Superalgos/Current/TaskServer/EventServerClient.js

exports.newEventsServerClient = function newEventsServerClient(host, port) {

    const MODULE = "Task Server "

    const INFO_LOG = false

    let thisObject = {
        initialize: initialize,
        finalize: finalize,
        createEventHandler: createEventHandler,
        deleteEventHandler: deleteEventHandler,
        listenToEvent: listenToEvent,
        stopListening: stopListening,
        raiseEvent: raiseEvent
    }

    let eventListeners = new Map()
    let responseWaiters = new Map()

    let WEB_SOCKETS_CLIENT
    const WEB_SOCKET = require('ws')

    if (host === undefined) {
        host = 'localhost'
    }
    if (port === undefined) {
        port = process.env.WEB_SOCKETS_INTERFACE_PORT  
    }
     
    let messageCounter = 0
    let commandCounter = 0 

    return thisObject

    function initialize(callBackFunction) {

        setuptWebSockets(callBackFunction)

    }

    function setuptWebSockets(callBackFunction) {
        try {

            if (INFO_LOG === true) {
                console.log('setuptWebSockets at ' + host + ':' + port)
            }
            WEB_SOCKETS_CLIENT = new WEB_SOCKET('ws://' + host + ':' + port ) 

            WEB_SOCKETS_CLIENT.onerror = err => {
                console.log('[ERROR] Task Server -> Event Server Client -> setuptWebSockets -> On connection error -> error = ' + err.stack)
                console.log('[ERROR] This could mean that the port '+ port +' is taken by some other app running at your system. To resolve this issue, please pick another port number and change it at the .ENV file inside the Superalgos folder AND at the .ENV file inside the TaskServer folder. After that run the app again. ')
            }
            WEB_SOCKETS_CLIENT.onopen = () => {
                try {
                    if (INFO_LOG === true) {
                        console.log('Websocket connection opened.')
                    }
    
                    if (callBackFunction !== undefined) {
                        callBackFunction()
                    }
                } catch(err) {
                    console.log('[ERROR] Task Server -> Event Server Client -> setuptWebSockets ->  onopen -> err = ' + err.stack) 
                }
            }
            WEB_SOCKETS_CLIENT.onmessage = e => {
                try {
                    if (INFO_LOG === true) {
                        console.log('Websocket Message Received: ' + e.data.substring(0, 1000))
                    }

                    let message = JSON.parse(e.data)

                    if (message.action === 'Event Raised') {
                        let key
                        if (message.callerId !== undefined) {
                            key = message.eventHandlerName + '-' + message.eventType + '-' + message.callerId
                        } else {
                            key = message.eventHandlerName + '-' + message.eventType
                        }
                        let handler = eventListeners.get(key)
                        if (handler) {             
                            handler.callBack(message)
                        }
                        return
                    }

                    if (message.action === 'Event Server Response') {
                        let handler = responseWaiters.get(message.callerId)
                        if (handler) {
                            handler(message)
                        }
                        return
                    }
                } catch (err) {
                     console.log('[ERROR] Task Server -> Event Server Client -> setuptWebSockets ->  onmessage -> err = ' + err.stack) 
                }
            }
        } catch (err) {
             console.log('[ERROR] Task Server -> Event Server Client -> setuptWebSockets ->  err = ' + err.stack) 
        }
    }

    function finalize() {
        /* Before disconnecting we will forze all eventListeners to stop listening. */
        const eventListenersArray = [...eventListeners.values()]
        for (let i = 0; i < eventListenersArray.length; i++) {
            let handler = eventListenersArray[i]
            let eventCommand = {
                action: 'stopListening',
                eventHandlerName: handler.eventHandlerName,
                eventType: handler.eventType,
                callerId: handler.callerId
            }
            sendCommand(eventCommand)
        }
        WEB_SOCKETS_CLIENT.close();
    }

    function sendCommand(command, responseCallBack, eventsCallBack) {
        try {
            if (command.action === 'listenToEvent') {
                let key
                if (command.callerId) {
                    key = command.eventHandlerName + '-' + command.eventType + '-' + command.callerId
                } else {
                    key = command.eventHandlerName + '-' + command.eventType
                }
                let handler = {
                    eventHandlerName: command.eventHandlerName,
                    eventType: command.eventType,
                    callerId: command.callerId,
                    callBack: eventsCallBack
                }
                eventListeners.set(key, handler)
            }
            if (command.callerId && responseCallBack) {
                responseWaiters.set(command.callerId, responseCallBack)
            }
    
            if (WEB_SOCKETS_CLIENT.readyState === 1) { // 1 means connected and ready.
    
                WEB_SOCKETS_CLIENT.send("Task Server" + "|*|" + "|*|"  + JSON.stringify(command))
    
            } else {
                console.log('[ERROR] Task Server -> Event Server Client -> setuptWebSockets -> sendCommand -> WebSocket message could not be sent because the connection was not ready. Message = ' + JSON.stringify(command))
            }
        } catch(err) {
             console.log('[ERROR] Task Server -> Event Server Client -> sendCommand ->  err = ' + err.stack) 
        }
    }

    function createEventHandler(eventHandlerName, callerId, responseCallBack) {
        let eventCommand = {
            action: 'createEventHandler',
            eventHandlerName: eventHandlerName,
            callerId: callerId
        }
        sendCommand(eventCommand, responseCallBack)
    }

    function deleteEventHandler(eventHandlerName, callerId, responseCallBack) {
        let eventCommand = {
            action: 'deleteEventHandler',
            eventHandlerName: eventHandlerName,
            callerId: callerId
        }
        sendCommand(eventCommand, responseCallBack)
    }

    function listenToEvent(eventHandlerName, eventType, extraData, callerId, responseCallBack, eventsCallBack) {
        let eventCommand = {
            action: 'listenToEvent',
            eventHandlerName: eventHandlerName,
            eventType: eventType,
            extraData: extraData,
            callerId: callerId
        }
        sendCommand(eventCommand, responseCallBack, eventsCallBack)
    }

    function stopListening(eventHandlerName, eventType, eventSubscriptionId, callerId, responseCallBack) {
        /* User either needs to specify a valid eventSubscriptionId OR the 3 params: eventHandlerName, eventType, callerId which were used when start listening to events. */
        let eventCommand = {
            action: 'stopListening',
            eventHandlerName: eventHandlerName,
            eventType: eventType,
            eventSubscriptionId: eventSubscriptionId,
            callerId: callerId
        }
        sendCommand(eventCommand, responseCallBack)
    }

    function raiseEvent(eventHandlerName, eventType, event, callerId, responseCallBack) {
        let eventCommand = {
            action: 'raiseEvent',
            eventHandlerName: eventHandlerName,
            eventType: eventType,
            event: event,
            callerId: callerId
        }
        sendCommand(eventCommand, responseCallBack)
    }
}