[FIX][ENTERPRISE] Make AutoSelect algo take current agent load in consideration

app/livechat/server/lib/routing/AutoSelection.js

@@ -1,5 +1,6 @@
 import { RoutingManager } from '../RoutingManager';
 import { LivechatDepartmentAgents, Users } from '../../../../models/server';
+import { callbacks } from '../../../../callbacks';
 
 /* Auto Selection Queuing method:
 	*
@@ -20,11 +21,12 @@ class AutoSelection {
 	}
 
 	getNextAgent(department, ignoreAgentId) {
+		const extraQuery = callbacks.run('livechat.applySimultaneousChatRestrictions', { ...department ? { departmentId: department } : {} });
 		if (department) {
-			return LivechatDepartmentAgents.getNextAgentForDepartment(department, ignoreAgentId);
+			return LivechatDepartmentAgents.getNextAgentForDepartment(department, ignoreAgentId, extraQuery);
 		}
 
-		return Users.getNextAgent(ignoreAgentId);
+		return Users.getNextAgent(ignoreAgentId, extraQuery);
 	}
 }
 

app/models/server/models/LivechatDepartmentAgents.js

@@ -54,7 +54,7 @@ export class LivechatDepartmentAgents extends Base {
 		this.remove({ departmentId });
 	}
 
-	getNextAgentForDepartment(departmentId, ignoreAgentId) {
+	getNextAgentForDepartment(departmentId, ignoreAgentId, extraQuery) {
 		const agents = this.findByDepartmentId(departmentId).fetch();
 
 		if (agents.length === 0) {
@@ -65,10 +65,13 @@ export class LivechatDepartmentAgents extends Base {
 
 		const onlineUsernames = _.pluck(onlineUsers.fetch(), 'username');
 
+		// get the current agent load, sorted by the username & current chat count
+		const currentAvailableAgents = Promise.await(Users.getAgentLoadByUsernames(onlineUsernames, extraQuery));
+
 		const query = {
 			departmentId,
 			username: {
-				$in: onlineUsernames,
+				$in: currentAvailableAgents.map((u) => u.username),
 			},
 			...ignoreAgentId && { agentId: { $ne: ignoreAgentId } },
 		};

app/models/server/models/Users.js

@@ -174,10 +174,16 @@ export class Users extends Base {
 		return this.find(query);
 	}
 
-	getNextAgent(ignoreAgentId) { // TODO: Create class Agent
+	getNextAgent(ignoreAgentId, extraQuery) { // TODO: Create class Agent
+		// fetch all available agents (available = haven't reached max active chats)
+		const availableAgents = Promise.await(this.getAgentLoadByUsernames(null, extraQuery));
+		const availableUsernames = availableAgents.map((u) => u.username);
 		const extraFilters = {
 			...ignoreAgentId && { _id: { $ne: ignoreAgentId } },
+			// limit query to consider only those agents
+			username: { $in: availableUsernames },
 		};
+
 		const query = queryStatusAgentOnline(extraFilters);
 
 		const collectionObj = this.model.rawCollection();
@@ -204,6 +210,64 @@ export class Users extends Base {
 		return null;
 	}
 
+	// get next agent ignoring the ones reached the max amount of active chats
+	getAgentLoadByUsernames(usernames, customFilter) {
+		const usernameFilter = Array.isArray(usernames) ? { username: { $in: usernames } } : {};
+		const col = this.model.rawCollection();
+		return col.aggregate([
+			{
+				$match: {
+					...usernameFilter,
+					status: { $exists: true, $ne: 'offline' },
+					statusLivechat: 'available',
+					roles: 'livechat-agent',
+				},
+			},
+			{
+				$lookup: {
+					from: 'rocketchat_subscription',
+					localField: '_id',
+					foreignField: 'u._id',
+					as: 'subs',
+				},
+			},
+			{
+				$project: {
+					agentId: '$_id',
+					'livechat.maxNumberSimultaneousChat': 1,
+					username: 1,
+					lastAssignTime: 1,
+					lastRoutingTime: 1,
+					'queueInfo.chats': {
+						$size: {
+							$filter: {
+								input: '$subs',
+								as: 'sub',
+								cond: {
+									$and: [
+										{ $eq: ['$$sub.t', 'l'] },
+										{ $eq: ['$$sub.open', true] },
+										{ $ne: ['$$sub.onHold', true] },
+									],
+								},
+							},
+						},
+					},
+				},
+			},
+			...customFilter ? [customFilter] : [],
+			{
+				$sort: {
+					'queueInfo.chats': 1,
+					lastAssignTime: 1,
+					lastRoutingTime: 1,
+					username: 1,
+				},
+			},
+		]).toArray();
+	}
+
+
 	getNextBotAgent(ignoreAgentId) { // TODO: Create class Agent
 		const query = {
 			roles: {

ee/app/livechat-enterprise/server/hooks/applySimultaneousChatsRestrictions.ts

@@ -0,0 +1,33 @@
+import { callbacks } from '../../../../../app/callbacks/server';
+import { LivechatDepartment } from '../../../../../app/models/server';
+import { settings } from '../../../../../app/settings/server';
+
+callbacks.add('livechat.applySimultaneousChatRestrictions', ({ departmentId }: { departmentId?: string }) => {
+	if (departmentId) {
+		const departmentLimit = LivechatDepartment.findOneById(departmentId)?.maxNumberSimultaneousChat || 0;
+		if (departmentLimit > 0) {
+			return { $match: { 'queueInfo.chats': { $lt: Number(departmentLimit) } } };
+		}
+	}
+
+	const maxChatsPerSetting = settings.get('Livechat_maximum_chats_per_agent') as number;
+	const agentFilter = { $and: [{ 'livechat.maxNumberSimultaneousChat': { $gt: 0 } }, { $expr: { $lt: ['queueInfo.chats', 'livechat.maxNumberSimultaneousChat'] } }] };
+	// apply filter only if agent setting is 0 or is disabled
+	const globalFilter = maxChatsPerSetting > 0
+		? {
+			$and: [
+				{
+					$or: [
+						{
+							'livechat.maxNumberSimultaneousChat': { $exists: false },
+						},
+						{ 'livechat.maxNumberSimultaneousChat': 0 },
+					],
+				},
+				{ 'queueInfo.chats': { $lt: maxChatsPerSetting } },
+			],
+		}
+		: {};
+
+	return { $match: { $or: [agentFilter, globalFilter] } };
+}, callbacks.priority.HIGH, 'livechat-apply-simultaneous-restrictions');

ee/app/livechat-enterprise/server/hooks/index.js

@@ -20,3 +20,4 @@ import './afterOnHoldChatResumed';
 import './afterReturnRoomAsInquiry';
 import './applyDepartmentRestrictions';
 import './afterForwardChatToAgent';
+import './applySimultaneousChatsRestrictions';