MqttMonitor/MqttMonitorWidget.py

# -*- coding: utf-8 -*-

# Copyright (c) 2018 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing the MQTT Monitor widget.
"""

from __future__ import unicode_literals

try:
    str = unicode       # __IGNORE_EXCEPTION__
except NameError:
    pass

import os
import collections
import copy

from PyQt5.QtCore import pyqtSlot, Qt, QTimer
from PyQt5.QtGui import QFont, QTextCursor, QBrush
from PyQt5.QtWidgets import QWidget, QDialog

from E5Gui import E5MessageBox
from E5Gui.E5PathPicker import E5PathPickerModes

from .Ui_MqttMonitorWidget import Ui_MqttMonitorWidget

from .MqttClient import MqttClient, mqttConnackMessage, mqttErrorMessage, \
    mqttLogLevelString

import UI.PixmapCache
import Utilities


class MqttMonitorWidget(QWidget, Ui_MqttMonitorWidget):
    """
    Class implementing the MQTT Monitor widget.
    """
    BrokerStatusTopicPrefix = "$SYS/broker/"
    BrokerStatusTopic = "$SYS/broker/#"
    BrokerStatusTopicLoadPrefix = "$SYS/broker/load/"
    
    def __init__(self, plugin, parent=None):
        """
        Constructor
        
        @param plugin reference to the plug-in object
        @type MqttMonitorPlugin
        @param parent reference to the parent widget
        @type QWidget
        """
        super(MqttMonitorWidget, self).__init__(parent)
        self.setupUi(self)
        
        self.__plugin = plugin
        
        self.__connectedToBroker = False
        self.__brokerStatusTopicSubscribed = False
        
        self.pixmapLabel.setPixmap(UI.PixmapCache.getPixmap(
            os.path.join("MqttMonitor", "icons", "mqtt48.png")))
        
        self.publishPayloadFilePicker.setMode(E5PathPickerModes.OpenFileMode)
        self.publishPayloadFilePicker.setFilters(self.tr("All Files (*)"))
        
        self.__messagesFormat = self.messagesEdit.currentCharFormat()
        self.__messagesTopicFormat = self.messagesEdit.currentCharFormat()
        self.__messagesTopicFormat.setFontWeight(QFont.Bold)
        self.__messagesQosFormat = self.messagesEdit.currentCharFormat()
        self.__messagesQosFormat.setFontItalic(True)
        
        self.__isAlternate = False
        
        # TODO: Messages Edit improvements:
        #   1. add capability to search
        #   2. add capability to save contents to a file
        
        for logLevel in (MqttClient.LogDisabled,
                         MqttClient.LogDebug,
                         MqttClient.LogInfo,
                         MqttClient.LogNotice,
                         MqttClient.LogWarning,
                         MqttClient.LogError):
            self.logLevelComboBox.addItem(mqttLogLevelString(
                logLevel, isMqttLogLevel=False), logLevel)
        self.logLevelComboBox.setCurrentIndex(
            self.logLevelComboBox.count() - 1)
        
        # TODO: Log Edit improvements:
        #   1. add capability to search
        #   2. add configuration capability for colors
        
        self.__logMessagesBackgrounds = {
            MqttClient.LogDebug: QBrush(Qt.white),
            MqttClient.LogInfo: QBrush(Qt.lightGray),
            MqttClient.LogNotice: QBrush(Qt.green),
            MqttClient.LogWarning: QBrush(Qt.yellow),
            MqttClient.LogError: QBrush(Qt.red),
            MqttClient.LogDisabled: QBrush(Qt.magenta)
            # reuse LogDisabled for unknown log levels
        }
        
        self.brokerWidget.setCurrentIndex(0)
        
        self.__connectionModeProfile = True
        self.__setConnectionMode(True)  # initial mode is 'profile connection'
        self.__populateProfileComboBox()
        
        self.connectButton.setIcon(UI.PixmapCache.getIcon("ircConnect.png"))
        self.brokerConnectionOptionsButton.setIcon(UI.PixmapCache.getIcon(
            os.path.join("MqttMonitor", "icons", "connectionOptions.png")))
        self.__populateBrokerComboBoxes()
        self.brokerStatusLabel.hide()
        
