(Node.js) Firebase Receive Server-Sent Events (text/event-stream)

Demonstrates how to start receiving server-sent events and update your JSON database with each event.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    // Demonstrates how to begin receiving server-sent events, and to update
    // your JSON database for each event.

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example assumes a JWT authentication token, if required, has been previously obtained.
    // See Get Firebase Access Token from JSON Service Account Private Key for sample code.

    // Load the previously obtained Firebase access token into a string.
    var fac = new chilkat.FileAccess();
    var accessToken = fac.ReadEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8");
    if (fac.LastMethodSuccess !== true) {
        console.log(fac.LastErrorText);
        return;
    }

    var rest = new chilkat.Rest();

    // Make the initial connection (without sending a request yet).
    // Once connected, any number of requests may be sent.  It is not necessary to explicitly
    // call Connect before each request.  
    var success = rest.Connect("chilkat.firebaseio.com",443,true,true);
    if (success !== true) {
        console.log(rest.LastErrorText);
        return;
    }

    var authGoogle = new chilkat.AuthGoogle();
    authGoogle.AccessToken = accessToken;
    rest.SetAuthGoogle(authGoogle);

    rest.AddHeader("Accept","text/event-stream");
    rest.AddHeader("Cache-Control","no-cache");

    var responseBody = rest.FullRequestNoBody("GET","/.json");

    // A 307 redirect response is expected.
    if (rest.ResponseStatusCode !== 307) {
        console.log("Unexpected response code: " + rest.ResponseStatusCode);
        console.log(responseBody);
        console.log("Failed.");
        return;
    }

    // Get the redirect URL
    // url: Url
    var url = rest.RedirectUrl();
    if (rest.LastMethodSuccess !== true) {
        console.log(rest.LastErrorText);
        return;
    }

    console.log("redirect URL domain: " + url.Host);
    console.log("redirect URL path: " + url.Path);
    console.log("redirect URL query params: " + url.Query);
    console.log("redirect URL path with query params: " + url.PathWithQueryParams);

    // Our text/event-stream will be obtained from the redirect URL...
    var rest2 = new chilkat.Rest();

    success = rest2.Connect(url.Host,443,true,true);
    if (success !== true) {
        console.log(rest2.LastErrorText);

        return;
    }

    rest2.AddHeader("Accept","text/event-stream");
    rest2.AddHeader("Cache-Control","no-cache");

    // Add the redirect query params to the request
    rest2.AddQueryParams(url.Query);

    // In our case, we don't actually need the auth query param,
    // so remove it.
    rest2.RemoveQueryParam("auth");

    // Send the request.  (We are only sending the request here.
    // We are not yet getting the response because the response
    // will be a text/event-stream.)
    success = rest2.SendReqNoBody("GET",url.Path);
    if (success !== true) {
        console.log(rest2.LastErrorText);

        return;
    }

    // Read the response header.  
    // We want to first get the response header to see if it's a successful
    // response status code.  If not, then the response will not be a text/event-stream
    // and we should read the response body normally.
    var responseStatusCode = rest2.ReadResponseHeader();
    if (responseStatusCode < 0) {
        console.log(rest2.LastErrorText);
        return;
    }

    // If successful, a 200 response code is expected.
    // If the reponse code is not 200, then read the response body and fail..
    if (responseStatusCode !== 200) {
        console.log("Response Code: " + responseStatusCode);
        console.log("Response Status Text: " + rest2.ResponseStatusText);
        console.log("Response Header: " + rest2.ResponseHeader);
        responseBody = rest2.ReadRespBodyString();
        if (rest2.LastMethodSuccess == true) {
            console.log("Error Response Body: " + responseBody);
        }

        console.log("Failed.");
        return;
    }

    // For this example, our JSON database will be empty at the beginning.
    // The incoming events (put and patch) will be applied to this database.
    var jsonDb = new chilkat.JsonObject();

    // Make sure to set the JSON path delimiter to "/".  The default is "." and this
    // is not compatible with Firebase paths.
    jsonDb.DelimiterChar = "/";

    // At this point, we've received the response header.  Now it's time to begin
    // receiving the event stream.  We'll start a background thread to read the 
    // stream.  (Our main application (foreground) thread can cancel it at any time.)  
    // While receiving in the background thread, our foreground thread can read the stream
    // as it desires..
    var eventStream = new chilkat.Stream();

    // This sse object will be used as a helper to parse the server-sent event stream.
    var sse = new chilkat.ServerSentEvent();

    // task: Task
    var task = rest2.ReadRespBodyStreamAsync(eventStream,true);
    task.Run();

    // For this example, we'll just read a few events, and then cancel the
    // async task.
    var count = 0;
    while ((count < 3) && (task.Finished == false)) {

        // Get the next event, which is a series of text lines ending with
        // a blank line. 
        // Note: This method blocks the calling thread until a message arrives.
        // a program might instead periodically check the availability of
        // data via the stream's DataAvailable property, and then do the read.

        // An alternative to writing a while loop to read the event stream
        // would be to setup some sort of timer event in your program (using whatever timer functionality
        // is provided in a programming language/environment), to periodically check the eventStream's
        // DataAvailable property and consume the incoming event.
        var eventStr = eventStream.ReadUntilMatch("\r\n\r\n");
        if (eventStream.LastMethodSuccess !== true) {
            console.log(eventStream.LastErrorText);
            // Force the loop to exit by setting the count to a high number.
            count = 99999;
        }
        else {
            console.log("Event: [" + eventStr + "]");

            // We have an event. Let's update our local copy of the JSON database.
            success = sse.LoadEvent(eventStr);
            if (success !== true) {
                console.log("Failed to load sse event: " + eventStr);
            }
            else {
                // Now we can easily access the event name and data, and apply it to our JSON database:
                success = jsonDb.FirebaseApplyEvent(sse.EventName,sse.Data);
                if (success !== true) {
                    console.log("Failed to apply event: " + sse.EventName + ": " + sse.Data);
                }
                else {
                    console.log("Successfully applied event: " + sse.EventName + ": " + sse.Data);
                }

            }

        }

        count = count+1;
    }

    // Make sure the background task is cancelled if still running.
    task.Cancel();

    // Examine the JSON database after applying events..
    jsonDb.EmitCompact = false;
    console.log("----");
    console.log(jsonDb.Emit());

}

chilkatExample();