298 lines
8.0 KiB
PHP
298 lines
8.0 KiB
PHP
<?php
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namespace app\services\chat;
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use app\models\chat\ChatSession;
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use app\models\chat\ChatAdminStatus;
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use think\facade\Db;
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use think\facade\Cache;
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/**
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* 会话分配服务
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* Class AssignService
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* @package app\services\chat
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*/
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class AssignService
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{
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// Redis Key 前缀 (specs.md Section 3)
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private const LOCK_PREFIX = 'cs:lock:assign:';
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private const ONLINE_PREFIX = 'cs:online:agent:';
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private const LOAD_PREFIX = 'cs:agent:load:';
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private const QUEUE_KEY = 'cs:queue:pending';
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private const SESSION_OWNER_PREFIX = 'cs:session:owner:';
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// 约束参数 (specs.md CC-01~CC-04)
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private const LOCK_TTL = 3000; // 分配锁超时 3秒
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private const MAX_SESSIONS = 10; // 单客服最大会话数
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/**
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* 分配会话给客服
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* @param int $userId 用户ID
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* @param int $sessionId 会话ID
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* @return int|null 分配的客服ID，null表示无可用客服
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*/
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public function assignSession($userId, $sessionId): ?int
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{
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$redis = $this->getRedis();
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$lockKey = self::LOCK_PREFIX . $userId;
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// 1. 获取分配锁 (防止并发双分配)
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$lockValue = uniqid('', true);
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$acquired = $redis->set($lockKey, $lockValue, ['NX', 'PX' => self::LOCK_TTL]);
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if (!$acquired) {
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// 锁被占用，检查是否已有活跃会话
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return $this->getExistingSessionAgent($userId);
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}
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try {
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// 2. 检查用户是否已有活跃会话
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$existingAgent = $this->getExistingSessionAgent($userId);
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if ($existingAgent !== null) {
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return $existingAgent;
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}
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// 3. 获取所有在线客服
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$onlineAgents = $this->getOnlineAgents();
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if (empty($onlineAgents)) {
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// 无在线客服，进入留言队列
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$this->addToOfflineQueue($userId, $sessionId);
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return null;
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}
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// 4. 选择会话数最少的客服
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$selectedAgent = $this->selectLeastLoadAgent($onlineAgents);
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if ($selectedAgent === null) {
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// 所有客服已满载
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$this->addToOfflineQueue($userId, $sessionId);
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return null;
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}
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// 5. 更新会话归属
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$this->bindSessionToAgent($sessionId, $selectedAgent);
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// 6. 增加客服负载计数
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$redis->incr(self::LOAD_PREFIX . $selectedAgent);
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return $selectedAgent;
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} finally {
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// 释放锁 (仅释放自己持有的锁)
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$this->releaseLock($lockKey, $lockValue);
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}
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}
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/**
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* 获取在线客服列表
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*/
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public function getOnlineAgents()
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{
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$redis = $this->getRedis();
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$enabledAdmins = ChatAdminStatus::getEnabledAdminIds();
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$onlineAgents = [];
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foreach ($enabledAdmins as $adminId) {
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if ($redis->exists(self::ONLINE_PREFIX . $adminId)) {
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$onlineAgents[] = $adminId;
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}
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}
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return $onlineAgents;
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}
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/**
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* 选择会话数最少的客服
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*/
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public function selectLeastLoadAgent($onlineAgents): ?int
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{
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$redis = $this->getRedis();
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$loads = [];
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foreach ($onlineAgents as $agentId) {
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$load = (int)$redis->get(self::LOAD_PREFIX . $agentId) ?: 0;
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$maxSessions = $this->getAgentMaxSessions($agentId);
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if ($load < $maxSessions) {
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$loads[$agentId] = $load;
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}
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}
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if (empty($loads)) {
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return null;
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}
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// 返回负载最小的客服
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asort($loads);
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return array_key_first($loads);
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}
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/**
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* 添加到离线队列 (按余额降序)
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*/
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public function addToOfflineQueue($userId, $sessionId)
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{
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$redis = $this->getRedis();
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// 获取用户余额
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$user = Db::name('user')->where('id', $userId)->find();
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$balance = $user['money'] ?? 0;
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// ZSET score 使用负余额实现降序 (余额高的先处理)
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$score = -$balance;
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$member = json_encode([
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'userId' => $userId,
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'sessionId' => $sessionId,
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'time' => time()
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]);
