Rocket.Chat/app/message-snippet/client/snippetMessage.js

import { Meteor } from 'meteor/meteor';

import { settings } from '../../settings';
import { ChatMessage, Subscriptions } from '../../models';

Meteor.methods({
	snippetMessage(message) {
		if (typeof Meteor.userId() === 'undefined' || Meteor.userId() === null) {
			return false;
		}
		if ((typeof settings.get('Message_AllowSnippeting') === 'undefined')
			|| (settings.get('Message_AllowSnippeting') === null)
			|| (settings.get('Message_AllowSnippeting') === false)) {
			return false;
		}

		const subscription = Subscriptions.findOne({ rid: message.rid, 'u._id': Meteor.userId() });

		if (subscription === undefined) {
			return false;
		}
		ChatMessage.update({
			_id: message._id,
		}, {
			$set: {
				snippeted: true,
			},
		});
	},
});