        self.subscribeButton.setIcon(UI.PixmapCache.getIcon("plus.png"))
        self.subscribeButton.setEnabled(False)
        self.unsubscribeButton.setIcon(UI.PixmapCache.getIcon("minus.png"))
        
        self.__subscribedTopics = []
        self.__topicQueue = {}
        self.__updateUnsubscribeTopicComboBox()
        
        self.__publishedTopics = []
        self.__updatePublishTopicComboBox()
        self.publishButton.setEnabled(False)
        
        self.__connectionOptions = None
        
        prefix = MqttMonitorWidget.BrokerStatusTopicPrefix
        self.__statusLabelMapping = {
            # broker
            prefix + "version": self.versionLabel,
            prefix + "timestamp": self.timestampLabel,
            prefix + "uptime": self.uptimeLabel,
            prefix + "subscriptions/count": self.subscriptionsLabel,
            # clients
            prefix + "clients/connected": self.clientsConnectedLabel,
            prefix + "clients/disconnected": self.clientsDisconnectedLabel,
            prefix + "clients/expired": self.clientsExpiredLabel,
            prefix + "clients/maximum": self.clientsMaximumLabel,
            prefix + "clients/total": self.clientsTotalLabel,
            # messages
            prefix + "messages/sent": self.messagesSentLabel,
            prefix + "messages/received": self.messagesReceivedLabel,
            prefix + "messages/stored": self.messagesStoredLabel,
            prefix + "store/messages/count": self.messagesStoredLabel,
            prefix + "messages/inflight": self.messagesInflightLabel,
            prefix + "retained messages/count": self.messagesRetainedLabel,
            # publish messages
            prefix + "publish/messages/sent": self.publishMessagesSentLabel,
            prefix + "publish/messages/received":
                self.publishMessagesReceivedLabel,
            prefix + "publish/messages/dropped":
                self.publishMessagesDroppedLabel,
            # traffic
            prefix + "bytes/sent": self.bytesSentLabel,
            prefix + "bytes/received": self.bytesReceivedLabel,
            # load
            prefix + "load/bytes/sent": self.loadBytesSentLabel,
            prefix + "load/bytes/received": self.loadBytesReceivedLabel,
            prefix + "load/messages/sent": self.loadMessagesSentLabel,
            prefix + "load/messages/received": self.loadMessagesReceivedLabel,
            prefix + "load/publish/sent": self.loadPublishSentLabel,
            prefix + "load/publish/received": self.loadPublishReceivedLabel,
            prefix + "load/publish/dropped": self.loadPublishDroppedLabel,
            prefix + "load/connections": self.loadConnectionsLabel,
            prefix + "load/sockets": self.loadSocketsLabel,
        }
        
        self.__statusLoadValues = collections.defaultdict(
            self.__loadDefaultDictFactory)
        
        self.__client = MqttClient()
        
        # connect the MQTT client signals
        self.__client.onConnect.connect(self.__brokerConnected)
        self.__client.onDisconnected.connect(self.__brokerDisconnected)
        self.__client.onLog.connect(self.__clientLog)
        self.__client.onMessage.connect(self.__messageReceived)
        self.__client.onPublish.connect(self.__messagePublished)
        self.__client.onSubscribe.connect(self.__topicSubscribed)
        self.__client.onUnsubscribe.connect(self.__topicUnsubscribed)
        
        self.__client.connectTimeout.connect(self.__connectTimeout)
    
    #######################################################################
    ## Slots handling MQTT related signals
    #######################################################################
    
    @pyqtSlot(dict, int)
    def __brokerConnected(self, flags, rc):
        """
        Private slot to handle being connected to a broker.
        
