute([$hits, $bucket]);
            $pdo->commit();
            if ($hits > $limit) {
                return ['allowed' => false, 'retryAfter' => max(1, $windowSeconds - ($now - (int)$row['window_start']))];
            }
            return ['allowed' => true, 'retryAfter' => 0];
        } catch (Throwable $e) {
            if ($pdo->inTransaction()) {
                $pdo->rollBack();
            }
            Log::warn('Rate limit storage failed; allowing request', ['error' => $e->getMessage()]);
            return ['allowed' => true, 'retryAfter' => 0];
        }
    }

    /** Stable, non-reversible bucket key for an IP. */
    public static function ipBucket(string $prefix, string $ip): string
    {
        return $prefix . ':' . substr(hash('sha256', $ip . '|' . (Config::get('HASH_SALT') ?? 'visit')), 0, 32);
    }
}