<?php
// +----------------------------------------------------------------------
// | YwxApp [ WE CAN DO IT JUST THINK ]
// +----------------------------------------------------------------------
// | Copyright (c) 2026-2036 http://ywxapp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Author: ywxapp<admin@ywxapp.cn>
// +----------------------------------------------------------------------
namespace addon\mqttbroker\service;

use Workerman\Mqtt\Client;

/**
 * 外部 Broker 转发器（规则引擎的投递通道）
 *
 * 将本地匹配到的消息转发到外部 MQTT Broker（如 EMQX），实现"桥接到 EMQX"。
 * 每个目标 Broker 维护一个异步常驻连接（基于 Workerman\Mqtt\Client，复用 Broker 的事件循环），
 * 连接未就绪时消息进入待发缓冲（上限 200，避免无限堆积），连接成功后冲刷。
 *
 * 依赖 workerman/mqtt（composer require workerman/mqtt）。未安装时 isAvailable()=false，
 * 规则引擎自动跳过转发，不影响 Broker 其它功能。
 */
class Forwarder
{
    /** @var array key => ['client'=>Client|null,'connected'=>bool,'pending'=>callable[]] */
    protected $clients = [];

    
    public function isAvailable(): bool
    {
        return class_exists(Client::class);
    }

    /**
     * 按规则转发一条消息到外部 Broker
     */
    public function forward(array $rule, string $topic, string $msg, int $qos): void
    {
        if (!$this->isAvailable()) {
            return;
        }
        $key = md5(($rule['target_broker'] ?? '') . '|' . ($rule['target_clientid'] ?? '') . '|' . ($rule['target_username'] ?? ''));
        if (!isset($this->clients[$key]) || $this->clients[$key]['client'] === null) {
            $this->connect($key, $rule);
        }
        $entry  = &$this->clients[$key];
        $target = $this->buildTargetTopic((string) ($rule['target_topic'] ?? ''), $topic);
        $pubQos = min($qos, (int) ($rule['target_qos'] ?? 0));

        $send = function () use ($entry, $target, $msg, $pubQos) {
            try {
                $entry['client']->publish($target, $msg, ['qos' => $pubQos]);
            } catch (\Throwable $e) {
            }
        };

        if ($entry['connected']) {
            $send();
        } elseif (count($entry['pending']) < 200) {
            $entry['pending'][] = $send;
        }
    }

    /**
     * 建立到目标 Broker 的异步连接（懒连接）
     */
    protected function connect(string $key, array $rule): void
    {
        $this->clients[$key] = ['client' => null, 'connected' => false, 'pending' => []];
        try {
            $uri    = $this->buildUri((string) ($rule['target_broker'] ?? ''));
            $opts   = [];
            if (!empty($rule['target_clientid'])) {
                $opts['clientId'] = $rule['target_clientid'];
            }
            if (!empty($rule['target_username'])) {
                $opts['username'] = $rule['target_username'];
                $opts['password'] = $rule['target_password'] ?? '';
            }
            $client = new Client($uri, $opts);
            $self   = $this;
            $client->onConnect = function () use ($key, $self) {
                $self->clients[$key]['connected'] = true;
                foreach ($self->clients[$key]['pending'] as $cb) {
                    try { $cb(); } catch (\Throwable $e) {
                    }
                }
                $self->clients[$key]['pending'] = [];
            };
            $client->onError = function () use ($key, $self) {
                $self->clients[$key]['connected'] = false;
            };
            $client->onClose = function () use ($key, $self) {
                $self->clients[$key]['connected'] = false;
            };
            $client->connect();
            $this->clients[$key]['client'] = $client;
        } catch (\Throwable $e) {
            $this->clients[$key] = ['client' => null, 'connected' => false, 'pending' => []];
        }
    }

    
    protected function buildUri(string $broker): string
    {
        $broker = trim($broker);
        if ($broker === '' || strpos($broker, '://') !== false) {
            return $broker === '' ? 'mqtt://127.0.0.1:1883' : $broker;
        }
        return 'mqtt://' . $broker;
    }

    /**
     * 目标主题模板：空或 ${topic} 表示沿用原主题，否则替换变量
     */
    protected function buildTargetTopic(string $tpl, string $srcTopic): string
    {
        if ($tpl === '' || $tpl === '${topic}') {
            return $srcTopic;
        }
        return str_replace('${topic}', $srcTopic, $tpl);
    }
}