        @param flags flags set for the connection
        @type dict
        @param rc CONNACK result code
        @type int
        """
        self.brokerStatusLabel.hide()
        
        # TODO: add support for flags[‘session present’]
        if rc == 0:
            self.__connectedToBroker = True
            self.__connectionOptions = None
        
        msg = mqttConnackMessage(rc)
        self.__flashBrokerStatusLabel(msg)
        
        self.connectButton.setEnabled(True)
        if rc == 0:
            self.__connectedToBroker = True
            self.__connectionOptions = None
            
            self.connectButton.setIcon(
                UI.PixmapCache.getIcon("ircDisconnect.png"))
            
            self.subscribeGroup.setEnabled(True)
            self.unsubscribeGroup.setEnabled(True)
            self.publishGroup.setEnabled(True)
            self.brokerStatusButton.setEnabled(True)
            
            self.__statusLoadValues.clear()
            self.__clearBrokerStatusLabels()
            self.__setBrokerStatusSubscribed(False)
        else:
            self.__client.stopLoop()
    
    @pyqtSlot()
    def __connectTimeout(self):
        """
        Private slot handling a timeout during a connection attempt.
        """
        self.__flashBrokerStatusLabel(self.tr("Connection timed out"))
        self.__setConnectButtonState()
    
    @pyqtSlot(int)
    def __brokerDisconnected(self, rc):
        """
        Private slot to handle a disconnection from the broker.
        
        @param rc MQTT error result code
        @type int
        """
        self.__connectedToBroker = False
        
        # ensure, the client loop is stopped
        self.__client.stopLoop()
        
        if rc > 0:
            msg = mqttErrorMessage(rc)
        else:
            msg = self.tr("Connection to Broker shut down cleanly.")
        self.__flashBrokerStatusLabel(msg)
        
        self.connectButton.setIcon(UI.PixmapCache.getIcon("ircConnect.png"))
        self.__setConnectButtonState()

        self.__subscribedTopics = []
        self.__topicQueue = {}
        self.__updateUnsubscribeTopicComboBox()
        self.__updatePublishTopicComboBox()
        
        self.subscribeGroup.setEnabled(False)
        self.unsubscribeGroup.setEnabled(False)
        self.publishGroup.setEnabled(False)
        self.brokerStatusButton.setEnabled(False)
        
        self.__statusLoadValues.clear()
    
    @pyqtSlot(int, str)
    def __clientLog(self, level, message):
        """
        Private slot to handle the receipt of a log message.
        
        @param level log level
        @type int
        @param message log message
        @type str
        """
        try:
            if MqttClient.LogLevelMap[level] < self.logLevelComboBox.itemData(
                    self.logLevelComboBox.currentIndex()):
                return
        except KeyError:
            # always show unknown log levels
            pass
        
        scrollbarValue = self.logEdit.verticalScrollBar().value()
        
        textCursor = self.logEdit.textCursor()
        if not self.logEdit.document().isEmpty():
            textCursor.movePosition(QTextCursor.End)
            self.logEdit.setTextCursor(textCursor)
            self.logEdit.insertPlainText("\n")
        
        textBlockFormat = textCursor.blockFormat()
        try:
            textBlockFormat.setBackground(
                self.__logMessagesBackgrounds[MqttClient.LogLevelMap[level]])
        except KeyError:
            textBlockFormat.setBackground(
                self.__logMessagesBackgrounds[MqttClient.LogDisabled])
        textCursor.setBlockFormat(textBlockFormat)
        textCursor.movePosition(QTextCursor.End)
        self.logEdit.setTextCursor(textCursor)
        
        txt = self.tr("{0}: {1}").format(mqttLogLevelString(level), message)
        self.logEdit.insertPlainText(Utilities.filterAnsiSequences(txt))
        
        if self.followLogMessagesCheckBox.isChecked():
            self.logEdit.ensureCursorVisible()
        else:
            self.logEdit.verticalScrollBar().setValue(scrollbarValue)
    
    @pyqtSlot(str, bytes, int, bool)
    def __messageReceived(self, topic, payload, qos, retain):
        """
        Private slot to handle the receipt of a message.
        