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$redis->zAdd(self::QUEUE_KEY, $score, $member);
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}
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/**
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* 客服上线时处理队列
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*/
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public function processOfflineQueue($adminId)
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{
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$redis = $this->getRedis();
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$processed = [];
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while (true) {
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// 获取队列中优先级最高的会话 (score最小 = 余额最高)
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$items = $redis->zRange(self::QUEUE_KEY, 0, 0);
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if (empty($items)) {
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break;
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}
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$item = json_decode($items[0], true);
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// 检查客服是否还能接单
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$currentLoad = (int)$redis->get(self::LOAD_PREFIX . $adminId) ?: 0;
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$maxSessions = $this->getAgentMaxSessions($adminId);
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if ($currentLoad >= $maxSessions) {
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break;
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}
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// 从队列移除
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$redis->zRem(self::QUEUE_KEY, $items[0]);
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// 分配会话
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$this->bindSessionToAgent($item['sessionId'], $adminId);
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$redis->incr(self::LOAD_PREFIX . $adminId);
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$processed[] = $item;
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}
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return $processed;
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}
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/**
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* 释放会话 (会话结束时调用)
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*/
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public function releaseSession($sessionId, $adminId)
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{
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$redis = $this->getRedis();
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// 删除会话归属
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$redis->del(self::SESSION_OWNER_PREFIX . $sessionId);
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// 减少客服负载
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$load = (int)$redis->get(self::LOAD_PREFIX . $adminId) ?: 0;
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if ($load > 0) {
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$redis->decr(self::LOAD_PREFIX . $adminId);
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}
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}
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/**
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* 设置客服在线状态
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*/
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public function setAgentOnline($adminId)
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{
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$redis = $this->getRedis();
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$redis->setex(self::ONLINE_PREFIX . $adminId, 60, '1');
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ChatAdminStatus::updateLastOnlineTime($adminId);
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}
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/**
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* 刷新客服在线状态 (心跳续期)
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*/
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public function refreshAgentOnline($adminId)
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{
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$redis = $this->getRedis();
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$redis->expire(self::ONLINE_PREFIX . $adminId, 60);
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}
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/**
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* 设置客服离线
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*/
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public function setAgentOffline($adminId)
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{
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$redis = $this->getRedis();
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$redis->del(self::ONLINE_PREFIX . $adminId);
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$redis->del(self::LOAD_PREFIX . $adminId);
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}
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/**
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* 获取客服最大会话数
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*/
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private function getAgentMaxSessions($adminId)
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{
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$status = ChatAdminStatus::getByAdminId($adminId);
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return $status['max_sessions'] ?? self::MAX_SESSIONS;
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}
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/**
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* 获取用户已有会话的客服ID
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*/
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private function getExistingSessionAgent($userId): ?int
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{
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$session = ChatSession::getActiveByUserId($userId);
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return $session['admin_id'] ?? null;
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}
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/**
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* 绑定会话到客服
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*/
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private function bindSessionToAgent($sessionId, $adminId)
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{
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$redis = $this->getRedis();
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// 更新数据库
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ChatSession::where('id', $sessionId)->update([
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'admin_id' => $adminId,
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'status' => ChatSession::STATUS_ACTIVE,
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'update_time' => time(),
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]);
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// 设置Redis映射
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$redis->set(self::SESSION_OWNER_PREFIX . $sessionId, $adminId);
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}
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/**
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* 释放分配锁
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*/
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private function releaseLock($key, $value)
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{
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$redis = $this->getRedis();
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// Lua脚本保证原子性：仅当值匹配时才删除
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$script = <<<LUA
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if redis.call('get', KEYS[1]) == ARGV[1] then
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return redis.call('del', KEYS[1])
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else
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return 0
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end
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LUA;
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$redis->eval($script, [$key, $value], 1);
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}
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/**
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* 获取Redis实例
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*/
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private function getRedis()
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{
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return Cache::store('redis')->handler();
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}
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}
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