<?php

namespace Msr\LaravelBitunixApi\Support;

use Illuminate\Contracts\Cache\Repository;
use Msr\LaravelBitunixApi\Contracts\RateLimiterContract;

class CacheRateLimiter implements RateLimiterContract
{
    public function __construct(
        protected Repository $cache,
    ) {
    }

    public function throttle(
        string $bucket,
        string $identity,
        int $maxRequests,
        float $perSeconds
    ): void {
        if ($maxRequests <= 0 || $perSeconds <= 0) {
            return;
        }

        $cacheKey = $this->makeCacheKey($bucket, $identity);
        $minIntervalMicroseconds = (int) (($perSeconds / $maxRequests) * 1_000_000);

        $lastRequestAt = $this->cache->get($cacheKey);

        if (is_numeric($lastRequestAt)) {
            $elapsedMicroseconds = (int) ((microtime(true) - (float) $lastRequestAt) * 1_000_000);

            if ($elapsedMicroseconds < $minIntervalMicroseconds) {
                $sleepMicroseconds = $minIntervalMicroseconds - $elapsedMicroseconds;

                if ($sleepMicroseconds > 0) {
                    usleep($sleepMicroseconds);
                }
            }
        }

        $this->cache->put(
            $cacheKey,
            microtime(true),
            now()->addSeconds((int) max(1, ceil($perSeconds * 2)))
        );
    }

    protected function makeCacheKey(string $bucket, string $identity): string
    {
        return sprintf(
            'laravel_bitunix_api:rate_limit:%s:%s',
            $bucket,
            sha1($identity)
        );
    }
}