        @param topic topic of the message
        @type str
        @param payload payload (i.e. data) of the message
        @type bytes
        @param qos quality of service indicator
        @type int
        @param retain flag indicating a retained message
        @type bool
        """
        if topic.startswith(MqttMonitorWidget.BrokerStatusTopicPrefix):
            # handle broker status messages
            self.__handleBrokerStatusMessage(topic, payload)
        else:
            self.__appendMessage(topic, payload, qos)
    
    @pyqtSlot(int)
    def __messagePublished(self, mid):
        """
        Private slot to handle a message being published.
        
        @param mid ID of the published message
        @type int
        """
        pass
    
    @pyqtSlot(int, tuple)
    def __topicSubscribed(self, mid, grantedQos):
        """
        Private slot to handle being subscribed to topics.
        
        @param mid ID of the subscribe request
        @type int
        @param grantedQos tuple of granted quality of service
        @type tuple of int
        """
        if mid in self.__topicQueue:
            topic = self.__topicQueue.pop(mid)
            self.__subscribedTopics.append(topic)
            self.subscribeTopicEdit.clear()
            
            self.__updateUnsubscribeTopicComboBox()
            self.__updatePublishTopicComboBox()
    
    @pyqtSlot(int)
    def __topicUnsubscribed(self, mid):
        """
        Private slot to handle being unsubcribed from a topic.
        
        @param mid ID of the unsubscribe request
        @type int
        """
        if mid in self.__topicQueue:
            topic = self.__topicQueue.pop(mid)
            try:
                self.__subscribedTopics.remove(topic)
                self.__updateUnsubscribeTopicComboBox()
                self.__updatePublishTopicComboBox()
            except ValueError:
                # ignore it
                pass
    
    #######################################################################
    ## Slots handling UI interactions
    #######################################################################
    
    @pyqtSlot()
    def __flashBrokerStatusLabel(self, message):
        """
        Private slot to show the broker status label with some text for
        5 seconds.
        
        @param message message to be shown
        @type str
        """
        self.brokerStatusLabel.setText(message)
        self.brokerStatusLabel.show()
        QTimer.singleShot(5000, self.brokerStatusLabel.hide)
    
    @pyqtSlot()
    def on_modeButton_clicked(self):
        """
        Private slot to switch between connection profiles and direct
        connection mode.
        """
        self.__setConnectionMode(not self.__connectionModeProfile)
    
    @pyqtSlot(str)
    def on_profileComboBox_currentIndexChanged(self, profileName):
        """
        Private slot handling the change of the selected profile.
        
        @param profileName name of the selected profile
        @type str
        """
        self.__setConnectButtonState()
    
    @pyqtSlot(str)
    def on_brokerComboBox_editTextChanged(self, host):
        """
        Private slot to handling entering or selecting a broker host name.
        
        @param host host name of the broker
        @type str
        """
        self.__setConnectButtonState()
    
    @pyqtSlot()
    def on_brokerConnectionOptionsButton_clicked(self):
        """
        Private slot to show a dialog to modify connection options or a
        dialog to edit connection profiles.
        """
        if self.__connectionModeProfile:
            from .MqttConnectionProfilesDialog import \
                MqttConnectionProfilesDialog
            dlg = MqttConnectionProfilesDialog(
                self.__client, self.__plugin.getPreferences("BrokerProfiles"),
                parent=self)
            if dlg.exec_() == QDialog.Accepted:
                profilesDict = dlg.getProfiles()
                self.__plugin.setPreferences("BrokerProfiles", profilesDict)
                self.__populateProfileComboBox()
        else:
            from .MqttConnectionOptionsDialog import \
                MqttConnectionOptionsDialog
            dlg = MqttConnectionOptionsDialog(
                self.__client, self.__connectionOptions, parent=self)
            if dlg.exec_() == QDialog.Accepted:
                self.__connectionOptions = dlg.getConnectionOptions()
                if self.__connectionOptions["TlsEnable"]:
                    port = self.brokerPortComboBox.currentText().strip()
                    if port == "1883":
                        # it is default non-encrypted port => set to TLS port
                        self.brokerPortComboBox.setEditText("8883")
                else:
                    port = self.brokerPortComboBox.currentText().strip()
                    if port == "8883":
                        # it is default TLS port => set to non-encrypted port
                        self.brokerPortComboBox.setEditText("1883")
    
