<?php

namespace Slack\Http\Middleware;

use Carbon\Carbon;
use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Log;

use Slack\Base;

class CheckSignature
{
	private const LOGKEY = 'MCS';

	/**
	 * Validate a slack request
	 * by the slack signing secret (not the token)
	 *
	 * @param Request  $request
	 * @param Closure $next
	 * @return mixed
	 */
	public function handle(Request $request,Closure $next)
	{
		// Make sure we are not an installation call
		if (! in_array($request->path(),config('slack.bypass_routes'))) {
			// get the remote sign
			$remote_signature = $request->header('X-Slack-Signature');
			Log::info(sprintf('%s:Incoming request - check slack SIGNATURE [%s]',static::LOGKEY,$remote_signature),['m'=>__METHOD__]);

			// Load the secret, you also can load it from env(YOUR_OWN_SLACK_SECRET)
			$secret = config('slack.signing_secret');

			$body = $request->getContent();

			// Compare timestamp with the local time, according to the slack official documents
			// the gap should under 5 minutes
			// @codeCoverageIgnoreStart
			if (! $timestamp = $request->header('X-Slack-Request-Timestamp')) {
				Log::alert(sprintf('%s:No slack timestamp - aborting...',static::LOGKEY),['m'=>__METHOD__]);

				return response('',444);
			}

			if (($x=Carbon::now()->diffInMinutes(Carbon::createFromTimestamp($timestamp))) > 5) {
				Log::alert(sprintf('%s:Invalid slack timestamp [%d]',static::LOGKEY,$x),['m'=>__METHOD__]);

				return response('',444);
			}
			// @codeCoverageIgnoreEnd

			// generate the string base
			$sig_basestring = sprintf('%s:%s:%s',Base::signature_version,$timestamp,$body);

			// generate the local sign
			$hash = hash_hmac('sha256',$sig_basestring,$secret);
			$local_signature = sprintf('%s=%s',Base::signature_version,$hash);

			// check two signs, if not match, throw an error
			if ($remote_signature !== $local_signature) {
				Log::alert(sprintf('%s:Invalid slack signature [%s]',static::LOGKEY,$remote_signature),['m'=>__METHOD__]);

				return response('',444);
			}
		}

		return $next($request);
	}
}