    @pyqtSlot()
    def on_connectButton_clicked(self):
        """
        Private slot to handle a connect or disconnect request.
        """
        if self.__connectedToBroker:
            self.__client.disconnectFromServer()
        else:
            if self.__connectionModeProfile:
                self.__profileConnectToBroker()
            else:
                self.__directConnectToBroker()
    
    @pyqtSlot(str)
    def on_subscribeTopicEdit_textChanged(self, topic):
        """
        Private slot to handle a change of the entered topic.
        
        @param topic entered topic text
        @type str
        """
        self.subscribeButton.setEnabled(bool(topic))
    
    @pyqtSlot()
    def on_subscribeTopicEdit_returnPressed(self):
        """
        Private slot handling the user pressing the return button to subscribe
        a topic.
        """
        self.on_subscribeButton_clicked()
    
    @pyqtSlot()
    def on_subscribeButton_clicked(self):
        """
        Private slot to subscribe to the entered topic.
        """
        topic = self.subscribeTopicEdit.text()
        qos = self.subscribeQosSpinBox.value()
        if topic:
            if topic.startswith(MqttMonitorWidget.BrokerStatusTopicPrefix):
                E5MessageBox.warning(
                    self,
                    self.tr("Subscribe to Topic"),
                    self.tr("Subscriptions to the Status topic '$SYS' shall"
                            " be done on the 'Status' tab."))
            else:
                self.__topicQueue[
                    self.__client.subscribe(topic, qos)[1]] = topic
    
    @pyqtSlot(str)
    def on_unsubscribeTopicComboBox_currentIndexChanged(self, topic):
        """
        Private slot to handle the selection of a topic to unsubscribe from.
        
        @param topic topic text
        @type str
        """
        self.unsubscribeButton.setEnabled(bool(topic))
    
    @pyqtSlot()
    def on_unsubscribeButton_clicked(self):
        """
        Private slot to unsubscribe from the selected topic.
        """
        topic = self.unsubscribeTopicComboBox.currentText()
        if topic:
            self.__topicQueue[
                self.__client.unsubscribe(topic)[1]] = topic
    
    @pyqtSlot(str)
    def on_publishTopicComboBox_editTextChanged(self, topic):
        """
        Private slot to handle changes of the publish topic name.
        
        @param topic topic text
        @type str
        """
        self.publishButton.setEnabled(bool(topic))
    
    @pyqtSlot()
    def on_publishButton_clicked(self):
        """
        Private slot to publish the entered message.
        """
        topic = self.publishTopicComboBox.currentText()
        qos = self.publishQosSpinBox.value()
        retain = self.publishRetainCheckBox.isChecked()
        payloadFile = self.publishPayloadFilePicker.text()
        if bool(payloadFile) and os.path.exists(payloadFile) and \
           os.path.getsize(payloadFile) <= 268435455:
            # payload size limit is 268,435,455 bytes
            try:
                f = open(payloadFile, "rb")
                payloadStr = f.read()
                f.close()
            except (IOError, OSError) as err:
                E5MessageBox.critical(
                    self,
                    self.tr("Read Payload from File"),
                    self.tr("""<p>The file <b>{0}</b> could not be read."""
                            """ Aborting...</p><p>Reason: {1}</p>""").format(
                        payloadFile, str(err)))
                return
        else:
            payloadStr = self.publishPayloadEdit.toPlainText()
            if not payloadStr:
                # use empty string together with the retain flag to clean
                # a retained message by sending None instead
                payloadStr = None
        
        msgInfo = self.__client.publish(topic, payloadStr, qos, retain)
        if msgInfo.rc == 0:
            if topic not in self.__publishedTopics:
                self.__publishedTopics.append(topic)
            self.__updatePublishTopicComboBox(resetTopic=False)
            if self.clearPublishCheckBox.isChecked():
                self.on_publishClearButton_clicked()
    
    @pyqtSlot()
    def on_publishClearButton_clicked(self):
        """
        Private slot to clear the publish data fields.
        """
        self.publishTopicComboBox.clearEditText()
        self.publishPayloadEdit.clear()
        self.publishQosSpinBox.setValue(0)
        self.publishRetainCheckBox.setChecked(False)
        self.publishPayloadFilePicker.clear()
    
    @pyqtSlot(str)
    def on_publishPayloadFilePicker_textChanged(self, path):
        """
        Private slot handling a change of path of the payload file.
        
        @param path path of the payload file
        @type str
        """
        self.publishPayloadEdit.setEnabled(not bool(path))
    
    @pyqtSlot()
    def on_brokerStatusButton_clicked(self):
        """
        Private slot to subscribe or unsubscribe the broker status topic.
        """
        if self.__brokerStatusTopicSubscribed:
            # unsubscribe status topic
            rc, _ = self.__client.unsubscribe(
                MqttMonitorWidget.BrokerStatusTopic)
            if rc == 0:
                # successfully sent
                self.__setBrokerStatusSubscribed(False)
        else:
            # subscribe status topic
            rc, _ = self.__client.subscribe(
                MqttMonitorWidget.BrokerStatusTopic)
            if rc == 0:
                # successfully sent
                self.__setBrokerStatusSubscribed(True)
    
    #######################################################################
    ## Utility methods
    #######################################################################
    
    def __setBrokerStatusSubscribed(self, subscribed):
        """
        Private method to set the subscription status for the broker status
        topics.
        
        @param subscribed subscription status for the broker status topics
        @type bool
        """
        self.__brokerStatusTopicSubscribed = subscribed
        if subscribed:
            self.brokerStatusButton.setText(self.tr("Unsubscribe"))
            self.brokerStatusButton.setToolTip(
                self.tr("Press to deactivate the status display"))
        else:
            self.brokerStatusButton.setText(self.tr("Subscribe"))
            self.brokerStatusButton.setToolTip(
                self.tr("Press to activate the status display"))
    
    def __addBrokerToRecent(self, host, port):
        """
        Private method to add a host name to the list of recently connected
        brokers.
        
        @param host host name of broker
        @type str
        @param port port number of the connection
        @type int
        """
        brokerList = self.__plugin.getPreferences("RecentBrokersWithPort")
        hostAndPort = [host, port]
        if hostAndPort in brokerList:
            brokerList.remove(hostAndPort)
        brokerList.insert(0, hostAndPort)
        # limit to most recently used 20 entries
        brokerList = brokerList[:20]
        self.__plugin.setPreferences("RecentBrokersWithPort", brokerList)
        
        self.__populateBrokerComboBoxes()
    
    def __populateBrokerComboBoxes(self):
        """
        Private method to populate the broker name and port combo boxes.
        """
        brokerPortList = self.__plugin.getPreferences("RecentBrokersWithPort")
        
        # step 1: clear combo boxes
        self.brokerComboBox.clear()
        self.brokerPortComboBox.clear()
        
        # step 2a: populate the broker name list
        if brokerPortList:
            currentBroker = brokerPortList[0][0]
        else:
            currentBroker = ""
        brokerSet = {b[0].strip() for b in brokerPortList}
        self.brokerComboBox.addItems(sorted(brokerSet))
        index = self.brokerComboBox.findText(currentBroker)
        self.brokerComboBox.setCurrentIndex(index)
        
        # step 2b: populate the broker ports list
        if brokerPortList:
            currentPort = brokerPortList[0][1]
        else:
            currentPort = 1883
        currentPortStr = "{0:5}".format(currentPort)
        portsSet = {b[1] for b in brokerPortList}
        portsSet.update({1883, 8883})
        self.brokerPortComboBox.addItems(
            sorted("{0:5}".format(p) for p in portsSet))
        index = self.brokerPortComboBox.findText(currentPortStr)
        self.brokerPortComboBox.setCurrentIndex(index)
        
        # step 3: update the connect button state
        self.__setConnectButtonState()
    
    def __populateProfileComboBox(self):
        """
        Private method to populate the profiles selection box.
        """
        profilesDict = self.__plugin.getPreferences("BrokerProfiles")
        mostRecentProfile = self.__plugin.getPreferences("MostRecentProfile")
        
        self.profileComboBox.clear()
        self.profileComboBox.addItems(sorted(profilesDict.keys()))
        if mostRecentProfile:
            index = self.profileComboBox.findText(mostRecentProfile)
            if index >= 0:
                self.profileComboBox.setCurrentIndex(index)
        
        self.__setConnectButtonState()
    
    def __updateUnsubscribeTopicComboBox(self):
        """
        Private method to update the unsubcribe topic combo box.
        """
        self.unsubscribeTopicComboBox.clear()
        self.unsubscribeTopicComboBox.addItems(sorted(self.__subscribedTopics))
        self.unsubscribeButton.setEnabled(len(self.__subscribedTopics) > 0)
    
    def __updatePublishTopicComboBox(self, resetTopic=True):
        """
        Private method to update the publish topic combo box.
        
        @param resetTopic flag indicating to reset the topic
        @type bool
        """
        currentTopic = self.publishTopicComboBox.currentText()
        self.publishTopicComboBox.clear()
        self.publishTopicComboBox.addItems(
            list(set(self.__publishedTopics + self.__subscribedTopics)))
        if resetTopic:
            self.publishTopicComboBox.clearEditText()
        else:
            topicIndex = self.publishTopicComboBox.findText(currentTopic)
            self.publishTopicComboBox.setCurrentIndex(topicIndex)
    
    def __appendMessage(self, topic, payload, qos):
        """
        Private method to append a received message to the output.
        
        @param topic topic of the received message
        @type str
        @param payload payload of the received message
        @type bytes
        @param qos quality of service indicator (0, 1, 2)
        @type int
        """
        scrollbarValue = self.messagesEdit.verticalScrollBar().value()
        
        textCursor = self.messagesEdit.textCursor()
        if not self.messagesEdit.document().isEmpty():
            textCursor.movePosition(QTextCursor.End)
            self.messagesEdit.setTextCursor(textCursor)
            self.messagesEdit.insertPlainText("\n")
        
        textBlockFormat = textCursor.blockFormat()
        if self.__isAlternate:
            textBlockFormat.setBackground(
                self.messagesEdit.palette().alternateBase())
        else:
            textBlockFormat.setBackground(
                self.messagesEdit.palette().base())
        textCursor.setBlockFormat(textBlockFormat)
        textCursor.movePosition(QTextCursor.End)
        self.messagesEdit.setTextCursor(textCursor)
        
        self.messagesEdit.setCurrentCharFormat(self.__messagesTopicFormat)
        self.messagesEdit.insertPlainText(topic + "\n")
        
        self.messagesEdit.setCurrentCharFormat(self.__messagesQosFormat)
        self.messagesEdit.insertPlainText(self.tr("QoS: {0}\n").format(qos))
        
        payloadStr = str(payload, encoding="utf-8", errors="replace")
        self.messagesEdit.setCurrentCharFormat(self.__messagesFormat)
        self.messagesEdit.insertPlainText(
            Utilities.filterAnsiSequences(payloadStr))
        
        if self.followMessagesCheckBox.isChecked():
            self.messagesEdit.ensureCursorVisible()
        else:
            self.messagesEdit.verticalScrollBar().setValue(scrollbarValue)
        
        self.__isAlternate = not self.__isAlternate
    
    def __handleBrokerStatusMessage(self, topic, payload):
        """
        Private method to append a received message to the output.
        
        @param topic topic of the received message
        @type str
        @param payload payload of the received message
        @type bytes
        """
        payloadStr = str(payload, encoding="utf-8", errors="replace").strip()
        topic = topic.strip()
        
        if topic.startswith(MqttMonitorWidget.BrokerStatusTopicLoadPrefix):
            self.__handleBrokerLoadStatusMessage(topic, payloadStr)
        else:
            try:
                label = self.__statusLabelMapping[topic]
                label.setText(payloadStr)
            except KeyError:
                # ignore topics not shown in display
                pass
    
    def __handleBrokerLoadStatusMessage(self, topic, payloadStr):
        """
        Private method to append a received message to the output.
        
        @param topic topic of the received message
        @type str
        @param payloadStr string representation of the payload of the
            received message
        @type str
        """
        subtopic, topicElement = topic.rsplit("/", 1)
        self.__statusLoadValues[subtopic][topicElement] = payloadStr
        
        try:
            label = self.__statusLabelMapping[subtopic]
            label.setText("{0} / {1} / {2}".format(
                self.__statusLoadValues[subtopic]["1min"],
                self.__statusLoadValues[subtopic]["5min"],
                self.__statusLoadValues[subtopic]["15min"],
            ))
        except KeyError:
            # ignore topics not shown in display
            pass
    
    def __clearBrokerStatusLabels(self):
        """
        Private method to clear the broker status labels.
        """
        for statusLabelKey in self.__statusLabelMapping:
            if statusLabelKey.startswith(
                    MqttMonitorWidget.BrokerStatusTopicLoadPrefix):
                label = "- / - / -"
            else:
                label = "-"
            self.__statusLabelMapping[statusLabelKey].setText(label)
    
    def __loadDefaultDictFactory(self):
        """
        Private method to populate non-existing load items.
        
        @return default dictionary entry
        @rtype dict
        """
        return {
            "1min": "-",
            "5min": "-",
            "15min": "-",
        }
    
    def __setConnectionMode(self, profileMode):
        """
        Private method to set the connection mode.
        
        @param profileMode flag indicating the profile connection mode
        @type bool
        """
        self.__connectionModeProfile = profileMode
        if profileMode:
            self.modeButton.setIcon(UI.PixmapCache.getIcon(
                os.path.join("MqttMonitor", "icons", "profiles.png")))
        else:
            self.modeButton.setIcon(UI.PixmapCache.getIcon(
                os.path.join("MqttMonitor", "icons", "quickopen.png")))
        
        self.profileComboBox.setVisible(profileMode)
        self.brokerConnectionWidget.setVisible(not profileMode)
        self.__setConnectButtonState()
    
    def __setConnectButtonState(self):
        """
        Private method to set the enabled state of the connect button.
        """
        if self.__connectionModeProfile:
            self.connectButton.setEnabled(
                bool(self.profileComboBox.currentText()))
        else:
            self.connectButton.setEnabled(
                bool(self.brokerComboBox.currentText()))
    
    def __directConnectToBroker(self):
        """
        Private method to connect to the broker with entered data.
        """
        host = self.brokerComboBox.currentText()
        port = self.brokerPortComboBox.currentText().strip()
        try:
            port = int(port)
        except ValueError:
            # use standard port at 1883
            port = 1883
        if host:
            self.brokerStatusLabel.setText(
                self.tr("Connecting to {0}:{1} ...").format(
                    host, port))
            self.brokerStatusLabel.show()
            
            self.__addBrokerToRecent(host, port)
            self.connectButton.setEnabled(False)
            if self.__connectionOptions is None:
                self.__client.connectToServer(host, port=port)
            else:
                self.__client.connectToServerWithOptions(
                    host, port=port, options=self.__connectionOptions)
    
    def __profileConnectToBroker(self):
        """
        Private method to connect to the broker with selected profile.
        """
        profileName = self.profileComboBox.currentText()
        if profileName:
            self.__plugin.setPreferences("MostRecentProfile", profileName)
            
            profilesDict = self.__plugin.getPreferences("BrokerProfiles")
            profile = copy.copy(profilesDict[profileName])      # play it save
            host = profile["BrokerAddress"]
            port = profile["BrokerPort"]
            
            self.brokerStatusLabel.setText(
                self.tr("Connecting to {0}:{1} ...").format(
                    host, port))
            self.brokerStatusLabel.show()
            
            self.connectButton.setEnabled(False)
            self.__client.connectToServerWithOptions(host, port=port,
                                                     options=profile)